Source: https://patents.google.com/patent/JP3684578B2/en
Timestamp: 2020-01-17 13:26:08
Document Index: 436244341

Matched Legal Cases: ['art 1', 'art 2', 'art 3', 'art 4', 'art 946', 'arts 944', 'art 946']

JP3684578B2 - Liquid crystal device and electronic device - Google Patents
JP3684578B2
JP3684578B2 JP53819399A JP53819399A JP3684578B2 JP 3684578 B2 JP3684578 B2 JP 3684578B2 JP 53819399 A JP53819399 A JP 53819399A JP 53819399 A JP53819399 A JP 53819399A JP 3684578 B2 JP3684578 B2 JP 3684578B2
JP53819399A
1999-03-19 Application filed by セイコーエプソン株式会社 filed Critical セイコーエプソン株式会社
1999-03-19 Priority to PCT/JP1999/001433 priority patent/WO1999047972A1/en
2005-08-17 Publication of JP3684578B2 publication Critical patent/JP3684578B2/en
The present invention belongs to the technical field of an active matrix driving type liquid crystal device driven by a thin film transistor (hereinafter referred to as TFT as appropriate), and is particularly used for a liquid crystal projector or the like, in which a light shielding film is provided on the lower side of a TFT. It belongs to the technical field of equipment.
Conventionally, when this type of liquid crystal device is used as a light valve in a liquid crystal projector or the like, projection light is generally incident from the side of the counter substrate that is disposed opposite to the TFT array substrate with the liquid crystal layer interposed therebetween. Here, when the projection light is incident on a channel region composed of an a-Si (amorphous silicon) film or a p-Si (polysilicon) film of the TFT, a photocurrent is generated in this region due to a photoelectric conversion effect, The transistor characteristics of the TFT deteriorate. Therefore, a light shielding film made of a metal material such as Cr (chromium) or resin black is generally formed on the counter substrate at a position facing each TFT. This light shielding film defines the opening area of each pixel (that is, the area through which the projection light is transmitted), thereby improving the contrast and preventing color mixture of the color material in addition to shielding the TFT p-Si layer. Plays.
In this type of liquid crystal device, a positive stagger type or coplanar type a-Si or p-Si TFT employing a top gate structure (that is, a structure in which a gate electrode is provided above the channel on the TFT array substrate) is used. In this case, it is necessary to prevent a part of the projection light from entering the TFT channel from the TFT array substrate side as return light by the projection optical system in the liquid crystal projector. Similarly, the projection light passes through the projection optical system after being emitted from the reflected light from the surface of the TFT array substrate when the projection light passes or from other liquid crystal devices when a plurality of liquid crystal devices are used in combination for color. It is also necessary to prevent a part of the incoming projection light from entering the TFT channel as return light from the TFT array substrate side. For this reason, in Japanese Patent Application Laid-Open No. 9-127497, Japanese Patent Publication No. 3-52611, Japanese Patent Application Laid-Open No. 3-125123, Japanese Patent Application Laid-Open No. 8-171101, etc., a TFT is formed on a TFT array substrate made of a quartz substrate. A liquid crystal device has also been proposed in which a light-shielding film is formed from, for example, an opaque refractory metal at an opposing position (that is, below the TFT).
On the other hand, in this type of liquid crystal device, by applying a scanning signal to the gate electrode, the time for holding the voltage in the pixel electrode is made longer than the time for supplying the image signal to the pixel electrode by making the TFT conductive. Therefore, in general, a storage capacitor is generally added to the pixel electrode so that the liquid crystal driving voltage can be applied for a sufficient time even when the duty ratio is small. In this case, a system in which a part of the capacitor line formed along the scanning line is configured as the other storage capacitor electrode is generalized.
In the liquid crystal device, there is a strong general demand for image quality improvement, and for this reason, it is important to increase the driving frequency of the liquid crystal device.
However, in order to add a storage capacitor to the pixel electrode as described above, for example, when using a high temperature process having a process of exposing the substrate temperature to a high temperature such as 900 degrees, a capacitor line including one storage capacitor electrode is connected. Since it is formed of the same polysilicon film as the scanning line, it is difficult to reduce the resistance as compared with a wiring made of a low-resistance metal film such as Al like a data line. For this reason, the resistance and time constant of the capacitance line increase, and the capacitance of the capacitance line fluctuates due to the capacitive coupling with each data line in the capacitance line crossed under the plurality of data lines, thereby causing a transverse crosstalk. There is a problem that image degradation occurs due to ghosts and the like.
More specifically, as shown in FIG. 20, when displaying an image 801 in which a black portion is drawn with high contrast against a gray background, other pixels are arranged on a pixel column in one row along the scanning line. When an image signal having a voltage (here, a voltage corresponding to black) that is partially different from a voltage of the image signal (here, a voltage corresponding to gray) is applied to the capacitor line due to such capacitive coupling Before the potential fluctuation becomes stable, writing to each pixel in the pixel row is performed. For this reason, in the actually displayed image 802, voltage shortage occurs at the left and right pixels of the pixel to which an image signal of a partially different voltage to be displayed in black is given, and the entire row to be displayed in gray becomes whitish. That is, horizontal crosstalk, ghost, etc. occur.
In this case, in particular, the point in time when the image signal having a partially different voltage to be displayed in black is closer to the end point of writing for each scanning line, that is, the number of pixels to be displayed in black is one. When the scanning signal is supplied from one of the left and right sides on the scanning line, the closer the pixel is to the other side, or the closer the pixel is to the center when the scanning signal is supplied from both sides, the capacitive line by capacitive coupling. Since the writing to each pixel in the pixel row is performed before the potential fluctuation becomes stable, horizontal crosstalk, ghost, and the like are likely to occur remarkably.
Such lateral crosstalk, ghost, and the like are likely to occur because the time constant of the capacitance line relatively increases as the drive frequency increases as in the case of so-called XGA, SXGA and other types of liquid crystal devices. . Further, when precharging is performed to supply a precharge signal of a predetermined voltage level to the data line in advance of the image signal so that the voltage of the image signal can be written to the data line with a small load, Since it is necessary to ensure a certain length of the horizontal blanking period, after image signals having partially different voltages are applied at a time close to the end of writing of each scanning line, It is impossible to secure a sufficient time until the fluctuation of the potential becomes stable. For this reason, there is a problem that the above-described lateral crosstalk, ghost, and the like are difficult to prevent when precharging.
In order to solve such problems as lateral crosstalk and ghost, for example, a data line inversion driving method (1S inversion driving method) in which the polarity of the driving voltage applied to the liquid crystal is inverted for each data line, or for each pixel. The dot inversion driving method that inverts is effective, but according to these methods, the liquid crystal disclination (alignment failure) along the data lines and the scanning lines is strongly generated to cause display deterioration. Under the basic requirement of increasing the aperture ratio of the pixel region, these methods are not practical.
The present invention has been made in view of the above-described problems, and an object thereof is to provide a liquid crystal device capable of displaying a high-quality image with a relatively simple configuration using a storage capacitor and a light shielding film.
In order to solve the above problems, a first liquid crystal device according to the present invention has a liquid crystal sandwiched between a pair of substrates, and on one of the pair of substrates, a plurality of crossing data lines and a plurality of data lines are provided. A plurality of thin film transistors provided corresponding to intersections of the plurality of data lines and the plurality of scanning lines, a plurality of pixel electrodes provided corresponding to the plurality of thin film transistors, and the plurality of thin film transistors A plurality of capacitor lines each extending in a direction intersecting with the data lines, and each of the plurality of thin film transistors extending in a direction intersecting with the plurality of data lines; At least partially covering the plurality of data lines and at least partially facing each of the plurality of capacitor lines. On the other hand, each of the plurality of pixels includes a plurality of light shielding films electrically connected to the plurality of capacitor lines, and an interlayer insulating film interposed between the plurality of light shielding films and the plurality of thin film transistors. The capacitor line and the plurality of light shielding films are electrically connected through a contact hole opened in the interlayer insulating film at a position overlapping the plurality of data lines when viewed from the one substrate side. To do.
According to the first liquid crystal device of the present invention, the plurality of capacitor lines that respectively provide the storage capacitors for the plurality of pixel electrodes are arranged in a direction intersecting with the plurality of data lines along with the plurality of scanning lines (that is, Each of the lines is extended (parallel to or substantially parallel to each scanning line). On the other hand, the plurality of light-shielding films extend in directions intersecting with the plurality of data lines (that is, parallel or substantially parallel to the scanning lines), and at least channel regions of the plurality of thin film transistors are formed on one substrate. It is provided on one of the substrates at positions covering each when viewed from the side. Accordingly, in the channel region of the thin film transistor, the return light and the like incident from the one substrate side are shielded by the plurality of light shielding films, so that deterioration of characteristics due to the return light and the like of the thin film transistor can be prevented.
The plurality of light-shielding films are provided on one substrate at positions that at least partially face the plurality of capacitance lines, and each one or a plurality of pixels in a direction intersecting the plurality of data lines, Each of the capacitor lines is electrically connected. For this reason, the resistance of the capacitor line can be significantly reduced by the resistance of the plurality of light shielding films. For example, if the capacitor line is formed of a polysilicon film and the plurality of light shielding films are formed of a conductive refractory metal film, the resistance of the capacitor line in the direction along the scanning line is dominated by the resistance of the plurality of light shielding films. it can. That is, the resistance of the capacitor line can be greatly reduced.
As a result, since the storage capacitors are respectively provided to the plurality of pixel electrodes by the low-resistance capacitor lines, even if the drive frequency of the liquid crystal device is increased, the data lines and the capacitor lines as in the conventional example described above are used. Lateral crosstalk, ghosts, and the like resulting from potential fluctuations of the capacitance line due to capacitive coupling are reduced, and high-quality image display can be performed. Even if the precharge method described above is employed, the problem as in the conventional example does not occur.
Further, the plurality of light shielding films extend in the direction intersecting with the data lines, and are composed of striped light shielding films divided into a plurality of directions along the data lines. Compared to the case where a grid-like light shielding film wiring formed integrally around the opening region is provided, each film in the laminated structure composed of the light shielding film wiring, the interlayer insulating film, the polysilicon film, the metal film, etc. Stress caused by heating and cooling during the manufacturing process due to the difference in physical properties of the materials is remarkably reduced. Therefore, it is possible to prevent the occurrence of cracks in the light shielding film and the like and improve the yield.
In addition to these, a redundant structure can be realized in which a plurality of light-shielding films can replace the capacitance lines even if the capacitance lines are broken in the middle due to foreign matters or the like.
In order to solve the above-described problem, the second liquid crystal device of the present invention has a liquid crystal sandwiched between a pair of substrates. On one of the pair of substrates, a plurality of data lines and a plurality of intersecting data lines are provided. A plurality of thin film transistors provided corresponding to intersections of the plurality of data lines and the plurality of scanning lines, a plurality of pixel electrodes provided corresponding to the plurality of thin film transistors, and the plurality of thin film transistors A plurality of capacitor lines each extending in a direction intersecting with the data lines, and each of the plurality of pixel electrodes being provided with a storage capacitor, and extending in a direction intersecting with the plurality of data lines, and at least one of the plurality of thin film transistors. The channel region is provided at a position covering each of the one substrate when viewed from the one substrate side and a position at least partially facing each of the plurality of scanning lines, and in a direction intersecting the plurality of data lines. Or a plurality of light shielding films electrically connected to the plurality of capacitance lines for each of the plurality of pixels, and an interlayer insulating film interposed between the plurality of light shielding films and the plurality of thin film transistors, and the plurality of capacitance lines. The plurality of light shielding films are electrically connected through contact holes formed in the interlayer insulating film at positions overlapping the plurality of data lines when viewed from the one substrate side.
