JPH1039332A - Liquid crystal panel and substrate for liquid crystal panel as well as projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of obtaining a sufficient holding capacitance even if the size of pixel electrodes is small and decreasing leak currents by decreasing the quantity of leak light in a reflection type LCD(liquid crystal display device) using semiconductors as substrates. SOLUTION: Conductive layers 9 which constitute holding capacitors are formed by each of respective pixels below the pixel electrodes 14 which are reflection electrodes. Semiconductor regions 8 or another conductive layers which are the other terminals of these holding capacitors are formed via insulating films below or above the conductive layers 9. The conductive layers 9 are electrically connected to transistors (MOSFETs) for driving the pixel electrodes 14. The semiconductor regions 8 or the other conductive layers are electrically connected to wiring layers 12 which apply the potential near the common potential or near the central potential of the frequency of the voltage impressed on the reflection electrodes described above or the intermediate potential of both potentials so as to fix the potential.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and, more particularly, to a reflection type liquid crystal display device, and more particularly to an active matrix type LCD in which pixel electrodes are driven by MOSFETs (insulated gate type field effect transistors) formed on a semiconductor substrate. (Liquid crystal display device).

[0002]

2. Description of the Related Art Conventionally, a reflective active matrix L
As a CD, a TFT array using amorphous silicon is formed on a glass substrate, and a pixel electrode serving as a reflection electrode is formed thereon via an acrylic resin or the like to form a TF.
An LCD having a structure driven by T has been put to practical use.

[0003]

The reflection type active matrix LCD using the above TFT has a relatively large device size. For example, in a projection type display device such as a video projector incorporating this as a light valve, There is a problem that the entire device is enlarged.

On the other hand, as a reflection type LCD having a smaller size than the reflection type active matrix LCD, there is a type in which a pixel electrode serving as a reflection electrode is driven by a MOSFET array formed on a semiconductor substrate.

However, in an LCD using a semiconductor as a substrate, the size of each pixel becomes smaller as the device size is reduced. Therefore, only a pixel electrode alone has a sufficient capacity (100 fF) to hold a voltage necessary for driving the liquid crystal. (Necessary degree) cannot be obtained.

Further, light leaks from a gap between each pixel electrode and a PN junction (a source electrode of a pixel electrode driving FET).
There is a problem that a leak current flows when the light passes through the (drain region). However, in an LCD using a semiconductor as a substrate, there is a well region, so that light leaks not only from a transistor portion but also from a semiconductor substrate separated therefrom. However, there is a disadvantage that a leak current may flow, and a light leak current is increased as compared with an LCD having a glass substrate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reflection type LCD using a semiconductor as a substrate, in which a sufficient storage capacity can be obtained even if the size of a pixel electrode is small, and a leakage current can be reduced by reducing an amount of leakage light. To provide technology.

Another object of the present invention is to increase the reflectance of a pixel electrode and the device strength in a reflective LCD using a semiconductor as a substrate.

[0009]

According to the present invention, in order to achieve the above object, a conductive layer constituting a storage capacitor for each pixel is formed below a pixel electrode serving as a reflective electrode, and a conductive layer is formed under the conductive layer. A semiconductor region or another conductive layer serving as the other terminal of the storage capacitor is formed above via an insulating film, and the conductive layer is electrically connected to a source / drain region of a MOSFET for driving a pixel electrode. The semiconductor region or the other conductive layer is electrically connected to a wiring layer that provides a potential near the common potential or near the center potential of the amplitude of the voltage applied to the reflective electrode or an intermediate potential between the two potentials so that the potential is fixed. did.

Thus, the value of the storage capacitor is secured, and the voltage of the storage capacitor becomes the same as the voltage applied between the pixel electrode and the counter electrode, and the voltage is symmetric even when the data line is driven by AC. A waveform can be obtained.

In the above case, the conductive layer forming the storage capacitor and the wiring layer for applying the common potential are formed so as to overlap with each other, or the insulating film of the storage capacitor is formed as a gate insulating film of a MOSFET for driving the reflection electrode. By making the film thickness smaller, a larger capacity can be provided.

Further, the conductive layer forming the storage capacitor may be a polysilicon layer formed in the same step as the gate electrode forming the MOSFET, or the insulating film of the storage capacitor may be formed by the MOSFET or the MOSFET driving the pixel electrode. By using an insulating film formed in the same step as the gate insulating film of the MOSFET forming the peripheral circuit, a storage capacitor can be formed without complicating the process.

Also, MOSFETs for driving each pixel electrode
Was disposed near the center of the pixel electrode, and a conductive layer constituting the above-mentioned protection capacitor was formed around the pixel electrode. Thereby, the conductive layer of the storage capacitor serves as a light-shielding film, so that a leak current can be reduced.

