Crystalline semiconductor film, semiconductor device, and method for manufacturing thereof

A method for manufacturing is: forming an insulating film over a substrate; forming an amorphous semiconductor film over the insulating film; forming over the amorphous semiconductor film, a silicon nitride film in which a film thickness is equal to or more than 200 nm and equal to or less than 1000 nm, equal to or less than 10 atomic % of oxygen is included, and a relative proportion of nitrogen to silicon is equal to or more than 1.3 and equal to or less than 1.5; irradiating the amorphous semiconductor film with a continuous-wave laser light or a laser light with repetition rate of equal to or more than the wave length of 10 MHz transmitting the silicon nitride film to melt and later crystallize the amorphous semiconductor film to form a crystalline semiconductor film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor film having a crystal structure formed by using a technique of laser crystallization and a semiconductor device such as a thin film transistor (hereinafter, TFT) including the semiconductor film and methods for manufacturing thereof. More specifically, the present invention relates to a semiconductor film having a specific crystal structure formed by a technique of laser crystallization, in other words, a plane orientation of crystal grains of three directions that are perpendicular to each other is aligned at equal to or more than a certain ratio. The present invention also relates to a semiconductor device including the semiconductor film, and a method for manufacturing thereof.

2. Description of the Related Art

In recent years, the technique of crystallizing an amorphous semiconductor film formed over a glass substrate by laser irradiation to form a semiconductor film having a crystal structure (hereinafter referred to as a crystalline semiconductor film) has been widely researched, and numerous suggestions are given. Since that crystalline semiconductor film has higher mobility compared to an amorphous semiconductor film, this crystalline semiconductor film is utilized for manufacturing of TFTs for, for example, an active matrix type liquid crystal display device, an organic EL display device, and the like in which over a single glass substrate, TFTs are formed for a pixel portion or for the pixel portion and a driver circuit.

As the method of crystallization, except for the laser crystallization, there are a thermal annealing using a furnace and a rapid thermal annealing (RTA); however, when the laser crystallization is used, without much raise in temperature, heat is only absorbed by the semiconductor film and crystallization is performed; therefore, material such as glass, plastic, and the like that have low melting point can be used as the substrate. As a result, a glass substrate which is inexpensive and is easily processed to have large area can be used, and production efficiency can be drastically improved by the laser crystallization; therefore the laser crystallization is an excellent technique of crystallization.

This applicant focused attention on excellent characteristics of the crystallization, eagerly strived to manufacture a semiconductor film by laser crystallization, and consequently succeeded in the development of many techniques. Among the successful techniques, there is a technique of obtaining excellent semiconductor characteristics: a non-crystallized film which has reduced concentration of oxygen, nitrogen, and carbon is irradiated with a laser light, and melting and re-crystallization steps are performed to obtain a crystalline semiconductor film having high mobility (Patent Document 1). In the suggestion of this technique, it is disclosed that at laser irradiation, it is preferable for a protective film to be formed over the non-crystallized film, and it is also disclosed that by the placement of the protective film, impurity mixing into a silicon film can be evaded.[Patent Document 1] Japanese Published Patent Application No. H5-299339

SUMMARY OF THE INVENTION

This applicant, without being content with the development of the crystallization technique, continued research and development in order to manufacture a crystalline semiconductor film with superior characteristics, ultimately, a single-crystal semiconductor film from a non-single crystal semiconductor film, and as a result, the inventor discovered that a crystalline semiconductor film having a specific crystal structure can be made from a non-single crystal semiconductor film, and it became clear that the semiconductor film has a structure in which the plane orientation of crystal grains of three directions that are perpendicular to each other is aligned at equal to or more than a certain ratio.

As set forth, this inventor succeeded in the development of a crystalline semiconductor film having a specific crystal structure and a method for manufacturing thereof. In addition, the inventor, with the use of the crystalline semiconductor film and the method for manufacturing thereof, also succeeded in the development of a semiconductor device including the crystalline semiconductor film and a manufacturing method thereof. Therefore, a problem to be solved by the present invention, in other words, a purpose of the present invention is to provide a semiconductor film having a specific crystal structure close to a single crystal structure and a manufacturing method thereof, and a semiconductor device having excellent electrical characteristics and reduced variation in electrical characteristics among semiconductor elements in a similar manner to using a single crystalline semiconductor substrate and a method for manufacturing thereof.

The present invention is as aforementioned, to provide a crystalline semiconductor film, a semiconductor device, and a method for manufacturing thereof, and the crystalline semiconductor film and the semiconductor device each have two modes. A first mode of the crystalline semiconductor film is a semiconductor film structured with plural crystal grains over a substrate. In a first surface of the semiconductor film, as to a plane orientation of crystal grains, an orientation of <001> within a range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. In a second surface of the semiconductor film, as to a plane orientation of crystal grains, an orientation of any one of <001>, <101>, <201>, <301>, <401>, <501>, or <601> within a range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. In a third surface of the semiconductor film, as to a plane orientation of crystal grains, an orientation of any one of <001>, <101>, <201>, <301>, <401>, <501>, or <601> within a range of ±10° of angle fluctuation is equal to or more than 60% and equal to or less than 100%. As to the first surface, a first direction is a direction perpendicular to the surface of the substrate, and the first surface is a surface to which the first direction serves as a normal vector. As to the second surface, a second direction is a direction parallel to the surface of the substrate, and the second surface is a surface to which the second direction serves as a normal vector. And as to the third surface, a third direction is a direction parallel to the surface of the substrate and is perpendicular to the direction of crystal growth of crystal grains, and the third surface is a surface to which the third direction serves as a normal vector.

A second mode of the crystalline semiconductor film is a semiconductor film structured with plural crystal grains over a substrate. In a first surface of the semiconductor film, as to a plane orientation of crystal grains, an orientation of <001> within a range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. In a second surface of the semiconductor film, as to a plane orientation of crystal grains, an orientation of <x01> (x=0, 1, 2, 3, 4, 5, 6) within a range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. In a third surface of the semiconductor film, as to a plane orientation of crystal grains, an orientation of <x01> (x=0, 1, 2, 3, 4, 5, 6) within a range of ±10° of angle fluctuation is equal to or more than 60% and equal to or less than 100%. As to the first surface of the semiconductor film, a first direction is a direction perpendicular to the surface of the substrate, and the first surface is a surface to which the first direction serves as a normal vector. As to the second surface, a second direction is a direction parallel to the surface of the substrate, and the second surface is a surface to which the second direction serves as a normal vector. And as to the third surface, a third direction is a direction parallel to the surface of the substrate and is perpendicular to the direction of crystal growth of crystal grains, and the third surface is a surface to which the third direction serves as a normal vector.

In addition, a first mode of the semiconductor device is a semiconductor device having a semiconductor element provided with a semiconductor film structured with plural crystal grains over a substrate. In a first surface of the semiconductor film, as to the plane orientation of crystal grains, an orientation of <001> within a range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. In a second surface of the semiconductor film, as to the plane orientation of crystal grains, an orientation of any one of <001>, <101>, <201>, <301>, <401>, <501>, or <601> within a range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. In a third surface of the semiconductor film, as to the plane orientation of crystal grains, an orientation of any one of <001>, <101>, <201>, <301>, <401>, <501>, or <601> within a range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. As to the first surface of the semiconductor film, a first direction is a direction perpendicular to the surface of the substrate, and the first surface is a surface to which the first direction is serves as a normal vector. As to the second surface of the semiconductor film, a second direction is a direction parallel to the surface of the substrate, and the second surface is a surface to which the second direction serves as a normal vector. And as to the third surface of the semiconductor film, a third direction is a direction parallel to the surface of the substrate and is perpendicular to the direction of crystal growth of crystal grain, and the third surface is a surface to which the third direction serves as a normal vector.

In addition, a second mode of the semiconductor device is a semiconductor device having a semiconductor element provided with a semiconductor film structured with plural crystal grains over a substrate. In a first surface of the semiconductor film, as to the plane orientation of crystal grains, the orientation of <001> within the range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. In a second surface of the semiconductor film, as to the plane orientation of crystal grains, the direction of <x01> (x=0, 1, 2, 3, 4, 5, 6) within a range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. In a third surface of the semiconductor film, as to the plane orientation of crystal grains, the direction of <x01> (x=0, 1, 2, 3, 4, 5, 6) within the range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%. As to the first surface of the semiconductor film, a first direction is a direction perpendicular to the surface of the substrate, and the first surface is a surface to which the first direction serves as a normal vector. As to the second surface of the semiconductor film, a second direction is a direction parallel to the surface of the substrate, and the second surface is a surface to which the second direction serves as a normal vector. And as to the third surface of the semiconductor film, a third direction is a direction parallel to the surface of the substrate and is perpendicular to the direction of crystal growth of crystal grains, and the third surface is a surface to which the third direction serves as a normal vector.

Moreover, with respect to the semiconductor film and the semiconductor device, in the first mode, the following are preferable respectively.

1) In the first surface of the semiconductor film, a plane orientation of crystal grains within a range of ±10° of angle fluctuation includes: a direction of <001> is equal to or more than 70% and less than 100%. In the second surface of the semiconductor film, the plane orientation of crystal grains within a range of ±10° of angle fluctuation includes: a direction of any one of <301>, <401>, <501>, or <601> is equal to or more than 70% and less than 100%. In the third surface of the semiconductor film, the plane orientation of crystal grains in a range of ±10° of angle fluctuation includes: a direction of any one of <301>, <401>, <501>, or <601> is equal to or more than 70% and less than 100%,

2) a size of crystal grain of the semiconductor film is: a width is equal to or more than 0.1 μm and equal to or less than 10 μm and a length is equal to or more than 5 μm and equal to or less than 50 μm,

3) the semiconductor is Si, Si1-xGex(0<x<0.1),

4) the semiconductor element is a thin film transistor, a diode, a resistance element, capacitative element, a CCD, or a photoelectric conversion element (correspond to only semiconductor device).

In addition, with respect to the plane orientation of crystal grains in the present invention, the following is a description with examples. For example, with respect to a plane orientation <001>, [100], [010], and [001], and in addition, an equivalent orientation family such as plane orientations in which each 1 in the aforementioned plane orientations is −1 are collectively referred to as <001>. In addition, with respect to a plane orientation <301>, [310], [301], [130], [103], [013], and [031], and an equivalent orientation family such as plane orientations in which any one or both of each 1 and 3 in each the aforementioned plane orientations are negative are collectively referred to as <301>.

In addition, signification of plane orientation <x01> (x=0, 1, 2, 3, 4, 5, 6) is described below. Aforementioned <x01> is a summation of orientation ratios of plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101>. In addition, in that case, when plane orientations of <001> to <601> are simply totaled, a portion of each plane orientation has a part that overlaps; therefore, a result of overlapping portion of each plane orientation <001> to <601> calculated as either one orientation ratio of plane orientation is referred to as plane orientation <x01>.

Note that the range of an angle fluctuation of ±10° shows that a deviation from a certain plane orientation is within the range of −10 to ±10°, which means that the angle fluctuation of a certain plane orientation is allowed within the range of ±10°. For example, the plane orientation <001> of a crystal grain within the range of an angle fluctuation of +10′ includes a crystal grain, which is deviated from the plane orientation <001> by −10° to a crystal grain, which is deviated from the plane orientation <001> by +100.

In addition, a method for manufacturing a crystalline semiconductor film includes: forming an insulating film over a substrate; forming an amorphous semiconductor film over the insulating film, forming, over the amorphous semiconductor film a silicon nitride film in which a film thickness is 200 nm to 1000 nm, equal to or less than 10 atomic % of oxygen is included, and a relative proportion of nitrogen in silicon is equal to or more than 1.3 and equal to or less than 1.5; and irradiating the amorphous semiconductor film with a laser light transmitting the silicon nitride film which is a continuous-wave laser light or a laser light with repetition rate of equal to or more than the wave length of 10 MHz to melt and later crystallize the amorphous semiconductor film.

In addition, a method for manufacturing a semiconductor device includes: forming an insulating film over a substrate; forming an amorphous semiconductor film over the insulating film; forming, over the amorphous semiconductor film, a silicon nitride film in which a film thickness is equal to or more than 200 nm and equal to or less than 1000 nm, and equal to or less than 10 atomic % of oxygen is included, and a relative proportion of nitrogen in silicon is equal to or more than 1.3 and equal to or less than 1.5; irradiating the amorphous semiconductor film with a laser light transmitting the silicon nitride film which is a continuous-wave laser light or a laser light with repetition rate of equal to or more than 10 MHz to melt and later crystallize the amorphous semiconductor film to form a crystalline semiconductor film, and forming a semiconductor element using the crystalline semiconductor film.

In addition, in the method for manufacturing thereof, the following is preferable.

1) The silicon nitride including oxygen is formed by plasma CVD in an atmosphere including SiH4, NH3, and N2O, or an atmosphere including SiH4and NH3,

2) the amorphous semiconductor film has a film thickness of equal to or more than 20 nm and equal to or less than 80 nm,

3) the continuous-wave laser light or the laser light with repetition rate of equal to or more than 10 MHz has a wavelength which is absorbed by the amorphous semiconductor film.

A crystalline semiconductor film of the present invention includes: a specific crystal structure, in other words, plane orientations of crystal grains in three surfaces that are perpendicular to each other are aligned at a certain ratio; therefore, an excellent semiconductor characteristic can be expressed. Specifically, according to the first mode, in the first surface of the semiconductor film, in a plane orientation of crystal grains within a range of ±10° of angle fluctuation, in a direction of <001> is equal to or more than 60% and less than 100%, preferably equal to or more than 70% and less than 100%, in the second surface of the semiconductor film, in a plane orientation of crystal in a range of ±10° of angle fluctuation, in any direction of <301> <401>, <501>, or <601> is equal to or more than 60% and less than 100%, preferably equal to or more than 70% and less than 100%, in the third surface of the semiconductor film, in a plane orientation of crystal within a range of ±10° of angle fluctuation, in any direction of <301> <401>, <501>, or <601> is equal to or more than 60% and less than 100%, preferably equal to or more than 70% and less than 100%, the first surface of the semiconductor film includes: a first direction is a direction perpendicular to the surface of the substrate and, the first surface is a surface to which the first direction serves as a normal vector, the second surface of the semiconductor film includes: a second direction is a direction parallel to the surface of the substrate and is parallel to the direction of crystal growth of crystal grains, and the second surface is a surface to which the second direction serves as a normal vector, and the third surface of the semiconductor film includes: a third direction is a direction parallel to the surface of the substrate and is perpendicular to the direction of crystal growth of crystal grains, and the third surface is a surface to which the third direction serves as a normal vector.

In other words, the crystalline semiconductor film of the present invention has the aforementioned crystal structure, and the invention can provide a semiconductor device such as a thin film transistor (hereinafter referred to as TFT) in which a variation of electrical characteristics is reduced among adjacent semiconductor elements due to the semiconductor film, and a method for manufacturing thereof. In addition, in that case, a silicon nitride film with optimized thickness and composition ratios is formed over the amorphous semiconductor film. The amorphous semiconductor film is irradiated with a laser light which is a continuous-wave laser light or a laser light with repetition rate of equal to or more than 10 MHz through the silicon nitride film to melt and later crystallize the amorphous semiconductor film. Thus a crystalline semiconductor film is formed in which plane orientation of crystal grains in three surfaces that are perpendicular to each other are aligned at equal to or more than a certain ratio. As a result, a semiconductor device having excellent characteristics in which electrical characteristic is excellent and a variation of electrical characteristics is reduced among adjacent semiconductor elements can be manufactured. In addition, a similar regard can also be applied to the second mode.

DETAILED DESCRIPTION OF THE INVENTION

Described briefly below with reference to figures are embodiment modes and embodiments including the best mode for carrying out the invention; however, the present invention is not limited in any ways by the embodiment modes and embodiments, and is needless to say specified by the scope of claim.

In Embodiment Mode 1, first, an abstract of a manufacturing process of a crystalline semiconductor film of the present invention is described usingFIGS. 1A to 1CandFIG. 18, and subsequently, a basic matter regarding a crystal structure, a crystal structure of a semiconductor film of the present invention is specifically described with reference toFIG. 2,FIGS. 19A to 19D, andFIGS. 20A to 20DandFIGS. 21A to 21C. However, the present invention can be implemented in many different modes, and it is easily understood by those skilled in the art that modes and details herein disclosed can be modified in various ways without departing from the spirit and the scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiment modes and embodiments to be given below.

First, as shown inFIG. 1A, a silicon oxide film containing nitrogen having a thickness of 50 to 150 nm is formed as an insulating film101which functions as a base film on one surface of a glass substrate having a thickness of 0.7 mm, for example, as a substrate100having an insulating surface. Further, an amorphous semiconductor film is formed by a plasma CVD, as a semiconductor film102, over the insulating film101to have a thickness of greater than or equal to 20 nm and less than or equal to 100 nm, preferably, 20 nm to 80 nm.

In addition, the insulating film101may be provided if needed, and when the substrate100is made of glass, the insulating film101prevents impurity from diffusing to the semiconductor film102; however, when quartz is used as the substrate100, the insulating film101which functions as the base film is not needed to be provided. Moreover, a peeling film may be provided between the insulating film101and the substrate100to peel a semiconductor element from the substrate100after the process.

With respect to the semiconductor film102, in this embodiment mode, amorphous silicon is used; however, polycrystalline silicon may be used, and silicon germanium (Si1-xGex(0<x<0.1)) and the like may be used, and silicon carbide (SiC) in which a single crystal has a diamond structure can also be used.