According to the second liquid crystal device of the present invention, as in the case of the above-described first liquid crystal device of the present invention, the plurality of capacitance lines that respectively provide the storage capacitors to the plurality of pixel electrodes are the plurality of scanning lines. Each of them extends in a direction crossing a plurality of data lines alongside each other. On the other hand, the plurality of light shielding films extend in the direction intersecting with the plurality of data lines, respectively, and cover at least the channel regions of the plurality of thin film transistors when viewed from the one substrate side. Is provided. The plurality of light shielding films are electrically connected to the plurality of capacitor lines for each of one or a plurality of pixels in the direction intersecting the plurality of data lines. For this reason, the same operations and effects as those of the first liquid crystal device of the present invention described above can be obtained.
In the second liquid crystal device, in particular, the light shielding film is provided on one substrate at a position at least partially facing the scanning line. That is, at this position, a scanning line is formed on the light shielding film via a first interlayer insulating film that is much thicker than, for example, a gate insulating film constituting a thin film transistor. For this reason, even if an abnormally shaped portion such as an unintended protrusion in the manufacturing process is formed on the light shielding film, the light shielding film may be short-circuited with the scanning line due to the protrusion breaking through the first interlayer insulating film. Can be made extremely low. In particular, when a semiconductor layer, a gate insulating film, and a capacitor line are further stacked on the projection formed on the light shielding film, the gate insulating film is extremely thin through the semiconductor layer. The structure in which the light shielding film is formed at the position facing the scanning line in the second liquid crystal device of the present invention has been described above in consideration of the possibility that the semiconductor layer and the capacitor line are short-circuited through Compared with the first liquid crystal device of the present invention, it is more advantageous in improving the process yield.
In one aspect of the first or second liquid crystal device of the present invention, the storage capacitor is provided by a first storage capacitor electrode and a second storage capacitor electrode, and the first storage capacitor electrode is connected to the pixel electrode of the thin film transistor. The second storage capacitor electrode is formed of the capacitor line, and the first storage capacitor electrode is lower than the second storage capacitor electrode. It is formed in the side.
According to this aspect, the capacitor line and the scanning line are made of the same conductive thin film such as a polysilicon film, and the dielectric film of the storage capacitor and the gate insulating film of the thin film transistor are, for example, a high-temperature thermal oxide film or the like The storage capacitor electrode made of the same insulating thin film and arranged opposite to the capacitor line is extended from a semiconductor layer such as a polysilicon film, for example, so that the laminated structure formed on one substrate can be simplified. Further, since both the capacitor line and the scanning line can be formed at the same time, or both the dielectric film and the gate insulating film can be formed at the same time in the same thin film forming process, it is very advantageous in manufacturing.
In this aspect, each of the plurality of light shielding films is provided on the lower layer side of the thin film transistor, and is disposed opposite to the first storage capacitor electrode via the first interlayer insulating film, so that a storage capacitor is provided. You may comprise.
With this configuration, a structure in which storage capacitors are provided on both sides of the first storage capacitor electrode, that is, a double storage capacitor structure is constructed, so that the storage capacity is further increased, and flicker and burn-in in the display image are prevented. The function to prevent is improved.
In another aspect of the first or second liquid crystal device of the present invention, the first interlayer insulating film is interposed between the capacitance line and the plurality of light shielding films, and the plurality of capacitance lines The plurality of light shielding films are electrically connected to the first interlayer insulating film through contact holes opened for each of the one or a plurality of pixels.
According to this aspect, the plurality of capacitance lines and the plurality of light shielding films are connected to the first interlayer insulating film via the contact holes opened for each one or a plurality of pixels. A highly electrical connection state can be realized between the two.
In the aspect in which the contact hole is opened, the contact hole may be formed below the data line as viewed from the other substrate side of the pair of substrates.
With this configuration, the contact hole is opened under the data line, that is, the contact hole is out of the opening region of the pixel portion, and is extended from the thin film transistor and the semiconductor layer of the thin film transistor. Since one electrode of the storage capacitor is provided in the portion of the first interlayer insulating film where the electrode is not formed, the pixel region can be effectively used.
In each aspect in which these contact holes are opened, the contact hole may be configured such that a planar shape parallel to the one substrate is, for example, a circle such as a true circle or an ellipse.
With this configuration, when a wet etching process is used in the manufacturing process to open the contact hole, an etching solution is formed at the interface between the plurality of light shielding films and the adjacent films (that is, the first interlayer insulating film, etc.). Can reduce the possibility of cracks entering. That is, if an attempt is made to open a contact hole having a square shape such as a square shape, the etching solution is particularly likely to enter the corner portion and stress concentration is likely to occur, and cracks are likely to occur at the corner portion.
In each of the embodiments in which these contact holes are opened, the plurality of light-shielding films each have a first region in which a planar shape parallel to the one substrate is formed along the scanning line, and the first region. And a second region extending along the data line, and the contact hole may be formed in the second region.
With this configuration, the stress applied to the light-shielding film is relieved during the manufacturing process depending on how close the tip of the second region is to the contact hole, thereby preventing cracks more effectively. Thus, the yield can be improved.
In another aspect of the first or second liquid crystal device of the present invention, the capacitor line and the plurality of light shielding films are connected to a constant potential source.
According to this aspect, since the plurality of light shielding films are connected to the constant potential source, the light shielding films are set to a constant potential. Accordingly, it is possible to prevent the potential fluctuation of the light shielding film wiring from adversely affecting the thin film transistor disposed opposite to the light shielding film. Since the capacitor line is also at a constant potential, it can function well as a storage capacitor electrode. In this case, the constant potential of the constant potential source may be equal to the ground potential, for example.
In this aspect, the constant potential source may be configured to be a constant potential source supplied to a peripheral circuit for driving the liquid crystal device.
According to this configuration, the constant potential source is a constant potential source such as a negative power source or a positive power source supplied to peripheral circuits such as a scanning line driving circuit and a data line driving circuit. The light shielding film and the capacitor line can be set to a constant potential without providing a circuit connection terminal.
Alternatively, a counter electrode may be formed on the other of the pair of substrates, and the constant potential source may be a constant potential source supplied to the counter electrode.
With this configuration, the constant potential source is a constant potential source such as a negative power source or a positive power source supplied to the counter electrode, so that there is no need to provide a special potential wiring or an external circuit connection terminal. The capacitor line can be set to a constant potential.
In another aspect of the first or second liquid crystal device of the present invention, each of the plurality of light shielding films is electrically connected to a capacitor line for forming a storage capacitor to be applied to adjacent upstream or downstream pixels. .
With this configuration, each of the plurality of light-shielding films serves as a capacitor line for providing a storage capacitor to its own capacitor line, that is, a pixel electrode connected to the TFT in which the channel region is located on the light-shielding film. Compared with the case of electrical connection, there are fewer steps with respect to other regions where the pixel TFT, the capacitor line, and the light shielding film are formed so as to overlap the data line along the edge of the opening region of the pixel portion. Here, the adjacent capacitance line, the previous-stage capacitance line, or the subsequent-stage capacitance line is adjacent to the capacitance line for forming a storage capacitor to be applied to the pixel electrode connected to the TFT in which the channel region is located on the light shielding film. It means a capacitor line for providing a storage capacitor to the pixel electrode. Thus, when there are few steps, the liquid crystal disclination caused by the steps can be reduced.
In another aspect of the first or second liquid crystal device of the present invention, each of the plurality of light shielding films is electrically connected to the capacitor line of its own stage.
With such a configuration, the level difference between the region where the pixel TFT, the capacitor line, and the light shielding film are formed over the data line becomes large, but the capacitance line and the light shielding film can be relatively easily formed by a contact hole or the like. Can be electrically connected.
In another aspect of the first or second liquid crystal device of the present invention, at least one of the plurality of interlayer insulating films formed on the substrate includes the thin film transistor, the data line, the scanning line, and the capacitor. A portion facing at least one of the lines is formed in a concave shape so that the side facing the liquid crystal of the film formed at a position closest to the liquid crystal among the plurality of interlayer insulating films is flattened. ing. In this configuration, since the side facing the liquid crystal of the interlayer insulating film formed at the position closest to the liquid crystal is flattened, the surface of the interlayer insulating film formed at the position closest to the liquid crystal according to the degree of the flattening The disclination (defective alignment) caused by the unevenness of the liquid crystal can be reduced.
The present invention is a projection type comprising a light source, a liquid crystal light valve that performs modulation corresponding to image information when light emitted from the light source is incident, and a projection unit that projects light modulated by the liquid crystal light valve. In the display device, the liquid crystal light valve includes a liquid crystal device in which liquid crystal is sandwiched between a first substrate disposed on a light incident side and a second substrate disposed on an emission side, and an outer side of the first substrate. A plurality of pixel electrodes arranged in a matrix on the second substrate, and a plurality of the pixel electrodes arranged on the second substrate. A plurality of thin film transistors that respectively drive the pixel electrodes, a plurality of data lines and a plurality of scanning lines that are respectively connected to the plurality of thin film transistors and intersect each other, and the plurality of data lines aligned with the plurality of scanning lines. Those who cross Each of the plurality of thin film transistors, and each of the plurality of thin film transistors is extended in a direction intersecting with the plurality of data lines. The plurality of capacitors provided for each of one or a plurality of pixels provided in a position covering each of the plurality of capacitor lines as viewed from the substrate side and a position at least partially facing each of the plurality of capacitor lines. And a plurality of light shielding films electrically connected to the lines, and a first interlayer insulating film interposed between the plurality of light shielding films and the thin film transistor.
According to this aspect, the leakage current due to the return light can be prevented by forming the light shielding film between the second substrate and the thin film transistor. Further, since it is possible to prevent the return light from affecting the liquid crystal device, it is not necessary to attach the polarizing means with the antireflection film to the liquid crystal device as in the prior art. Therefore, the second polarizing means can be formed apart without being attached to the liquid crystal device, so that the temperature rise of the liquid crystal device can be prevented.
The present invention is an electronic device including the first or second liquid crystal device.
According to this aspect, since the electronic apparatus includes the above-described liquid crystal device of the present invention, the reliability of the device is high due to the redundant structure, display deterioration such as lateral crosstalk is reduced, and the return light is not affected. A liquid crystal device with excellent light shielding performance enables high-quality image display.
FIG. 1 is an equivalent circuit of various elements, wirings, and the like provided in a plurality of matrix pixels that form an image display area in the first embodiment of the liquid crystal device.
FIG. 2 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light shielding films and the like are formed in the first embodiment of the liquid crystal device.
3 is a cross-sectional view taken along line AA ′ of FIG.
FIG. 4 is a block diagram of a pixel unit and peripheral circuits provided on the TFT array substrate in the first embodiment of the liquid crystal device.
FIG. 5 is a timing chart of various signals related to precharging.
FIG. 6 is a process diagram (part 1) illustrating the manufacturing process of the first embodiment of the liquid crystal device in order.
FIG. 7 is a process diagram (part 2) illustrating the manufacturing process of the first embodiment of the liquid crystal device in order.
FIG. 8 is a process diagram (part 3) illustrating the manufacturing process of the first embodiment of the liquid crystal device in order.
FIG. 9 is a process diagram (part 4) illustrating the manufacturing process of the first embodiment of the liquid crystal device in order.
FIG. 10 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light shielding films and the like are formed in the second embodiment of the liquid crystal device.
FIG. 11 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light-shielding films and the like are formed in the third embodiment of the liquid crystal device.
FIG. 12 is a plan view of a plurality of adjacent pixel groups on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light-shielding films and the like are formed in the fourth embodiment of the liquid crystal device.
FIG. 13 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light shielding films and the like are formed in the fifth embodiment of the liquid crystal device.
FIG. 14 is a plan view of a plurality of adjacent pixel groups on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light-shielding films, and the like are formed in the sixth embodiment of the liquid crystal device.
FIG. 15 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light shielding films and the like are formed in the seventh embodiment of the liquid crystal device.