Further, a layer having a light-shielding property is formed below the slit between the pixel electrodes. In this case, the light-shielding layer is formed of the same conductive layer as the data line, and is applied near the LC common potential, near the center potential of the amplitude of the voltage applied to the reflective electrode, or an intermediate potential between both potentials. good.

When forming a pixel electrode serving as a reflective electrode, a concave portion corresponding to the shape of each pixel electrode is formed on the surface of an insulating film covering a MOSFET for driving the pixel electrode, and then a metal layer is entirely covered. Then, polishing is performed by CMP (Chemical Mechanical Polishing) so that the metal layer remains only in the recesses, and the surface is flattened. Thereby, the reflectance of the pixel electrode can be increased.

Further, a support base made of glass or ceramic or the like is fixed to the back surface of the semiconductor substrate using an adhesive or the like. As a result, the device strength of a reflective LCD using a semiconductor as a substrate can be increased.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of a reflective substrate of a reflective LCD to which the present invention is applied. 1 and 2 show a cross-sectional view and a planar layout of one pixel portion of the pixels arranged in a matrix. FIG. 1 shows a cross section taken along line II in FIG.

In FIG. 1, 1 is a P-type semiconductor substrate such as single crystal silicon, 2 is a P-type well region formed on the surface of the semiconductor substrate 1, and 3 is an element isolation formed on the surface of the semiconductor substrate 1. Field oxide film (so-called LOC)
OS). Although the well region 2 is not particularly limited, the well region 2 is formed as a common well region of a pixel such as 768 × 1024, and includes a data line driving circuit, a gate line driving circuit, an input circuit, It is formed separately from a well region where a component constituting a peripheral circuit such as a timing control circuit is formed.

An opening is formed in the field oxide film 3, and a gate electrode 4a made of polysilicon or the like is formed at the center of the inside of the opening with a gate oxide film interposed therebetween. Is formed with source and drain regions 5a and 5b formed of an N-type diffusion layer having a high impurity concentration to constitute a MOSFET. One of the source and drain regions 5a and 5b (5a in the figure)
Above this, a data line 7 made of a first aluminum layer is formed via an insulating film 6 such as a PSG film, and a part of this data line 7 is formed by a contact hole formed in the insulating film 6. It is electrically connected to the source and drain regions 5a.

An annular opening is formed in the field oxide film 3 around the MOSFET, and a low impurity concentration N-type diffusion layer 8 is formed on the substrate surface inside the opening. An electrode 9 made of a polysilicon layer or the like is formed on the surface of the diffusion layer 8 with an insulating film formed in the same step as the gate insulating film interposed between the electrode 9 and the diffusion layer 8. Is configured. The electrode 9 and the insulating film therebelow can be formed in the same step as the polysilicon layer and the insulating film serving as the gate electrode and the gate insulating film of the MOSFET.

An aluminum wiring 1 having one end in contact with the other (5b in the figure) of the source and drain regions 5a and 5b of the MOSFET is provided on a part of the inner edge of the electrode 9.
0 is electrically connected to the other end. In addition, the inside of the diffusion layer 8 has a high impurity concentration of N
A contact portion 11 formed of a mold diffusion layer is formed. The contact portion 11 is provided with a wiring (hereinafter referred to as an LC common line) for transmitting an LC common potential made of an aluminum layer to a first layer formed above the insulating film 6 via the insulating film 6. 1)
Part 2 is electrically connected to a contact hole formed in the insulating film 6. Here, the LC common potential is a voltage applied to an electrode opposed to the pixel electrode 14 with the liquid crystal interposed therebetween, and is a so-called push-down (substantial writing voltage due to capacitive coupling) which is a problem in driving the liquid crystal. Is a voltage shifted in advance by that amount in consideration of the phenomenon in which the voltage shifts to the negative side.

As a result, the insulation film capacitance formed between the electrode 9 and the diffusion layer 8 is connected to the source / drain region 5b of the MOSFET as a storage capacitance having one end fixed to the LC common potential. The Rukoto. As a result, the capacitance existing between the electrode 9 and the LC common line 12 is connected to the MOSFET, and the value of the storage capacitance is ensured. Further, by setting one end of the storage capacitor to the LC common potential, the voltage of the storage capacitor becomes the same as the voltage applied between the pixel electrode and the counter electrode, and a symmetrical voltage waveform is obtained even when the data line is AC driven. Is obtained. Note that the LC common line 12 is
Since the electrode 9 overlaps with the electrode 9, a storage capacitor can be formed between the electrode 9 and the LC common line 12. Furthermore, as shown by the two-dot chain line A in FIG. 1, the LC common line 12 largely overlaps with the electrode 9 so that a larger storage capacity can be provided.

A part of the aluminum wiring 10 has the MO
LTO made of an insulator such as silicon dioxide formed so as to cover the SFET and the electrode 9 of the storage capacitor.
(Low Tenperature Oxide) A pixel electrode 14 serving as a reflection electrode made of a second aluminum layer formed on the surface of the film 13 via a film 13 is electrically connected by a connection plug 15 made of a refractory metal such as tungsten. ing.