Moreover, after the semiconductor film102is formed, the semiconductor film102may be heated in an electrical furnace at 500° C. for 1 hour, and in this heat treatment the amorphous silicon film is dehydrogenated. In addition, the reason of dehydrogenation is to prevent hydrogen gas from spouting out from the semiconductor film102when irradiation is performed with a laser beam, and this heat treatment may be omitted if hydrogen included in the semiconductor film102is little. In this embodiment mode, an example of using the amorphous silicon film as the semiconductor film102is shown; however, a polycrystalline silicon film may also be used. For example, after forming an amorphous silicon film, a polycrystalline silicon film can be formed by adding a minute amount of an element such as nickel, palladium, germanium, iron, palladium, tin, lead, cobalt, platinum, copper, or gold to the amorphous silicon film, and then performing heat treatment at 550° C. for 4 hours.

Subsequently, a silicon nitride film which has a thickness of 200 nm to 1000 nm, includes equal to or less than 10 atomic % of oxygen, and has equal to or more than 1.3 and equal to or less than 1.5 of relative proportion of nitrogen to silicon is formed over the semiconductor film102as a cap film103. It is particularly to be noted that if the cap film103is too thin, it will become difficult to control plane orientation of a crystalline semiconductor film that is later formed; therefore, the cap film103is preferably formed with a thickness of equal to or more than 200 nm and equal to or less than 1000 nm.

As this cap film103, in this embodiment mode, a silicon nitride film including oxygen with a thickness of 300 nm is formed by plasma CVD with monosilane (SiH4), ammonium (NH3), and nitrous oxide (N2O) as gas material. Note that nitrous oxide (N2O) is used as oxidizer, and instead of nitrous oxide, oxygen which has an oxidizing effect may be used.

As the cap film103, a film having enough transmittance with respect to a wavelength of the laser beam, and having a thermal value such as a thermal expansion coefficient and a value such as ductility close to those of an adjacent semiconductor film is preferably used. Further, the cap film103is preferably a solid and dense film similarly to a gate insulating film of a thin film transistor to be formed later. Such a solid and dense film can be formed by reducing a deposition rate, for example. Note that when much hydrogen is included in the cap film, in a similar manner to the semiconductor film102, heat treatment is performed for dehydrogenation.

Next, a laser oscillator and an optical system for forming a beam spot, which are used for the crystallization by irradiating the amorphous semiconductor film with a laser, will be explained. As shown inFIG. 18, as each of laser oscillators11aand11b, a laser oscillator emitting a wavelength that is absorbed in the semiconductor film102for several tens % or more is used. Typically, a second harmonic or a third harmonic can be used. Here, a CW laser with LD (Laser Diode) excitation (YVO4, a second harmonic (a wavelength of 532 nm)), maximum output of which is 20 W, is prepared. It is not necessary to particularly limit the wavelength of the laser to a second harmonic; however, the second harmonic is superior to a further higher order harmonic in terms of energy efficiency.

Laser power used in this invention is within the range which can melt the semiconductor film completely and is within the range which can form a crystalline semiconductor film having aligned plane orientation of crystal grains. When laser power that is lower than this range is used, a semiconductor film can not be completely melted, and a crystalline semiconductor film in which crystal grains are small and plane orientation of crystal grains is not aligned in one direction is formed. Therefore, the two laser oscillators are prepared in the case ofFIG. 18; however, one laser oscillator may be prepared as long as the output is enough. When a laser power higher than this range is used, many crystal nucleation is caused in the semiconductor film, and from the crystal nucleus, disorderly crystal growth is generated, thus a crystalline semiconductor film with uneven position, size, and plane orientation of crystal grain is formed.

When the semiconductor film102is irradiated with the CW laser, energy is continuously provided to the semiconductor film102; therefore, when the semiconductor film is once brought to a melted state, the melted state can be continued. Further, a solid-liquid interface of the semiconductor film can be moved by scanning the CW laser beam; therefore, a crystal grain which is long in one direction along this movement direction can be formed. In addition, a solid laser is used because, as compared with a gas laser or the like, output has high stability and stable process is expected. Note that, without limitation to the CW laser, it is possible to use a pulse laser having a repetition rate of equal to or more than 10 MHz.

When a pulse laser having a high repetition rate is used, the semiconductor film can be always kept melting in the direction of film thickness, as long as a pulse interval of the laser is shorter than a time between melt and solidification of the semiconductor film. Thus, a semiconductor film composed of the crystal grain which is laterally grown and long in one direction by the movement of the solid-liquid interface can be formed.

In this embodiment mode, a YVO4laser is used for the laser oscillators11aand11b; however, other CW laser and pulse laser having a repetition rate of greater than or equal to 10 MHz can also be used. For example, as a gas laser, there is an Ar laser, a Kr laser, a CO2laser, or the like. As a solid-sate laser, there is a YAG laser, a YLF laser, a YAlO3laser, a GdVO4laser, a KGW laser, a KYW laser, an alexandrite laser, a Ti: sapphire laser, a Y2O3laser, a YVO4laser, or the like. Moreover, there is a ceramic laser such as a YAG laser, a Y2O3laser, a GdVO4laser, or YVO4laser. As a metal vapor laser, there is a helium cadmium laser or the like.

In addition, in the laser oscillator11aand the laser oscillator11b, energy uniformity of a linear beam spot that is obtained on the surface to be irradiated can be increased, when the laser beam is emitted with oscillation of TEM00(a single transverse mode), which is preferable.

The brief description of optical treatment of laser emitted from these laser oscillators is as follows. Laser beams12aand12bare each emitted with the same energy from the laser oscillators11aand11b. A polarization direction of the laser beam12bemitted from the laser oscillator11bis changed through a wavelength plate13. The polarization direction of the laser beam12bis changed because the two laser beams each having a polarization direction different from each other are synthesized by a polarizer14.

After the laser beam12bis passed through the wavelength plate13, the laser beam12bis reflected by a mirror22and made to enter the polarizer14. Then, the laser beam12aand the laser beam12bare synthesized by the polarizer14. The wavelength plate13and the polarizer14are adjusted so that light that has transmitted the wavelength plate13and the polarizer14has appropriate energy. Note that, in this embodiment mode, the polarizer14is used for synthesizing the laser beams; however, other optical element such as a polarization beam splitter may also be used.

A laser beam12that is synthesized by the polarizer14is reflected by a mirror15, and a cross section of the laser beam is formed into a linear shape on the surface to be irradiated18by a cylindrical lens16having a focal length of 150 mm, and a cylindrical lens17having a focal length of 20 mm, for example. The mirror15may be provided depending on an arrangement of an optical system of a laser irradiation apparatus.

The cylindrical lens16operates in a length direction of the beam spot that is formed on the surface to be irradiated18, whereas the cylindrical lens17operates in a width direction thereof. Accordingly, on the surface to be irradiated18, a linear beam spot having a length of approximately 500 μm and a width of approximately 20 μm, for example, is formed. Note that, in this embodiment mode, the cylindrical lenses are used to form the beam spot into a linear shape; however, the present invention is not limited thereto, and other optical element such as a spherical lens may also be used. Moreover, the focal lengths of the cylindrical lenses are not limited to the above values and can be arbitrarily set.

Further, in this embodiment mode, the laser beam is shaped using the cylindrical lenses16and17; however, an optical system for extending the laser beam to a linear shape and an optical system for converging thin on the surface to be irradiated may be additionally provided. For example, in order to obtain the linear cross section of the laser beam, a cylindrical lens array, a diffractive optical element, an optical waveguide, or the like can be used. In addition, with the use of a rectangular-shape laser medium, the linear cross section of the laser beam can also be obtained at an emission stage.

The ceramic laser can form a shape of laser medium relatively freely; therefore, the ceramic laser is appropriate for manufacturing such a laser beam. Note that the cross-sectional shape of the laser beam which is formed in a linear shape is preferably as narrow as possible in the width, which increases an energy density of the laser beam in the semiconductor film; therefore, a process time can be shortened.

Then, an irradiation of the laser beam will be explained. Since the surface to be irradiated18, where the semiconductor film102covered by a cap film103is formed, is operated with a relatively high speed, the surface to be irradiated18is fixed to suction stage19. The suction stage19can operates in X and Y directions on a plane parallel to the surface to be irradiated18by an X-axis uniaxial robot20and a Y-axis uniaxial robot21. The uniaxial robots are disposed so that the length direction of the linear beam spot corresponds to the Y axis.

Next, the surface to be irradiated18is made to operate along the width direction of the beam spot, that is, the X axis, and the surface to be irradiated18is irradiated with the laser beam. Here, a scanning speed of the X-axis uniaxial robot20is 35 cm/sec, and the laser beam having an energy of 7.0 W is emitted from each of the two laser oscillators. The laser output after synthesizing the laser beams is to be 14 W. A region completely melted is formed in the semiconductor film by being irradiated with the laser beam. A crystal is grown in one plane orientation during a solidifying process; thus, a crystalline semiconductor film of the present invention can be obtained.

Note that energy distribution of the laser beams emitted from the laser oscillators in a TEM00mode is generally a Gaussian distribution. Note that a width of the region where crystal grains with plane orientation at three surfaces that are perpendicular to each other are formed can be changed by the optical system used for the laser beam irradiation. For example, intensity of the laser beam can be homogenized by using a lens array such as a cylindrical lens array or a fly eye lens; a diffractive optical element; an optical waveguide; or the like.

By irradiating the semiconductor film102with the laser beam, intensity of which is homogenized, almost all of the regions irradiated with the laser beam can be formed with crystal grains in which plane orientation is controlled at three surfaces that are perpendicular to each other. A scanning speed of the X-axis uniaxial robot20is appropriate when it is to be approximately several to several hundred cm/sec, and the speed may be appropriately decided by an operator in accordance with the output of the laser oscillators.

Note that, in this embodiment mode, a mode of moving the semiconductor film102, which is the surface to be irradiated18, by using the X-axis uniaxial robot20and the Y-axis uniaxial robot21is used. Without limitation thereto, the laser beam can be scanned by using a method for moving an irradiation system in which the surface to be irradiated18is fixed while an irradiation position of the laser beam is moved; a method for moving a surface to be irradiated in which the irradiation position of the laser beam is fixed while the surface to be irradiated18is moved; or a method in which these two methods are combined.

Note that, as described above, the energy distribution of the beam spot, which is formed by the above optical system, is a Gaussian distribution in a major axis direction; therefore, a small grain crystal is formed in a place having a low energy density at the both ends. Thus, part of the laser beam may be cut by providing a slit or the like in front of the surface to be irradiated18so that the surface to be irradiated18is irradiated only with energy enough to form crystal in which plane orientation is controlled at three surfaces that are perpendicular to each other. Alternatively, a metal film or the like that reflects the laser beam may be formed over the silicon nitride film containing oxygen, which is the cap film103, and a pattern may be formed so that the laser beam reaches only a place of the semiconductor film where crystal in which plane orientation is controlled at three surfaces that are perpendicular to each other is desired to be obtained may be formed.

Moreover, in order to efficiently use the laser beams emitted from the laser oscillator11aand the laser oscillator11b, the energy of the beam spot may be uniformly distributed in a length direction by using a beam homogenizer such as a lens array or a diffractive optical element. Further, the Y-axis uniaxial robot21is moved by a width of the crystalline semiconductor film that is formed, and the X-axis uniaxial robot20is rescanned with a scanning speed at 35 cm/sec. By repeating a series of such operations, the entire surface of the semiconductor film can be efficiently crystallized.

Thereafter, the cap film is removed by performing etching. Further, a resist is applied over the crystalline semiconductor film, light-exposed, and developed, thereby forming a resist into a desired shape. Furthermore, etching is performed using the resist formed here as a mask, and the crystalline semiconductor film, which is exposed by developing, is removed. Through this process, an island-shaped semiconductor film is formed. And, by using this island shape semiconductor film, a semiconductor device having a semiconductor element such as a thin film transistor, a diode, a resistance element, a capacitance element, and a CCD can be manufactured.

Subsequently, plane orientation of the crystalline semiconductor film manufactured by this embodiment mode is described. In this embodiment mode, in order to confirm the position, the size, and the plane orientation of crystal grains of the crystalline semiconductor film from which the cap film has been removed by etching, EBSP (Electron Back Scatter Diffraction Pattern) measurement is carried out. First, a basic matter of EBSP is explained, and a result is described while complementary explanation is being added.

EBSP refers to a method by which an EBSP detector is connected to a scanning electron microscope (SEM), a direction of a diffraction image (an EBSP image) of individual crystal, which is generated when a sample highly tilted in the scanning electron microscope is irradiated with a convergent electron beam, is analyzed, and the plane orientation of crystal grains of a sample is measured from direction data and position information of a measurement point (x, y).

When an electron beam is made to enter a crystalline semiconductor film, inelastic scatterings also occur at the back, and a linear pattern, which is peculiar to crystal plane orientation by Bragg diffraction, can also be observed in the sample. Here, this linear pattern has generally been referred to as a Kikuchi line. An EBSP obtains crystal plane orientation of a sample by analyzing a Kikuchi line reflected in a detector.

In a sample having a polycrystalline structure, each crystal grain has different plane orientation. Thus, every time the irradiation position of the crystalline semiconductor film is moved, the sample is irradiated with the electron beam and the crystal plane orientation in each irradiation position is analyzed. In such a manner, the crystal plane orientation or orientation information of a crystalline semiconductor film having a flat surface can be obtained. As a measurement region is broader, the tendency of the crystal plane orientation of the entire crystalline semiconductor film can be obtained more; and as there are more measurement points, the more information on the crystal plane orientation in the measurement region can be obtained in detail.

However, the plane orientation within the crystal grains cannot be decided only with the plane orientation from observation on one surface of the crystal grain. This is because, even when a plane orientation is aligned in one direction only in one viewing plane, it cannot be said that the plane orientation is aligned within the crystal grains, if the plane orientation is not aligned in other viewing planes. In order to decide the plane orientation within a crystal grain, the plane orientations from at least two surfaces are needed, and the more information is obtained from many planes, the precision becomes higher.

Therefore, when plane orientation distributions of all three surfaces are almost uniform within the measurement region, a crystal thereof can be regarded as, approximately, a single crystal. Actually, as shown inFIG. 2, the plane orientation within a crystal can be specified with high precision by putting together pieces of information on three surfaces (a viewing plane A, a viewing plane B, and a viewing plane C) where three vectors perpendicular to each other (a vector a, a vector b, and a vector c) are each to be a normal vector.

In a crystalline semiconductor film which is formed in this embodiment, the vectors a to c are set as described below. The vector c is parallel to a scanning direction of the laser beam (i.e., a direction of crystal growth of crystal grain) and the surface of the substrate, the vector a is perpendicular to the surface of the substrate and the vector c, and the vector b is parallel to the surface of the substrate, perpendicular to a direction of crystal growth of crystal grain, and perpendicular to each of the vector a and vector c. According to the information from these three viewing planes A to C, plane orientation of the crystalline film can be specified with high precision.

First,FIG. 19AtoFIG. 21Ceach show a result of analyzing the plane orientation (a crystal axis orientation in a direction perpendicular to a viewing plane) of a crystalline semiconductor film. The electron beam was entered the crystalline semiconductor film formed in this embodiment mode with an incidence angle of 60° with respect to the surface of the crystalline semiconductor film, and a crystal plane orientation was measured from the obtained EBSP image. The measurement region is 50 μm×50 μm. In this region, the measurement was carried out on lattice points each having 0.1 μm in length and width. Since the sample surface is a surface to be measured by an EBSP, the crystalline semiconductor film is necessary to be a top layer. Therefore, the measurement was carried out after etching the silicon nitride film containing oxygen which is the cap film.

FIG. 19Ashows a plane orientation distribution in the viewing plane A where the vector a serves as a normal vector, as well,FIG. 19Bshows a plane orientation distribution in the viewing plane B where the vector b serves as a normal vector, andFIG. 19Cshows a plane orientation distribution in the viewing plane C where the vector c serves as a normal vector.FIGS. 19A to 19Care each an orientation map image which shows that which plane orientation is indicated by each measurement point.FIG. 19Dis a diagram in which each plane orientation is color coded to be expressed, and plane orientation of measurement points ofFIGS. 19A to 19Care shown by the color corresponding to the plane orientation ofFIG. 19D.

Note that sinceFIGS. 19A to 19Care monochrome and the image is only displayed by lightness, distinction is difficult; however, in color display, it is found that orientation is strongly obtained in an orientation of <001> in the viewing plane A, an orientation of <301> in the viewing plane B, and an orientation of <301> in the viewing plane C. In addition, since the plane orientation within individual crystal grain is uniform, pieces of information on a shape, a size, or the like of individual crystal grain can be roughly obtained based on the color and shape. Moreover, plane orientation <401>, <501>, and <601> are close to plane orientation <301>; therefore, the plane orientation <401>, <501>, and <601> are approximately the same as the plane orientation <301>.

Here, according toFIGS. 19A to 19C, it is found that the crystal grains of the crystalline semiconductor film formed in this embodiment mode is composed of a domain extended long in a column shape. According toFIGS. 19A to 19C, the length of a domain is equal to or more than 5 μm and equal to or less than 50 μm, and moreover a domain with a length of equal to or more than 50 μm was found. In addition, a region to be measured inFIGS. 19A to 19Cis 50 μm×50 μm, and in a larger range, a domain of equal to or more than 5 μm to equal to or less than 100 μm is found.

In addition, according toFIGS. 19A to 19C, it is found that orientation is strongly obtained in the orientation of <001>, the orientation of <301>, and the orientation of <301> in the viewing planes A, B, and C, respectively. When it is found that orientation is strongly obtained in a specific index, an orientation degree can be grasped by obtaining a proportion of how much crystal grains are gathered in vicinity of the index.

