Wiring substrate, manufacturing method thereof, semiconductor device, and manufacturing method thereof

A wiring substrate is provided, including an insulating resin layer which is provided on both surfaces of a sheet-like fibrous body and with which the sheet-like fibrous body is impregnated, and a through wiring provided in a region surrounded by the insulating resin layer. The through wiring is formed using a conductive material, the conductive material is exposed on both surfaces of the insulating resin layer, the sheet-like fibrous body is positioned in the conductive material, and the sheet-like fibrous body is impregnated with the conductive material. A manufacturing method of the wiring substrate is also provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wiring substrate which electrically or mechanically connects a semiconductor integrated circuit or a circuit substrate, and a semiconductor device using the wiring substrate.

2. Description of the Related Art

Prepreg in which a sheet-like fibrous body as a reinforcing material is impregnated with a thermosetting resin and the thermosetting resin is made in a semi-cured state has been used as a member of a circuit substrate and the like. For example, prepreg is known in which a conductor passes through an insulating layer and which is formed by opening a through hole in a predetermined position and filling the through hole with a conductive paste to become the conductor by hot pressing (see Patent Document 1). In this case, the through hole is opened in the prepreg by a laser, a drill, a punching machine, or the like.

Further, prepreg used as a sealing material of a semiconductor device is disclosed (see Patent Document 2).

REFERENCES

Patent Document

SUMMARY OF THE INVENTION

However, formation of a through hole in a composite substrate, such as prepreg, in which a fibrous body is impregnated with a resin (hereinafter also referred to as a resin-impregnated fibrous-body composite substrate), damages a sheet-like fibrous body as a reinforcing material, whereby the strength of the resin-impregnated fibrous-body composite substrate is decreased. In the case of using the resin-impregnated fibrous-body composite substrate as a sealing body, if a through hole is opened in the sealing body for formation of a through wiring, airtightness cannot be maintained, and thus the resin-impregnated fibrous-body composite substrate cannot function as the sealing material. Further, since an opening has to be formed in both the sheet-like fibrous body and the resin layer, there is a problem in that the number of manufacturing steps is increased.

In view of the foregoing problems, it is an object of the present invention to provide a conductive pattern which penetrates a resin-impregnated fibrous-body composite substrate while maintaining the strength of the sheet-like fibrous body. It is another object to use the resin-impregnated fibrous-body composite substrate provided with the penetrating conductive pattern as a sealing body of a semiconductor device.

One embodiment of the present invention is a wiring substrate including an insulating resin layer which is provided on both surfaces of a sheet-like fibrous body and with which the sheet-like fibrous body is impregnated, and a through wiring provided in a region surrounded by the insulating resin layer. This through wiring is formed using a conductive material, the conductive material is exposed on both surfaces of the insulating resin layer, the conductive material penetrates the sheet-like fibrous body so that a portion of the sheet-like fibrous body is positioned in the conductive material, and the sheet-like fibrous body is impregnated with the conductive material. By impregnation of the sheet-like fibrous body with the conductive material, electrical connection between the front and rear sides of the insulating resin layer can be realized. In this case, since the sheet-like fibrous body remains in an entire region of the wiring substrate without any portion being removed, the sheet-like fibrous body serves as a reinforcing material.

Another embodiment of the present invention is a semiconductor device which includes a resin-impregnated fibrous-body composite substrate including an insulating resin layer which is provided on both surfaces of a sheet-like fibrous body and with which the sheet-like fibrous body is impregnated, and a through wiring which is provided in a region surrounded by the insulating resin layer and formed using a conductive material. The conductive material is exposed on both surfaces of the insulating resin layer and the sheet-like fibrous body is impregnated with the conductive material. An integrated circuit chip having a bump exposed to a surface of an insulating layer is fixed to the semiconductor device. The bump of the integrated circuit chip is in close contact with the through wiring of the resin-impregnated fibrous-body composite substrate. The through wiring is formed so that the sheet-like fibrous body is impregnated with the conductive material. The sheet-like fibrous body remains in an entire region of the resin-impregnated fibrous-body composite substrate without any portion being removed; accordingly, the sheet-like fibrous body functions to maintain mechanical strength and airtightness.

Another embodiment of the present invention is a manufacturing method of a wiring substrate, including the steps of forming a through wiring by impregnating a region of a sheet-like fibrous body with a conductive resin and impregnating a region of the sheet-like fibrous body which is not impregnated with the conductive resin with an insulating resin layer.