FIG. 16 is a cross-sectional view taken along the line AA ′ of FIG. 2 in the eighth embodiment of the liquid crystal device.
FIG. 17 is a cross-sectional view taken along the line AA ′ of FIG. 2 in the ninth embodiment of the liquid crystal device.
FIG. 18 is a plan view of the TFT array substrate in each embodiment of the liquid crystal device as viewed from the counter substrate side together with the components formed thereon.
19 is a cross-sectional view taken along the line HH ′ of FIG.
FIG. 20 is a conceptual diagram for explaining display deterioration due to lateral crosstalk.
FIG. 21 is a configuration diagram of a projection display device which is an example of an electronic apparatus using a liquid crystal device.
(Configuration and operation of liquid crystal device according to first embodiment)
The configuration and operation of the first embodiment of the liquid crystal device according to the present invention will be described with reference to FIGS. FIG. 1 is an equivalent circuit of various elements, wirings, and the like in a plurality of pixels formed in a matrix that forms an image display area of a liquid crystal device. 2 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light-shielding films, and the like are formed. FIG. 3 is a cross-sectional view taken along line AA ′ of FIG. It is. FIG. 4 is a plan view showing a two-dimensional wiring layout of the light shielding film on the TFT array substrate together with peripheral circuits, and FIG. 5 is a timing chart of various signals related to precharging. In FIG. 3, the scale of each layer and each member is different in order to make each layer and each member recognizable on the drawing.
In FIG. 1, a plurality of pixels formed in a matrix form constituting the image display area of the liquid crystal device according to the present embodiment has a plurality of pixel electrodes 9 a and a plurality of TFTs 30 for controlling the pixel electrodes 9 a formed in a matrix form. The data line 6 a for supplying an image signal is electrically connected to the source region of the TFT 30. The image signals S1, S2,..., Sn written to the data lines 6a may be supplied line-sequentially in this order, or may be supplied for each group to a plurality of adjacent data lines 6a. good. Further, the scanning line 3a is electrically connected to the gate of the TFT 30, and the scanning signals G1, G2,..., Gm are applied to the scanning line 3a in a pulse-sequential manner in this order at a predetermined timing. ing. The pixel electrode 9a is electrically connected to the drain of the TFT 30, and by closing the switch of the TFT 30 as a switching element for a certain period, the image signals S1, S2,. Write at the timing. Image signals S1, S2,..., Sn written to the liquid crystal via the pixel electrode 9a are held for a certain period with a counter electrode (described later) formed on a counter substrate (described later). . Here, in order to prevent the held image signal from leaking, a storage capacitor 70 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9a and the counter electrode. For example, the voltage of the pixel electrode 9a is held by the storage capacitor 70 for a time that is three orders of magnitude longer than the time when the source voltage is applied. Thereby, the holding characteristics are further improved, and a liquid crystal device with a high contrast ratio can be realized. As a method of forming the storage capacitor 70, it goes without saying that the capacitor line 3b, which is a wiring for forming a capacitor, may be provided, or a capacitor may be formed between the scanning line 3a in the previous stage. Yes.
In FIG. 2, on the TFT array substrate of the liquid crystal device, a plurality of transparent pixel electrodes 9a (outlined by dotted line portions 9a ′) are provided in a matrix, and the vertical and horizontal boundaries of the pixel electrodes 9a are provided. A data line 6a, a scanning line 3a, and a capacitor line 3b are provided along each line. The data line 6a is electrically connected to a source region to be described later in the semiconductor layer 1a made of a polysilicon film through the contact hole 5, and the pixel electrode 9a is to be described later in the semiconductor layer 1a through the contact hole 8. Electrically connected to the drain region. In addition, the scanning line 3a is disposed so as to face a channel region (a hatched region in the right-downward direction in the drawing) of the semiconductor layer 1a. A first light-shielding film 11a in the pixel portion is provided in a region indicated by a diagonal line rising to the right in the drawing. That is, the first light shielding film 11a is provided in the pixel portion at a position where the TFT including the channel region of the semiconductor layer 1a, the data line 6a, the scanning line 3a, and the capacitor line 3b overlap each other when viewed from the TFT array substrate side. .
As shown in FIG. 3, the liquid crystal device includes a TFT array substrate 10 that constitutes an example of one transparent substrate, and a counter substrate 20 that constitutes an example of the other transparent substrate disposed opposite thereto. Yes. The TFT array substrate 10 is made of, for example, a quartz substrate or a silicon substrate, and the counter substrate 20 is made of, for example, a glass substrate or a quartz substrate. A pixel electrode 9a is provided on the TFT array substrate 10, and an alignment film 16 that has been subjected to a predetermined alignment process such as a rubbing process is provided above the pixel electrode 9a. The pixel electrode 9a is made of a transparent conductive thin film such as an ITO (Indium Tin Oxide) film. The alignment film 16 is made of an organic thin film such as a polyimide thin film.
On the other hand, the counter substrate 20 is provided with a counter electrode (common electrode) 21 over the entire surface thereof, and an alignment film 22 subjected to a predetermined alignment process such as a rubbing process is provided below the counter electrode 20. ing. The counter electrode 21 is made of a transparent conductive thin film such as an ITO film. The alignment film 22 is made of an organic thin film such as a polyimide thin film.
As shown in FIG. 3, the TFT array substrate 10 is provided with a pixel switching TFT 30 that controls switching of each pixel electrode 9a at a position adjacent to each pixel electrode 9a.
As shown in FIG. 3, the counter substrate 20 is further provided with a second light shielding film 23 in a region other than the opening region of each pixel. Therefore, incident light does not enter the channel region 1a ′, the low concentration source region 1b, and the low concentration drain region 1c of the semiconductor layer 1a of the pixel switching TFT 30 from the counter substrate 20 side. Furthermore, the second light-shielding film 23 has functions such as improving contrast and preventing color mixture of color materials.
A sealing material 52 (see FIGS. 18 and 19), which will be described later, is arranged between the TFT array substrate 10 and the counter substrate 20 that are configured in this manner and are arranged so that the pixel electrode 9a and the counter electrode 21 face each other. Liquid crystal is sealed in the enclosed space, and the liquid crystal layer 50 is formed. The liquid crystal layer 50 takes a predetermined alignment state by the alignment film in a state where an electric field from the pixel electrode 9a is not applied.
As shown in FIG. 3, a first light shielding film 11a is provided in a mesh pattern along the pixel between the TFT array substrate 10 and each pixel switching TFT 30 at a position facing each pixel switching TFT 30. Yes. The first light-shielding film 11a is preferably made of a single metal, an alloy, a metal silicide, or the like containing at least one of Ti, Cr, W, Ta, Mo, and Pb, which are preferably opaque high melting point metals. If comprised from such a material, the 1st light shielding film 11a will not be destroyed or melt | dissolved by the high temperature process in the formation process of the pixel switching TFT30 performed after the formation process of the 1st light shielding film 11a on the TFT array substrate 10 You can Since the first light-shielding film 11a is formed, the return light from the TFT array substrate 10 is incident on the channel region 1a ′, the low-concentration source region 1b, and the low-concentration drain region 1c of the pixel switching TFT 30. This can be prevented, and the characteristics of the pixel switching TFT 30 are not deteriorated by the generation of the photocurrent.
Further, a first interlayer insulating film 12 is provided between the first light shielding film 11 a and the plurality of pixel switching TFTs 30. The first interlayer insulating film 12 is provided to electrically insulate the semiconductor layer 1a constituting the pixel switching TFT 30 from the first light shielding film 11a. Further, the first interlayer insulating film 12 has a function as a base film for the pixel switching TFT 30 by being formed on the entire surface of the TFT array substrate 10. That is, the TFT array substrate 10 has a function of preventing deterioration of the characteristics of the pixel switching TFT 30 due to roughness during polishing of the surface of the TFT array substrate 10 and dirt remaining after cleaning. The first interlayer insulating film 12 can also prevent the first light shielding film 11a from contaminating the pixel switching TFT 30 and the like.
In the present embodiment, the insulating thin film 2 serving as a gate insulating film is used as a dielectric film extending from a position facing the gate electrode formed of a part of the scanning line 3a, and the semiconductor layer 1a is extended to be used as the first accumulation. A storage capacitor 70 is configured by using the capacitor electrode 1f and a part of the capacitor line 3b facing the capacitor electrode 1f as a second storage capacitor electrode. More specifically, the high-concentration drain region 1e of the semiconductor layer 1a extends below the data line 6a and the scanning line 3a, and an insulating thin film is formed on the capacitor line 3b that extends along the data line 6a and the scanning line 3a. The first storage capacitor electrode 1f is disposed so as to be opposed to each other. In particular, the insulating thin film 2 as a dielectric of the storage capacitor 70 can be a thin and high withstand voltage insulating film in the case of the gate insulating film of the TFT 30 formed on the polysilicon film by high temperature oxidation. It can be configured as a large storage capacity with a relatively small area.
As a result, the storage capacitance of the pixel electrode 9a is effectively utilized by effectively utilizing the space outside the opening area, that is, the area under the data line 6a and the area parallel to the scanning line 3a (that is, the area where the capacitor line 3b is formed). Can be increased.
In the present embodiment, in particular, the capacitor line 3 b and the first light shielding film 11 a are electrically connected via the contact hole 13. For this reason, the resistance of the capacitor line 3b can be significantly lowered by the resistance of the first light shielding film 11a. In the present embodiment, the capacitor line 3b is formed of, for example, a polysilicon film having a sheet resistance value of about 25Ω / □, so that the capacitance line 3b is used in the case of a small liquid crystal device having a diagonal size of about 1.3 inches or 0.9 inches. Has a resistance of about 100 to 200 KΩ, but since the first light-shielding film 11a is formed of a conductive high melting point metal film, the resistance in the direction along the scanning line 3a in the capacitor line 3b is greatly increased. Reduced resistance.
As a result, the time constant of the capacitor line 3b can also be reduced to, for example, about several tens of microseconds to about several microseconds due to the presence of the first light shielding film 11a. Therefore, the generation of lateral crosstalk, ghost, etc. due to the fluctuation of the potential of the capacitance line 3b due to the capacitance coupling with each data line 6a in the capacitance line 3b crossed under the data line 6a is reduced. it can. That is, as shown in FIG. 20, when displaying an image 801 in which a black portion is drawn with high contrast against a gray background, each time point when an image signal having a partially different voltage to be displayed in black is given. Even at a time close to the end of writing for each scanning line, the problem of display deterioration like the image 802 does not occur. In particular, even if the liquid crystal device is configured as a model having a high driving frequency such as XGA or SXGA as described above, the time constant of the capacitance line 3b is sufficiently small. Generation can be reduced.
Therefore, there is no need to employ a method of inverting the polarity of the liquid crystal driving voltage for each data line 6a or for each pixel as described above in order to prevent such horizontal crosstalk and ghost. A scanning line inversion driving method (so-called 1H inversion driving method) in which the liquid crystal driving voltage is inverted for each scanning line 3a, which can reduce 50 disclinations and is suitable for increasing the pixel aperture ratio, can be employed.
Further, in the present embodiment, the first light shielding film 11a (and the capacitor line 3b electrically connected thereto) is electrically connected to a constant potential source, and the first light shielding film 11a and the capacitor line 3b are set to a constant potential. . Therefore, it is possible to prevent the potential fluctuation of the first light shielding film 11a from adversely affecting the pixel switching TFT 30 disposed opposite to the first light shielding film 11a. Further, the capacitor line 3 b can function well as the second storage capacitor electrode of the storage capacitor 70. In this case, as the constant potential source, a constant potential source such as a negative power source or a positive power source supplied to a peripheral circuit (for example, a scanning line driving circuit, a data line driving circuit, a sampling circuit, or the like) for driving the liquid crystal device. , A ground power source, a constant potential source supplied to the counter electrode 21, and the like. In this way, if the power source such as a peripheral circuit is used, the first light-shielding film 11a and the capacitor line 3b can be set to a constant potential without the need to provide a dedicated potential wiring or an external circuit connection terminal.