FIGS. 20A to 20Care inverse pole figures expressing frequency of appearance at viewing planes A to C inFIGS. 19A to 19C, andFIG. 20Dis a scale showing appearance frequency of plane orientation. AlthoughFIGS. 20A to 20Dare monochrome and the image is only displayed by lightness so that distinction is difficult,FIGS. 20A to 20Dshow that a region which is closer to black has a higher ratio of crystal having plane orientation. According to the inverse pole figure inFIG. 20A, it was confirmed that the viewing plane A, <001> is the closest to black, and specifically, orientation of <001> appears with a frequency of 14.0 times or more as often as a condition in which all directions appear with identical probability.

In addition, according to an inverse pole figure inFIG. 20B, it was confirmed that the orientation of <301> is the closest to black and specifically, the orientation of <301> appears with a frequency of equal to or more than 4.8 times as often as a condition in which all orientations of the viewing plane B appear with identical probability. Moreover, according to an inverse pole figure inFIG. 20C, it was confirmed that the orientation of <301> is the closest to black and specifically, the orientation of <301> appears with a frequency of equal to or more than 4.8 times as often as a condition in which all orientations of the viewing plane C appear with identical probability.

In the inverse pole figures ofFIGS. 20A to 20C, orientation ratios of plane orientations with high frequency of appearance were calculated, and the results are shown in theFIGS. 21A to 21C.FIG. 21Ashows a result of calculation to obtain orientation ratio at the viewing plane A, and in the inverse pole figure inFIG. 20A, the range of an angle fluctuation of the orientation of <001> is decided to be within ±10°, and a proportion of the number of the measurement points at which the angle fluctuation of the orientation of <001> with respect to all measurement points exist within ±10° is obtained; therefore, an orientation ratio can be obtained. Note that the colored region inFIG. 21Ashows a region which is crystal with the range of an angle fluctuation within ±10°.

In addition, a value of Partition Fraction is the value which is the result of calculation to obtain a ratio of a point having a specific orientation among all measured points. And, the value of Total Fraction is a value which is the result of calculation to obtain orientation ratio of highly reliable measuring points among the points having a specific orientation in all measured points. According to this result, in the viewing plane A of the crystalline semiconductor film formed in Embodiment Mode 1, the orientation of <001> occupies 71.2% within the range of an angle fluctuation of ±10°. Note that as aforementioned, [100], [010], and [001], and in addition, an equivalent orientation family such as plane orientations in which 1 in each of the aforementioned plane orientations is −1 are collectively referred to as <001>.

FIGS. 21B and 21Care results of calculation to obtain orientation ratios at the viewing planes B and C according toFIGS. 20B and 20Cin a similar manner toFIG. 21A. Note that the colored region inFIGS. 21B and 21Cis a region showing crystal where the orientation of <301> is in the range of an angle fluctuation within ±10°, and in the viewing plane B of the crystalline semiconductor film formed in this embodiment mode, the orientation of <301> occupies 71.1% within the range of an angle fluctuation of ±10°.

In the viewing plane C of the crystalline semiconductor film formed in this embodiment, the orientation of <301> occupies 73.9% within the range of an angle fluctuation of ±10°. Note that [310], [301], [130], [103], [013], and [031], and an equivalent orientation family such as plane orientations in which any one or both of each 1 and 3 in each of the aforementioned plane orientations is a negative value are collectively referred to as <301>. In addition, in the viewing planes B and C, ratio of the orientation of <301> was shown; however, the ratio may be the ratio of the orientation <401>, <501>, or <601>.

As described through the above, the plane orientation of crystal grains is aligned in one direction with a high proportion in all of the three viewing planes. In other words, it is found that a crystal, where it can be regarded that the plane orientation of crystal grains is aligned in one direction, is formed in a crystallized region. In such a manner, it was confirmed that a crystal, of which specific plane orientation occupies an extremely high ratio, is formed over a glass substrate in a region having one side of several ten μm.

In addition, the crystalline semiconductor film manufactured in the present invention is poly-crystal. Thus, in each of the orientation ratio of plane orientation of the viewing planes A to C, if crystal defect such as crystal grain boundaries is included, the orientation ratio of plane orientation of each viewing plane is less than 100%. In addition, the measurement of EBSP can be conducted in, for example, at a channel region of a thin film transistor. That is to say the measurement is possible at a semiconductor layer which is covered by a gate wiring and a gate insulating film.

With the above result, when plane orientation of the crystalline semiconductor film manufactured by Embodiment Mode 1 is measured by EBSP, in the viewing plane A, as to the plane orientation of crystal grains, the orientation of <001> within the range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%, preferably equal to or more than 70% and less than 100%. In addition, in the viewing plane B, as to the plane orientation of crystal grains, the orientation of <001> within the range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%, preferably equal to or more than 70% and less than 100%, and in the viewing plane C, as to the plane orientation of crystal grains, the orientation of <001> with in the range of ±10° of angle fluctuation is equal to or more than 60% and less than 100%, preferably equal to or more than 70% and less than 100%.

As discussed above, in the crystalline semiconductor film formed in this embodiment, the plane orientation of a crystal grain is aligned in one direction or in a direction that can be substantially regarded as one direction. In other words, the crystalline semiconductor film has a property close to that of a single crystal. By using such a semiconductor film, performance of a semiconductor device can be considerably improved. For example, when TFT is formed using this crystalline semiconductor film, an equivalent electric field-effect mobility (mobility) to a semiconductor device using a single crystalline semiconductor can be obtained.

In addition, in that TFT, it is possible to reduce variation of an on current value (a value of drain current value that flows when a TFT is in an on state), an off current value (a drain current value that flows when a TFT is in an off state), a threshold voltage, an S value, and electric field-effect mobility. Since there is such an advantageous effect, an electrical characteristic of a TFT is improved, and an operational characteristic and reliability of a semiconductor device using a TFT is improved. Thus, a semiconductor device capable of high speed operation with high current driving capacity and small variation of characteristics between a plurality of elements can be manufactured.

In this embodiment mode, liquid crystal display device which is one example of a semiconductor device is described with reference toFIG. 3AtoFIG. 4C. As shown inFIG. 3A, in a similar manner to Embodiment Mode 1, an insulating film101which functions as a base film is formed over a substrate100, an amorphous semiconductor film102is formed over the insulating film101, and a cap film103is formed over the amorphous semiconductor film102.

Here, as the substrate100, a glass substrate is used. As the insulating film101, a silicon nitride film including oxygen having a thickness of 40 to 60 nm and a silicon oxide film including nitrogen having a thickness of 80 to 120 nm are respectively formed by plasma CVD. In addition, an amorphous silicon film which has a thickness of 20 to 80 nm is formed as the amorphous silicon film102by plasma CVD. And, as the cap film103, a silicon nitride film which has a thickness of equal to or more than 200 nm and equal to or less than 1000 nm and has equal to or less than 10 atomic % of oxygen, and has equal to or more than 1.3 to equal to or less than 1.5 of relative proportion of nitrogen to silicon is formed.

Subsequently, as shown inFIG. 3B, irradiation of a laser light104is performed from the cap film103to the amorphous silicon film102. As a result, a crystalline semiconductor film105can be formed over the insulating film101. In addition, as the laser light104, a laser light which has energy which can melt the amorphous semiconductor film102and has a wave length that can be absorbed by the amorphous semiconductor film102is selected. In addition, a heat treatment to extract nitrogen which is included in the amorphous semiconductor film and the cap film may be performed.

Here, as the laser light104, second harmonic of YVO4is used, and after that the cap film103is removed. As a method for removing the cap film103, dry etching, wet etching, grinding and the like can be used. Here the cap film103is removed by dry etching.

Subsequently, as shown inFIG. 3C, the crystalline semiconductor film105is selectively etched to form semiconductor layers201to203. As a method for etching the crystalline semiconductor film105, dry etching, wet etching, and the like can be used. Here, after resist is applied over the crystalline semiconductor film105, light-exposure and development are performed to form a resist mask. By the use of the resist mask which was formed, dry etching in which flow ratio of SF6:O2is set to 4:15 is performed to selectively etch the crystalline semiconductor film105, and after that the resist mask is removed.

Subsequently, as shown inFIG. 3D, a gate insulating film204is formed over the semiconductor layers201to203, and the gate insulating film is formed with silicon nitride, silicon nitride including oxygen, silicon oxide, silicon oxide including nitrogen and the like of single layer or multi-layer structure. Here, silicon oxide including nitrogen with a thickness of 115 nm is formed by plasma CVD. After that, gate electrodes205to208can be formed with a metal or a poly-crystalline semiconductor doped with an impurity having one conductivity type.

In the case of using a metal, tungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), aluminum (Al), or the like can be used. Moreover, metal nitride obtained by nitriding the above metal can also be used. Alternatively, a structure in which a first layer including the metal nitride and a second layer including the metal are stacked may be used. Also, a paste including particles can be formed over the gate insulating film by a droplet discharging, and the paste is dried and burned to be formed. Further, a paste including particles can be formed over the gate insulating film by printing, and the paste is dried and burned to be formed. Typical examples of the particles are: gold, copper, alloy of gold and silver, alloy of gold and copper, alloy of silver and copper, alloy of gold, silver, and copper or the like.

Here, after a tantalum nitride film with a thickness of 30 nm and a tungsten film with a thickness of 370 nm are formed over the gate insulating film204by sputtering, a resist mask formed by photolithography is used to etch the tantalum nitride film and the tungsten film selectively, and the gate electrodes205to208each having a shape that an end portion of the tantalum nitride film extends out farther to the outside than an end portion of the tungsten film are formed.

Subsequently, with the gate electrodes205to208as a mask, impurity which imparts an n-type and impurity which imparts a p-type are added to the semiconductor layers201to203, and source regions and drain regions209to214and a high concentration impurity region215are formed. In addition, low concentration impurity regions216to223overlapping with a part of the gate electrodes205to208are formed. Moreover, channel regions201cto203c, and203doverlapping with the gate electrodes205to208are formed.

Note that here the source regions and the drain regions209,210,213,214, the high concentration impurity region215, and the low concentration impurity regions216,217, and220to223are doped with boron which imparts a p-type. In addition, source regions and drain regions211,212, and the low concentration impurity regions218and219are doped with phosphorus which imparts an n-type.

After this, in order to activate the impurity which is added to the semiconductor layer, a heat treatment is performed. Here, heating in nitrogen atmosphere at 550° C. for 4 hours is performed. With the above steps, thin film transistors225to227are formed. In addition, as the thin film transistors225and227, p channel-type thin film transistors are formed, and as the thin film transistor226, an n channel-type thin film transistor is formed. In doing so, a driver circuit is structured with the p channel-type thin film transistor225and the n channel-type thin film transistor226, and the p channel-type thin film transistor227functions as an element applying voltage to a pixel electrode.

Subsequently, as shown inFIG. 4A, a first interlayer insulating film which insulates the gate electrodes and wiring of the thin film transistors225to227is formed. Here, as the first interlayer insulating film, a silicon oxide film231, a silicon nitride film232, and a silicon oxide film233are stacked to be formed. Subsequently, wirings234to239connecting to source and drain regions of the thin film transistors225and227and a connecting terminal240are formed over the silicon oxide film233which is a part of the first interlayer insulating film. Here, after a Ti film with a thickness of 100 nm, an Al film with a thickness of 700 nm, and Ti film with the thickness of 100 nm are consecutively formed, with the use of a resist mask formed by photolithography process, etching is selectively performed, and the wirings234to239and the connecting terminal240are formed. After that, the resist mask is removed.

Next, a second interlayer insulating film241is formed over the first interlayer insulating film, the wirings234to239, and the connecting terminal240. As the second interlayer insulating film241, an inorganic insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film (a silicon oxide film containing nitrogen or a silicon nitride film containing oxygen) can be used, and these insulating films are formed with a single layer or two or more layers of a multiple-layer. In addition, as a method for forming the inorganic insulating film, sputtering, LPCVD, plasma CVD, and the like may be used.

Here, after plasma CVD is used to form a silicon nitride film containing oxygen with a thickness of 100 nm to 150 nm, the silicon nitride film containing oxygen is selectively etched with the use of a resist mask formed by photolithography process to form a contact hole reaching the wiring239of the thin film transistor227and the connecting terminal240, and at the same time the second interlayer insulating film241is formed. And after that, the resist mask is removed. In a similar manner to this embodiment mode 2, by formation of the second interlayer insulating film241, exposure of TFTs of a driver circuit portion, wiring and the like can be prevented, and the TFT can be protected from contaminating material.

Subsequently, a first pixel electrode242connecting to the wiring239of the thin film transistor227and a conductive layer244connecting to the connecting terminal240are formed, and when a liquid crystal display device is a light transmissive type liquid crystal display device, the first pixel electrode242is formed with a conductive film having a light-transmitting property. In addition, when a liquid crystal display device is a reflection type liquid crystal display device, the first pixel electrode242is formed with a conductive film having reflectivity. Here, the first pixel electrode242and the conductive layer244are formed in such a way that after ITO containing silicon oxide with a thickness of 125 nm is formed by sputtering, and etching is selectively performed with the use of a resist mask formed by photolithography.

Subsequently, an insulating film243which functions as an orientation film is formed, and the insulating film243is formed in such a way that a high molecular compound layer such as a layer of polyimide, a polyvinyl alcohol or the like is formed by roll coating, printing, and the like, and after that rubbing is performed. In addition, the insulating film243can be formed by deposition of SiO2from an oblique angle to a substrate, and the insulating film243can be formed by irradiation of polarized UV light to a photoreactive type high molecular compound and polymerization of the photoreactive type high molecular compound; however, here the insulating film243is formed by printing a high molecular compound layer such as a layer of a polyimide, a polyvinyl alcohol or the like, and baking, and rubbing the layer.

Subsequently, as shown inFIG. 4B, a second pixel electrode253is formed adjacent to an opposing substrate251, and an insulating film254is formed on the second pixel electrode as an orientation film. Note that a colored layer252may be formed between the opposing substrate251and the pixel electrode253. In this case, the opposing substrate may be formed by the same material of the substrate100. In addition, the second pixel electrode253is formed in a similar manner to the first pixel electrode242, and the insulating film254which functions as an orientation film can be formed in a similar manner to the insulating film243. Moreover, the colored layer252is a layer which is necessary when color display is performed, and in RGB, a colored layer in which dye and pigment corresponding to each color of red, green, and blue are dispersed is formed corresponding to each pixel.

Subsequently, the substrate100and the opposing substrate251are attached together with a sealing material257, and a liquid crystal layer255is formed between the substrate100and the opposing substrate251. The liquid crystal layer255is formed in such a way that liquid crystal material is injected into a region surrounded by the insulating films243and254which function as orientation films and the sealing material257by vacuum injection using capillary tube phenomenon. Moreover, the sealing material257is formed at one surface of the opposing substrate251, liquid crystal material is delivered by drops to a region surrounded by the sealing material, and after that the liquid crystal layer255can be formed by pressure bonding of the opposing substrate251and the substrate100under reduced pressure with the sealing material.

As the sealing material257, a thermoset epoxy resin, a UV curable acrylic resin, thermoplastic nylon, polyester, and the like are formed by a dispenser, a printing, a thermocompression and the like. Note that by application of filler to the sealing material257, a space between the substrate100and the opposing substrate251can be maintained. Here, as the sealing material257, thermoset epoxy resin is used.

In addition, in order to maintain the space between the substrate100and the opposing substrate251, a spacer256can be provided between the insulating films243and254which function as orientation films, and the spacer can be formed by application of organic resin, and by etching of the organic resin to be a desired shape typically a pillar or circular pillar shape. Moreover, as the spacer, a bead spacer may be used, and here as the spacer256, a bead spacer is used. In addition, although not shown, a polarizing plate is provided to one or both of the substrate100and the opposing substrate251.

Subsequently, as shown inFIG. 4C, at a terminal portion263, a connecting terminal connected to a gate wiring and a source wiring of a thin film transistor is formed (inFIG. 4C, the connecting terminal240connected to a source wiring or a drain wiring is shown). A FPC (flexible printed circuit)262is connected through the conductive layer244and an anisotropic conductive layer261to the connecting terminal240, and the connecting terminal240receives video signals and clock signals through the conductive layer244and the anisotropic conductive layer261.

At a driver circuit portion264, a circuit which drives a pixel such as a source driver, a gate driver, and the like is formed, and here the n channel-type thin film transistor226and the p channel-type thin film transistor225are placed. In addition, CMOS circuit is formed with the n channel-type thin film transistor226and the p channel-type thin film transistor225.

In a pixel portion265, a plurality of pixels is formed, and at each pixel, a liquid crystal element258is formed. This liquid crystal element258is a part where the first pixel electrode242, the second pixel electrode253, and the liquid crystal layer255which is filled between the first pixel electrode242and the second electrode253are overlapped. Moreover, the first pixel electrode242included in the liquid crystal element258is connected electrically to the thin film transistor227.

With the above process, a liquid crystal display device can be manufactured, and in a liquid crystal display device shown in Embodiment Mode 2, plane orientation of crystal grains is aligned in a certain direction in a semiconductor layer formed at the driver circuit portion264and the pixel portion265. Thus, a variation of electric characteristics of a plurality of thin film transistors can be suppressed, and as a result, a liquid crystal display device which is capable of high-resolution display with little partial discoloration and defect can be manufactured.