Still another embodiment of the present invention is a manufacturing method of a semiconductor device including the steps of: forming an integrated circuit chip having a bump exposed to a surface of an insulating layer, forming a through wiring by impregnating a region of a sheet-like fibrous body with a conductive resin so as to be in contact with the bump, and impregnating a region of the sheet-like fibrous body which is not impregnated with the conductive resin with an insulating resin layer.

In a wiring substrate which uses a resin-impregnation fibrous-body composite material, even when a through wiring is provided, a strong wiring substrate capable of maintaining mechanical strength can be provided.

In the case where the resin-impregnated fibrous-body composite substrate provided with a through wiring is used as a sealing body of a semiconductor device, mechanical strength and air tightness can be maintained.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 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 is not construed as being limited to description of the embodiments. Note that identical portions or portions having similar functions in the drawings are denoted by the same reference numerals and detailed descriptions thereof are omitted.

Note that in this specification, a semiconductor device refers to an element or a device in general which functions by utilizing a semiconductor. Electric devices including electric circuits, liquid crystal display devices, light-emitting devices, and the like and electronic devices on which the electric devices are mounted are included in the category of semiconductor devices.

In Embodiment 1, the structure of a wiring substrate and manufacturing methods thereof will be described with reference toFIGS. 1A and 1BandFIGS. 2A to 2D.

FIGS. 1A and 1Bare each a top view of a sheet-like fibrous body113which is a fabric woven using yarn bundles for warp yarns and weft yarns.

The sheet-like fibrous body113is a woven fabric or a nonwoven fabric of an organic compound or an inorganic compound. Further, the sheet-like fibrous body113may be formed using a high-strength fiber.

The sheet-like fibrous body113may be formed using a woven fabric which is woven using bundles of fiber (single yarn) (hereinafter, referred to as yarn bundles) for warp yarns and weft yarns, or a nonwoven fabric obtained by stacking yarn bundles of plural kinds of fiber in a random manner or in one direction. In the case of a woven fabric, a plain-woven fabric, a twilled fabric, a satin-woven fabric, or the like can be appropriately used.

The yarn bundle may have a circular shape or an elliptical shape in cross section. As the yarn bundle, a yarn bundle may be used which has been subjected to fiber opening with a high-pressure water stream, high-frequency vibration using liquid as a medium, continuous ultrasonic vibration, pressing with a roll, or the like. A yarn bundle which is subjected to fiber opening has a large width, can reduce the number of single yarns in the thickness direction, and has an elliptical shape or a flat shape in its cross section. Further, by using a loosely twisted yarn as the yarn bundle, the yarn bundle is easily flattened and has an elliptical shape or a flat shape in cross section. Using a yarn bundle having an elliptical shape or a flat shape in cross section in this manner can reduce the thickness of the sheet-like fibrous body113. Accordingly, the thickness of a structure body120(FIGS. 2C and 2D) can be made small, and a thin semiconductor device can be manufactured.

As illustrated inFIG. 1A, the sheet-like fibrous body113is woven using warp yarns113aspaced at regular intervals and weft yarns113bspaced at regular intervals. Such a fibrous body has a region without the warp yarns113aand the weft yarns113b(referred to as a basket hole113c). In such a sheet-like fibrous body113, the fibrous body is further impregnated with an organic resin such as an insulating resin or a conductive resin, whereby adhesiveness of the sheet-like fibrous body113can be further increased.

Alternatively, the density of the warp yarns113aand the weft yarns113bmay be high and the proportion of the basket holes113cmay be low like the sheet-like fibrous body113illustrated inFIG. 1B. Typically, the size of the basket hole113cis preferably smaller than the area of a locally pressed portion. More typically, the basket hole113cpreferably has a rectangular shape having a side with a length greater than or equal to 0.01 mm and less than or equal to 0.2 mm. When the basket hole113cof the sheet-like fibrous body113has such a small area, even when pressure is applied by a member with a sharp tip (typically, a writing material such as a pen or a pencil), the pressure can be absorbed by the entire sheet-like fibrous body113.

Further, in order to enhance permeability of an organic resin into the inside of the yarn bundle, the yarn bundle may be subjected to surface treatment. For example, as the surface treatment, corona discharge, plasma discharge, or the like for activating a surface of the yarn bundle can be given. Further, surface treatment using a silane coupling agent or a titanate coupling agent can be given.