The pixel electrode 14 is not particularly limited, but tungsten or the like constituting the connection plug 15 is formed by CVD.
After being deposited by the method, the tungsten and the LTO film 12 are flattened by CMP (chemical mechanical polishing),
For example, it is formed by low-temperature sputtering, and one side is about 20 μm.
m is shaped like a square. Above the pixel electrode 14, a glass substrate on the incident side having a counter electrode made of ITO is arranged at an appropriate interval, and a TN (Twisted Nematic) liquid crystal is disposed in a gap surrounded by a sealing material. Alternatively, a reflective LCD is formed by filling an SH (Super Homeotropic) liquid crystal or the like (see FIG. 7).

FIG. 2 is a plan layout of the liquid crystal panel substrate on the reflection side shown in FIG. As shown in the figure, in this embodiment, the data line 7 and the gate line 4 are formed so as to be orthogonal to each other, and the gate electrode 4a is formed so as to extend in the horizontal direction of the figure. , And one source / drain region 5 a of the MOSFET is also connected to a portion formed to project from the data line 7.

The common line 12 and the well region 2 for applying an LC common potential to the storage capacitor of each pixel.
A Vss line 16 for applying a potential such as Vss (for example, 0 V) to the data line 7 is provided in parallel with the data line 7. Vss is also applied to the semiconductor substrate (P-) 1. The Vss line 16 is connected to the well region at a contact region 2a (see FIG. 1) provided in the well region 2. The contact region 2a does not need to be provided for each pixel, and may be formed at appropriate intervals. Thereby, the well potential is fixed at Vss and the potential of the capacitor is fixed at LC-COM. Therefore, the potential variation due to the generation of carriers is less likely to occur, and stable operation can be realized.

Further, in this embodiment, the data lines 7 are arranged along the vertical slits 17a between the pixel electrodes adjacent to each other, and have a function of blocking light leaked from the slits. Is formed. on the other hand,
A light-shielding layer 18 made of an aluminum layer is also provided in the pixel electrode and the slit 17b in the lateral direction of the pixel electrode. Since the liquid crystal panel of this embodiment is in a normally black mode, the light-shielding layer 18 is connected to the LC common line 12 so that an LC common potential is applied and the potential of the light-shielding layer 18 is fixed. Is configured.

As shown in FIG. 8, a large voltage VG such as 15V is applied to the gate electrode 4a of a pixel driving FET (field effect transistor), while the transistor of the peripheral circuit is 5V. In order to improve the characteristics of the FET and increase the operation speed of the peripheral circuit, the gate insulating film of the FET constituting the peripheral circuit is formed thinner than the gate insulating film of the pixel driving FET. Technology is conceivable. When such a technique is applied, the thickness of the gate insulating film of the FET constituting the peripheral circuit can be reduced to about one third of the thickness of the gate insulating film of the pixel driving FET from the breakdown voltage of the gate insulating film. . First
In the embodiment, as shown in FIG. 8, the maximum voltage applied between the electrodes of the storage capacitor is about 5 V which is the difference between the voltage Vd applied to the data line and the center potential Vc of the amplitude of Vd.
(The LC common potential LC-COM is shifted by ΔV from Vc, but the voltage actually applied to the pixel electrode is also ΔV.
Vd-ΔV shifted by V). Therefore,
In the first embodiment, the gate insulating film of the pixel driving TFT and the insulating film of the storage capacitor are formed in the same step, but the polysilicon layer 9 forming one electrode of the storage capacitor is formed.
When the insulating film immediately below is modified so as to be formed simultaneously with the insulating film of the FET constituting the peripheral circuit instead of the gate insulating film of the pixel driving FET, the insulating film thickness of the storage capacitor is reduced by 3 times as compared with the first embodiment. There is an advantage that the capacitance value can be tripled by this.

FIG. 3 shows a second embodiment of the reflection side substrate of the reflection type LCD to which the present invention is applied. The plane layout is the same as that of FIG. FIG. 3 shows a cross section taken along the same location as FIG. 1, that is, along the line II in FIG.

In this embodiment, unlike the first embodiment,
The storage capacitor is constituted by an insulating film capacitor including a pair of conductive layers 9 and 19 opposed to each other via the insulating film 6a. In this embodiment, on the field oxide film 3, the lower conductive layer 9, which is one electrode of the storage capacitor, is formed of a polysilicon layer formed simultaneously with the polysilicon layer forming the gate electrode 4a. A conductive layer (for example, polysilicon or aluminum) 19 serving as the other electrode is formed via an HTO (High Tenperature Oxide) film 6a made of an insulator such as silicon nitride. The conductive layer 9 may be formed, for example, by stacking a polysilicon layer and a metal layer, and the metal layer may be silicided when the HTO film 6a is formed thereon. Alternatively, the surface of the conductive layer 9 (polysilicon) may be thermally oxidized to form an oxide film, and the oxide film may be used as a dielectric to form a capacitor.