Embodiment Mode 3 will explain a manufacturing process of a light-emitting device having a light-emitting element as an example of a semiconductor device. As shown inFIG. 5A, the thin film transistors225to227are formed over the substrate100with the insulating film101interposed therebetween by a similar process to that of Embodiment Mode 2. The first interlayer insulating film for insulating the gate electrodes and the wires of the thin film transistors225to227is formed by stacking the silicon oxide film231, the silicon nitride film232, and the silicon oxide film233. Moreover, wires308to313which connect to the semiconductor layers of the thin film transistors225to227, and a connection terminal314are formed over the silicon oxide film233, which is a part of the first interlayer insulating film.

Next, a second interlayer insulating layer315is formed over the first interlayer insulating film, the wires308to313, and the connection terminal314, and then a first electrode layer316which connects to the wire313of the thin film transistor227and a conductive layer320which connects to the connection terminal314are formed. The first electrode layer316and the conductive layer320are formed in such a way that after ITO including silicon oxide is formed in 125 nm by a sputtering method, the ITO is selectively etched by using a resist mask formed by a photolithography process. As is described in this embodiment mode, the formation of the second interlayer insulating layer315can prevent exposure of TFTs, wires, and the like of a driver circuit portion and protect TFTs from a contaminant.

Next, an organic insulating layer317is formed to cover an end portion of the first electrode layer316. Here, after applying and baking photosensitive polyimide, light-exposure and development are carried out, thereby forming the organic insulating layer317so that the driver circuit, the first electrode layer316in a pixel region, and the second interlayer insulating layer315in a periphery of the pixel region are exposed.

Next, a layer318containing a light-emitting substance is formed by an evaporation method over a part of the first electrode layer316and the organic insulating layer317. The layer318containing a light-emitting substance is formed of an organic or inorganic compound having a light-emitting property. It is to be noted that the layer318containing a light-emitting substance may be formed of an organic compound having a light-emitting property and an inorganic compound having a light-emitting property. Moreover, a red-light-emitting pixel, a blue-light-emitting pixel, and a green-light-emitting pixel are formed by using a red-light-emitting substance, a blue-light-emitting substance, and a green-light-emitting substance respectively for the layer318containing a light-emitting substance.

Here, the layer containing a red-light-emitting substance is formed by stacking DNTPD of 50 nm thick, NPB of 10 nm thick, NPB of 30 nm thick to which bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(acetylacetonate) (abbr.: Ir(Fdpq)2(acac)) is added, Alq3of 60 nm thick, and LiF of 1 nm thick. The layer containing a green-light-emitting substance is formed by stacking DNTPD of 50 nm thick, NPB of 10 nm thick, Alq3of 40 nm thick to which coumarin 545T (C545T) is added, Alq3of 60 nm thick, and LiF of 1 nm thick.

The layer containing a blue-light-emitting substance is formed by stacking DNTPD of 50 nm thick, NPB of 10 nm thick, 9-[4-(N-carbazolyl)]phenyl-10-phenylanthracene (abbr.: CzPA) of 30 nm thick to which 2,5,8,11-tetra(tert-butyl)perylene (abbr.: TBP) is added, Alq3of 60 nm thick, and LiF of 1 nm thick. Moreover, a white-light-emitting pixel may be formed by forming the layer containing a light-emitting substance with a white light-emitting substance, in addition to the red-light-emitting pixel, the blue-light-emitting pixel, and the green-light-emitting pixel. By the provision of a white-light-emitting pixel, power consumption can be reduced.

Next, a second electrode layer319is formed over the layer318containing a light-emitting substance and the organic insulating layer317. Here, an Al film is formed in 200 nm thick by an evaporation method. Accordingly, a light-emitting element321is formed by the first electrode layer316, the layer318containing a light-emitting substance, and the second electrode319.

Here, a structure, a material, a function, and the like of the light-emitting element321are described. When the layer318containing a light-emitting substance is formed by a layer which uses an organic compound and which has a light-emitting function (hereinafter, this layer is shown as a light-emitting layer343), the light-emitting element321functions as an organic EL (Electro Luminescence) element. The structure, the material, the function, and the like of the light-emitting element321will hereinafter be described in detail with reference to the drawings.

As shown inFIG. 6A, the light-emitting element321shown inFIG. 5Amay be formed by the layer318containing a light-emitting material and the second electrode layer319which are formed over the first electrode layer316. The layer318containing a light-emitting material includes a hole-injecting layer341formed of a material with a hole-injecting property, a hole-transporting layer342formed of a material with a hole-transporting property, the light-emitting layer343formed of an organic compound with a light-emitting property, an electron-transporting layer344formed of a material with an electron-transporting property, and an electron-injecting layer345formed of a material with an electron-injecting property.

Described above are the examples of the material with a hole-transporting property; however, the material is not limited to these. Among the above compounds, an aromatic amine compound typified by TDATA, MTDATA, m-MTDAB, TPD, NPB, DNTPD, BBPB, TCTA, or the like is preferable as the organic compound because it easily generates holes. The substances described here mainly have a hole mobility of 10−6cm2/Vs or higher.

The material with a hole-injecting property includes a chemically-doped conductive high-molecular compound, in addition to the aforementioned material with a hole-transporting property. For example, polyethylene dioxythiophene (abbr.: PEDOT) doped with polystyrene sulfonate (abbr.: PSS), polyaniline (abbr.: PAni), or the like can also be used. Moreover, a thin film of an inorganic semiconductor such as molybdenum oxide (MoOx), vanadium oxide (VOx), or nickel oxide (NiOx), or an ultrathin film of an inorganic insulator such as aluminum oxide (Al2O3) is also effective.

Here, the material with an electron-transporting property may be a material including a metal complex with a quinoline skeleton or a benzoquinoline skeleton, or the like such as the following: tris(8-quinolinolato)aluminum (abbr.: Alq3), tris(4-methyl-8-quinolinolato)aluminum (abbr.: Almq3), bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbr.: BeBq2), bis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbr.: BAlq), or the like. In addition to those, a metal complex having an oxazole ligand or a thiazole ligand, or the like can also be used, such as bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbr.: Zn(BOX)2), or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbr.: Zn(BTZ)2).

As the material with an electron-injecting property, an ultrathin film of an insulator such as the following is often used besides the aforementioned material with an electron-transporting property: a halide of alkali metal such as LiF or CsF, a halide of alkaline-earth metal such as CaF2, or an oxide of alkali metal such as Li2O. Moreover, an alkali metal complex such as lithium acetyl acetonate (abbr.: Li(acac)) or 8-quinolinolato-lithium (abbr.: Liq) is also effective. In addition, a material mixed by, for example, co-evaporating the aforementioned material with an electron-transporting property and metal with a low work function such as Mg, Li, or Cs can also be used.

As shown inFIG. 6B, the light-emitting element321shown inFIG. 5Amay be formed by the layer318containing a light-emitting material and the second electrode layer319which are formed over the first electrode layer316. The layer318containing a light-emitting material includes a hole-transporting layer346formed of an organic compound and an inorganic compound having an electron-accepting property with respect to the organic compound, the light-emitting layer343formed of an organic compound with a light-emitting property, and an electron-transporting layer347formed of an inorganic compound having an electron-donating property with respect to the organic compound with a light-emitting property.

As the organic compound of the hole-transporting layer346formed of the organic compound with a light-emitting property and the inorganic compound having an electron-accepting property with respect to the organic compound with a light-emitting property, the aforementioned organic compound with a hole-transporting property can be used. In addition, the inorganic compound may be any kind of compound as long as it can easily accept electrons from the organic compound. As the inorganic compound, various metal oxides or metal nitrides can be used. In particular, an oxide of transition metal belonging to any of Group 4 to Group 12 in the periodic table is preferable because it easily exhibits an electron-accepting property.

Specifically, titanium oxide, zirconium oxide, vanadium oxide, molybdenum oxide, tungsten oxide, rhenium oxide, ruthenium oxide, zinc oxide, or the like is given. Among these metal oxides, oxides of transition metal belonging to Group 4 to Group 8 in the periodic table are preferable because many of them have a high electron-accepting property. In particular, vanadium oxide, molybdenum oxide, tungsten oxide, and rhenium oxide are preferable because they can be formed by vacuum evaporation and easily treated.

As the organic compound of the electron-transporting layer347formed of the organic compound with a light-emitting property and the inorganic compound having an electron-donating property with respect to the organic compound with a light-emitting property, the aforementioned organic compound with an electron-transporting property can be used. In addition, the inorganic compound may be any kind of compound as long as it can easily donate electrons to the organic compound. As the inorganic compound, various metal oxides or metal nitrides can be used. In particular, an oxide of alkali metal, an oxide of alkaline-earth metal, an oxide of rare-earth metal, a nitride of alkali metal, a nitride of alkaline-earth metal, and a nitride of rare-earth metal are preferable because they easily exhibit an electron-donating property. Specifically, lithium oxide, strontium oxide, barium oxide, erbium oxide, lithium nitride, magnesium nitride, calcium nitride, yttrium nitride, lanthanum nitride, and the like are given. In particular, lithium oxide, barium oxide, lithium nitride, magnesium nitride, and calcium nitride are preferable because they can be formed by vacuum evaporation and easily treated.

The electron-transporting layer347or the hole-transporting layer346formed of the organic compound with a light-emitting property and the inorganic compound is superior in electron injecting/transporting properties; therefore, various materials can be used for the first electrode layer316and the second electrode layer319with their work functions hardly limited. Moreover, the drive voltage can be reduced.

In addition, the light-emitting element321functions as an inorganic EL element by having a layer which uses an inorganic compound and which has a light-emitting function (this layer is hereinafter called a light-emitting layer349) as the layer318containing a light-emitting substance. The inorganic EL elements are classified according to their element structures into a dispersed inorganic EL element and a thin-film inorganic EL element. They are different from each other in that the former includes a light emitting layer in which particles of a light emitting material are dispersed in a binder and the latter includes a light emitting layer formed of a thin film of a phosphor material. However, they are common in that they both require electrons accelerated by a high electric field.

In addition, the mechanism of light emission to be obtained includes donor-acceptor recombination light emission which uses a donor level and an acceptor level, and local light emission which uses core electron transition of a metal ion. In general, in many cases, a dispersed inorganic EL element uses donor-acceptor recombination light emission whereas a thin-film inorganic EL element uses local light emission. A structure of the inorganic EL element is shown below.

The light-emitting material that can be used in Embodiment Mode 3 includes a base material and an impurity element to become a light emission center, and can emit light with various colors by changing the impurity element to be contained. The light-emitting material can be manufactured by various methods such as a solid phase method and a liquid phase method (coprecipitation method). As a liquid phase method, a spray pyrolysis method, a double decomposition method, a method by precursor pyrolysis, a reverse micelle method, a method in which the above method is combined with high-temperature baking, or a freeze-drying method can be used.

In the solid phase method, a base material and an impurity element are weighed, mixed in a mortar, and reacted with each other by being heated and baked in an electric furnace so that the impurity element is contained in the base material. Baking temperatures are preferably 700 to 1500° C. This is because solid phase reaction does not progress at a temperature that is too low and the base material is decomposed at a temperature that is too high. The baking may be performed to the base material and the impurity element in a powder state; however, it is preferable to perform baking in a pellet state. This method requires baking at a comparatively high temperature but is simple; thus, this method has high productivity and is suitable for mass production.

In the liquid-phase method (coprecipitation method), a base material or a compound thereof, and an impurity element or a compound thereof are reacted with each other in a solution and dried, and thereafter, they are baked. In this method, particles of the base material as the light-emitting material are uniformly dispersed, and reaction can progress even at a low baking temperature and with the particles each having a small diameter. As the base material, a sulfide, an oxide, or a nitride can be used in the present invention.

As the sulfide, for example, zinc sulfide (ZnS), cadmium sulfide (CdS), calcium sulfide (CaS), yttrium sulfide (Y2S3), gallium sulfide (Ga2S3), strontium sulfide (SrS), barium sulfide (BaS), or the like can be used. As the oxide, for example, zinc oxide (ZnO), yttrium oxide (Y2O3), or the like can be used.

Further, as the nitride, for example, aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), or the like can be used. In addition, zinc selenide (ZnSe), zinc telluride (ZnTe), or the like can also be used. A ternary mixed crystal such as calcium-gallium sulfide (CaGa2S4), strontium-gallium sulfide (SrGa2S4), or barium-gallium sulfide (BaGa2S4) may also be used.

As the light emission center of local light emission, manganese (Mn), copper (Cu), samarium (Sm), terbium (Th), erbium (Er), thulium (Tm), europium (Eu), cerium (Ce), praseodymium (Pr), or the like can be used. A halogen element such as fluorine (F) or chlorine (Cl) may be added as charge compensation.

On the other hand, a light-emitting material including a first impurity element forming a donor level and a second impurity element forming an acceptor level may be used as the light emission center of donor-acceptor recombination light emission. For example, fluorine (F), chlorine (Cl), aluminum (Al), or the like can be used as the first impurity element, and copper (Cu), silver (Ag), or the like can be used as the second impurity element.

In a case of synthesizing a light-emitting material of donor-acceptor recombination light emission by a solid phase method, a base material, the first impurity element or a compound thereof, and the second impurity element or a compound thereof are weighed, mixed in a mortar, and heated and baked in an electric furnace. Baking temperatures preferably range from 700 to 1500° C. This is because solid phase reaction does not progress at a temperature that is too low and the base material is decomposed at a temperature that is too high. The baking may be performed on the base material and the impurity element in a powder state; however, it is preferable to perform baking in a pellet state.

The aforementioned base material can be used as the base material. As the first impurity element or the compound thereof, for example, fluorine (F), chlorine (Cl), aluminum sulfide (Al2S3), or the like can be used. As the second impurity element or the compound thereof, for example, copper (Cu), silver (Ag), copper sulfide (Cu2S), silver sulfide (Ag2S), or the like can be used.

As the impurity element in the case of using the solid phase reaction, a compound including the first impurity element and the second impurity element may be used in combination. In this case, the impurity element easily disperses so as to promote solid phase reaction. Therefore, a uniform light-emitting material can be obtained. Moreover, since no excessive impurity elements are included, a light-emitting material with high purity can be obtained. As the compound including the first impurity element and the second impurity element at that time, for example, copper chloride (CuCl), silver chloride (AgCl), or the like can be used. The concentration of these impurity elements may be in the range of 0.01 to 10 atom %, preferably in the range of 0.05 to 5 atom %, with respect to the base material.

FIG. 6Cshows a cross section of an inorganic EL element in which the layer318containing a light-emitting substance is formed by a first insulating layer348, the light-emitting layer349, and a second insulating layer350. It is to be noted that the inorganic EL light-emitting element emits light by application of voltage between a pair of electrode layers which sandwiches the layer containing a light-emitting substance and can be operated by either DC driving or AC driving. In the case of a thin film inorganic EL element, the light-emitting layer349is a layer containing the aforementioned light-emitting material and can be formed by a vacuum evaporation method such as a resistance heating evaporating method or an electron beam evaporation (EB evaporation) method, a physical vapor deposition (PVD) method such as a sputtering method, a chemical vapor deposition (CVD) method such as an organic metal CVD method or a low-pressure hydride transport CVD method, an atomic layer epitaxy (ALE) method, or the like.

The first insulating layer348and the second insulating layer350are not particularly limited; however, they preferably have dense film quality and moreover have a high dielectric constant. For example, a film of silicon oxide (SiO2), yttrium oxide (Y2O3), titanium oxide (TiO2), aluminum oxide (Al2O3), hafnium oxide (HfO2), tantalum oxide (Ta2O5), barium titanate (BaTiO3), strontium titanate (SrTiO3), lead titanate (PbTiO3), silicon nitride (Si3N4), zirconium oxide (ZrO2), or the like; a film in which these are mixed; or a film in which two or more of them are stacked can be used.

The first insulating layer348and the second insulating layer350can be formed by sputtering, evaporation, CVD, or the like. Their film thicknesses are not limited in particular, but are preferably in the range of 10 to 1000 nm. Since the light-emitting element of Embodiment Mode 3 does not always require hot electrons, the light-emitting element can be formed to be a thin film and has an advantage of low drive voltage. The film thickness is preferably 500 nm or less, more preferably 100 nm or less.

Although not shown, a buffer layer may be provided between the light-emitting layer349and the insulating layers348and350or between the light-emitting layer349and the electrode layers316and319. The buffer layer facilitates carrier injection and has a role of suppressing mixture of the both layers. The material of the buffer layer is not particularly limited; however, for example, ZnS, ZnSe, ZnTe, CdS, SrS, BaS, CuS, Cu2S, LiF, CaF2, BaF2, MgF2, or the like, which is the base material of the light-emitting layer, can be used.

Moreover, as shown inFIG. 6D, the layer318containing a light-emitting substance may be formed by the light-emitting layer349and the first insulating layer348. In this case, inFIG. 6D, the first insulating layer348is provided between the second electrode layer319and the light-emitting layer349. It is to be noted that the first insulating layer348may be provided between the first electrode layer316and the light-emitting layer349. Moreover, the layer318containing a light-emitting substance may be formed by only the light-emitting layer349. In other words, the light-emitting layer321may be formed by the first electrode layer316, the layer318containing a light-emitting substance, and the second electrode layer319.

In the case of a dispersed inorganic EL element, a film-form layer containing a light-emitting substance is formed by dispersing particles of light-emitting material in a binder. When particles with desired size cannot be obtained sufficiently depending on the manufacturing method of the light-emitting material, the material may be crushed in a mortar or the like to be processed into particles. The binder is a substance to fix the particles of the light-emitting material in a dispersed state and to keep the shape as the layer containing a light-emitting substance. The light-emitting material is thus fixed in such a way that the light-emitting material is uniformly dispersed in the layer containing the light-emitting substance by the binder.