The high-strength fiber is specifically fiber with a high tensile modulus of elasticity or fiber with a high Young's modulus. As typical examples of high-strength fiber, polyvinyl alcohol fiber, polyester fiber, polyamide fiber, polyethylene fiber, aramid fiber, polyparaphenylene benzobisoxazole fiber, glass fiber, carbon fiber, and the like can be given. As the glass fiber, glass fiber using E glass, S glass, D glass, Q glass, or the like can be used. The sheet-like fibrous body113may be formed from one or more kinds of the above-described high-strength fibers.

FIGS. 2A to 2Ceach illustrate a semiconductor element115and a structure body120in which electrical conduction is realized using a conductive resin101without a through-hole provided. Note that in this specification, part including the sheet-like fibrous body113, an insulating resin114, the conductive resin101is referred to as the structure body120; however, the structure body120may be the one which does not include the conductive resin101and includes only the sheet-like fibrous body113and the insulating resin114.

The sheet-like fibrous body113is impregnated with the conductive resin101(seeFIG. 2B). In this embodiment, as the conductive resin101, any of copper (Cu), silver (Ag), nickel (Ni), gold (Au), platinum (Pt), palladium (Pd), tantalum (Ta), molybdenum (Mo), and titanium (Ti) or a conductive paste including an organic resin is used. More specifically, silver paste is used as the conductive resin101.

The conductive resin101serves as a through wiring. The conductive resin101may be processed to have various shapes in order to serve as a wiring.

Next, a region of the sheet-like fibrous body113, which is not impregnated with the conductive resin101, is impregnated with the insulating resin114(seeFIG. 2C).

As the insulating resin114, an organic resin may be used, and a thermosetting resin such as an epoxy resin, an unsaturated polyester resin, a polyimide resin, a bismaleimide-triazine resin, or a cyanate resin can be used, for example. Further, a thermoplastic resin such as a polyphenylene oxide resin, a polyetherimide resin, or a fluorine resin can be used. Furthermore, a plurality of the above-described thermosetting resins and thermoplastic resins may be used. When the above-described organic resin is used, the fibrous body can be firmly fixed to the element layer by thermal treatment. Note that the higher the glass transition temperature of the insulating resin114is, the less the insulating resin114is damaged by local pressing force, which is preferable.

Highly thermally-conductive filler may be dispersed in the insulating resin114or in the yarn bundles of fibers. As the highly thermally-conductive filler, an aluminum nitride, a bromine nitride, a silicon nitride, alumina, or the like can be given. As the highly thermally-conductive filler, a metal particle such as silver or copper can also be given. When the highly thermally-conductive filler is included in the organic resin or the yarn bundle, heat generated in the element layer can be easily released to the outside. Accordingly, thermal storage of the semiconductor device can be suppressed, and breakdown of the semiconductor device can be reduced.

As illustrated inFIG. 2C, a conductive region by which one surface of the structure body120can be electrically connected to the other surface can be formed without formation of a through hole (also referred to as a contact hole) in the structure body120, that is, without division of the sheet-like fibrous body113; accordingly, the strength of the structure body120can be maintained.

Alternatively, the insulating resin114may be formed in a region other than a region103which is to be electrically conductive as illustrated inFIG. 2D, and then the conductive resin101may be formed in the region103to obtain the structure illustrated inFIG. 2C.

The thus-formed resin-impregnated fibrous-body composite substrate can maintain mechanical strength and airtightness while including a through wiring.

In Embodiment 2, a structure of a semiconductor device using a resin-impregnated fibrous-body composite substrate which is provided with a through wiring, and a manufacturing method thereof will be described with reference toFIGS. 3A to 3D,FIGS. 4A to 4E,FIGS. 5A to 5D, andFIGS. 7A and 7B.

FIGS. 3A to 3Dare cross-sectional views of element layers according to this embodiment.

An element layer51includes a thin film transistor52a, a thin film transistor52b, an insulating film65, an insulating film66, and an insulating film67over an insulating layer56. The thin film transistor52aincludes a semiconductor layer including impurity regions53awhich are a source region and a drain region and a channel formation region63a, a gate insulating layer54, and a gate electrode55a. The thin film transistor52bincludes a semiconductor layer including impurity regions53bwhich are a source region and a drain region and a channel formation region63b, the gate insulating layer54, and a gate electrode55b.