In FIG. 3, the pixel switching TFT 30 has an LDD (Lightly Doped Drain) structure, and includes a scanning line 3a, a channel region 1a ′ of the semiconductor layer 1a in which a channel is formed by an electric field from the scanning line 3a, and scanning. The insulating thin film 2 that insulates the line 3a from the semiconductor layer 1a, the data line 6a, the low concentration source region 1b and the low concentration drain region 1c of the semiconductor layer 1a, the high concentration source region 1d and the high concentration drain region 1e of the semiconductor layer 1a. I have. In this embodiment, in particular, the data line 6a is composed of a light-shielding thin film such as a metal film such as Al or an alloy film such as metal silicide. Further, on the scanning line 3a, the insulating thin film 2, and the first interlayer insulating film 12, a contact hole 5 leading to the high concentration source region 1d and a contact hole 8 leading to the high concentration drain region 1e are respectively formed. An insulating film 4 is formed. The data line 6a is electrically connected to the high concentration source region 1d through the contact hole 5. Further, a third interlayer insulating film 7 is formed on the data line 6 a and the second interlayer insulating film 4. The high concentration drain region 1e is electrically connected to the pixel electrode 9a through the contact hole 8. The pixel electrode 9a and the high concentration drain region 1e may be electrically connected by relaying the same Al film as the data line 6a or the same polysilicon film as the scanning line 3b.
The pixel switching TFT 30 preferably has an LDD structure as described above, but may have an offset structure in which impurity ions are not implanted into the low concentration source region 1b and the low concentration drain region 1c, and the gate electrode as a mask. It may be a self-aligned TFT in which impurity ions are implanted at a high concentration and high concentration source and drain regions are formed in a self-aligning manner.
In this embodiment, a single gate structure in which only one gate electrode composed of a part of the scanning line 3a of the pixel switching TFT 30 is arranged between the source and drain regions is used. However, two or more gate electrodes are interposed between these gate electrodes. May be arranged. At this time, the same signal is applied to each gate electrode. If the TFT is configured with dual gates (double gates) or triple gates or more as described above, the leakage current between the channel and the source / drain region junction can be prevented, and the off-time current can be reduced. If at least one of these gate electrodes has an LDD structure or an offset structure, the off-current can be further reduced and a stable switching element can be obtained.
Here, in general, the polysilicon film forming the channel region 1a ′, the low concentration source region 1b, the low concentration drain region 1c, and the like of the semiconductor layer 1a has a photocurrent due to the photoelectric conversion effect of the polysilicon when light enters. However, in this embodiment, since the data line 6a is formed of a light-shielding metal thin film such as Al so that the scanning line 3a is overlapped from the upper side, at least the transistor characteristics of the pixel switching TFT 30 are deteriorated. Incident light (that is, light from the upper side in FIG. 3) can be effectively prevented from entering the channel region 1a ′, the low concentration source region 1b, and the low concentration drain region 1c of the semiconductor layer 1a. Further, as described above, since the first light shielding film 11a is provided below the pixel switching TFT 30, at least the channel region 1a ′, the low concentration source region 1b, and the low concentration drain region 1c of the semiconductor layer 1a. It is possible to effectively prevent the return light (that is, the light from the lower side in FIG. 3) from entering.
Next, the configuration of the peripheral circuit provided on the TFT array substrate 10 in this embodiment will be described with reference to FIG.
In FIG. 4, the liquid crystal device includes, as peripheral circuits, a data line driving circuit 101 for driving the data line 6a, a scanning line driving circuit 104 for driving the scanning line 3a, and a precharge signal at a predetermined voltage level for the plurality of data lines 6a. .., Sn before the supply of the image signals S1, S2,..., Sn, and a plurality of image signals S1, S2,. And a sampling circuit 301 for supplying data lines 6a.
The scanning line driving circuit 104 pulse-sequentially scans the scanning signals G1, G2,..., Gm to the scanning line 3a at a predetermined timing based on the power supplied from the external control circuit, the reference clock CLY, its inverted clock, and the like. Apply with.
The data line driving circuit 101 is synchronized with the timing at which the scanning line driving circuit 104 applies the scanning signals G1, G2,..., Gm based on the power supplied from the external control circuit, the reference clock CLX, its inverted clock, and the like. Transfer signals X1, X2,..., Xn from the shift register as sampling circuit drive signals are supplied to the sampling circuit 301 via the sampling circuit drive signal line 306 for each data line 6a.
The precharge circuit 201 includes, for example, a TFT 202 as a switching element for each data line 6 a, the precharge signal line 204 is connected to the drain or source of the TFT 202, and the precharge circuit drive signal line 206 is connected to the TFT 202. Connected to the gate electrode. In operation, power of a predetermined voltage necessary for writing a precharge signal (NRS) is supplied from an external power supply via the precharge signal line 204, and each data is supplied via the precharge circuit drive signal line 206. A precharge circuit drive signal (NRG) is supplied from the external control circuit so that the precharge signal (NRS) is written to the line 6a at a timing preceding the supply of the image signals S1, S2,. The precharge circuit 201 preferably supplies a precharge signal (NRS) (image auxiliary signal) corresponding to the image signals S1, S2,.
The sampling circuit 301 includes a TFT 302 for each data line 6 a, the image signal line 304 is connected to the drain or source electrode of the TFT 302, and the sampling circuit drive signal line 306 is connected to the gate electrode of the TFT 302. . When image signals S1, S2,..., Sn are input via the image signal line 304, they are sampled. That is, when transfer signals X1, X2,..., Xn as sampling circuit drive signals are input from the data line drive circuit 101 via the sampling circuit drive signal line 306, the image signals S1, S2 from the image signal lines 304, respectively. ,..., Sn are sequentially applied to the data line 6a.
As described above, in the present embodiment, the data lines 6a are selected for each line. However, the data lines 6a may be selected for a plurality of lines at the same time. For example, the image signals S1, S2, serial-parallel converted into a plurality of phases (for example, three phases, six phases, twelve phases,...) According to the writing characteristics of the TFTs 302 constituting the sampling circuit 301 and the frequency of the image signals. ..., Sn may be supplied from the image signal line 304, and these may be sampled simultaneously for each group. At this time, it goes without saying that at least the number of image signal lines 304 required is the number of serial-parallel conversions.
Here, the precharge performed in the liquid crystal device of the present embodiment will be described with reference to FIG.
As shown in FIG. 5, a clock signal (CLX) that defines a selection time t1 per pixel is input to a shift register included in the data line driving circuit 101 as a reference for horizontal scanning, but a transfer start signal (DX ) Is input, transfer signals X1, X2,... Are sequentially supplied from the shift register. In each horizontal scanning period, the precharge circuit drive signal (NRG) is supplied to the precharge circuit 201 at a timing preceding the input of the transfer start signal (DX). More specifically, the clock signal (CLY) used as a reference for vertical scanning becomes a high level and the polarity of the image signal (VID) is inverted with reference to the voltage center value (VID center) of the signal. The precharge circuit drive signal (NRG) is set to a high level after elapse of time t3, which is a margin from precharge to precharge. On the other hand, the precharge signal (NRS) is set to a predetermined level having the same polarity as that of the image signal (VID) in the horizontal blanking period corresponding to the inversion of the image signal (VID). Therefore, precharge is performed at time t2 when the precharge circuit drive signal (NRG) is set to the high level. Then, the precharge circuit is driven by a time t4 before the time when the horizontal blanking period ends and the effective display period starts, that is, the time t4 is the margin from the end of the precharge to the time when the image signal is written. The signal (NRG) is at a low level. As described above, the precharge circuit 201 supplies the precharge signal (NRS) to the plurality of data lines 6a prior to the image signal in each horizontal blanking period.
In FIG. 5, the precharge is performed within the horizontal blanking period. However, the fluctuation of the potential of the capacitor line 3b due to the capacitive coupling between the data line 6a and the capacitor line 3b described above tends to be stable within the time t5. Accordingly, it can be considered that such potential fluctuation of the capacitor line 3b can be prevented by setting the timing of each signal so that the time t5 becomes longer. However, if this time t5 is made longer, then it becomes necessary to shorten the times t3, t2, and t4. Here, if the time t3 is made too short, the gate of the TFT 30 related to the preceding scanning line is turned on when the precharge circuit drive signal (NRG) becomes high level due to the gate delay of the TFT or the like constituting the precharge circuit. Danger comes out. Further, if the time t2 is shortened, the precharge capability is reduced, or a precharge circuit having a high charge supply capability is required. Furthermore, if the time t4 is shortened, the precharge signal and the image signal may be simultaneously applied to the data line 6a. Therefore, in order to satisfactorily precharge, the time t5 for stabilizing the potential fluctuation of the capacitive line 3b due to capacitive coupling cannot be easily increased. However, according to the present embodiment, the first light-shielding film 11a significantly lowers the resistance of the capacitor line 3b and greatly reduces the time constant, so that the time t5 with respect to the time constant of the capacitor line 3b can be made relatively long. It can be done.
Even when precharging is performed in this manner, in this embodiment, the horizontal blanking period for precharging is secured for a sufficient length, and the fluctuation of the potential of the capacitive line 3b due to capacitive coupling is stabilized. This time t5 can be substantially ensured.
As a result of the above, according to the present embodiment, even when the driving frequency is high, precharge and the above-described scanning line inversion driving can be performed well, and lateral crosstalk due to capacitive coupling can prevent ghosts and the like. An extremely high quality image can be displayed.
In addition to this, according to the present embodiment, a redundant structure is realized in which the first light-shielding film 11a replaces the capacitor line 3b even if the capacitor line 3b is broken in the middle due to foreign matter or the like. That is, even if the capacitor line 3b is disconnected in the middle, there is no practical problem if both sides of the disconnected part are electrically connected to each other by the first light shielding film 11a via the contact hole 13. Therefore, according to the present embodiment, a liquid crystal device capable of displaying a high-quality image with a low defective product rate and high reliability can be realized.
The capacitor line 3b and the scanning line 3a are made of the same polysilicon film, and the dielectric film of the storage capacitor 70 and the insulating thin film 2 that becomes the gate insulating film of the TFT 30 include the same high-temperature oxide film. The one storage capacitor electrode 1f, the channel region 1a ′, the high concentration source region 1d, the high concentration drain region 1e, etc. of the TFT 30 are made of the same semiconductor layer 1a. For this reason, the laminated structure formed on the TFT array substrate 10 can be simplified, and in the manufacturing method of the liquid crystal device described later, the capacitor line 3b and the scanning line 3a can be simultaneously formed in the same thin film forming process, and the storage capacitor 70 dielectric films and insulating thin film 2 can be formed simultaneously.
In particular, in the present embodiment, the capacitor line 3b and the first light shielding film 11a are reliably and highly reliable through the contact hole 13 opened in the first interlayer insulating film 12, and both are electrically connected. However, such a contact hole 13 may be opened for each pixel, or may be opened for each pixel group including a plurality of pixels.
When the contact hole 13 is opened for each pixel, the resistance of the capacitor line 3b can be reduced by the first light-shielding film 11a, and the degree of redundant structure between the two can be increased. On the other hand, when the contact hole 13 is opened for each pixel group composed of a plurality of pixels (for example, every 2 pixels or every 3 pixels), the sheet resistance, the driving frequency of the capacitor line 3b and the first light shielding film 11a, Taking into account the required specifications, etc., the benefits of the low resistance and redundant structure of the capacitor line 3b by the first light-shielding film 11a, the complexity of the manufacturing process by opening a large number of contact holes 13, or the liquid crystal device Since it is possible to properly balance the adverse effects such as the deterioration of the quality, it is very advantageous in practice.