In the case of the dispersed inorganic EL element, the layer containing a light-emitting substance can be formed by a droplet discharging method that can selectively form the layer containing the light-emitting substance, a printing method (such as screen printing or offset printing), a coating method such as a spin coating method, a dipping method, a dispenser method, or the like. The film thickness of the layer at that time is not particularly limited; however, it is preferably in the range of 10 to 1000 nm. In the layer containing a light-emitting substance, which includes the light-emitting material and the binder, the proportion of the light-emitting material is preferably in the range of 50 to 80 wt %.

An element shown inFIG. 6Ehas the first electrode layer316, the layer318containing a light-emitting substance, and the second electrode layer319. The layer318containing a light-emitting substance is formed by the insulating layer348and a light-emitting layer in which a light-emitting material352is dispersed in a binder351. The insulating layer348is in contact with the second electrode layer319inFIG. 6E; however, the insulating layer348may be in contact with the first electrode layer316. Moreover, insulating layers may be formed in contact with the first electrode layer316and the second electrode layer319. Further, the insulating layer does not have to be in contact with the first electrode layer316and the second electrode layer319in the element.

As the binder that can be used in Embodiment Mode 3, an insulating material such as an organic material and an inorganic material can be used, and moreover, a mixed material of an organic material and an inorganic material can be used. As the organic insulating material, polymer with a comparatively high dielectric constant such as a cyanoethylcellulose-based resin, a polyethylene-based resin, a polypropylene-based resin, a polystyrene-based resin, a silicone resin, a siloxane resin, an epoxy resin, vinylidene fluoride, or the like can be used. Moreover, a heat-resistant high-molecular material such as aromatic polyamide or polybenzimidazole can be used.

It is to be noted that a siloxane resin corresponds to a resin including a Si—O—Si bond, and siloxane includes a bond of silicon (Si) and oxygen (O) in its skeleton. As the substituent, an organic group including at least hydrogen (for example, an alkyl group and an aromatic hydrocarbon group) is used. In addition, a fluoro group may be used as the substituent. Furthermore, an organic group including at least hydrogen and a fluoro group may be used as the substituent.

In addition, a vinyl resin such as polyvinyl alcohol or polyvinyl butyral, a resin material such as a phenol resin, a novolac resin, an acrylic resin, a melamine resin, a urethane resin, or an oxazole resin (polybenzoxazole) may be used. Moreover, a photo curable type is also applicable. The dielectric constant can be adjusted by appropriately mixing microparticles with a high dielectric constant such as barium titanate (BaTiO3) or strontium titanate (SrTiO3) in these resins.

As the inorganic material used for the binder, silicon oxide (SiOx), silicon nitride (SiN), silicon including oxygen and nitrogen, aluminum nitride (AlN), aluminum including oxygen and nitrogen, aluminum oxide (Al2O3), titanium oxide (TiO2), BaTiO3, SrTiO3, lead titanate (PbTiO3), potassium niobate (KNbO3), lead niobate (PbNbO3), tantalum oxide (Ta2O5), barium tantalate (BaTa2O6), lithium tantalate (LiTaO3), yttrium oxide (Y2O3), zirconium oxide (ZrO2), ZnS, or another inorganic material can be used. When the organic material is mixed with the inorganic material with a high dielectric constant (by addition or the like), the dielectric constant of the layer containing a light-emitting substance, which includes the light-emitting material and the binder can be controlled more accurately so as to increase further.

In the manufacturing process, the light-emitting material is dispersed in a solution including the binder. A solvent of the solution including the binder which is applicable to this embodiment mode is preferably a solvent in which the binder material is dissolved and which can manufacture a solution with its viscosity suitable for forming the light-emitting layer with desired film thickness. As such a solvent, an organic solvent or the like can be used. For example, in a case of using a siloxane resin as the binder, propylene glycol monomethylether, propylene glycol monomethylether acetate (also called PGMEA), 3-methoxy-3-methyl-1-butanol (also called MMB), or the like can be used.

Next, as shown inFIG. 5B, a protective film322is formed over the second electrode layer319. The protective film322is to prevent intrusion of moisture, oxygen, and the like into the light-emitting element321and the protective film322. The protective film322is preferably formed using silicon nitride, silicon oxide, silicon nitride oxide, silicon oxynitride, aluminum oxynitride, aluminum oxide, diamond-like carbon (DLC), carbon containing nitrogen (CN), or another insulating material by a thin-film forming method such as a plasma CVD method or a sputtering method.

In addition, when a sealing substrate324is attached to the second interlayer insulating film315over the substrate100by the use of a sealant323, the light-emitting element321is provided in a space325surrounded by the substrate100, the sealing substrate324, and the sealant323. The space325is filled with filler, which may be an inert gas (such as nitrogen or argon) or the sealant323.

An epoxy-based resin is preferably used for the sealant323, and the material of the sealant323desirably does not transmit moisture and oxygen as much as possible. As the sealing substrate324, a glass substrate, a quartz substrate, or a plastic substrate formed of FRP (Fiberglass-Reinforced Plastics), PVF (Polyvinyl fluoride), Mylar, polyester, acrylic, or the like can be used.

Subsequently, as shown inFIG. 5C, an FPC327is attached to the conductive layer320which is in contact with the connection terminal314, by using an anisotropic conductive layer326similarly to Embodiment Mode 2. Through the above steps, a semiconductor device having an active matrix light-emitting element can be formed.

Here,FIG. 7shows an equivalent circuit diagram of a pixel in a case of full-color display in Embodiment Mode 3. InFIG. 7, a thin film transistor331surrounded by a dashed line corresponds to a thin film transistor which switches the thin film transistor227for driving inFIG. 5A, whereas a thin film transistor332surrounded by a dashed line corresponds to a thin film transistor which drives a light-emitting element. In the following description, the light-emitting element is an organic EL element (hereinafter referred to as OLED) in which a layer containing a light-emitting substance is formed by a layer containing an organic compound with a light-emitting property.

In a pixel displaying red color, an OLED334R emitting red light is connected to a drain region of the thin film transistor332, and a red-color anode-side power source line337R is provided in a source region thereof. The OLED334R is provided with a cathode-side power source line333, the thin film transistor331for switching is connected to a gate wire336, and a gate electrode of the thin film transistor332for driving is connected to a drain region of the thin film transistor331for switching. The drain region of the thin film transistor331for switching is connected to a capacitor338connected to the red-color anode-side power source line337R.

In a pixel displaying green color, an OLED334G emitting green light is connected to a drain region of the thin film transistor332for driving, and a green-color anode-side power source line337G is provided in a source region thereof. The OLED334G is provided with a cathode-side power source line333, the thin film transistor331for switching is connected to the gate wire336, and the gate electrode of the thin film transistor332for driving is connected to the drain region of the thin film transistor331for switching. The drain region of the thin film transistor331for switching is connected to the capacitor338connected to the green-color anode-side power source line337G.

In a pixel displaying blue color, an OLED334B emitting blue light is connected to a drain region of the thin film transistor332for driving, and a blue-color anode-side power source line337B is provided in a source region thereof. The OLED334B is provided with the cathode-side power source line333, the thin film transistor331for switching is connected to the gate wire336, and the gate electrode of the thin film transistor332for driving is connected to the drain region of the thin film transistor331for switching. The drain region of the thin film transistor331for switching is connected to the capacitor338connected to the blue-color anode-side power source line337B.

Different voltages depending on the material of the layer containing a light-emitting substance are applied respectively to the pixels with different colors. Here, although the source wire335and the anode-side power source lines337R,337G, and337B are formed in parallel, the present invention is not limited to this. The gate wire336and the anode-side power source lines337R,337G, and337B may be formed in parallel. In addition, the thin film transistor332for driving may have a multi-gate electrode structure.

In the light-emitting device, the driving method of screen display is not particularly restricted. For example, a dot-sequential driving method, a line-sequential driving method, a plane-sequential driving method, or the like may be used. Typically, the line sequential driving method is used, and may be appropriately combined with a time-division grayscale driving method or an area grayscale driving method. In addition, a video signal to be inputted into a source line of the light emitting device may be an analog signal or a digital signal. A driving circuit or the like may be appropriately designed in accordance with the video signal.

Further, in a light-emitting device using a digital video signal, there are two kinds of driving systems in which video signals inputted into a pixel are ones with constant voltage (CV) and in which video signals inputted into a pixel are ones with constant current (CC). Further, as for the driving system using video signals with constant voltage (CV), there are two kinds of systems in which voltage applied to a light emitting element is constant (CVCV), and in which current applied to a light emitting element is constant (CVCC). In addition, as for the driving system using video signals with constant current (CC), there are two kinds of systems in which voltage applied to a light emitting element is constant (CCCV), and in which current applied to a light emitting element is constant (CCCC). In the light-emitting device, a protective circuit for preventing electrostatic breakdown (such as a protective diode) may be provided.

Through the above steps, a light-emitting device having an active matrix light-emitting element can be manufactured. In the light-emitting device shown in this embodiment mode, plane orientations of crystals are aligned in a certain direction in semiconductor layers of thin film transistors formed in a driver circuit and a pixel portion. Therefore, variation in electrical characteristics of the thin film transistors for driving the light-emitting element can be suppressed. As a result, variation in luminance of the light-emitting element can be reduced, which allows the manufacturing of a light-emitting device capable of high-definition display with little color unevenness and few defects.

Embodiment Mode 4 will explain a manufacturing process of a semiconductor device capable noncontact data transmission with reference toFIGS. 8A to 11D. First, a structure of the semiconductor device is explained with reference toFIG. 12and application of the semiconductor device shown in this embodiment mode is explained with reference toFIGS. 13A to 13F.

As shown inFIG. 8A, a peeling film402is formed over a substrate401. Next, an insulating film403is formed over the peeling film402similarly to Embodiment Modes 1 and 2, thereby forming a thin film transistor404over the insulating film403. Subsequently, an interlayer insulating film405is formed to insulate a conductive film included in the thin film transistor404, and source and drain electrodes406to be connected to the semiconductor layer of the thin film transistor404are formed.

After that, an insulating film407is formed to cover the thin film transistor404, the interlayer insulating film405, and the source and drain electrodes406. Then, a conductive film408connected to the source and drain electrodes406with the insulating film407interposed therebetween is formed. As the substrate401, a substrate similar to the substrate100can be used. As the substrate, a metal substrate or a stainless-steel substrate with an insulating film formed on one surface thereof, a plastic substrate that can withstand treatment temperature of this process, or the like can be used. Here, a glass substrate is used as the substrate401.

The peeling layer402is formed of tungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), niobium (Nb), nickel (Ni), cobalt (Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), or silicon; an alloy material containing the element as its main component; or a compound material containing the element as its main component to have a single-layer or stacked-layer structure by a sputtering method, a plasma CVD method, a coating method, a printing method, or the like. The crystal structure of a layer including silicon as the peeling layer402may be amorphous, microcrystalline, or polycrystal.

When the peeling layer402has a single-layer structure, it is preferable to form a tungsten layer, a molybdenum layer, or a layer including a mixture of tungsten and molybdenum. Alternatively, a layer including tungsten oxide or tungsten oxynitride, a layer including molybdenum oxide or molybdenum oxynitride, or a layer including an oxide or an oxynitride of a mixture of tungsten and molybdenum is formed. The mixture of tungsten and molybdenum corresponds to, for example, an alloy of tungsten and molybdenum.

When the peeling layer402has a stacked-layer structure, a tungsten layer, a molybdenum layer, or a layer including a mixture of tungsten and molybdenum is preferably formed as a first layer, and a layer of an oxide, a nitride, an oxynitride, or a nitride oxide of tungsten, molybdenum, or a mixture of tungsten and molybdenum is preferably formed as a second layer. When the peeling layer402is formed to have a stacked-layer structure including a layer which includes tungsten and a layer which includes tungsten oxide, the layer which includes tungsten may be formed and an insulating film which includes an oxide may be formed thereover so that the layer which includes tungsten oxide is formed at an interface between the tungsten layer and the insulating layer.

Further, the layer which includes tungsten oxide may be formed by processing a surface of the layer which includes tungsten through thermal oxidation treatment, oxidation plasma treatment, N2O plasma treatment, treatment using a solution with strong oxidation power such as ozone water, treatment using water with hydrogen added, or the like. This similarly applies to the case of forming a layer including tungsten nitride, a layer including tungsten oxynitride, and a layer including tungsten nitride oxide. After forming the layer which includes tungsten, a silicon nitride layer, a silicon oxynitride layer, and a silicon nitride oxide layer are preferably formed on the layer which includes tungsten.

Tungsten oxide is expressed by WOx, where x satisfies 2≦x≦3. The x may be 2 (WO2), 2.5 (W2O5), 2.75 (W4O11), 3 (WO3), or the like. Here, the tungsten film is formed by a sputtering method to have a thickness of 20 to 100 nm, preferably 40 to 80 nm. Although the peeling layer402is formed in contact with the substrate401in the above process, the present invention is not limited to this process. An insulating film to be a base may be formed in contact with the substrate401and the peeling film402may be provided in contact with the insulating film.

The insulating film403formed over the peeling film can be formed similarly to the insulating film101. Here, the insulating film is formed in such a way that a tungsten oxide film is formed on a surface of the peeling film402by generating plasma in the flow of N2O gas and then a silicon oxide film including nitrogen is formed by a plasma CVD method. The thin film transistor404can be formed similarly to the thin film transistor225to227shown in Embodiment Mode 2. The source and drain electrodes406can be formed similarly to wires234to239shown in Embodiment Mode 2.

The interlayer insulating film405and the insulating film407covering the source and drain electrodes406are formed by applying and baking polyimide, acrylic, or siloxane polymer. Alternatively, they can be formed by using an inorganic compound to have a single-layer or stacked-layer structure by a sputtering method, a plasma CVD method, a coating method, a printing method, or the like. Typical examples of the inorganic compound include silicon oxide, silicon nitride, and silicon oxynitride.

Next, as shown inFIG. 8B, a conductive film411is formed over the conductive film408. Here, a composition including gold particles is printed by a printing method and heated at 200° C. for 30 minutes so that the composition is baked. Thus, the conductive film411is formed.

Subsequently, as shown inFIG. 8C, an insulating film412covering end portions of the insulating film407and the conductive film411is formed. Here, the insulating film412covering end portions of the insulating film407and the conductive film411is formed of an epoxy resin. At that time, a composition of an epoxy resin is applied by a spin coating method and heated at 160° C. for 30 minutes; then, a part of the insulating film that covers the conductive film411is removed to expose the conductive film411. Thus, the insulating film412with a thickness of 1 to 20 μm, preferably 5 to 10 μm, is formed. Here, a stacked-layer body from the insulating film403to the insulating film412is referred to as an element-forming layer410.

Next, the insulating films403,405,407, and412are irradiated with laser light413as shown inFIG. 8Dto form opening portions414as shown inFIG. 8E, so that a later peeling step is facilitated. After that, a sticking member415is attached to the insulating film412. The laser light used to form the opening portions414is preferably the laser light with a wavelength that is absorbed by the insulating films403,405,407, and412; typically, laser light of an ultraviolet region, a visible region, or an infrared region is selected appropriately to be used.

As a laser oscillator capable of emitting such laser light, the following can be used: an excimer laser such as a KrF excimer laser, an ArF excimer laser, or a XeCl excimer laser; a gas laser such as a He laser, a He—Cd laser, an Ar laser, a He—Ne laser, an HF laser, or a CO2laser; a solid-state laser such as a crystal laser in which a crystal like YAG, GdVO4, YVO4, YLF, or YAlO3is doped with Cr, Nd, Er, Ho, Ce, Co, Ti, or Tm, a glass laser, or a ruby laser; or a semiconductor laser such as a GaN laser, a GaAs laser, a GaAlAs laser, or an InGaAsP laser can be used. In a case of using a solid-state laser, any of the fundamental wave to the fifth harmonic wave is preferably used.

As a result of the laser irradiation, the insulating films403,405,407, and412absorb the laser light413to be melted, thereby forming the opening portions. When the step of irradiating the insulating films403,405,407, and412with the laser light413is omitted, throughput can be improved.

Subsequently, as shown inFIG. 9A, a part421of the element-forming layer is peeled from the substrate401having the peeling film402by a physical means at a metal oxide film formed at the interface between the peeling film402and the insulating film403. The physical means refers to a dynamic means or a mechanical means, which changes some kind of dynamic energy (mechanical energy). The typical physical means refers to mechanical power addition (for example, peeling by a human hand or grip tool, or separation treatment by rolling a roller).

The above peeling step is characterized in that a layer which does not contract by heat treatment, a layer which contracts by heat treatment, and an intermediate layer between the two layers are formed, and heat treatment is performed at the completion of the peeling step or during the peeling step, so that excess stress is applied to the intermediate layer or to a region in the vicinity of the intermediate layer, and after that, by stimulating the intermediate layer, separation occurs at the intermediate layer or in the region in the vicinity of the intermediate layer. As a result, the peeling film402does not contract by the heat treatment in crystallization of an amorphous silicon film, impurity activation, or dehydrogenation, while the insulating film403and the insulating film412contract, and further, a tungsten oxide layer (WOxwhere 2≦x≦3) is formed at the interface between the peeling film402and the insulating film403. Since the tungsten oxide layer is weak, it can easily be separated by the above physical means. As a result, the part421of the element-forming layer can be separated from the substrate401by the above physical method.

Although the metal oxide film is formed between the peeling film and the insulating film to peel the element-forming layer410by the physical means in Embodiment Mode 4, the present invention is not limited to this. A method can be used in which a light-transmitting substrate is used as the substrate, an amorphous silicon layer including hydrogen is used as the peeling film, and after the step ofFIG. 8E, the amorphous silicon film is irradiated with laser light from a substrate side so that hydrogen included in the amorphous silicon film is vaporized and separation occurs between the substrate and the peeling film.