FIG. 4 shows a third embodiment of the reflection-side substrate. The embodiment of FIG. 4 and the embodiments of FIGS. 1 and 3 have the same configuration in terms of circuit, but have different layouts.
The cross-sectional structure of the capacitor is the same as that of FIG.

As shown in FIG. 4, in this embodiment, the MOSFET driving the pixel electrode 14 is
4 and the MOSF
Conductive layers 9 and 19 forming electrodes of the storage capacitor are formed so as to surround the periphery of the ET. That is, in this embodiment, as in the second embodiment (FIG. 3), the storage capacitor is constituted by an insulating film capacitor including a pair of conductive layers 9 and 19 opposed to each other via an insulating film. Not using gate capacitance
The MO in which the conductive layer constituting the storage capacitor drives the pixel electrode
This is because they cross the gate electrode of the SFET. Therefore, in this embodiment, the conductive layer 9 serving as one electrode of the storage capacitor is formed of a polysilicon layer (second polysilicon) different from the gate electrode or a metal layer of aluminum or the like. A conductive layer 19 serving as the other electrode is formed on the layer 9 via the HTO film 6a, for example, a third metal layer such as polysilicon or aluminum.

In the third embodiment, the data line 7 is provided to cross the conductive layers 9 and 19 so as to pass near the MOSFET, and the Vss line 1 is used instead of the data line 7.
6 are arranged along a vertical slit 17a between the pixel electrodes 14 adjacent to each other, and are formed so as to also have a function of blocking light leaked from the slit. A light-shielding layer 18 made of an aluminum layer extending from the LC common line 12 is also provided in the pixel electrode and the slit 17 b in the lateral direction of the pixel electrode. Further, the light shielding layer 16a that shields a part of the horizontal slit 17b between the pixel electrodes is
It is formed so as to extend from the ss line 16.

As described above, in this embodiment, the MO
Since the SFET is arranged so as to be located substantially at the center of the pixel electrode 14, it is difficult for light entering from the slit 17 between the adjacent pixel electrodes to reach the MOSFET portion. In addition, the Vss line 16 extends along the vertical slit 17a and the horizontal slit 17
b, the light-shielding layers 16a and 18 are arranged along
The amount of leakage light reaching the semiconductor substrate itself can also be reduced, and the leakage current can be greatly reduced. In the above embodiment, the line 12 for applying the potential to the conductive layer of the holding electrode is not only the LC-COM potential but also the LC-C potential.
The potential near the OM potential, near the center potential of the voltage Vd applied to the pixel electrode shown in FIG. 8, or an intermediate potential between LC-COM and the center of Vd may be applied. However, the optimal potential is LC-COM.

FIGS. 5 and 6 show a fourth embodiment of the reflection-side substrate. 5 and 6 show a cross-sectional view and a planar layout of one pixel portion of the pixels arranged in a matrix. FIG. 5 shows a cross section along the line VV in FIG.

In this embodiment, as in the first embodiment, the storage capacitance is the insulation film capacitance between the polysilicon layer 9 formed simultaneously with the gate electrode and the diffusion layer 8 'formed on the substrate surface. It is composed of The gate electrode of the transistor and the insulating film of the storage capacitor are formed in the same step. However,
In this embodiment, a P-type diffusion layer 8 'is used instead of the N-type diffusion layer 8 of the first embodiment as a diffusion layer serving as the other electrode of the storage capacitor. A Vss line 16 is connected instead of the LC common line 12 in the example. According to this embodiment, since the LC common line becomes unnecessary, if the thickness of the insulating film (gate insulating film) between the electrodes is the same, the area of the conductive layer 9 is maintained larger than that of the first embodiment. There is an advantage that the capacity can be increased.

FIG. 7 shows an embodiment of a method for forming the pixel electrode 14. In the above embodiment, after the LTO film 13 is formed and its surface is flattened by the CMP (Chemical Mechanical Polishing) method, an aluminum layer is applied by a low temperature sputtering method and patterned by selective etching to form the pixel electrode 14. In the embodiment shown in FIG. 7, after the LTO film 13 is formed, a concave portion 13a is formed in a portion where a pixel electrode is formed, and an aluminum layer 14 'is formed thereon by a low-temperature sputtering method or the like. It is attached (FIG. 7A). Then, the surface is CMP
The surface of the aluminum layer and the LTO film is polished by the (chemical mechanical polishing) method until the LTO film appears. In this case, the polishing by the above-mentioned CMP is performed in the first stage, for example, when the particle size is 400 to
The polishing is performed using an abrasive containing 800 (preferably 500) angstroms of a rough slurry, and in a second step using an abrasive containing a fine slurry having a particle size of, for example, 50 to 200 (preferably 100) angstroms. It is desirable to do. In general, it is known that a scratch of one tenth of a diameter of a slurry remains on a polished surface in polishing by CMP. According to the two-stage polishing, only a scratch of 20 Å or less remains on the surface of the aluminum layer 14.
A reflective electrode having optically sufficient characteristics can be obtained.