In the present embodiment, in particular, the contact hole 13 provided for each pixel or each pixel group is formed under the data line 6a when viewed from the counter substrate 20 side. For this reason, the contact hole 13 is located outside the pixel opening region and is provided in the portion of the first interlayer insulating film 12 where the TFT 30 and the first storage capacitor electrode 1f are not formed. Thus, it is possible to prevent the TFT 30 and other wirings from being defective due to the formation of the contact hole 13. (Manufacturing process of the first embodiment of the liquid crystal device)
Next, a manufacturing process of the first embodiment of the liquid crystal device having the above configuration will be described with reference to FIGS. 6 to 9 are process diagrams showing each layer on the TFT array substrate side in each process corresponding to the AA ′ cross section of FIG.
As shown in step (1) of FIG. 6, a TFT array substrate 10 such as a quartz substrate, a hard glass substrate, or a silicon substrate is prepared. Where preferably N 2 Annealing is performed in an inert gas atmosphere such as (nitrogen) and at a high temperature of about 900 to 1300 ° C., and pretreatment is performed so as to reduce distortion generated in the TFT array substrate 10 in a high-temperature process to be performed later. That is, the TFT array substrate 10 is heat-treated in advance at the same temperature or higher in accordance with the temperature at which the high temperature treatment is performed at the maximum temperature in the manufacturing process.
A metal alloy film such as a metal such as Ti, Cr, W, Ta, Mo, and Pb or a metal silicide is sputtered on the entire surface of the TFT array substrate 10 thus processed, and the thickness is preferably about 100 to 500 nm. Forms a light-shielding film 11 having a thickness of about 200 nm.
Subsequently, as shown in step (2), the light shielding film 11 is etched to form the first light shielding film 11a.
Next, as shown in step (3), TEOS (tetra-ethyl ortho-silicate) gas, TEB (tetra-ethyl boat rate) is formed on the first light-shielding film 11a by, for example, normal pressure or low pressure CVD. ) Gas, TMOP (tetra-methyl-oxy-phosphate) gas, etc., such as NSG (non-silicate glass), PSG (phosphorus silicate glass), BSG (boron silicate glass), BPSG (boron phosphorus silicate glass), etc. A first interlayer insulating film 12 made of a silicate glass film, a silicon nitride film, a silicon oxide film or the like is formed. The film thickness of the first interlayer insulating film 12 is, for example, about 500 to 2000 nm.
Next, as shown in step (4), a monosilane gas having a flow rate of about 400 to 600 cc / min on the first interlayer insulating film 12 in a relatively low temperature environment of about 450 to 550 ° C., preferably about 500 ° C., An amorphous silicon film is formed by low pressure CVD (for example, CVD at a pressure of about 20 to 40 Pa) using disilane gas or the like. Thereafter, an annealing process is performed in a nitrogen atmosphere at about 600 to 700 ° C. for about 1 to 10 hours, preferably 4 to 6 hours, so that the polysilicon film 1 has a thickness of about 50 to 200 nm, preferably Is solid-phase grown to a thickness of about 100 nm.
At this time, when an n-channel type pixel switching TFT 30 is formed as the pixel switching TFT 30 shown in FIG. 3, Vb such as Sb (antimony), As (arsenic), P (phosphorus), etc. is formed in the channel region. Group element impurity ions may be slightly doped by ion implantation or the like. When the pixel switching TFT 30 is a p-channel type, impurity ions of group III elements such as B (boron), Ga (gallium), and In (indium) may be slightly doped by ion implantation or the like. . Note that the polysilicon film 1 may be directly formed by a low pressure CVD method or the like without going through an amorphous silicon film. Alternatively, the polysilicon film 1 may be formed by implanting silicon ions into a polysilicon film deposited by a low pressure CVD method or the like to make it amorphous (amorphized) and then recrystallizing it by annealing or the like.
Next, as shown in step (5), a semiconductor layer 1a having a predetermined pattern as shown in FIG. 2 is formed. That is, in particular, in a region where the capacitor line 3b is formed under the data line 6a and a region where the capacitor line 3b is formed along the scanning line 3a, the first layer extending from the semiconductor layer 1a constituting the pixel switching TFT 30 is provided. One storage capacitor electrode 1f is formed.
Next, as shown in step (6), by thermally oxidizing the first storage capacitor electrode 1f together with the semiconductor layer 1a constituting the pixel switching TFT 30 at a temperature of about 900 to 1300 ° C., preferably about 1000 ° C. A thermal oxide silicon film having a relatively thin thickness of about 30 nm is formed, and a high temperature silicon oxide film (HTO film) or a silicon nitride film is further deposited to a relatively thin thickness of about 50 nm by a low pressure CVD method or the like. An insulating thin film 2 is formed as a capacitor forming dielectric film together with the gate insulating film of the pixel switching TFT 30 having a structure (see FIG. 3). As a result, the thickness of the semiconductor layer 1a and the first storage capacitor electrode 1f is about 30 to 150 nm, preferably about 35 to 50 nm, and the insulating thin film 2 is about 20 to 150 nm. The thickness is preferably about 30 to 100 nm. By shortening the high-temperature thermal oxidation time in this way, it is possible to prevent warpage due to heat, particularly when a large substrate of about 8 inches is used. However, the insulating thin film 2 having a single layer structure may be formed only by thermally oxidizing the polysilicon film 1.
Although not particularly limited in the step (6), for example, P ions are dosed to about 3 × 10 6 in the semiconductor layer portion to be the first storage capacitor electrode 1f. 12 / Cm 2 May be doped to reduce the resistance.
Next, in step (7), a contact hole 13 reaching the first light shielding film 11a is formed in the first interlayer insulating film 12 by dry etching such as reactive ion etching, reactive ion beam etching, or wet etching. At this time, opening the contact hole 13 or the like by anisotropic etching such as reactive ion etching or reactive ion beam etching has an advantage that the opening shape can be made substantially the same as the mask shape. However, if a hole is formed by combining dry etching and wet etching, these contact holes 13 and the like can be tapered, so that an advantage of preventing disconnection at the time of wiring connection can be obtained.
Next, as shown in step (8), after the polysilicon film 3 is deposited by a low pressure CVD method or the like, P is thermally diffused to make the polysilicon film 3 conductive. Alternatively, a doped silicon film in which P ions are introduced simultaneously with the formation of the polysilicon film 3 may be used.
Next, as shown in step (9) of FIG. 7, the capacitor line 3b is formed together with the scanning line 3a having a predetermined pattern as shown in FIG. The film thickness of the scanning line 3a and the capacitor line 3b is, for example, about 350 nm.
Next, as shown in step (10), when the pixel switching TFT 30 shown in FIG. 3 is an n-channel TFT having an LDD structure, the low concentration source region 1b and the low concentration drain region are first formed in the semiconductor layer 1a. In order to form 1c, a gate electrode which is a part of the scanning line 3a is used as a diffusion mask, and impurity ions 60 of a V group element such as P are formed at a low concentration (for example, P ions are added to 1 to 3 × 10 6). 13 / Cm 2 Dope). As a result, the semiconductor layer 1a under the scanning line 3a becomes a channel region 1a ′. The resistance of the capacitor line 3b and the scanning line 3a is also reduced by doping of the impurity ions.
Subsequently, as shown in step (11), in order to form the high concentration source region 1d and the high concentration drain region 1e constituting the pixel switching TFT 30, the resist layer 62 is formed with a mask wider than the scanning line 3a. After forming on the scanning line 3a, the impurity ions 61 of a V group element such as P are similarly formed at a high concentration (for example, P ions are added to 1 to 3 × 10 3. 15 / Cm 2 Dope). Further, when the pixel switching TFT 30 is a p-channel type, in order to form the low concentration source region 1b and the low concentration drain region 1c, the high concentration source region 1d and the high concentration drain region 1e in the semiconductor layer 1a, B ( Doping using impurity ions of group III elements such as boron. For example, an TFT having an offset structure may be used without doping with low-concentration impurity ions, and an ion implantation technique using P ions, B ions, or the like using a gate electrode which is a part of the scanning line 3a as a mask. Thus, a self-aligned TFT may be used.
The resistance of the capacitor line 3b and the scanning line 3a is further reduced by doping the impurities.
Further, by repeating the step (10) and the step (11) again and performing impurity ions of group III elements such as B ions, a p-channel TFT can be formed. As a result, the data line driving circuit 101 and the scanning line driving circuit 104 having a complementary structure composed of n-channel TFTs and p-channel TFTs can be formed on the periphery of the TFT array substrate 10. Thus, if the semiconductor layer 1a constituting the pixel switching TFT 30 is formed of a polysilicon film, the data line driving circuit 101 and the scanning line driving circuit 104 are formed in substantially the same process when the pixel switching TFT 30 is formed. This is advantageous in manufacturing.
Next, as shown in step (12), NSG, PSG, BSG, and the like using, for example, atmospheric pressure or reduced pressure CVD or TEOS gas so as to cover the capacitor line 3b together with the scanning line 3a in the pixel switching TFT 30. A second interlayer insulating film 4 made of a silicate such as BPSG and a glass film, a silicon nitride film, a silicon oxide film or the like is formed. The film thickness of the second interlayer insulating film 4 is preferably about 500 to 1500 nm.
Next, in step (13), annealing is performed at about 1000 ° C. for about 20 minutes in order to activate the high concentration source region 1d and the high concentration drain region 1e, and then the contact hole 5 for the data line 6a is formed. It is formed by dry etching such as reactive ion etching or reactive ion beam etching or by wet etching. Further, contact holes for connecting the scanning lines 3 a and the capacitor lines 3 b to wirings (not shown) are also formed in the second interlayer insulating film 4 by the same process as the contact holes 5.
Next, as shown in step (14) of FIG. 8, on the second interlayer insulating film 4, a low-resistance metal such as light-shielding Al or a metal silicide or the like is formed on the second interlayer insulating film 4 by sputtering or the like as a metal film 6. The film is deposited to a thickness of 500 nm, preferably about 300 nm, and further, as shown in step (15), the data line 6a is formed by a photolithography process, an etching process, and the like.
Next, as shown in step (16), a silicate glass film such as NSG, PSG, BSG, BPSG, or the like is nitrided using, for example, atmospheric pressure or reduced pressure CVD method or TEOS gas so as to cover the data line 6a. A third interlayer insulating film 7 made of a silicon film, a silicon oxide film or the like is formed. The thickness of the third interlayer insulating film 7 is preferably about 500 to 1500 nm.
Next, in the step (17) of FIG. 9, in the pixel switching TFT 30, the contact hole 8 for electrically connecting the pixel electrode 9a and the high concentration drain region 1e is formed by reactive ion etching or reactive ion beam etching. It is formed by dry etching.
Next, as shown in step (18), a transparent conductive thin film 9 such as an ITO film is deposited on the third interlayer insulating film 7 by sputtering or the like to a thickness of about 50 to 200 nm. As shown in 19), the pixel electrode 9a is formed. When the liquid crystal device is used for a reflective liquid crystal device, the pixel electrode 9a may be formed from an opaque material having a high reflectance such as Al.
Subsequently, after applying a polyimide alignment film coating solution on the pixel electrode 9a, the alignment film 16 (see FIG. 3) is subjected to a rubbing process so as to have a predetermined pretilt angle and in a predetermined direction. Is formed.
On the other hand, for the counter substrate 20 shown in FIG. 3, a glass substrate or the like is first prepared, and the second light shielding film 23 and a third light shielding film (see FIGS. 18 and 19) as a frame to be described later are made of, for example, metallic chromium. After sputtering, it is formed through a photolithography process and an etching process. These second light shielding films may be formed of a metal material such as Cr, Ni (nickel), Al, or a material such as resin black in which carbon or Ti is dispersed in a photoresist.