After the step ofFIG. 8E, alternatively, a method of removing the substrate by mechanical polishing, or a method of removing the substrate by using a solution such as HF which can dissolve the substrate can be employed. In that case, the peeling layer can be omitted. As a further alternative, the following method can be used: before attaching the sticking member415to the insulating film412inFIG. 8E, a fluoride gas such as NF3, BrF3, or ClF3is introduced into the opening portions414so that the peeling film is etched away by the fluoride gas; the sticking member415is attached to the insulating film412; and then the part421of the element-forming layer is peeled from the substrate.

As a further alternative, the following method can be used: before attaching the sticking member415to the insulating film412inFIG. 8E, a fluoride gas such as NF3, BrF3, or ClF3is introduced into the opening portions414so that the peeling layer is partially etched away by the fluoride gas; the sticking member415is attached to the insulating film412; and then the part421of the element-forming layer is peeled from the substrate by a physical means.

Subsequently, as shown inFIG. 9B, a flexible substrate422is attached to the insulating film403in the part421of the element-forming layer; then, the sticking member415is peeled off from the part421of the element-forming layer. Here, a film formed of polyaniline by a cast method is used as the flexible substrate422; then, the flexible substrate422is attached to a UV sheet431of a dicing frame432as shown inFIG. 9C. Since this UV sheet431is adhesive, the flexible substrate422is fixed onto the UV sheet431. After that, the conductive film411may be irradiated with laser light to increase adhesiveness between the conductive film411and the conductive film408. Subsequently, a connection terminal433is formed over the conductive film411as shown inFIG. 9D. By the formation of the connection terminal433, alignment and adhesion with the conductive film which later functions as an antenna can be conducted easily.

Next, as shown inFIG. 10A, the part421of the element-forming layer is cut. Here, the part421of the element-forming layer is cut into plural sections as shown inFIG. 10Bby irradiating the part421of the element-forming layer and the flexible substrate422with the laser light434. As the laser light434, laser light described for the laser light413can be used as appropriate. Here, laser light which can be absorbed by the insulating films403,405,407, and412and the flexible substrate422is preferably selected. Here, although the part of the element-forming layer is cut into plural sections by a laser cut method, a dicing method, a scribing method, or the like can be appropriately used instead. The element-forming layers cut into sections are shown as thin film integrated circuits442aand442b.

Next, as shown inFIG. 10C, the UV sheet of the dicing frame432is irradiated with UV light to decrease the adhesiveness of the UV sheet431. Then, the UV sheet431is supported by an expander frame444. At this time, by supporting the UV sheet431with the expander frame444while stretching the UV sheet431, the width of a groove441which is formed between the thin film integrated circuits442aand442bcan be increased. An expanded groove446desirably corresponds to the size of an antenna substrate to be later attached to the thin film integrated circuits442aand442b.

Subsequently, as shown inFIG. 11A, a flexible substrate456having conductive films452aand452bfunctioning as antennas is attached to the thin film integrated circuits442aand442bwith anisotropic conductive adhesives455aand455b. The flexible substrate456having the conductive films452aand452bfunctioning as antennas is provided with opening portions so as to partially expose the conductive films452aand452b. An insulating film453covering the conductive films452aand452bfunctioning as antennas is formed over the flexible substrate456.

Accordingly, the flexible substrate456is attached to the thin film integrated circuits442aand442bwhile adjusting their positions so that the conductive films452aand452bfunctioning as antennas are connected to connection terminals of the thin film integrated circuits442aand442bwith conductive particles454aand454bincluded in the anisotropic conductive adhesives455aand455b. Here, the conductive film452afunctioning as an antenna is connected to the thin film integrated circuit442aby the conductive particle454ain the anisotropic conductive adhesive455a, while the conductive film452bfunctioning as an antenna is connected to the thin film integrated circuit442bby the conductive particle454bin the anisotropic conductive adhesive455b.

Subsequently, as shown inFIG. 11B, the insulating film453and the flexible substrate456are cut in a region where the conductive films452aand452bfunctioning as antennas and the thin film integrated circuits442aand442bare not formed. Here, they are cut by a laser cut method in which the insulating film453and the flexible substrate456are irradiated with laser light461. In accordance with the above steps, semiconductor devices462aand462bcapable of noncontact data transmission can be manufactured as shown inFIG. 11C.

A semiconductor device464shown inFIG. 11Dmay be manufactured in such a way that the flexible substrate456having the conductive films452aand452bfunctioning as antennas is attached to the thin film integrated circuits442aand442bwith the anisotropic conductive adhesives455aand455binFIG. 11A; a flexible substrate463is provided so as to seal the flexible substrate456and the thin film integrated circuits442aand442b; and the region where the conductive films452aand452bfunctioning as antennas and the thin film integrated circuits442aand442bare not formed is irradiated with laser light461as shown inFIG. 11B. In this case, the thin film integrated circuits are sealed by the cut flexible substrates456and463; therefore, deterioration of the thin film integrated circuits can be suppressed.

In accordance with the above steps, thin and lightweight semiconductor devices can be manufactured with high yield. In addition, since plane orientations of crystals of the semiconductor layers of the thin film transistors in the semiconductor device can be aligned in a specific direction, variation in electrical characteristics of the thin film transistors can be suppressed. Therefore, the semiconductor device with high reliability can be manufactured.

Next, a structure of the semiconductor device capable of noncontact data transmission is explained with reference toFIG. 12. The semiconductor device of Embodiment Mode 4 includes an antenna portion2001, a power source portion2002, and a logic portion2003as its main components. The antenna portion2001includes an antenna2011which receives external signals and transmits data. The signal transmission method of the semiconductor device can be any of an electromagnetic coupling method, an electromagnetic induction method, and a microwave method. The transmission method may be selected appropriately in consideration of usage by a practitioner, and an optimum antenna may be provided in accordance with the transmission method.

The power source portion2002includes a rectifying circuit2021which produces power source based on a signal received from the outside through the antenna2011; a storage capacitor2022for storing the produced power source; and a constant voltage circuit2023. The logic portion2003includes a demodulating circuit2031which demodulates a received signal, a clock generating/compensating circuit2032which produces a clock signal, a code recognizing and judging circuit2033, a memory controller2034which produces a signal for reading data from a memory based on a received signal, a modulating circuit2035for superposing an encoded signal on a received signal, an encoding circuit2037which encodes the read data, and a mask ROM2038which stores data. The modulating circuit2035has a resistor2036for modulation.

A code recognized and judged by the code recognition/judgment circuit2033is a frame termination signal (EOF, End of Frame), a frame starting signal (SOF, Start of Frame), a flag, a command code, a mask length, a mask value, and the like. The code recognizing/judging circuit2033also has a cyclic redundancy check (CRC) function for discriminating transmission errors.

Next, application of the semiconductor device capable of noncontact data transmission is shown inFIGS. 13A to 13F. A semiconductor device9210capable of sending data without contact can be applied to various uses, such as bills, coins, securities, bearer bonds, documents (e.g., driver's licenses or resident's cards, seeFIG. 13A), packaging containers (e.g., wrapping paper or bottles, seeFIG. 13C), storage media (e.g., DVD software or video tapes, seeFIG. 13B), vehicles (e.g., bicycles, seeFIG. 13D), personal ornaments and accessories (e.g., shoes or glasses), foods, plants, animals, human body, clothing, commodities, or tags on goods such as electronic devices or on bags (seeFIGS. 13E and 13F).

The semiconductor device9210of Embodiment Mode 4 is fixed to a product by being mounted on a printed board, attached to a surface thereof, embedded therein, and so on. For example, if the product is a book, the semiconductor device is fixed to the book by embedding it inside a paper, and if the product is a package made of an organic resin, the semiconductor device is fixed to the package by embedding it inside the organic resin. Since the semiconductor device9210of the present invention can be compact, thin, and lightweight, the design quality of the product itself is not degraded even after the device is fixed to the product.

By providing the semiconductor device9210to bills, coins, securities, bearer bonds, documents, and the like, a certification function can be provided and the forgery can be prevented by using the certification function. Moreover, when the semiconductor device of this embodiment mode is provided in containers for package, recording media, personal belongings, foods, clothes, commodities, electronic appliances, and the like, systems such as an inspection system can become more efficient.

As an electronic appliance having the semiconductor device shown in any of Embodiment Modes 2 to 4, a television device (also simply called a TV or a television receiver), a digital camera, a digital video camera, a mobile phone device (also simply called a mobile phone appliance or a mobile phone), a mobile information terminal such as a PDA, a mobile game machine, a monitor for a computer, a computer, a sound reproducing device such as a car audio device, an image reproducing device provided with a recording medium, such as a home-use game machine, or the like is given. Specific examples of these are explained with reference toFIGS. 14A to 14Fin Embodiment Mode 5.

A mobile information terminal shown inFIG. 14Aincludes a main body9201, a display portion9202, and the like. By the use of the semiconductor device shown in Embodiment Mode 2 or 3 for the display portion9202, the mobile information terminal capable of high-definition display can be provided at low price. A digital video camera shown inFIG. 14Bincludes a display portion9701, a display portion9702, and the like. By the use of the semiconductor device shown in Embodiment Mode 2 or 3 for the display portion9701, the digital video camera capable of high-definition display can be provided at low price. A mobile terminal shown inFIG. 14Cincludes a main body9101, a display portion9102, and the like. By the use of the semiconductor device shown in Embodiment Mode 2 or 3 for the display portion9102, the mobile terminal with high reliability can be provided at low price.

A mobile television device shown inFIG. 14Dincludes a main body9301, a display portion9302, and the like. By the use of the semiconductor device shown in Embodiment Mode 2 or 3 for the display portion9302, the mobile television device capable of high-definition display can be provided at low price. Such a television device can be widely applied to a small-sized device to be mounted to a mobile terminal such as a mobile phone, a middle-sized device that is portable, and a large-sized device (for example, 40 inches or more).

The mobile computer shown inFIG. 14Eincludes a main body9401, a display portion9402, and the like. By the use of the semiconductor device shown in Embodiment Mode 2 or 3 for the display portion9402, the mobile computer capable of high-definition display can be provided at low price. The television device shown inFIG. 14Fincludes a main body9501, a display portion9502, and the like. By the use of the semiconductor device shown in Embodiment Mode 2 or 3 for the display portion9502, the television device capable of high-definition display can be provided at low price.

Here, a structure of the television device is explained with reference toFIG. 15, which is a block diagram showing the main structure of the television device. A tuner9511receives a video signal and an audio signal. The video signal is processed through a video detecting circuit9512, a video signal processing circuit9513which converts the signal outputted from the video detecting circuit9512into a color signal corresponding to red, green, or blue, and a controlling circuit9514which converts the video signal in accordance with input specification of a driver IC.

The controlling circuit9514outputs signals to a scanning line driver circuit9516and a signal line driver circuit9517of a display panel9515. In a case of digital driving, a signal dividing circuit9518may be provided on a signal line side so that the inputted digital signal is divided into m number of signals to be supplied. The scanning line driver circuit9516and the signal line driver circuit9517are circuits for driving a pixel portion. Among the signals received by the tuner9511, the audio signal is sent to an audio detecting circuit9521and its output is supplied to a speaker9523through an audio signal processing circuit9522. The controlling circuit9524receives control information such as a receiving station (receiving frequency) and sound volume, and sends signals to the tuner9511and the audio signal processing circuit9522.

The television device is formed by the inclusion of the display panel9515; therefore, the television device consumes less electric power and can display high-definition images. The present invention is not limited to the television receiver and is applicable to a display medium particularly with a large area such as an information display board at a railway station, an airport, or the like, or an advertisement display board on the street as well as a monitor of a personal computer.

Next, a mobile phone appliance is explained with reference toFIG. 16as a mode of an electronic appliance with the semiconductor device of the present invention mounted. The mobile phone appliance includes cases2700and2706, a panel2701, a housing2702, a printed wiring board2703, an operation button2704, and a battery2705(seeFIG. 16), in which the panel2701is detachably incorporated into the housing2702and the housing2702is fitted into the printed wiring board2703. The shape and size of the housing2702are appropriately changed in accordance with the electronic appliance to which the panel2701is incorporated.

A plurality of semiconductor devices that are packaged are mounted on the printed wiring board2703. The semiconductor device of the present invention can be used as one of them. The semiconductor devices mounted on the printed wiring board2703have any function of a controller, a central processing unit (CPU), a memory, a power source circuit, an audio processing circuit, a sending/receiving circuit, and the like.

The panel2701is connected to the printed wiring board2703with a connection film2708interposed therebetween. The panel2701, the housing2702, and the printed wiring board2703are housed in the cases2700and2706together with the operation buttons2704and the battery2705. A pixel region2709in the panel2701is provided so as to be observed through an opening window provided in the case2700.

In the panel2701, a pixel portion and a part of a peripheral driver circuit (a driver circuit with low operating frequency among plural driver circuits) may be formed over one substrate by using TFTs whereas another part of a peripheral driver circuit (a driver circuit with high operating frequency among plural driver circuits) may be formed over an IC chip. The IC chip may be mounted on a panel2701by COG (Chip On Glass), or the IC chip may be connected to a glass substrate by using TAB (Tape Automated Bonding) or a printed board.

FIG. 17Ashows an example of a structure of a panel in which a pixel portion and a part of a peripheral driver circuit are formed over one substrate and an IC chip including the other part of the peripheral driver circuit is mounted by COG or the like. The panel shown inFIG. 17Aincludes a substrate3900, a signal line driver circuit3901, a pixel portion3902, a scanning line driver circuit3903, a scanning line driver circuit3904, an FPC3905, an IC chip3906, an IC chip3907, a sealing substrate3908, and a sealant3909. With such a structure, the power consumption of the display device can be reduced, and the mobile phone appliance can be used for a longer period per charge. Moreover, cost reduction of the mobile phone is possible.

In order to further reduce the power consumption, as shown inFIG. 17B, a pixel portion may be formed over a substrate using TFTs and the entire peripheral driving circuit may be formed over an IC chip, and then the IC chip may be mounted on a display panel by COG (Chip On Glass) or the like. A display panel inFIG. 17Bincludes a substrate3910, a signal line driver circuit3911, a pixel portion3912, a scanning line driver circuit3913, a scanning line driver circuit3914, an FPC3915, an IC chip3916, an IC chip3917, a sealing substrate3918, and a sealant3919.

As thus described, the semiconductor device of the present invention is compact, thin, and lightweight. With these features, the limited space in the cases2700and2706of the electronic appliance can be used efficiently. Moreover, the cost reduction is possible, and an electronic appliance having the semiconductor device with high reliability can be manufactured.

The present invention is hereinafter explained in more detail based on the following embodiments. It goes without saying that the present invention is not limited by any of the embodiments, but is specified by the claims. Note that a method for manufacturing a crystalline silicon film according to the present invention and its crystallographic properties are described giving a comparative example in addition to the embodiments.

A method for manufacturing a crystalline silicon film of Embodiment 1 is described with reference toFIG. 18. As already described in Embodiment Mode 1 with reference toFIGS. 1A to 1C, the base film (insulating film)101, the amorphous semiconductor film102, and the cap film103were formed over the substrate100. As shown inFIG. 1B, the amorphous semiconductor film102was irradiated with the laser light104through the cap film103and was crystallized, thereby forming the crystalline semiconductor film105. As the substrate100, a glass substrate having a thickness of 0.7 mm manufactured by Corning, Inc. was used. As the insulating film101, a stacked film of a silicon nitride film containing oxygen and a silicon oxide film containing nitrogen was formed using a parallel-plate plasma CVD apparatus.

The deposition conditions were as follows.

As the amorphous semiconductor film102, an amorphous silicon film was formed using a parallel-plate plasma CVD apparatus. The deposition conditions of the amorphous silicon film were as follows.

After the amorphous semiconductor film was formed under the above-mentioned deposition conditions, it was heated at 500° C. for an hour in an electric furnace, and then at 550° C. for four hours. This heat treatment is treatment for extracting hydrogen from the amorphous silicon film. Hydrogen is extracted in order to prevent a hydrogen gas from spouting from the amorphous silicon film when the amorphous silicon film is irradiated with a laser beam. After the heat treatment, an oxide film formed on the surface of the amorphous semiconductor film102was removed by hydrofluoric acid treatment for 70 seconds, and then a silicon nitride film containing oxygen was formed over the amorphous semiconductor film102as the cap film103by using a parallel-plate plasma CVD apparatus.

The deposition conditions were as follows.

Table 1 shows compositions of the insulating film (base film)101and the cap film103obtained. Table 1 also shows a composition of a cap film of a comparative example to be described below. The values of the compositions of the films in Table 1 are those in a state before heat treatment or laser irradiation. The composition ratios were measured using Rutherford backscattering spectrometry (RBS) and hydrogen forward scattering (HFS). The measurement sensitivity was approximately ±2%.

TABLE 1COMPOSITIONRATIO (%)MATERIALSiNOHSILICON NITRIDE FILMCAP FILM OF EMBODIMENT32.245.55.217.2CONTAINING OXYGENLOWER LAYER OF BASE FILMSILICON OXIDE FILMCAP FILM OF COMPARATIVE32.10.066.01.9EXAMPLESILICON OXIDE FILMUPPER LAYER OF BASE FILM32.60.265.81.4CONTAININGNITROGEN

After the cap film103was formed, it was heated at 500° C. for an hour in an electric furnace. This heat treatment is treatment for extracting hydrogen from the silicon nitride film containing oxygen that is the cap film. Hydrogen is extracted in order to prevent a hydrogen gas from spouting from the silicon nitride film containing oxygen when the silicon nitride film containing oxygen is irradiated with a laser beam.