The impurity regions53aof the thin film transistor52aand the impurity regions53bof the thin film transistor52beach include an impurity element imparting one conductivity type. As an impurity element imparting n-type conductivity, phosphorus (P), arsenic (As), or the like may be used. As an impurity element imparting p-type conductivity, boron (B) or the like may be used. The impurity regions53aand the impurity regions53bmay include different impurity elements imparting different conductivity types or the same impurity element imparting one conductivity type. In this embodiment, the impurity regions53ainclude phosphorus (P) and are n-type impurity regions, and the impurity regions53binclude boron (B) and are p-type impurity regions. In other words, the thin film transistor52ais an n-channel thin film transistor and the thin film transistor52bis a p-channel thin film transistor.

In each of the thin film transistor52aand the thin film transistor52b, the semiconductor layer is a layer formed of non-single-crystal semiconductor having a thickness greater than or equal to 10 nm and less than or equal to 100 nm, and more preferably greater than or equal to 20 nm and less than or equal to 70 nm. As the non-single-crystal semiconductor layer, a crystalline semiconductor layer, an amorphous semiconductor layer, a microcrystalline semiconductor layer, or the like can be given. As the semiconductor, silicon, germanium, a silicon-germanium compound, or the like can be given. In particular, it is preferable to apply a crystalline semiconductor which is formed by crystallization through rapid thermal annealing (RTA) or thermal treatment using an annealing furnace, or a crystalline semiconductor which is formed by crystallization through heat treatment and laser beam irradiation. In the heat treatment, a crystallization method using a metal element such as nickel which can promote crystallization of silicon semiconductor can be used.

In the case of performing crystallization by laser beam irradiation in addition to heat treatment, crystallization can be performed by continuously moving a melted zone of the crystalline semiconductor, which is melted by irradiation with a continuous wave laser beam or a high-repetition-rate ultrashort pulsed laser beam having a repetition rate of 10 MHz or higher and a pulse width of 1 nanosecond or shorter, preferably in the range of 1 to 100 picoseconds inclusive, along the laser beam irradiation direction. By using such a crystallization method, a crystalline semiconductor having a large grain diameter with a crystal grain boundary extending in one direction can be obtained.

The gate insulating layer54is formed using an inorganic insulator such as a silicon oxide or a silicon oxynitride with a thickness greater than or equal to 5 nm and less than or equal to 50 nm, preferably greater than or equal to 10 nm and less than or equal to 40 nm.

The gate electrode55aand the gate electrode55bcan be formed using metal, or a polycrystalline semiconductor to which an impurity element imparting one conductivity type is added. When 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 metal can 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 employed. At this time, by forming the first layer using metal nitride, the first layer can serve as a barrier metal. In other words, the metal of the second layer can be prevented from diffusing into the gate insulating layer or into the semiconductor layer that is provided in the lower than the gate insulating layer. In the case of employing a stacked structure, the gate electrode may have a shape in which the edge of the first layer extends beyond the edge of the second layer.

The thin film transistor52aand the thin film transistor52bwhich are formed by combination of the semiconductor layers, the gate insulating layer54, the gate electrode55a, the gate electrode55b, and the like can have various structures such as a single drain structure, an LDD (lightly doped drain) structure, and a gate overlapped drain structure. Here, the thin film transistors have a single-drain structure. Alternatively, the thin film transistor can have a multi-gate structure which is equivalent to a plurality of transistors connected in series, to which the same gate voltage is applied, a dual gate structure where a semiconductor layer is interposed between gate electrodes, an inverted staggered structure where a gate electrode is formed over the insulating layer56and a gate insulating layer and a semiconductor layer are formed over the gate electrode, or the like.

Wirings57a,57b,58a, and58bwhich are in contact with the impurity regions53aand the impurity regions53bwhich are the source regions and the drain regions are preferably formed by combination of a low-resistance material such as aluminum (Al) and a barrier metal using a high-melting-point metal material such as titanium (Ti) or molybdenum (Mo), e.g., a stacked structure of titanium (Ti) and aluminum (Al) or a stacked structure of molybdenum (Mo) and aluminum (Al).

As the thin film transistor, a thin film transistor using a metal oxide or an organic semiconductor material for a semiconductor layer can be used. As typical examples of the metal oxide, a zinc oxide, an oxide of zinc gallium indium, and the like can be given.

A typical example of a semiconductor device including the element layer51is a microprocessor (MPU) which controls another device or performs calculation and processing of data. An MPU includes a CPU, a main memory, a controller, an interface, an I/O port, and the like, and each of them can be formed using a thin film transistor, a resistor, a capacitor, a wiring, or the like.

A memory element62illustrated inFIG. 3Bis a nonvolatile memory element including a semiconductor layer including a channel formation region91and impurity regions92, a tunnel oxide layer64, a floating gate93, a control insulating layer94, and a control gate95.