Then, the counter electrode 21 is formed by depositing a transparent conductive thin film such as ITO on the entire surface of the counter substrate 20 by sputtering or the like to a thickness of about 50 to 200 nm. Further, after applying a polyimide-based alignment film coating solution over the entire surface of the counter electrode 21, the alignment film 22 (see FIG. 3) is formed by performing a rubbing process in a predetermined direction so as to have a predetermined pretilt angle. It is formed.
Finally, the TFT array substrate 10 on which the respective layers are formed as described above and the counter substrate 20 are bonded together with a sealing material 52 so that the alignment films 16 and 22 face each other, and a space between the two substrates is obtained by vacuum suction or the like. In addition, for example, liquid crystal formed by mixing a plurality of types of nematic liquid crystals is sucked to form a liquid crystal layer 50 having a predetermined thickness.
(Second Embodiment of Liquid Crystal Device)
A second embodiment of the liquid crystal device according to the present invention will be described with reference to FIG.
In the first embodiment described above, the first light-shielding film 11a is provided in a mesh shape along the pixels, whereby the resistance of the capacitor line 3b can be reduced and the degree of the redundant structure is further increased. In the embodiment, the first light shielding film 11a is provided in a stripe shape (stripe shape). Since other configurations are the same as those in the first embodiment, the same reference numerals are given to the same components in the drawing, and descriptions thereof are omitted. FIG. 10 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light shielding films, and the like are formed.
In FIG. 10, the first light-shielding film 11a is composed of a plurality of striped (stripe-shaped) portions extending along the scanning line 3a. That is, the first light shielding film 11a is divided at a predetermined region facing the data line 6a. Accordingly, it is possible to promote a reduction in resistance of the capacitor line 3b electrically connected to the first light shielding film 11a, particularly in the direction along the scanning line 3a. In addition, the degree of redundant structure between the capacitor line 3b and the first light shielding film 11a can be increased.
As a modification of the second embodiment, the first light-shielding film 11a is further provided in stripes at positions where the scanning line 3a and the capacitor line 3b overlap each other when viewed from the TFT array substrate 10 side. A plurality of striped portions arranged along the line may be electrically connected to each other via the capacitor line 3b. Even if comprised in this way, the resistance reduction of the capacity | capacitance line 3b can be accelerated | stimulated and the degree of a redundant structure can be raised.
(Third embodiment of liquid crystal device)
A third embodiment of the liquid crystal device according to the present invention will be described with reference to FIG.
In the first embodiment described above, by providing the first light-shielding film 11a in a mesh shape (lattice shape), the resistance of the capacitor line 3b can be reduced, and the degree of the redundant structure is further increased. In the embodiment, the first light-shielding film 11a is provided in a stripe shape, and is not formed at a position facing the scanning line 3a except for a position covering the channel region 1a ′. Since other configurations are the same as those in the first embodiment, the same reference numerals are given to the same components in the drawing, and descriptions thereof are omitted. FIG. 12 is a plan view of a plurality of adjacent pixel groups on the TFT array substrate on which data lines, scanning lines, pixel electrodes, light-shielding films, and the like are formed.
As shown in FIG. 11, first light shielding films 11 a are respectively provided between the TFT array substrate 10 and the pixel switching TFTs 30 at positions facing the pixel switching TFTs 30.
As shown in FIG. 11, in the present embodiment, the first light-shielding film 11a is electrically connected to the capacitor line 3b provided in the adjacent preceding or succeeding stage via the contact hole 13. Accordingly, compared with the case where each first light shielding film 11a is electrically connected to the capacitor line of its own stage, the capacitor line 3b and the first light shielding are superimposed on the data line 6a along the edge of the opening region of the pixel portion. There are few steps with respect to the other area | region in which the film | membrane 11a is formed. Thus, if there are few steps along the edge of the opening area of the pixel portion, the liquid crystal disclination (alignment failure) caused by the step can be reduced, so that the opening area of the pixel portion can be widened. Become.
Further, in the first light shielding film 11a, the contact hole 13 is opened at the protruding portion protruding from the main line portion extending linearly as described above. Here, the inventors of the present application have found that cracks are less likely to occur in the contact hole 13 due to the reason that stress is dissipated from the edge as it is closer to the edge. Therefore, in this case, depending on how close to the tip of the protruding portion the contact hole 13 is opened (preferably, depending on whether the contact hole 13 is close to the tip of the margin), the first light shielding film 11a is formed during the manufacturing process. Such stress is relieved, cracks can be prevented more effectively, and the yield can be improved.
Further, particularly in the present embodiment, the first light shielding film 11a is not formed at a position facing the scanning line 3a except for a position covering the channel region 1a ′. Accordingly, since the capacitive coupling between the first light-shielding film 11a and each scanning line 3a hardly or practically occurs, the potential fluctuation in the first light-shielding film 11a is caused by the potential fluctuation in the scanning line 3a. As a result, there is no potential fluctuation in the capacitance line 3b.
In the third embodiment, since the capacitor line 3b provided in the adjacent upstream or downstream pixel is connected to the first light shielding film 11a, the first light shielding is applied to the uppermost or lowermost pixel. The capacitor line 3b for supplying a constant potential to the film 11a is required. Therefore, it is preferable to provide one extra capacity line 3b with respect to the number of vertical pixels.
In FIG. 11, the linear main line portion of the first light shielding film 11 a is formed so as to substantially overlap the linear main line portion of the capacitor line 3 b, but the first light shielding film 11 a is formed in the channel of the TFT 30. If it is provided at a position that covers the region and overlaps with the capacitor line 3b at any point so that the contact hole 13 can be formed, the light shielding function for the TFT and the resistance reducing function for the capacitor line 3b can be exhibited. It is. Therefore, for example, the first light-shielding film 11a is provided even in the longitudinal gap region along the scanning line 3a between the adjacent scanning line 3a and the capacitance line 3b or a position slightly overlapping with the scanning line 3a. May be.
(Fourth Embodiment of Liquid Crystal Device)
A fourth embodiment of the liquid crystal device according to the present invention will be described with reference to FIG.
In the first to third embodiments described above, the main line portion along the scanning line 3a and the capacitor line 3b in the first light shielding film 11a is formed substantially below the capacitor line 3b. In the sixth embodiment, Thus, the main line portion along the scanning line 3a and the capacitor line 3b is formed in a striped pattern under the scanning line 3a and is not formed under the capacitor line 3b. Since other configurations are the same as those in the first embodiment, the same reference numerals are given to the same components in the drawing, and descriptions thereof are omitted. FIG. 12 is a plan view of a plurality of adjacent pixel groups on the TFT array substrate on which data lines, scanning lines, pixel electrodes, light-shielding films, and the like are formed.
In FIG. 12, particularly in the liquid crystal device, a main line portion extending along the scanning line 3a of the striped first light shielding film 11a is disposed below the scanning line 3a. That is, in the main line portion, the scanning line 3a is formed on the first light shielding film 11a via the first interlayer insulating film that is much thicker than the gate insulating film constituting the TFT in the pixel portion, for example. For this reason, even if an abnormally shaped portion such as an unintended projection in the manufacturing process is formed on the first light shielding film 11a, the projection or the like breaks through the first interlayer insulating film, so that the first light shielding film 11a is The possibility of shorting with the scanning line 3a can be extremely reduced.
When the semiconductor layer 1a, the insulating thin film 2, and the capacitor line 3b are further laminated on the protrusions formed on the first light shielding film 11a as in the first to third embodiments described above (FIG. 3). In consideration of the fact that this projection or the like breaks through the very thin insulating thin film 2 through the semiconductor layer 1a and the semiconductor layer 1a and the capacitor line 3b are likely to be short-circuited, the scanning line in the fourth embodiment The configuration in which the first light shielding film 11a is formed at a position facing 3a is more advantageous in improving the process yield.
Therefore, from the viewpoint of improving the yield in this way, the region on the substrate formed by the first light shielding film 11a and the capacitor line 3b facing each other is made as small as possible, and the first light shielding film 11a and the scanning line 3a It is desirable to enlarge the regions on the substrate formed to face each other as much as possible. For this reason, in the fourth embodiment, as shown in FIG. 12, the minimum area required for electrically connecting the first light-shielding film 11a and the capacitor line 3b through the contact hole 13 and the channel area of the TFT 30 (right in the figure). In a region excluding the minimum necessary region for shielding light from the lower shaded portion), the first light shielding film 11a is disposed opposite to the scanning line 3a without being disposed opposite to the capacitor line 3b.
As a result, according to the fourth embodiment, even if the first light-shielding film 11a is used to reduce the resistance of the capacitor line 3b, the capacitor line 3b and the semiconductor layer 1a that are arranged to face each other with the very thin insulating thin film 2 therebetween. In practice, there is little or no possibility of short-circuiting, and ultimately the yield of the liquid crystal device can be improved.
(Fifth embodiment of liquid layer device)
A fifth embodiment of a liquid crystal device according to the present invention will be described with reference to FIG.
In the first to fourth embodiments described above, the contact hole 13 for electrically connecting the capacitor line 3b and the first light shielding film 11a has a quadrangular planar shape, but in the fifth embodiment, this contact The planar shape of the hole is a circle such as a perfect circle or an ellipse. Other configurations are the same as those in the first to fourth embodiments. In the present embodiment, the shape of the contact hole 13 in the third embodiment is modified, and the same components in FIG. Are given the same reference numerals and their description is omitted. FIG. 13 is a plan view of a plurality of adjacent pixel groups on the TFT array substrate on which data lines, scanning lines, pixel electrodes, light-shielding films, and the like are formed.
In FIG. 13, the contact hole 13 for electrically connecting the capacitor line 3b and the first light shielding film 11a is configured so that the planar shape parallel to the substrate is circular.
With this configuration, when a wet etching process is used in the manufacturing process to open the contact hole 13, the etching solution enters the interface between the first light shielding film 11a and the first interlayer insulating film 12, The possibility of generating cracks can be reduced. That is, as in the third embodiment, if the contact hole 13 having a square shape such as a square is to be opened by wet etching, the etching solution is particularly likely to enter the corner and stress concentration also occurs. Therefore, cracks are likely to occur in the first light-shielding film 11a and the like at this corner portion.
On the other hand, when the contact hole 13 in the first embodiment is opened by the dry etching process, the thickness of the contact hole 13 is extremely thin due to the selection ratio between the first interlayer insulating film 12 and the first light shielding film 11a. There is a high possibility that etching will penetrate through the light shielding film 11a. For this reason, as in this embodiment, the wet etching process using the circular contact hole 13 ′ is very advantageous in practice from the viewpoint of preventing penetration and cracking.
As a result, according to the third embodiment, the reliability of the wiring near the contact hole can be improved, and the yield of the liquid crystal device can be improved. In addition, the shape of the contact hole of the present embodiment is modified from the shape of the contact hole of the configuration of the third embodiment as an example, but the present embodiment is different from the first embodiment, the second embodiment, and the fourth embodiment. Is also applicable.
(Sixth Embodiment of Liquid Crystal Device)
A sixth embodiment of the liquid crystal device according to the present invention will be described with reference to FIG.
In the first and fifth embodiments described above, the first light-shielding film 11a is electrically connected to the previous-stage or rear-stage capacitor line 3b via the contact hole 13 or 13 ′. The membrane is electrically connected to its own capacity line. Since other configurations are the same as those in the fifth embodiment, the same reference numerals are given to the same components in the drawing, and descriptions thereof are omitted. FIG. 14 is a plan view of a plurality of pixel groups adjacent to each other on a TFT array substrate on which data lines, scanning lines, pixel electrodes, light shielding films, and the like are formed.
In FIG. 14, the first light-shielding film 11a is provided at a position covering the TFT including the channel region of the semiconductor layer 1a when viewed from the TFT array substrate side in the pixel portion, and further the linear main line of the capacitor line 3b. A main line portion extending linearly along the scanning line 3a facing the portion, and a projecting portion projecting to the next stage side (that is, downward in the figure) along the data line 6a from a location intersecting the data line 6a, And a projecting portion projecting from the portion intersecting with the data line 6a to the previous stage side (that is, upward in the figure) along the data line 6a.