As a result, as shown in FIG. 7B, the aluminum pixel electrode 14 is formed so as to remain in the recess 13a, and the whole is flattened. Moreover, at this time, since the surface of the pixel electrode 14 is polished by the CMP method,
The reflectivity is much higher than that of the embodiment without the CMP treatment. The material of the pixel electrode 14 is not limited to the aluminum of the above embodiment, but may be any material as long as it has a high reflectance and is a conductor. Alternatively, platinum or silver may be thinly formed on the surface of the pixel electrode 14 to increase the reflectance.

FIG. 9 shows a planar layout configuration of a liquid crystal panel substrate (reflection side substrate) to which the above embodiment is applied.

As shown in FIG. 9, in this embodiment, a light-shielding layer 25 for preventing light from entering a peripheral circuit provided on the peripheral portion of the substrate is provided.
Here, the peripheral circuit means a data line driving circuit 21 and a gate line 4 which are provided around a pixel region 20 in which the pixel electrodes are arranged in a matrix and drive the data lines 7 according to image data. A gate line driving circuit 22 for scanning and driving, an input circuit 23 for taking in image data input from the outside via a pad area 26, and a timing control circuit 24 for controlling these circuits. A MOSFET formed in the same step as the electrode driving MOSFET is used as an active element or a switching element, and is combined with a load element such as a resistor or a capacitor.

In this embodiment, the light shielding layer 25
Is composed of a second aluminum layer formed in the same step as the pixel electrode 14 shown in FIGS. 1, 3 and 5, and is configured to apply an LC common potential. Reference numeral 26 denotes a pad region in which pads or terminals used to supply a power supply voltage are formed. By applying the LC common potential, the reflection can be reduced as compared with the case of floating or other potential.

FIG. 10 shows a sectional structure of a reflection type liquid crystal panel to which the liquid crystal panel substrate 31 is applied. As shown in FIG. 10, a support substrate 32 made of glass, ceramic, or the like is adhered to the back surface of the liquid crystal panel substrate 31 with an adhesive. At the same time, L
An incident side glass substrate 35 having a counter electrode 33 made of a transparent conductive film (ITO) to which a C common potential is applied is disposed at an appropriate interval, and TN is disposed in a gap surrounded by a sealing material 36. (Twisted Nematic) type liquid crystal or S
The liquid crystal panel 30 is filled with an H (Super Homeotropic) type liquid crystal 37 or the like. It should be noted that a signal is externally input or the pad area 26 is
The position where the sealing material is provided is designed so as to come to the outside of the device.

The light-shielding layer 25 on the peripheral circuit is configured to face the counter electrode 33 with the liquid crystal 37 interposed. Since the LC common potential is applied to the light shielding layer 25 and the counter electrode 33, no DC voltage is applied to the liquid crystal interposed therebetween. Therefore, in the case of the TN type liquid crystal, the liquid crystal molecules are always kept twisted, and in the case of the SH type liquid crystal, the liquid crystal molecules are always kept in a vertically aligned state.

In this embodiment, the strength of the liquid crystal panel substrate 31 made of a semiconductor substrate is significantly increased because a support substrate 32 made of glass, ceramic, or the like is bonded to the back surface thereof with an adhesive. In particular, in the case of ceramics, the processing accuracy is excellent and the accuracy when incorporated into an optical component is easily obtained. As a result, when the support substrate 32 is bonded to the liquid crystal panel substrate 31 and then bonded to the counter substrate, there is an advantage that the gap becomes uniform over the entire panel.

FIG. 11 shows a configuration example of a video projector as an example of a projection type display device in which the reflection type liquid crystal panel of the above embodiment is applied as a light valve.

In FIG. 11, reference numeral 100 denotes a lamp as a light source, and reference numerals 101 to 103 denote right-angle prisms.
The two right-angle prisms form a cube prism by coating an inclined surface with a selective reflection film and bonding them together with an adhesive. Prisms 101 and 103, 102 and 10
3 is also bonded with an adhesive. The adhesive whose refractive index is closer to the refractive index of the prism is used. Reference numerals 111 and 112 denote light valves for blue light, green light, and red light using the reflection type liquid crystal panel of the above embodiment, and 120 synthesizes the color light modulated by each light valve. Color image on screen 130
Is a projection lens that projects light to

In the above configuration, the light from the light source is separated, modulated, synthesized, and projected as described below. 10
Reference numeral 2a denotes a polarization beam splitter layer that selectively transmits P-polarized light of the light from the light source 100 and selectively reflects an S-polarized component. Of course, the polarization component splitter may be configured to transmit the S polarization component and reflect the P polarization component.