The amorphous silicon film was irradiated with a laser beam from a laser irradiation apparatus through the cap film103and was crystallized, thereby forming a crystalline silicon film. Although the laser irradiation apparatus used at that time is already described in Embodiment Mode 1, the brief description thereof is repeated here with reference toFIG. 18. As shown in theFIG. 18, the laser irradiation apparatus includes the two laser oscillators11aand11band can perform irradiation with the laser beam12that is obtained by combining the laser beams12aand12bemitted from the laser oscillators11aand11b, respectively.

The polarization direction of the laser beam12bemitted from the laser oscillator11bis changed through the wavelength plate13. This is in order to combine two laser beams having different polarization directions by the polarizer14. After the laser beam12bpasses through the wavelength plate13, the laser beam12bis reflected by the mirror22and made to enter the polarizer14. Then, the laser beam12aand the laser beam12bare combined by the polarizer14. The wavelength plate13and the polarizer14are adjusted so that the combined laser beam12has suitable energy.

The laser beam12that is combined by the polarizer14is reflected by the mirror15, and is shaped so as to have a linear cross section through the cylindrical lens16and the cylindrical lens17. The cylindrical lens16acts in a lengthwise direction of a beam spot formed on an irradiation surface, and the cylindrical lens17acts in a crosswise direction thereof.

The laser irradiation apparatus includes the suction stage19to which the irradiation surface18is fixed, and the suction stage19can be moved in X-Y directions by the X-axis uniaxial robot20and the Y-axis uniaxial robot21. As discussed above, the substrate1over which the insulating film101, the amorphous semiconductor film102, and the cap film103were formed was fixed to the suction stage19, and was irradiated with a laser beam while the substrate1was moved along a crosswise direction of a beam spot, that is, the X axis with a lengthwise direction of a linear laser beam aligned with the Y axis.

In this embodiment, the movement speed of the substrate was set to 35 cm/sec. An LD excitation YVO4laser was used as each of the two laser oscillators, and its second harmonic (wavelength: 532 nm) was used for irradiation. The laser beam had an intensity of 14 W on the irradiation surface and had a linear shape on the irradiation surface with a length of approximately 500 μm and a width of approximately 20 μm.

EBSP measurement was carried out to confirm the position, the size, and the plane orientation of crystal grains of the crystalline silicon film. In order to carry out EBSP measurement, the cap film103was removed by etching from the surface of the crystalline silicon film. In the EBSP measurement, the plane orientation of crystal grains was measured from on an EBSP image which is obtained by making an electron beam incident on the surface of the crystalline silicon film at an incidence angle of 60°.

The measurement region was 50 μm×50 μm and the measurement pitch was 0.1 μm. EBSP images of three viewing planes A to C which are perpendicular to each other as shown inFIG. 2were measured. Vectors a to c inFIG. 2indicate normal vectors of the viewing planes A to C, respectively. The viewing plane A is parallel to the surface of the substrate, which corresponds to the upper surface of the crystalline silicon film. The viewing plane C is a plane where the normal vector c is parallel to the scan direction of the laser beam. In accordance with pieces of information obtained from these three viewing planes A to C, the plane orientation of the crystalline silicon film can be specified with high accuracy.

FIGS. 19A to 21Cshow analysis results of plane orientations (crystal axis orientations perpendicular to viewing planes) of the crystalline silicon film.FIGS. 19A to 19Care orientation map images each showing distribution of plane orientation in the measurement area of 50 μm×50 μm.FIG. 19Dis an inverse pole figure of single crystal silicon, in which each color indicates orientation.

Although it is difficult to determine fromFIGS. 19A to 19Cbecause these figures are monochrome and show only lightness, it is found from color display that orientation is strongly obtained in the orientation of <001> on the viewing plane A, in the orientation of <301> on the viewing plane B, and in the orientation of <301> on the viewing plane C. Further, it is found according to the shape and color of patterns ofFIGS. 19A to 19Cthat the crystalline silicon film of Embodiment 1 is composed of domains each extended long in a columnar shape. InFIGS. 19A to 19C, the length of each domain is 5 μm to 50 μm, and further, a domain having a length of 50 μm or more is also observed.

FIGS. 20A to 20Care inverse pole figures showing distributions of appearance frequency of plane orientation on the viewing planes A to C.FIG. 20Dshows a scale of frequency. Although it is difficult to determine fromFIGS. 20A to 20Dbecause these figures are also monochrome and show only lightness, it is found from the inverse pole figure ofFIG. 20Athat the orientation of <001> appears at a frequency 14.0 times or more as high as that of a state in which all directions appear with identical probability on the viewing plane A. In addition, it is found from the inverse pole figure ofFIG. 20Bthat the orientation of <301> is closest to black on the viewing plane B; specifically, the orientation of <301> appears at a frequency 4.8 times or more as high as that of a state in which all orientations appear with identical probability. Further, it is found from the inverse pole figure ofFIG. 20Cthat the orientation of <301> is closest to black on the viewing plane C; specifically, the orientation of <301> appears at a frequency 4.8 times or more as high as that of a state in which all orientations appear with identical probability.

FIGS. 21A to 21Cshow calculation results of orientation ratios of orientations that have high appearance frequency in the inverse pole figures ofFIGS. 20A to 20C.FIG. 21Ashows a calculation result of an orientation ratio on the viewing plane A based onFIG. 20A. In the inverse pole figure ofFIG. 20A, the range of an angle fluctuation with respect to <001> is set within ±10°, and the orientation ratio was obtained by obtaining a rate of the number of measurement points having the orientation <001> within the range of angle fluctuation ±10° to all of measurement points.

The value of the obtained ratio of points having a specific orientation to all measurement points is a Partition Fraction value. The value of an orientation ratio, to all measurement points, of measurement points having high orienting reliability of the points having a specific orientation is a Total Fraction value. According to the results, it is found that the orientation <001> within the range of angle fluctuation ±10° occupies 71.2% on the viewing plane A of the present invention.

Similarly,FIGS. 21B and 21Cshow calculation results of orientation ratios of <301> on the viewing planes B and C based on the inverse pole figures ofFIGS. 20B and 20C. The orientation ratios were obtained with the range of angle fluctuation with respect to <301> set within ±10°. It is found that the orientation of <301> occupies 71.1% and 73.9% on the viewing planes B and C, respectively. Note that although the ratios of the orientation <301> were obtained on the viewing planes B and C, an orientation ratio of the plane orientation of <401>, <501>, or <601> close to the orientation of <301> may alternatively be obtained.

Comparative Example

As a comparative example, the crystalline silicon film was formed using a different material for the cap film103. In the comparative example, a silicon oxide film with a thickness of 500 nm was formed as the cap film103by using a parallel-plate plasma CVD apparatus. The deposition conditions of the insulating film101and the amorphous semiconductor film102were the same as those in the embodiment, and specific deposition conditions of the cap film103were as follows.

In this comparative example, heat treatment for extracting hydrogen from the amorphous silicon film was carried out similarly to the embodiment. However, heat treatment for extracting hydrogen from the cap film103was not carried out because the cap film103contained little hydrogen. The intensity of a laser beam used for irradiation was 15 W, and the movement speed of the substrate was 35 cm/sec. Other than that, the crystalline silicon film was formed similar to the embodiment. The crystalline silicon film thus formed was subjected to EBSP measurement similarly to the embodiment. In the comparative example, the measurement area was 100 μm×50 μm, in which measurement was carried out at every lattice point with a pitch of 0.25 μm. Viewing planes A to C were similar to those in Embodiment 1.

FIGS. 22A to 22Care orientation map diagrams respectively showing plane orientations on the viewing planes A to C;FIGS. 23A to 23Care inverse pole figures; andFIGS. 24A to 24Cshow calculation results of orientation ratios.FIGS. 23A to 23Care inverse pole figures showing distributions of appearance frequency of plane orientation on the viewing planes A to C shown inFIGS. 22A to 22C.FIG. 23Dshows a scale of appearance frequency of plane orientation. Similarly toFIGS. 20A to 20C,FIGS. 23A to 23Cshow that a region closer to black has a higher rate of crystal grains having plane orientation.

It is found from the inverse pole figure ofFIG. 23Athat the orientation of <211> is closest to black on the viewing plane A; specifically, the orientation of <211> appears at a frequency 3.9 times or more as high as that of a state in which all orientations appear with identical probability. In addition, it is found from the inverse pole figure ofFIG. 23Bthat the orientation of <111> is closest to black on the viewing plane B; specifically, the orientation of <111> appears at a frequency 9.7 times or more as high as that of a state in which all orientations appear with identical probability.

It is further found from the inverse pole figure ofFIG. 23Cthat the orientation of <101> is closest to black on the viewing plane C; specifically, the orientation <101> appears at a frequency 9.7 times or more as high as that of a state in which all orientations appear with identical probability. A colored region inFIG. 24Ais a region showing crystal grains having the orientation of <211> within the range of angle fluctuation of ±10°. A colored region inFIG. 24Bis a region showing crystal grains having the orientation of <111> within the range of angle fluctuation of ±10°. A colored region inFIG. 24Cis a region showing crystal grains having the orientation of <101> within the range of angle fluctuation between ±10°.

In the comparative example, as can be seen inFIGS. 23A to 23C, orientation was strongly obtained in the orientations of <211>, <111>, and <101> on the viewing planes A, B, and C, respectively. As can be seen inFIGS. 24A to 24C, the orientation ratio of <211> on the viewing plane A was 42.1%; that of <111> on the viewing plane B, 41.2%; and that of <101> on the viewing plane C, 52.3%. Note that a family of equivalent plane orientations of crystal grains such as [101], [001], and [110] are collectively referred to as <101>.

(Comparison Between Embodiment and Comparative Example)

A comparison between the orientation map images ofFIGS. 19A to 19Cand those ofFIGS. 22A to 22Cshows that each of the embodiment and the comparative example is composed of domains each extended long in a columnar shape, but the size (length, width) of a crystal grain of the embodiment is significantly larger. Further, the calculation results of the orientation ratios of the viewing planes A to C in the embodiment and the comparative example, which are shown inFIGS. 21A to 21CandFIGS. 24A to 24C, are arranged in Table 2.

As can be seen in Table 2, the plane orientation with high appearance frequency on each of the viewing planes A to C is different between the embodiment and the comparative example. It is found that in the embodiment, the plane orientation is aligned in one direction at a significantly high rate as high as 70% or more on each of the three viewing planes. In other words, it is found that a crystalline semiconductor, in which the plane orientation of crystal grains can be considered to be aligned in one direction, is formed in a crystallized region.

This embodiment describes orientation ratios of the plane orientation <301> and other plane orientations on the viewing planes B and C of the sample described in Embodiment 1, with reference toFIGS. 25A to 26H.FIGS. 25A to 25Dare orientation map images showing distributions of the orientations of <601>, <501>, <401>, and <301> in the measurement area of 50 μm×50 μm on the viewing plane B, respectively. Each map diagram has a length of 50 μm on each side. Note that the measurement pitch was 0.1 μm. InFIGS. 25A to 25D, a crystalline silicon film having plane orientations of <601>, <501>, <401>, and <301> is formed in colored portions, respectively.

Colored regions inFIGS. 25E to 25Hare regions showing crystal grains having the orientations of <601>, <501>, <401>, and <301> with the range of angle fluctuation between ±10° or less, respectively.FIGS. 25E to 25Hshow calculation results of orientation ratios of the plane orientations. Each orientation ratio was obtained by obtaining a rate of the number of measurement points having each orientation with the range of angle fluctuation between ±10° or less. The value of the obtained rate of points having a specific orientation to all measurement points is a Partition Fraction value. The value of an orientation ratio, to all measurement points, of measurement points having high orienting reliability of the points having a specific orientation is a Total Fraction value.

Table 3 shows orientation ratios of the plane orientations. Note that the ratios are rounded off to the nearest whole number. Table 3 shows that each of the orientation ratios of the plane orientations of <601>, <501>, <401>, and <301> of crystal grains on the viewing plane B is 60% or more.

FIGS. 26A to 26Dare orientation map images showing distributions of plane orientations of <601>, <501>, <401>, and <301> in the measurement area of 50 μm×50 μm on the viewing plane C, respectively. Each map image has a length of 50 μm on each side. Note that the measurement pitch was 0.1 μm. InFIGS. 26A to 26D, a crystalline silicon film having plane orientations of <601>, <501>, <401>, and <301> is formed in colored portions, respectively.

Colored regions inFIGS. 26E to 26Hare regions showing crystal grains having the orientations of <601>, <501>, <401>, and <301> with the range of angle fluctuation between ±10° or less, respectively.FIGS. 26E to 26Hshow calculation results of orientation ratios of the plane orientations. Each orientation ratio was obtained by obtaining a rate of the number of measurement points having each orientation with the range of angle fluctuation between ±10° or less. Table 4 shows orientation ratios of the plane orientations. Note that the ratios have been rounded off to the nearest whole number.

Table 4 shows that each of the orientation ratios of the plane orientations of <601>, <501>, <401>, and <301> on the viewing plane C is 60% or more. From the foregoing, it is found that each of the orientation ratios of the plane orientations of <601>, <501> and <401> other than <301> is also 60% or more on the viewing planes B and C.

This embodiment describes an orientation ratio of plane orientation of a crystalline silicon film which is formed with the energy and scan speed of the laser beam and the thickness of the cap film different from those in Embodiment 1, with reference toFIGS. 27 and 28Ato28G.

First, a method for manufacturing a crystalline silicon film of Embodiment 3 is described with reference toFIG. 18. A stacked film of a silicon nitride film containing oxygen and a silicon oxide film containing nitrogen, which is the insulating film101, was formed by using a parallel-plate plasma CVD apparatus over a substrate similar to the substrate described in Embodiment 1 under conditions similar to those in Embodiment 1. Next, an amorphous silicon film was formed as the amorphous semiconductor film102by using a parallel-plate plasma CVD apparatus under conditions similar to those in Embodiment 1.

Next, the substrate was heated at 500° C. for an hour in an electric furnace. After the heat treatment, an oxide film formed on the surface of the amorphous semiconductor film102due to heating was removed by hydrofluoric acid treatment. The hydrofluoric acid treatment was performed for 90 seconds. After that, a silicon nitride film containing oxygen was formed over the amorphous semiconductor film102as the cap film103by using a parallel-plate plasma CVD apparatus.

The deposition conditions were as follows. Note that the deposition conditions except for the thickness were similar to those in Embodiment 1.

After the cap film103was formed, it was heated at 600° C. for four hours in an electric furnace. This heat treatment is treatment for extracting hydrogen from the silicon nitride film containing oxygen that is the cap film. Hydrogen is extracted in order to prevent a hydrogen gas from spouting from the silicon nitride film containing oxygen when the silicon nitride film containing oxygen is irradiated with a laser beam. The heat treatment may be omitted if the cap film contains little hydrogen.

The amorphous silicon film was irradiated with a laser beam through the cap film103by using a laser irradiation apparatus and was crystallized, thereby forming a crystalline silicon film. In this embodiment, the movement speed of the substrate was set to 20 cm/sec. An LD excitation YVO4laser was used as each of the two laser oscillators, and its second harmonic (wavelength: 532 nm) was used for irradiation. The laser beam had an intensity of 8.4 W on the irradiation surface and had a linear shape on the irradiation surface with a length of approximately 500 μm and a width of approximately 20 μm.

EBSP measurement was carried out to confirm the position, the size, and the plane orientation of crystal grains of the crystalline silicon film. In order to carry out EBSP measurement, the cap film103was removed by etching from the surface of the crystalline silicon film. In the EBSP measurement, an EBSP image was obtained by making an electron beam incident on the surface of the crystalline silicon film at an incidence angle of 60°. The plane orientation of crystal grains was measured from the EBSP image obtained. The measurement area was 50 μm×50 μm and the measurement pitch was 0.5 μm. EBSP images of three viewing planes A to C which are perpendicular to each other as shown inFIG. 2were measured.

FIGS. 27 to 30Fshow analysis results of plane orientations (crystal axis orientations perpendicular to viewing planes) of the crystalline silicon film.FIG. 27shows a calculation result of an orientation ratio of a plane orientation which has high appearance frequency in an inverse pole figure (not shown) showing distribution of appearance frequency of plane orientation on the viewing plane A. Note that a colored region is a region showing crystal grains having the orientation of <101> with the range of angle fluctuation between ±10° or less.FIG. 27shows that the orientation of <001> within the range of angle fluctuation of ±10° occupies 80%, i.e., 60% or more on the viewing plane A of this embodiment.

Each ofFIGS. 28A to 28Gshows a calculation result of an orientation ratio of a plane orientation which has high appearance frequency in an inverse pole figure (not shown) showing distribution of appearance frequency of plane orientation on the viewing plane B. InFIG. 28A, a colored region is a region showing crystal grains having the plane orientation <001> with the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <001> is shown. InFIG. 28B, a colored region is a region showing crystal grains having the plane orientation <601> with the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <601> is shown. InFIG. 28C, a colored region is a region showing crystal grains having the plane orientation <501> with the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation of <501> is shown. InFIG. 28D, a colored region is a region showing crystal grains having the plane orientation <401> with the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <401> is shown. InFIG. 28E, a colored region is a region showing crystal grains having the plane orientation <301> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <301> is shown. InFIG. 28F, a colored region is a region showing crystal grains having the plane orientation of <201> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <201> is shown. InFIG. 28G, a colored region is a region showing crystal grains having the plane orientation <101> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <101> is shown. The orientation ratios of the plane orientations are arranged in Table 5. Note that the ratios have been rounded off to the nearest whole number.