The tunnel oxide layer64can be formed from a silicon oxide or formed to have a stacked structure of a silicon oxide and a silicon nitride, with a thickness of 1 nm to 10 nm, preferably 1 nm to 5 nm, by a low pressure CVD method, a plasma CVD method, or the like. Further, the tunnel oxide layer can be formed by oxidizing or nitriding a semiconductor layer by plasma treatment. Furthermore, a silicon oxide formed by a plasma CVD method may be oxidized or nitrided by plasma treatment. An insulating layer formed by the plasma treatment is dense, has high withstand voltage, and is excellent in reliability.

The floating gate93can be formed using a conductive layer, a polysilicon layer, a silicon dot, or the like. Instead of the floating gate, a charge storage layer formed from a silicon nitride, a germanium nitride, or the like may be used.

The control insulating layer94is formed of a single layer or a plurality of layers of a silicon oxide, a silicon nitride, a silicon oxynitride, an aluminum oxide, or the like by a low pressure CVD method, a plasma CVD method, or the like. The control insulating layer94is formed to have a thickness of 1 nm to 20 nm, preferably 5 nm to 10 nm.

The control gate95may be formed using a material similar to that of the gate electrode55aor the gate electrode55billustrated inFIG. 3A.

As a driving element for driving the memory element62, a thin film transistor52bmay be formed.

After the memory element62and the thin film transistor52bare formed, an insulating film65and an insulating film66are formed to cover the memory element62and the thin film transistor52b. A wiring97and a wiring98are formed over the insulating film66so as to be electrically connected to the impurity regions92. For the thin film transistor52b, a wiring57band a wiring58bas described above are formed. An insulating film67is formed to cover the insulating film66, the wiring97, the wiring98, the wiring57b, and the wiring58b. Thus, an element layer61including the memory element62is formed.

Examples of the memory element include, in addition to the structure of the memory element62, a nonvolatile memory element including a charge accumulation layer; a thin film transistor and a capacitor which is connected to the thin film transistor; a thin film transistor and a capacitor which is connected to the thin film transistor and includes a ferroelectric layer; an organic memory element in which an organic compound layer is interposed between a pair of electrodes; and the like.

As semiconductor devices having such a memory element, memory devices such as DRAM (dynamic random access memory), SRAM (static random access memory), FeRAM (ferroelectric random access memory), mask ROM (read only memory), EPROM (electrically programmable read only memory), EEPROM (electrically erasable and programmable read only memory), and flash memory can be given.

A photodiode72illustrated inFIG. 3Cincludes a wiring58afunctioning as a first electrode, a light receiving portion73, and a second electrode74. The light receiving portion73can be formed using a semiconductor layer containing amorphous or crystalline silicon. As typical examples of the semiconductor layer, a silicon layer, a silicon germanium layer, a silicon carbide layer, and a PN junction layer and a PIN junction layer of these layers can be given.

A thin film transistor52ais electrically connected to the photodiode72through the wiring58aand functions as a driving element. An insulating film65and an insulating film66are formed over the thin film transistor52a. A wiring57aand a wiring58aare formed over the insulating film66so as to be electrically connected to impurity regions of the thin film transistor52a. Further, the light receiving portion73which is electrically connected to the wiring58ais formed over the insulating film66and the second electrode74is formed over the light receiving portion73.

An insulating film67is formed to cover the insulating film66, the wiring57a, the wiring58a, the light receiving portion73, and the second electrode74. Thus, an element layer71including the photodiode72and the thin film transistor52ais formed.

As semiconductor devices including the photodiode72illustrated inFIG. 3C, an optical sensor, a solar cell, and the like can be given.

An element layer81illustrated inFIG. 3Dincludes a thin film transistor52a, a thin film transistor52b, an electrode84which is formed over an insulating film66and electrically connected to the thin film transistor52aor52b, and an antenna83which is formed over an insulating film67and electrically connected to the electrode84. The electrode84may be formed using a material and a manufacturing method similar to those of a wiring57a, a wiring58a, a wiring57b, or a wiring58bwhich is electrically connected to the thin film transistor52aor the thin film transistor52b.

The antenna83illustrated inFIG. 3Dis formed in such a manner that a droplet or paste which includes metal particles of one or more of silver (Ag), gold (Au), copper (Cu), nickel (Ni), platinum (Pt), palladium (Pd), tantalum (Ta), molybdenum (Mo), titanium (Ti), and the like is discharged by a droplet discharge method (an ink-jet method, a dispenser method, or the like), and it is dried and baked. Formation of the antenna by a droplet discharge method enables the number of steps to be reduced, and cost can be reduced accordingly.