The S-polarized light component reflected by the polarization beam splitter layer 102a enters the prism 101. 1
Reference numeral 01a denotes a wavelength selective reflection layer (a dichroic mirror) that transmits only the wavelength component of blue light and reflects other wavelength components. Thereby, blue light is incident on the liquid crystal panel 111. On the other hand, the P-polarized light component transmitted through the polarization beam splitter layer 102a enters the prism 103. 10
Reference numeral 3a denotes a dichroic mirror that reflects a wavelength component of green light and transmits other wavelength components. The green light reflected by the light 103a enters the liquid crystal panel 112. The color light transmitted through 103a includes not only a red light component but also a blue light component. Therefore, the prism 10
A red filter is formed on the exit surface of the third liquid crystal panel 113 so that red light is incident on the liquid crystal panel 113.

The liquid crystal panels 111, 112 and 113 are TN
A reflective liquid crystal panel employing a liquid crystal or SH liquid crystal. When a TN type liquid crystal is employed, in a pixel where the voltage applied to the liquid crystal layer is almost 0 (OFF state), the incident color light is elliptically polarized by the liquid crystal layer and reflected by the pixel electrode.
Since the light is again elliptically polarized by the liquid crystal layer, the light is reflected and emitted as light having a polarization axis that is shifted from the polarization axis of the incident color light by approximately 90 degrees. On the other hand, in a pixel (ON state) in which a voltage is applied to the liquid crystal layer, the incident color light reaches the pixel electrode as it is, is reflected, and is reflected and emitted with the same polarization axis as at the time of incidence.
Since the alignment angle of the liquid crystal molecules of the TN liquid crystal changes according to the voltage applied to the pixel electrode, the angle of the polarization axis of the reflected light with respect to the incident light depends on the voltage applied to the pixel electrode via the transistor of the pixel. Variable.

When the SH type liquid crystal is adopted, in a pixel where the voltage applied to the liquid crystal layer is almost 0 (OFF state),
The incident color light reaches the pixel electrode as it is, is reflected, and is reflected and emitted with the same polarization axis as at the time of incidence. On the other hand, in a pixel (ON state) in which a voltage is applied to the liquid crystal layer, the incident color light is elliptically polarized by the liquid crystal layer, reflected by the pixel electrode, and again elliptically polarized by the liquid crystal layer. And reflected as light with a polarization axis that is almost 90 degrees
Is emitted. Since the alignment angle of the liquid crystal molecules of the SH type liquid crystal changes according to the voltage applied to the pixel electrode, the angle of the polarization axis of the reflected light with respect to the incident light depends on the voltage applied to the pixel electrode via the transistor of the pixel. Variable.

For example, when S-polarized blue light is incident on the liquid crystal panel 111, it is turned off in the case of a TN type liquid crystal.
The state pixel converts to P-polarized light and reflects and emits light, and the ON state pixel reflects and emits S-polarized light. In the case of SH type liquid crystal,
The OFF state pixel reflects and emits S-polarized light, and the ON state pixel converts to P-polarized light and reflects and emits. On the other hand, since the P-polarized color light is incident on the liquid crystal panels 112 and 113, in the case of the TN type liquid crystal, the OFF state pixel is converted to S-polarized light and reflected and emitted, and the ON state pixel is reflected as P-polarized light.・ Exit. In the case of SH type liquid crystal, the OFF state pixel is P
The reflected / emitted, ON state pixel is converted to S-polarized light while being polarized and reflected / emitted.

The blue light reflected by the liquid crystal panel 111 passes through the dichroic mirror 101a and reaches the polarization beam splitter 102a that reflects the S-polarized component and transmits the P-polarized light. Therefore, in the case of the TN type liquid crystal, the reflected light of the liquid crystal panel 111 transmits the P-polarized reflected light from the OFF-state pixel to the projection lens 120, but reflects the S-polarized reflected light of the ON-state pixel. Does not reach the lens 120. on the other hand,
In the case of the SH type liquid crystal, the OFF state pixel reflects the S-polarized reflected light and does not transmit to the lens 120, and the ON state pixel transmits the P-polarized reflected light to reach the lens 120. By the above-described modulation control, the amount of transmitted light at 102a is controlled for each pixel in accordance with the application of a voltage to each pixel of the liquid crystal panel, and a blue light image is formed.

On the other hand, the liquid crystal panels 112 and 113
Is reflected by the dichroic mirror 103a
And reaches the polarizing beam splitter 102a.
Accordingly, in the case of the TN type liquid crystal, the reflected light of the liquid crystal panels 112 and 113 reflects the S-polarized reflected light from the OFF state pixel to reach the projection lens 120, but the P-polarized reflected light of the ON state pixel reflects The light does not pass through the lens 120. On the other hand, in the case of the SH type liquid crystal, the OFF state pixel transmits the P-polarized reflected light and does not reach the lens 120, and the ON state pixel reflects the S-polarized reflected light and reaches the lens 120. By the above modulation control, the amount of transmitted light at 102a is controlled for each pixel in accordance with the application of a voltage to each pixel of the liquid crystal panel,
Green and red light images are formed.