Each ofFIGS. 29A to 29Gshows a calculation result of an orientation ratio of a plane orientation which has high appearance frequency in an inverse pole figure (not shown) showing distribution of appearance frequency of plane orientation on the viewing plane C. InFIG. 29A, a colored region is a region showing crystal grains having the plane orientation <001> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <001> is shown. InFIG. 29B, a colored region is a region showing crystal grains having the plane orientation <601> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <601> is shown. InFIG. 29C, a colored region is a region showing crystal grains having the plane orientation <501> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <501> is shown. InFIG. 29D, a colored region is a region showing crystal grains having the plane orientation <401> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <401> is shown. InFIG. 29E, a colored region is a region showing crystal grains having the plane orientation <301> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <301> is shown. InFIG. 29F, a colored region is a region showing crystal grains having the plane orientation <201> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <201> is shown. InFIG. 29G, a colored region is a region showing crystal grains having the plane orientation <101> within the range of angle fluctuation between ±10° or less, and an orientation ratio of crystal grains having the plane orientation <101> is shown. The orientation ratios of the plane orientations are arranged in Table 6. Note that the ratios have been rounded off to the nearest whole number.

The sum of the orientation ratios of the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> shown in Table 5 is 218.3%. The sum of the orientation ratios of the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> shown in Table 6 is 244.4%.FIGS. 30A to 30Fshow calculation results of orientation ratios obtained regarding each of overlaps between the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> as an orientation ratio only of any one of the plane orientations.

Note that the sum of orientation ratios of all of <001>, <601>, <501>, <401>, <301>, <201>, and <101>, each of which is calculated regarding each of overlaps between the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> as an orientation ratio only in any one of the plane orientations, is denoted by <x01> (x=0, 1, 2, 3, 4, 5, 6) as described above.

FIG. 30Ais an orientation map image showing distribution of the plane orientation <001> in the measurement area of 50 μm×50 μm on the viewing plane A.FIG. 30Bis an orientation map image showing distribution of the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> in the measurement area of 50 μm×50 μm on the viewing plane B.FIG. 30Cis an orientation map image showing distribution of the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> in the measurement area of 50 μm×50 μm on the viewing plane C. Each map diagram has a length of 50 μm on each side.

InFIG. 30A, a crystalline silicon film having the plane orientation <001> is formed in a colored portion. In each ofFIGS. 30B and 30C, a crystalline silicon film having the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> is formed in a colored portion.

FIG. 30Dshows a calculation result of an orientation ratio of crystal grains having the plane orientation <001> on the viewing plane A, in which a colored region is a region showing crystal grains having the plane orientation <001> with the range of angle fluctuation between +10° or less.

FIG. 30Eshows calculation results of orientation ratios of crystal grains having the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> on the viewing plane B. The whole region of the colored regions is a region showing crystal grains having the plane orientation <x01> (x=0, 1, 2, 3, 4, 5, 6) with the range of angle fluctuation between ±10° or less. The regions have different colors according to the value of x to differentiate regions corresponding to the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101>. Here, an overlap between the plane orientations is excluded.

FIG. 30Fshows calculation results of orientation ratios of crystal grains having the plane orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> on the viewing plane C. The whole region of the colored regions is a region showing crystal grains having the plane orientation <x01> (x=0, 1, 2, 3, 4, 5, 6) with the range of angle fluctuation between ±10° or less. Similarly toFIG. 30E, regions corresponding to the plane orientations are differentiated according to the value of x.

Table 7 shows orientation ratios of the plane orientations and orientation ratios of <x01> (x=0, 1, 2, 3, 4, 5, 6) (i.e., the sum of orientation ratios in the orientations <001>, <601>, <501>, <401>, <301>, <201>, and <101> excluding an overlap) on the viewing planes A to C. Note that the ratios have been rounded off to the nearest whole number.

Table 7 shows that the orientation of <001> within the range of angle fluctuation of ±10° occupies 60% or more of plane orientations of crystal grains on the viewing plane A. In addition, it shows that <x01> (x=0, 1, 2, 3, 4, 5, 6) occupies 60% or more on the viewing plane B. Further, it shows that <x01> (x=0, 1, 2, 3, 4, 5, 6) occupies 60% or more on the viewing plane C. Furthermore, it shows that an orientation ratio of <x01> (x=0, 2, 3, 4, 5, 6) excluding a plane orientation when x is 1 also occupies 60% or more on each of the viewing planes B and C.

This embodiment describes an orientation ratio of plane orientation of a crystalline silicon film which is formed with the energy and scan speed of the laser beam and the thickness of the cap film different from those in Embodiment 1, with reference toFIGS. 31A to 31F.

First, a method for manufacturing a crystalline silicon film of Embodiment 4 is described with reference toFIG. 18. A stacked film of a silicon nitride film containing oxygen and a silicon oxide film containing nitrogen, which is the insulating film101, was formed by using a parallel-plate plasma CVD apparatus over a substrate similar to the substrate described in Embodiment 1 under conditions similar to those in Embodiment 1. Next, an amorphous silicon film was formed by using a parallel-plate plasma CVD apparatus as the amorphous semiconductor film102under conditions similar to those in Embodiment 1. After the formation, an amorphous semiconductor film was formed under the above-described deposition conditions and then heated at 500° C. for an hour in an electric furnace and further at 550° C. for four hours.

Next, an oxide film formed on the surface of the amorphous semiconductor film102due to heating was removed by hydrofluoric acid treatment. The hydrofluoric acid treatment was performed for 90 seconds. After that, an oxide film was formed on the amorphous semiconductor film102using an aqueous solution including ozone, and the oxide film was removed by hydrofluoric acid treatment. This is in order to fully remove an impurity on the surface of the amorphous silicon film. The treatment with the aqueous solution including ozone was performed for 40 seconds, and the hydrofluoric acid treatment was performed for 90 seconds. Next, a silicon nitride film containing oxygen was formed over the amorphous semiconductor film102as the cap film103by using a parallel-plate plasma CVD apparatus.

The deposition conditions were as follows. Note that the deposition conditions except for the thickness were similar to those in Embodiment 1.

After the cap film103was formed, it was heated at 600° C. for four hours in an electric furnace. This heat treatment is treatment for extracting hydrogen from the silicon nitride film containing oxygen that is the cap film. Hydrogen is extracted in order to prevent a hydrogen gas from spouting from the silicon nitride film containing oxygen when the silicon nitride film containing oxygen is irradiated with a laser beam.

The amorphous silicon film was irradiated with a laser beam through the cap film103by using a laser irradiation apparatus and was crystallized, thereby forming a crystalline silicon film. In this embodiment, the movement speed of the substrate was set to 10 cm/sec. An LD excitation YVO4laser was used as each of the two laser oscillators, and its second harmonic (wavelength: 532 nm) was used for irradiation. The laser beam had an intensity of 6.4 W on the irradiation surface and had a linear shape on the irradiation surface with a length of approximately 500 μm and a width of approximately 20 μm.

EBSP measurement was carried out to confirm the position, the size, and the plane orientation of crystal grains of the crystalline silicon film. In order to carry out EBSP measurement, the cap film103was removed by etching from the surface of the crystalline silicon film. In the EBSP measurement, an EBSP image was obtained by making an electron beam incident on the surface of the crystalline silicon film at an incidence angle of 60°. The plane orientation of crystal grains was measured from the EBSP image obtained.

The measurement area was 50 μm×50 μm and the measurement pitch was 0.5 μm. EBSP images of three viewing planes A to C which are perpendicular to each other as shown inFIG. 2were measured.FIGS. 31A to 31Fshow analysis results of plane orientations (crystal axis orientations perpendicular to viewing planes) of the crystalline silicon film.

FIG. 31Ais an orientation map image showing distribution of the plane orientation <001> in the measurement area of 50 μm×50 μm on the viewing plane A.FIG. 31Bis an orientation map image showing distribution of the plane orientations <001>, <301>, <201>, and <101> in the measurement area of 50 μm×50 μm on the viewing plane B.FIG. 31Cis an orientation map image showing distribution of the plane orientations <001>, <301>, <201>, and <101> in the measurement area of 50 μm×50 μm on the viewing plane C. Each map image has a length of 50 μm on each side.

InFIG. 31A, a crystalline silicon film having the plane orientation <001> is formed in a colored portion. In each ofFIGS. 31B and 31C, a crystalline silicon film having the plane orientations <001>, <301>, <201>, and <101> is formed in a colored portion.

FIG. 31Dshows a calculation result of an orientation ratio of crystal grains having the plane orientation <001> on the viewing plane A, in which a colored region is a region showing crystal grains having the plane orientation <001> with the range of angle fluctuation between ±10° or less.

FIG. 31Eshows calculation results of orientation ratios of crystal grains having the plane orientations <001>, <301>, <201>, and <101> on the viewing plane B. The whole region of the colored regions is a region showing crystal grains having the plane orientation <x01> (x=0, 1, 2, 3) with the range of angle fluctuation between ±10° or less. The regions have different colors according to the value of x to differentiate regions corresponding to the plane orientations <001>, <301>, <201>, and <101>. Here, an overlap between plane orientations is excluded.

FIG. 31Fshows calculation results of orientation ratios of crystal grains having the plane orientations <001>, <301>, <201>, and <101> on the viewing plane C. The whole region of the colored regions is a region showing crystal grains having the plane orientation <x01> (x=0, 1, 2, 3) within the range of angle fluctuation between ±10° or less. Similarly toFIG. 31E, regions corresponding to the plane orientations are differentiated according to the value of x.

Table 8 shows orientation ratios of plane orientations on the viewing planes A to C and orientation ratios of <x01> (x=0, 1, 2, 3) (i.e., the sum of orientation ratios in the orientations <001>, <301>, <201>, and <101> excluding an overlap) on the viewing planes B and C. Note that the ratios have been rounded off to the nearest whole number.

Table 8 shows that the orientation <001> with the range of angle fluctuation between +10° occupies 76%, i.e., 60% or more of plane orientations of crystal grains on the viewing plane A. In addition, it shows that <x01> (x=0, 1, 2, 3) occupies 72%, i.e., 60% or more on the viewing plane B. Note that an orientation ratio of <x01> (x=0, 1, 2, 3, 4, 5, 6) obtained according to similar calculation is 79%, i.e., 60% or more on the viewing plane B.

In addition, it shows that <x01> (x=0, 1, 2, 3) occupies 86%, i.e., 60% or more on the viewing plane C. Note that an orientation ratio of <x01> (x=0, 1, 2, 3, 4, 5, 6) obtained according to similar calculation is 88%, i.e., 60% or more on the viewing plane C. In other words, the orientation ratio of <x01> (x=0, 1, 2, 3) is 60% or more, and the orientation ratio of <x01> (x=0, 1, 2, 3, 4, 5, 6) exceeds that of <x01> (x=0, 1, 2, 3). Further, it shows that an orientation ratio of <x01> (x=0, 2, 3) excluding a plane orientation when x is 1 is also 60% or more on each of the viewing planes B and C.

This embodiment describes an orientation ratio of plane orientation of a crystalline silicon film which is formed with the energy and scan speed of the laser beam and the composition and thickness of the cap film different from those in Embodiment 1, with reference toFIGS. 32A to 32F.

First, a method for manufacturing a crystalline silicon film of Embodiment 5 is described with reference toFIG. 18. A stacked film of a silicon nitride film containing oxygen and a silicon oxide film containing nitrogen, which is the insulating film101, was formed by using a parallel-plate plasma CVD apparatus over the substrate100similar to the substrate described in Embodiment 1. As the substrate100, a glass substrate having a thickness of 0.7 mm manufactured by Corning, Inc. was used.

The deposition conditions were as follows.

As the amorphous semiconductor film102, an amorphous silicon film was formed by using a parallel-plate plasma CVD apparatus. The deposition conditions of the amorphous silicon film were as follows.

Next, a silicon nitride film containing oxygen at a concentration below the detection limit of SIMS was formed over the amorphous semiconductor film102as the cap film103by using a parallel-plate plasma CVD apparatus. The deposition conditions were as follows.

<Silicon Nitride Film Containing Oxygen At Concentration Below Detection Limit>

FIG. 33shows the concentration of oxygen in the cap film103deposited. The values of the oxygen concentrations of the films shown inFIG. 33are those in a state before heat treatment or laser irradiation. The oxygen concentrations were measured using secondary ion mass spectrometry (SIMS). InFIG. 33, the oxygen concentration of the cap film103of Embodiment 5 is almost equal to or below the detection limit of current SIMS. Therefore, in practice, the concentration is thought to be further lower (1×1017atoms/cm3or lower).

After the cap film103was formed, it was heated at 500° C. for an hour in an electric furnace, and then at 550° C. for four hours. This heat treatment is treatment for extracting hydrogen from the silicon nitride film containing oxygen at a concentration below the detection limit, which is the cap film. Hydrogen is extracted in order to prevent a hydrogen gas from spouting from the silicon nitride film containing oxygen at a concentration below the detection limit when the silicon nitride film containing oxygen is irradiated with a laser beam.

The amorphous silicon film was irradiated with a laser beam through the cap film103by using a laser irradiation apparatus and was crystallized, thereby forming a crystalline silicon film. In this embodiment, the movement speed of the substrate was set to 20 cm/sec. An LD excitation YVO4laser was used as each of the two laser oscillators, and its second harmonic (wavelength: 532 nm) was used for irradiation. The laser beam had an intensity of 9.6 W on the irradiation surface and had a linear shape on the irradiation surface with a length of approximately 500 μm and a width of approximately 20 μm.

EBSP measurement was carried out to confirm the position, the size, and the plane orientation of crystal grains of the crystalline silicon film. In order to carry out the EBSP measurement, the cap film103was removed by etching from the surface of the crystalline silicon film. In the EBSP measurement, the plane orientation of crystal grains was measured from an EBSP image obtained by making an electron beam incident on the surface of the crystalline silicon film at an incidence angle of 60°.

The measurement region was 50 μm×50 μm and the measurement pitch was 0.5 μm. EBSP images of three viewing planes A to C which are perpendicular to each other as shown inFIG. 2were measured.FIGS. 32A to 32Fshow analysis results of plane orientations (crystal axis orientations perpendicular to viewing planes) of the crystalline silicon film.

FIG. 32Ais an orientation map image showing distribution of the plane orientation <001> in the measurement area of 50 μm×50 μm on the viewing plane A.FIG. 32Bis an orientation map image showing distribution of the plane orientations <001>, <301>, <201>, and <101> in the measurement area of 50 μm×50 μm on the viewing plane B.FIG. 32Cis an orientation map image showing distribution of the plane orientations <001>, <301>, <201>, and <101> in the measurement area of 50 μm×50 μm on the viewing plane C. Each map image has a length of 50 μm on each side.

InFIG. 32A, a crystalline silicon film having the plane orientation <001> is formed in a colored portion. In each ofFIGS. 32B and 32C, a crystalline silicon film having the plane orientations <001>, <301>, <201>, and <101> is formed in a colored portion.

FIG. 32Dshows a calculation result of an orientation ratio of crystal grains having the plane orientation <001> on the viewing plane A, in which a colored region is a region showing crystal grains having the plane orientation <001> within the range of angle fluctuation between ±10° or less.

FIG. 32Eshows calculation results of orientation ratios of crystal grains having the plane orientations <001>, <301>, <201>, and <101> on the viewing plane B. The whole region of the colored regions is a region showing crystal grains having the plane orientation <x01> (x=0, 1, 2, 3) within the range of angle fluctuation between ±10° or less. The regions have different colors according to the value of x to differentiate regions corresponding to the plane orientations <001>, <301>, <201>, and <101>. Here, an overlap between plane orientations is excluded.

FIG. 32Fshows calculation results of orientation ratios of crystal grains having the plane orientations <001>, <301>, <201>, and <101> on the viewing plane C. The whole region of the colored regions is a region showing crystal grains having the plane orientation <x01> (x=0, 1, 2, 3) within the range of angle fluctuation between ±10° or less. Similarly toFIG. 32E, regions corresponding to the plane orientations are differentiated according to the value of x.

Table 9 shows orientation ratios of plane orientations on the viewing planes A to C and an orientation ratio of <x01> (x=0, 1, 2, 3) (i.e., the sum of orientation ratios of the orientations <001>, <301>, <201>, and <101> excluding an overlap) on the viewing planes B and C. Note that the ratios have been rounded off to the nearest whole number.

Table 9 shows that the orientation <001> within the range of an angle fluctuation of ±10° occupies 68%, i.e., 60% or more on the viewing plane A. In addition, it shows that <x01> (x=0, 1, 2, 3) occupies 72%, i.e., 60% or more on the viewing plane B. Note that an orientation ratio of <x01> (x=0, 1, 2, 3, 4, 5, 6) obtained according to similar calculation is 81%, i.e., 60% or more on the viewing plane B.

Further, it shows that <x01> (x=0, 1, 2, 3) occupies 81%, i.e., 60% or more on the viewing plane C. Note that an orientation ratio of <x01> (x=0, 1, 2, 3, 4, 5, 6) obtained according to similar calculation is 85%, i.e., 60% or more on the viewing plane C. In other words, the orientation ratio of <x01> (x=0, 1, 2, 3) is 60% or more, and the orientation ratio of <x01> (x=0, 1, 2, 3, 4, 5, 6) exceeds that of <x01> (x=0, 1, 2, 3). Furthermore, it shows that an orientation ratio of <x01> (x=0, 2, 3) excluding a plane orientation when x is 1 also is 60% or more on each of the viewing planes B and C.

This application is based on Japanese Patent Application serial no. 2006-077484 filed in Japan Patent Office on Mar. 20, 2006, the entire contents of which are hereby incorporated by reference.