The downward projecting portion of the first light shielding film 11a covers the channel region and further extends downward to a position covering the contact hole 5.
On the other hand, the upward projecting portion of the first light shielding film 11a overlaps the upward projecting portion of the capacitor line 3b below the data line 6a, and the first light shielding film 11a and the capacitor line 3b are located near the tip of the overlap. A circular contact hole 13 ′ is provided to electrically connect the two. In other words, in the present embodiment, the first light-shielding film 11a in each stage (that is, the row of each pixel) is electrically connected to the capacitor line 3b in its own stage through the contact hole 13 ′.
If configured in this manner, the level difference between the region where the TFT 30, the capacitor line 3b, and the first light-shielding film 11a are formed over the data line 6a becomes large, but the capacitor line 3b and the first line can be relatively easily formed. It is possible to electrically connect the light shielding film 11a.
Further, with this configuration, the upward projecting portion of the first light shielding film 11a overlaps the first storage capacitor electrode 1f. Therefore, the first storage capacitor electrode as the third storage capacitor electrode is utilized using the space below the data line 6a. There is also an advantage that the storage capacitor 70 formed between the light shielding film 11a and the first storage capacitor electrode 1f can be increased.
In this embodiment as well, as in the case of the third embodiment, the contact hole may be square and the capacitor line of the own stage may be electrically connected to the light shielding film. In the third embodiment, since the capacitor line 3b provided in the pixel of the own stage is connected to the first light shielding film 11a, it is not necessary to provide an extra capacitor line 3b in the uppermost or lowermost pixel. This is advantageous.
(Seventh Embodiment of Liquid Crystal Device)
A liquid crystal device according to a seventh embodiment of the invention will be described with reference to FIG. In the third or fourth embodiment described above, the first light-shielding film 11a is formed along the scanning line 3a or the capacitor line 3b. In the present embodiment, however, the first light-shielding film 11a is formed along the data line 6a. . In the drawings, the same components are denoted by the same reference numerals, and description thereof is omitted. FIG. 15 is a plan view of a plurality of adjacent pixel groups on the TFT array substrate on which data lines, scanning lines, pixel electrodes, light-shielding films, and the like are formed.
As shown in FIG. 15, the first light-shielding film 11a is connected through a contact hole 13 ′. According to such a configuration, the distance from the first light shielding film 11a to the contact hole 8 for connecting the pixel electrode 9a and the semiconductor film 1a can be increased, so that the metal film that forms the first light shielding film 11a can be separated. It is possible to prevent the capacitor line 3b and the semiconductor 1a from being short-circuited by the stress and causing a point defect. The first light shielding film 11a may be fixed at a potential by being connected to a constant potential line around the pixel region.
(Eighth embodiment of liquid crystal device)
In the first to seventh embodiments described above, any flattening process is applied to the step with respect to other regions in the stacked region where the TFT 30, the scanning line 3a, the capacitor line 3b, the data line 6a, and the like are formed. However, in the eighth embodiment, the planarization process is performed by forming the first interlayer insulating film 12 in a concave shape. Since other configurations are the same as those in the first to seventh embodiments, the same reference numerals are given to the same components in the drawings, and description thereof will be omitted. 16 is a cross-sectional view taken along the line AA ′ of FIG. That is, the plan view of the liquid crystal device of the eighth embodiment is the same as that of the first to seventh embodiments.
In FIG. 16, the first interlayer insulating film 12 ′ is formed such that the portions facing the TFT 30, the data line 6a, the scanning line 3a, and the capacitor line 3b are recessed in a concave shape. Thereby, the side of the third interlayer insulating film 7 facing the liquid crystal layer 50 is flattened. Therefore, according to the fourth embodiment, since the side facing the liquid crystal layer 50 of the third interlayer insulating film 7 is flattened, the unevenness of the surface of the third interlayer insulating film 7 depends on the degree of the flattening. The disclination (orientation failure) of the liquid crystal caused can be reduced. As a result, according to the eighth embodiment, higher-quality image display can be performed, and the opening area of the pixel portion can be widened.
As a method of forming the first interlayer insulating film 12 ′ in this way, the first interlayer insulating film 12 ′ is formed in a two-layer structure, and a thin portion consisting of only one layer is used as a concave hollow portion, and a thick portion of two layers is formed. Thin film formation and etching may be performed so as to form a concave bank portion. Alternatively, the first interlayer insulating film 12 ′ may have a single layer structure, and a concave recess may be opened by etching. In these cases, when dry etching such as reactive ion etching or reactive ion beam etching is used, there is an advantage that a concave portion can be formed as designed. On the other hand, when wet etching is used alone or in combination with dry etching, the sidewall surface of the concave recess can be formed in a tapered shape as shown in FIG. Since the remaining of the polysilicon film, resist, etc. formed around the side wall can be reduced, there is an advantage that the yield is not lowered. A groove may be formed in the TFT array substrate 10, and wirings and TFTs 30 may be formed in the groove region and planarized.
In the present embodiment, the first interlayer insulating film 12 ′ is thin even in the portion where the first light-shielding film 11a is opposed to the first storage capacitor electrode 1f as the third storage capacitor electrode. Increased benefits are also obtained. Note that the planarization technique in the eighth embodiment as described above can be applied to any of the first to seventh embodiments.
(Ninth Embodiment of Liquid Crystal Device)
A ninth embodiment of a liquid crystal device according to the present invention will be described with reference to FIG.
In the above-described eighth embodiment, the planarization process is performed by forming a concave recess in the first interlayer insulating film 12, but in the ninth embodiment, the third interlayer insulating film is formed in a concave shape. Such a flattening process is performed. Since other configurations are the same as those in the first to eighth embodiments, the same reference numerals are given to the same components in the drawings, and description thereof will be omitted. FIG. 17 is a cross-sectional view corresponding to the cross section AA ′ of FIG. That is, the plan view of the liquid crystal device of the eighth embodiment is the same as that of the first to seventh embodiments.
In FIG. 17, the third interlayer insulating film 7 ′ is formed such that portions facing the TFT 30, the data line 6 a, the scanning line 3 a, and the capacitor line 3 b are recessed in a concave shape. More specifically, a CMP (Chemical Mechanical Polishing) process is performed on the upper surface of the third interlayer insulating film 7 ′. Thus, the side of the third interlayer insulating film 7 ′ facing the liquid crystal layer 50 is flattened. Therefore, according to the fifth embodiment, it is possible to reduce liquid crystal disclination (alignment failure) caused by unevenness of the surface of the third interlayer insulating film 7 ′ according to the degree of planarization. As a result, according to the fifth embodiment, higher-quality image display can be performed, and the opening area of the pixel portion can be widened.
In addition to such a CMP process, SOG (spin-on glass) may be formed by spin coating or the like to planarize the upper surface of the third interlayer insulating film 7 ′.
Furthermore, in the above-described eighth and ninth embodiments, the recessed portions are formed in the first and third interlayer insulating films, respectively, but the recessed portions may be formed in the second interlayer insulating film, and May combine these.
In addition to these, the concave portion formed in the first, second, or third interlayer insulating film is not a portion facing the TFT 30, the data line 6a, the scanning line 3a, and the capacitor line 3b. Is at least a portion facing the data line 6a where the total film thickness is the largest when no flattening process is performed, so that the flattening process as in the eighth or ninth embodiment is performed. Also good. Note that the planarization technique in the eighth and ninth embodiments as described above can be applied to any of the first to seventh embodiments.
The overall configuration of each embodiment of the liquid crystal device configured as described above will be described with reference to FIGS. FIG. 18 is a plan view of the TFT array substrate 10 as viewed from the side of the counter substrate 20 together with the components formed thereon. FIG. It is H 'sectional drawing.
In FIG. 18, a sealing material 52 is provided on the TFT array substrate 10 along the edge thereof, and in parallel with the inner side thereof, for example, as a frame made of the same or different material as the second light shielding film 23. A third light shielding film 53 is provided. A data line driving circuit 101 and an external circuit connection terminal 102 are provided along one side of the TFT array substrate 10 in a region outside the sealing material 52, and the scanning line driving circuit 104 has two sides adjacent to the one side. It is provided along. Needless to say, if the delay of the scanning signal supplied to the scanning line 3a is not a problem, the scanning line driving circuit 104 may be provided on only one side. Further, the data line driving circuit 101 may be arranged on both sides along the side of the image display area. For example, the odd-numbered data lines 6a supply an image signal from a data line driving circuit arranged along one side of the image display area, and the even-numbered data lines extend along the opposite side of the image display area. Alternatively, an image signal may be supplied from a data line driving circuit arranged in this manner. If the data line 6a is driven in a comb-like shape in this way, the area occupied by the data line driving circuit can be expanded, so that a complicated circuit can be configured. Further, a plurality of wirings 105 are provided on the remaining side of the TFT array substrate 10 to connect between the scanning line driving circuits 104 provided on both sides of the image display area. Further, a third light shielding film 53 as a frame is provided. Alternatively, a precharge circuit 201 (see FIG. 4) may be provided behind the screen. Further, at least one corner portion of the counter substrate 20 is provided with a conductive material 106 for electrical conduction between the TFT array substrate 10 and the counter substrate 20. As shown in FIG. 19, the counter substrate 20 having substantially the same outline as the sealing material 52 shown in FIG. 18 is fixed to the TFT array substrate 10 by the sealing material 52.
On the TFT array substrate 10 of the liquid crystal device in each of the embodiments described above with reference to FIGS. 1 to 19, an inspection circuit for inspecting the quality, defects, etc. of the liquid crystal device during manufacturing or at the time of shipment. May be formed. Further, instead of providing the data line driving circuit 101 and the scanning line driving circuit 104 on the TFT array substrate 10, the peripheral portion of the TFT array substrate 10 is mounted on, for example, a driving LSI mounted on a TAB (Tape Automated Bonding) substrate. You may make it connect electrically and mechanically through the anisotropic conductive film provided in this. Further, for example, a TN (Twisted Nematic) mode, a VA (Vertically Aligned) mode, and a PDLC (Polymer Dipersed Liquid Crystal) are respectively provided on the side on which the projection light of the counter substrate 20 enters and the side on which the emission light of the TFT array substrate 10 exits. ) Mode or the like, or a normally white mode / normally black mode, a polarizing film, a retardation film, a polarizing means, etc. are arranged in a predetermined direction.
Since the liquid crystal device in each of the embodiments described above is applied to a color liquid crystal projector (projection display device), three liquid crystal devices are used as RGB light valves, and each light valve has an RGB color. The light of each color decomposed through the decomposition dichroic mirror is incident as projection light. Therefore, in each embodiment, the counter substrate 20 is not provided with a color filter. However, an RGB color filter may be formed on the counter substrate 20 together with the protective film in a predetermined region facing the pixel electrode 9a where the second light shielding film 23 is not formed. In this way, the liquid crystal device according to each embodiment can be applied to a color liquid crystal device such as a direct-view type or a reflective type color liquid crystal television other than the liquid crystal projector. Furthermore, a microlens may be formed on the counter substrate 20 so as to correspond to one pixel. In this way, a bright liquid crystal device can be realized by improving the collection efficiency of incident light. Furthermore, a dichroic filter that creates RGB colors using light interference may be formed by depositing multiple layers of interference layers having different refractive indexes on the counter substrate 20. According to this counter substrate with a dichroic filter, a brighter color liquid crystal device can be realized.