Further, the antenna83may be formed by a screen printing method. In the case of using a screen printing method, as a material for the antenna83, a conductive paste where conductive particles having a particle size of several nanometers to several tens of micrometers are dissolved or dispersed in an organic resin is selectively printed. As the conductive particles, metal particles of one or more of silver (Ag), gold (Au), copper (Cu), nickel (Ni), platinum (Pt), palladium (Pd), tantalum (Ta), molybdenum (Mo), titanium (Ti), and the like; fine particles of silver halide; or dispersible nanoparticles can be used. In addition, as the organic resin included in the conductive paste, one or a plurality of organic resins each functioning as a binder, a solvent, a dispersant, or a coating of the metal particle can be used. Typically, an organic resin such as an epoxy resin or a silicone resin can be used. Further, in forming the conductive layer, baking is preferably performed after the conductive paste is printed.

Alternatively, the antenna83may be formed using gravure printing or the like instead of a screen printing method or may be formed using a conductive material by a plating method, a sputtering method, or the like.

As typical examples of semiconductor devices including the element layer81illustrated inFIG. 3D, an ID tag, an IC tag, an RF (radio frequency) tag, a wireless tag, an electronic tag, an RFID (radio frequency identification) tag, an IC card, an ID card, and the like (hereinafter, referred to as an RFID), which can transmit and receive information wirelessly, can be given. Further, semiconductor devices of this embodiment include an inlet in which an integrated circuit portion including a thin film transistor and the like and an antenna are sealed; and the inlet formed into a sticker or card shape. Further, when the area of a top surface of the semiconductor device is greater than or equal to 4 mm2, more preferably greater than or equal to 9 mm2, the antenna can be formed to have a large area. Accordingly, an RFID with a long communication distance with a communication instrument can be obtained.

As a signal transmission method of an RFID, an electromagnetic coupling method or an electromagnetic induction method (e.g., 13.56 MHz band) is applied. In the case of utilizing electromagnetic induction caused by a change in magnetic flux density, the top view of the antenna can be a ring shape (e.g., a loop antenna) or a spiral shape (e.g., a spiral antenna).

Alternatively, a microwave method (e.g., a UHF band (860 to 960 MHz band), a 2.45 GHz band, or the like) can be employed as the signal transmission method of an RFID. In that case, the shape such as the length of the antenna may be appropriately determined in consideration of the wavelength of the electromagnetic wave used for the signal transmission.

FIG. 7Aillustrates a structure in which a structure body120of this embodiment is applied to the element layer51including the thin film transistors52aand52b.

InFIG. 7A, the structure body120is provided so as to cover the element layer51including the thin film transistors52aand52b. The thin film transistor52bcan be electrically connected to an external terminal through the wiring58b, a wiring102, and a conductive resin101.

Further, a structure body may be provided on the other surface of the element layer51. In other words, both surfaces of the element layer51may each be provided with a structure body so that the element layer51is covered with a pair of facing structure bodies on both surfaces.

In the structure illustrated inFIG. 7B, one surface of the element layer51illustrated inFIG. 7Ais provided with a structure body120aand the other surface of the element layer51is provided with a structure body120b. At this time, it is preferable that a fibrous body and an insulating organic resin of the structure body120ahave the properties same as those of the structure body120bin order to reduce warpage. However, in the case of a use in which the front and the rear are distinguished from each other, it is not necessary that the structure bodies120aand120bare formed using materials having the same properties.

The organic resin with which the fibrous body is impregnated is firmly fixed in such a manner, whereby both surfaces of the element layer are supported by the fibrous bodies. Therefore, warpage of the entire semiconductor device can be reduced, which facilitates mounting of the semiconductor device including the element layer51on a laminate film, a sticker, or the like.

In the drawings of this specification, a sheet-like fibrous body113is illustrated as a woven which is plain-woven using a yarn bundle having an elliptical shape in cross section. Although the size of the thin film transistors52aand52bis larger than that of a yarn bundle of the sheet-like fibrous body113, the size of the thin film transistors52aand52bmay be smaller than that of a yarn bundle of the sheet-like fibrous body113.

Next, a manufacturing method to obtain the structure illustrated inFIG. 7Awill be described with reference toFIGS. 4A to 4EandFIGS. 5A to 5D.