Therefore, an image in which the three primary colors are combined is formed by reflection and transmission by the polarization beam splitter 102, and is projected on the screen 130 by the projection lens 120. When TN type liquid crystal panels are used as the reflection type liquid crystal panels 111 to 113, the reflected light of the OFF-state pixels reaches the projection lens 120, so that normally white display is performed. On the other hand, when the liquid crystal panel of the SH type liquid crystal is used, the reflected light of the OFF state pixel does not reach the lens 120, so that a normally black display is performed.

As described with reference to FIG. 9, the peripheral circuit portion of the liquid crystal panel is covered with a light-shielding film, and has the same voltage (for example, an LC common potential or the same potential) together with a counter electrode formed at a position opposing the counter substrate. If the potential is different from this, the potential may be different from that of the counter electrode of the pixel portion.
In this case, the peripheral counter electrode is separated from the counter electrode of the pixel portion. ) Is applied, approximately 0 V is applied to the liquid crystal interposed between them, and the liquid crystal becomes the same as the OFF state. Therefore, in the liquid crystal panel of the TN type liquid crystal, all the periphery of the image region can be displayed white in accordance with the normally white display, and in the liquid crystal panel of the SH type liquid crystal, the periphery of the image region can be entirely black in accordance with the normally black display. Can be displayed.

According to the above embodiment, the reflection type liquid crystal panel 1
The voltage applied to each of the pixel electrodes 11 to 113 is sufficiently maintained, and a clear image is obtained because the reflectance of the pixel electrodes is extremely high.

[0058]

As described above, according to the present invention, a conductive layer constituting a storage capacitor for each pixel is formed below a pixel electrode serving as a reflective electrode, and an insulating film is formed below or above this conductive layer. A semiconductor region or another conductive layer serving as the other terminal of the storage capacitor is formed through the transistor, the conductive layer is electrically connected to a transistor for driving a pixel electrode, and the semiconductor region or another conductive layer is connected to a common potential. The potential is fixed by being electrically connected to a wiring layer that gives a potential near the center or near the center potential of the amplitude of the voltage applied to the reflective electrode or between the two potentials. Since the storage capacitor is connected to the storage capacitor and the charge applied to the pixel electrode is held, the potential is not reduced due to leakage, and the other terminal of the storage capacitor is fixed at the common potential. Large capacitance value stable is obtained.

Further, the transistor for driving each pixel electrode is arranged near the center of the pixel electrode, and the conductive layer forming the above-mentioned protection capacitor is formed around the transistor.
Light leaked from the gap between the pixel electrodes hardly reaches the pixel driving transistor, and the leak current is reduced.

Further, since a layer having a light-shielding property is formed below the slit between the pixel electrodes, light leaked from the gap between the pixel electrodes hardly reaches the semiconductor substrate, and the leak current is further reduced. can do.

When a pixel electrode serving as a reflective electrode is formed, a concave portion corresponding to the shape of each pixel electrode is formed on the surface of an insulating film covering a transistor for driving the pixel electrode.
A metal layer with a refractive index close to that of the liquid crystal is completely deposited, and the CMP
Since the surface is flattened by the chemical mechanical polishing method so that the metal layer remains only in the concave portion, the reflectance of the pixel electrode can be increased.

Further, since a support base made of glass or ceramic is fixed to the back surface of the semiconductor substrate using an adhesive or the like, the device strength of a reflective LCD using a semiconductor as a substrate is reduced. The intensity can be increased to about the same as or higher than that of the reflective LCD.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a reflection side substrate of a reflection type LCD to which the present invention is applied.

FIG. 2 is a plan layout view showing a first embodiment of a reflection-side substrate of a reflection type LCD to which the present invention is applied.

FIG. 3 is a sectional view showing a second embodiment of the reflection-side substrate of the reflection type LCD to which the present invention is applied.

FIG. 4 is a plan layout view showing a third embodiment of the reflection-side substrate of the reflection type LCD to which the present invention is applied.

FIG. 5 is a sectional view showing a fourth embodiment of the reflection-side substrate of the reflection type LCD to which the present invention is applied.

FIG. 6 is a plan layout view showing a fourth embodiment of the reflection side substrate of the reflection type LCD to which the present invention is applied.

FIG. 7 is a sectional view showing an embodiment of a method for forming a pixel electrode.

FIG. 8 is a waveform diagram showing an example of a gate drive waveform and a data line drive waveform of a pixel electrode driving FET of a reflection type LCD to which the present invention is applied.

FIG. 9 is a plan view showing a layout configuration example of a liquid crystal panel substrate (reflection side substrate) according to the embodiment.