In the liquid crystal device in each of the embodiments described above, incident light is incident from the counter substrate 20 side as in the conventional case. However, since the first light shielding film 11a is provided, the incident light is incident from the TFT array substrate 10 side. Light may be incident and emitted from the counter substrate 20 side. That is, even when the liquid crystal device is attached to the liquid crystal projector in this way, it is possible to prevent light from entering the channel region 1a ′, the low concentration source region 1b, and the low concentration drain region 1c of the semiconductor layer 1a. An image can be displayed. Here, conventionally, in order to prevent reflection on the back surface side of the TFT array substrate 10, it is necessary to separately arrange anti-reflection (AR) -coated polarizing means or to paste an AR film. there were. However, in each embodiment, the first light shielding film 11a is formed between the surface of the TFT array substrate 10 and at least the channel region 1a ′ and the low concentration source region 1b and the low concentration drain region 1c of the semiconductor layer 1a. There is no need to use such AR-coated polarizing means or AR film, or to use an AR-treated substrate of the TFT array substrate 10 itself. Therefore, according to each embodiment, the material cost can be reduced, and it is very advantageous that the yield is not lowered due to dust, scratches, or the like when the polarizing means is attached. In addition, since the light resistance is excellent, even when a bright light source is used or polarization conversion is performed by a polarization beam splitter to improve light use efficiency, image quality degradation such as crosstalk due to light does not occur.
In addition, the switching element provided in each pixel has been described as a normal staggered type or coplanar type polysilicon TFT, but other types of TFTs such as an inverted staggered type TFT and an amorphous silicon TFT are also used. Each embodiment is effective.
As an example of an electronic apparatus using the above liquid crystal device, a configuration of a projection display device will be described with reference to FIG. In FIG. 21, a projection display device 1100 is provided with three liquid crystal devices as described above, and shows a schematic configuration diagram of an optical system of the projection liquid crystal device used as RGB liquid crystal devices 962R, 962G, and 962B. The light source device 920 and the uniform illumination optical system 923 described above are employed in the optical system of the projection display device of this example. The projection display device includes a color separation optical system 924 as color separation means for separating the light beam W emitted from the uniform illumination optical system 923 into red (R), green (G), and blue (B); The three light valves 925R, 925G, and 925B as modulation means for modulating the color light beams R, G, and B, and the color synthesis prism 910 as color synthesis means for recombining the modulated color light beams are combined. A projection lens unit 906 is provided as projection means for enlarging and projecting the light beam onto the surface of the projection surface 100. Further, a light guide system 927 for guiding the blue light beam B to the corresponding light valve 925B is also provided.
The uniform illumination optical system 923 includes two lens plates 921 and 922 and a reflection mirror 931, and the two lens plates 921 and 922 are arranged to be orthogonal to each other with the reflection mirror 931 interposed therebetween. The two lens plates 921 and 922 of the uniform illumination optical system 923 each include a plurality of rectangular lenses arranged in a matrix. The light beam emitted from the light source device 920 is divided into a plurality of partial light beams by the rectangular lens of the first lens plate 921. These partial light beams are superimposed in the vicinity of the three light valves 925R, 925G, and 925B by the rectangular lens of the second lens plate 922. Therefore, by using the uniform illumination optical system 923, even when the light source device 920 has a non-uniform illumination distribution in the cross section of the emitted light beam, the three light valves 925R, 925G, and 925B can be uniformly illuminated. It can be illuminated.
Each color separation optical system 924 includes a blue-green reflecting dichroic mirror 941, a green reflecting dichroic mirror 942, and a reflecting mirror 943. First, in the blue-green reflecting dichroic mirror 941, the blue light beam B and the green light beam G included in the light beam W are reflected at right angles and travel toward the green reflecting dichroic mirror 942. The red light beam R passes through the mirror 941, is reflected at a right angle by the rear reflecting mirror 943, and is emitted from the emission unit 944 of the red light beam R to the color synthesis prism 910 side.
Next, in the green reflecting dichroic mirror 942, only the green light beam G of the blue and green light velocities B and G reflected by the blue-green reflecting dichroic mirror 941 is reflected at a right angle, and the green light beam G is emitted from the emitting portion 945. The light is emitted to the side of the combining optical system. The blue light beam B that has passed through the green reflecting dichroic mirror 942 is emitted from the emission part 946 of the blue light beam B to the light guide system 927 side. In this example, the distances from the light beam W emission part of the uniform illumination optical element to the color light emission parts 944, 945, and 946 in the color separation optical system 924 are set to be substantially equal.
Condensing lenses 951 and 952 are disposed on the emission side of the emission portions 944 and 945 for the red and green light beams R and G of the color separation optical system 924, respectively. Therefore, the red and green light beams R and G emitted from the respective emission portions are incident on these condenser lenses 951 and 952 and are collimated.
The collimated red and green light beams R and G are incident on the light valves 925R and 925G and modulated, and image information corresponding to each color light is added. That is, these liquid crystal devices are subjected to switching control according to image information by a driving unit (not shown), and thereby each color light passing therethrough is modulated. On the other hand, the blue light beam B is guided to the corresponding light valve 925B via the light guide system 927, where it is similarly modulated according to the image information. The light valves 925R, 925G, and 925B in this example further include incident-side polarization means 960R, 960G, and 960B, emission-side polarization means 961R, 961G, and 961B, and liquid crystal devices 962R and 962G disposed therebetween. , 962B.
The light guide system 927 includes a condensing lens 954 arranged on the emission side of the emission part 946 of the blue light beam B, an incident-side reflection mirror 971, an emission-side reflection mirror 972, and an intermediate lens arranged between these reflection mirrors. 973 and a condensing lens 953 disposed on the front side of the light valve 925B. The blue light beam B emitted from the condenser lens 946 is guided to the liquid crystal device 962B via the light guide system 927 and modulated. The optical path length of each color beam, that is, the distance from the emitting part of the beam W to each of the liquid crystal devices 962R, 962G, 962B is the longest for the blue beam B, and therefore the most light loss of the blue beam. However, the light loss can be suppressed by interposing the light guide system 927.
The color light beams R, G, and B modulated through the light valves 925R, 925G, and 925B are incident on the color synthesis prism 910 and synthesized there. Then, the light synthesized by the color synthesis prism 910 is enlarged and projected onto the surface of the projection surface 100 at a predetermined position via the projection lens unit 906.
In this example, since the liquid crystal devices 962R, 962G, and 962B are provided with a light shielding layer on the lower side of the TFT, the liquid crystal devices 962R, 962G, and 962B depend on the projection optical system in the liquid crystal projector based on the projection light from the liquid crystal devices 962R, 962G, and 962B. Reflected light, reflected light from the surface of the TFT array substrate when the projected light passes, a part of the projected light that penetrates the projection optical system after being emitted from another liquid crystal device, etc. as return light of the TFT array substrate Even if the light is incident from the side, the light shielding for the channel of the switching TFT of the pixel electrode can be sufficiently performed.
For this reason, even if a prism unit suitable for miniaturization is used in the projection optical system, a film for preventing return light is separately arranged between the liquid crystal devices 962R, 962G, 962B and the prism unit, or the polarizing means is used. Since it is not necessary to perform a return light prevention process, it is very advantageous in reducing the size and simplification of the configuration.
In this embodiment, since the influence of the return light on the channel region of the TFT can be suppressed, the polarizing means 961R, 961G, and 961B subjected to the return light prevention process directly on the liquid crystal device need not be attached. Therefore, as shown in FIG. 18, the polarizing means is formed away from the liquid crystal device. More specifically, one polarizing means 961R, 961G, 961B is attached to the color combining prism 910, and the other polarizing means 960R, 960G and 960B can be attached to the condenser lenses 953, 945, and 944. In this way, by attaching the polarizing means to the prism unit or the condenser lens, the heat of the polarizing means is absorbed by the prism unit or the condenser lens, and thus the temperature rise of the liquid crystal device can be prevented.
Although not shown, an air layer is formed between the liquid crystal device and the polarizing unit by forming the liquid crystal device and the polarizing unit apart from each other, so a cooling unit is provided between the liquid crystal device and the polarizing unit. By sending air such as cold air into the liquid crystal, it is possible to further prevent the temperature of the liquid crystal device from rising and to prevent malfunction due to the temperature rise of the liquid crystal device.
According to the liquid crystal device of the present invention, the storage capacitor is provided to each of the plurality of pixel electrodes by the low resistance capacitance line using the plurality of light shielding films, so that the drive frequency of the liquid crystal device is increased. However, lateral crosstalk, ghosts, and the like caused by potential fluctuation of the capacitor line due to capacitive coupling between the data line and the capacitor line are reduced, and high-quality image display can be performed. Further, precharge and scanning line inversion driving can be performed satisfactorily. In addition to these, even if the capacitance line is disconnected due to foreign matter, the wiring by the light shielding film replaces the capacitance line, so that a redundant structure can be realized, and the occurrence of cracks related to the wiring by the light shielding film is reduced and the reliability is reduced. In addition, a liquid crystal device with a high yield rate can be realized.
A liquid crystal is sandwiched between a pair of substrates, and on one of the pair of substrates,
A plurality of intersecting data lines and a plurality of scanning lines;
A plurality of thin film transistors provided corresponding to intersections of the plurality of data lines and the plurality of scanning lines;
A plurality of pixel electrodes provided corresponding to the plurality of thin film transistors;
A plurality of capacitance lines extending in a direction intersecting the plurality of data lines, respectively, and a plurality of capacitance lines for providing storage capacitors to the plurality of pixel electrodes, respectively.
A position that extends in a direction intersecting the plurality of data lines and covers at least a channel region of the plurality of thin film transistors when viewed from the one substrate side, and a position that at least partially faces the plurality of capacitance lines, respectively. A plurality of light-shielding films electrically connected to the plurality of capacitor lines for each of one or a plurality of pixels in a direction intersecting the plurality of data lines,
An interlayer insulating film interposed between the plurality of light shielding films and the plurality of thin film transistors;
The plurality of capacitor lines and the plurality of light shielding films are electrically connected through contact holes formed in the interlayer insulating film at positions overlapping the plurality of data lines when viewed from the one substrate side. A liquid crystal device characterized by the above.
A plurality of capacitance lines extending in directions intersecting the plurality of data lines, respectively, and a plurality of capacitance lines each providing storage capacitance to the plurality of pixel electrodes;
A position that extends in a direction intersecting the plurality of data lines and covers at least a channel region of each of the plurality of thin film transistors when viewed from the one substrate side and a position that at least partially faces the plurality of scanning lines. A plurality of light-shielding films electrically connected to the plurality of capacitor lines for each of one or a plurality of pixels in a direction intersecting the plurality of data lines,
The storage capacitor is provided by a first storage capacitor electrode and a second storage capacitor electrode,
The first storage capacitor electrode is extended from a semiconductor layer constituting a source or drain region on the side connected to the pixel electrode of the thin film transistor,
The second storage capacitor electrode comprises the capacitor line;
3. The liquid crystal device according to claim 1, wherein the first storage capacitor electrode is formed on a lower layer side than the second storage capacitor electrode. 4.
4. The liquid crystal device according to claim 1, wherein the capacitor line and the plurality of light shielding films are connected to a constant potential source.
5. The liquid crystal device according to claim 1, wherein each of the plurality of light shielding films is electrically connected to the capacitor line at an adjacent stage.
The plurality of light-shielding films are formed at positions facing the scanning lines only at positions covering the channel region, respectively. Liquid crystal device.
6. The interlayer insulating film formed at a position closest to the liquid crystal among the plurality of interlayer insulating films formed on the substrate is flat on the side facing the liquid crystal. The liquid crystal device according to item.
At least one of the plurality of interlayer insulating films formed on the substrate is formed such that a portion facing at least one of the thin film transistor, the data line, the scanning line, and the capacitor line is recessed in a concave shape. The side facing the liquid crystal of the film formed at a position closest to the liquid crystal among the plurality of interlayer insulating films is flattened. Liquid crystal device.
An electronic apparatus comprising the liquid crystal device according to any one of claims 1 to 8.
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2019-03-19 EXPY Cancellation because of completion of term