As illustrated inFIG. 4A, a separation layer112is formed over a substrate111having an insulating surface. Then, the element layer51including the thin film transistor52aand the thin film transistor52bis formed over the separation layer112.

As the substrate111having an insulating surface, a substrate which can withstand a temperature at which the element layer51is formed is preferably used. Typically, a glass substrate, a quartz substrate, a ceramic substrate, a metal substrate in which an insulating layer is formed over at least one surface, an organic resin substrate, or the like can be used. Here, a glass substrate is used as the substrate111having an insulating surface.

The separation layer112is formed in such a manner that a layer having a thickness of 30 nm to 200 nm and includes an element selected from 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 (Si); an alloy material containing any of the elements described above as its main component; or a compound containing any of the elements described above as its main component is formed by a sputtering method, a plasma CVD method, a coating method, a printing method, or the like to be a single layer or a laminate. The crystalline structure of a layer containing silicon may be any one of an amorphous structure, a microcrystalline structure, or a polycrystalline structure. Here, a coating method means a method by which a solution is discharged on an object to form a film, and includes a spin coating method and a droplet discharge method, for example. A droplet discharge method is a method of forming a predetermined pattern by discharging a droplet of a composition containing particulates from a small hole.

In the case where the separation layer112has a single-layer structure, a tungsten layer, a molybdenum layer, or a layer containing a mixture of tungsten and molybdenum is preferably formed. Alternatively, a layer containing an oxide or an oxynitride of tungsten, a layer containing an oxide or an oxynitride of molybdenum, or a layer containing an oxide or an oxynitride of a mixture of tungsten and molybdenum is formed. Note that the mixture of tungsten and molybdenum corresponds, for example, to an alloy of tungsten and molybdenum.

In the case where the separation layer112has a stacked structure, preferably, a metal layer is formed as a first layer, and a metal oxide layer is formed as a second layer. Typically, a layer containing tungsten, molybdenum, or a mixture of tungsten and molybdenum is formed as the first-layer metal layer. As the second layer, a layer containing an oxide of tungsten, molybdenum, or a mixture of tungsten and molybdenum; a nitride of tungsten, molybdenum, or a mixture of tungsten and molybdenum; an oxynitride of tungsten, molybdenum, or a mixture of tungsten and molybdenum; or a nitride oxide of tungsten, molybdenum, or a mixture of tungsten and molybdenum is formed.

When the separation layer112has a stacked structure in which a metal layer is formed as the first layer and a metal oxide layer is formed as the second layer, the stacked structure may be formed by utilizing the following: a layer containing tungsten is formed as the metal layer, and an insulating layer formed of an oxide is formed thereover, whereby a layer containing an oxide of tungsten is formed as the metal oxide layer at the interface between the layer containing tungsten and the insulating layer. Moreover, the metal oxide layer may be formed in such a manner that the surface of the metal layer is subjected to thermal oxidation treatment, oxygen plasma treatment, treatment using a solution having strong oxidizing power such as ozone water, or the like.

Examples of an oxide of tungsten include WO2, W2O5, W4O11, WO3, and the like.

Although the separation layer112is formed to be in contact with the substrate111having an insulating surface according to the above process, the present invention is not limited to this process. An insulating layer to be a base may be formed so as to be in contact with the substrate111having an insulating surface, and the separation layer112may be provided to be in contact with the insulating layer. Here, as the separation layer112, a tungsten layer with a thickness of 30 nm to 70 nm is formed by a sputtering method.

An insulating layer56serving as a base layer is formed between the separation layer112and the thin film transistors52aand52b.

Next, the wiring102which is electrically connected to the wiring58bis formed over the insulating film67(seeFIG. 4B). The wiring102may be formed using a material similar to that of the wiring58b. The wiring102is also referred to as a bump and has a function of electrically connecting the element layer51to the conductive resin101to be formed later.

Then, the sheet-like fibrous body113is provided to cover the insulating film67and the wiring102(seeFIG. 4C).

Next, a region of the sheet-like fibrous body113over the wiring102is impregnated with the conductive resin101(seeFIG. 4D).

After impregnation with the conductive resin101, the other region of the sheet-like fibrous body113is impregnated with the insulating resin114(seeFIG. 4E).

Next, the structure body120is heated and pressure-bonded so that the insulating resin114, or the conductive resin101and the insulating resin114of the structure body120are plasticized or cured. In the case where the insulating resin114is an organic plastic resin, the insulating resin114which is plasticized is then cured by cooling to room temperature.

The insulating resin114uniformly spreads over surfaces of the insulating film67and the wiring102and is cured by heating and pressure bonding. Thus, the sheet-like fibrous body113is impregnated with the insulating resin114and the structure body120is firmly fixed to one side of the insulating film67and one side of the wiring102. A step of pressure-bonding the structure body120is performed under an atmospheric pressure or a reduced pressure.

Alternatively, the insulating resin114may be cured in the following manner: first heating is performed after the sheet-like fibrous body113is impregnated with the conductive resin101, and the sheet-like fibrous body113is impregnated with the insulating resin114, and then second heating is performed.

Note that in a manner similar to that ofFIG. 2D, the sheet-like fibrous body113may be impregnated with the insulating resin114in a region other than a region to be electrically conductive, and then the sheet-like fibrous body113may be impregnated with the conductive resin101in the region to be electrically conductive.

Next, in order to facilitate a subsequent separation step, a groove123as illustrated inFIG. 5Bmay be formed by irradiating the structure body120, the element layer51, and the separation layer112with a laser beam122from the side of the structure body120as illustrated inFIG. 5A. As the laser beam used for forming the groove123, a laser beam with a wavelength which is absorbed by any of layers included in the separation layer112, the element layer51, or the structure body120is preferably used. Typically, a laser beam in the ultraviolet region, visible region, or infrared region is appropriately selected for irradiation.

As a laser capable of emitting such a laser beam, 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 such as 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 appropriate.

Next, as illustrated inFIG. 5C, by using the groove123as a trigger, the substrate111having an insulating surface over which the separation layer112is formed and part of the element layer51are separated from each other by physical means at the interface between the separation layer112and the insulating layer56.

The physical means refers to dynamic means or mechanical means, which applies some dynamical energy (mechanical energy). Typically, the physical means is an action of applying mechanical force (e.g., a peeling process with human hands or with a gripper, or a separation process by rotating a roller). At this time, when an adhesive sheet which can be separated by light or heat is provided over a surface of the structure body120, separation can be performed more easily.

Further, the element layer51may be separated from the separation layer112after a liquid is dropped into the groove123to allow the liquid to be infiltrated into the interface between the separation layer112and the insulating layer56. In this case, a liquid may be dropped only into the groove123, or the substrate111having an insulating surface, the element layer51, and the structure body120may be wholly soaked in a liquid so that the liquid may be infiltrated from the groove123into the interface between the separation layer112and the element layer51.

Alternatively, inFIG. 5B, a method can be employed in which a fluoride gas such as NF3, BrF3, or ClF3is introduced into the groove123, and the separation layer is removed by etching with the use of the fluoride gas so that part of the element layer51is separated from the substrate111having an insulating surface.

In the above-described manner, a semiconductor device can be obtained in which the element layer51formed in contact with one surface of the structure body120is electrically connected to a terminal, a wiring, a circuit, another semiconductor element, or the like formed on the other surface of the structure body120without forming a through hole in the structure body120.

In the case where a plurality of semiconductor devices are included in the element layer51, the plurality of semiconductor devices may be obtained by dividing the element layer51and the structure body120. With such a step, a plurality of semiconductor devices can be manufactured.

When the element layer51and the structure body120are divided to obtain a plurality of semiconductor devices, selective division is possible by dicing, scribing, using a cutting machine having an edged tool such as scissors or a knife, laser cutting, or the like.

In the case where the resin-impregnated fibrous-body composite substrate provided with a through wiring as described above is used as a sealing body or a protective material of a semiconductor device, mechanical strength and airtightness can be maintained.

The prepreg of Example 1 was manufactured in the following manner: a conductive resin was printed on a glass cloth, heating was performed, an insulating resin was printed, and then heating was performed.

As the conductive resin, silver paste including silver powder, 2-(2-butoxyethoxy)ethyl acetate, and an epoxy resin was used. As the insulating resin, an insulating resin including an epoxy resin and an amine curing agent was used.

FIG. 6Ashows an optical micrograph of the thus-formed prepreg seen from the side on which the conductive resin is printed.FIG. 6Bshows an optical micrograph seen from the rear side.

As shown inFIG. 6A, the conductive resin and the insulating resin were arranged without being mixed with each other.

In addition, it is seen fromFIG. 6Bthat the conductive resin has gone through the glass cloth and is exposed on the rear surface.

This application is based on Japanese Patent Application serial no. 2008-151227 filed with Japan Patent Office on Jun. 10, 2008, the entire contents of which are hereby incorporated by reference.