FIG. 10 is a cross-sectional view illustrating an example of a reflective liquid crystal panel to which the liquid crystal panel substrate according to the embodiment is applied.

FIG. 11 is a schematic configuration diagram of a video projector as an example of a projection display device in which the reflective liquid crystal panel of the embodiment is applied as a light valve.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 4 gate line (gate electrode) 5a, 5b source / drain region 7 data line 9 electrode of storage capacitor (conductive layer) 12 LC common line 14 pixel electrode 20 pixel region 21 data line drive circuit 22 gate line drive circuit 23 Input circuit 24 Timing control circuit 25 Light shielding layer 26 Pad area 31 Liquid crystal panel substrate 32 Support substrate 33 Counter electrode 35 Glass substrate on incident side 36 Seal material 37 Liquid crystal 100 Lamp 101-103 Right angle prism 111-113 Reflective liquid crystal panel 120 Projection lens 130 screen

Claims (14)

[Claims] 1. A structure in which reflective electrodes are formed in a matrix on a semiconductor substrate, transistors are formed corresponding to the respective reflective electrodes, and a voltage is applied to the reflective electrodes via the transistors. In the liquid crystal panel substrate, one conductive layer forming a storage capacitor for each pixel is formed below the reflective electrode, and the other of the storage capacitor is formed below or above the conductive layer via an insulating film. And the other conductive layer is electrically connected to the transistor, and the other conductive layer has an amplitude of a voltage applied near the common potential of the liquid crystal panel or to the reflective electrode. A wiring layer for giving a potential near the center potential or an intermediate potential between the two potentials. 2. The liquid crystal panel substrate according to claim 1, wherein a conductive layer forming the storage capacitor and a wiring layer for giving the common potential are formed so as to overlap with each other. 3. A data line is provided along one slit under one of the slits between the reflective electrodes, and is formed of the same conductive layer as the data line below the other slit orthogonal to the slit. The light-shielding layer is connected to the light-shielding layer so that a potential near the common potential, near the center potential of the amplitude of the voltage applied to the reflective electrode, or an intermediate potential between the two potentials is applied. The substrate for a liquid crystal panel according to claim 1, wherein: 4. The semiconductor device according to claim 1, wherein the conductive layer forming the storage capacitor is a polysilicon layer formed in the same step as a gate electrode forming the transistor.
4. The liquid crystal panel substrate according to 2 or 3. 5. The liquid crystal panel according to claim 1, wherein the insulating film of the storage capacitor has a smaller thickness than a gate insulating film of a transistor connected to the reflective electrode. Substrate. 6. A liquid crystal panel substrate in which a transistor connected to each of the reflective electrodes and a transistor constituting a peripheral circuit for driving the gate electrode and the data line of the transistor are formed on the same semiconductor substrate. So,
6. The liquid crystal panel according to claim 5, wherein the insulating film between the pair of conductive layers forming the storage capacitor is an insulating film formed in the same step as a gate insulating film forming the transistor of the peripheral circuit. Substrate. 7. A structure in which reflective electrodes are formed in a matrix on a semiconductor substrate, transistors are formed corresponding to the respective reflective electrodes, and a voltage is applied to the reflective electrodes via the transistors. In the liquid crystal panel substrate, the transistor is disposed near the center of the corresponding reflective electrode, and one conductive layer constituting a storage capacitor for each pixel is formed below the reflective electrode around the transistor. Below or above the conductive layer, another conductive layer serving as the other terminal of the storage capacitor is formed via an insulating film, and the other conductive layer is applied near the common potential of the liquid crystal panel or to the reflective electrode. The one conductive layer is connected to the transistor which is connected to a wiring layer which gives a potential near the center potential of the voltage amplitude or an intermediate potential between the two potentials; Substrate for a liquid crystal panel according to symptoms. 8. A wiring for applying a bias potential to the semiconductor substrate is provided along one of the slits between the reflective electrodes and a conductive layer is formed below the other slit orthogonal to the slit. A light-shielding layer is provided, and the light-shielding layer is connected so that a potential near the common potential, near a center potential of the amplitude of the voltage applied to the reflective electrode, or an intermediate potential between the two potentials is applied. The liquid crystal panel substrate according to claim 6, wherein: 9. The reflection electrode and the transistor connected to the reflection electrode are formed in a central portion of a semiconductor substrate, and a peripheral circuit for driving a gate line connected to the data line and the gate electrode is formed around the reflection electrode and the transistor. 9. The liquid crystal panel substrate according to claim 1, wherein a light shielding layer made of a conductive layer is provided above the peripheral circuit. 10. A structure in which reflective electrodes are formed in a matrix on a semiconductor substrate, transistors are formed corresponding to the respective reflective electrodes, and a voltage is applied to the reflective electrodes via the transistors. In the liquid crystal panel substrate, one conductive layer forming a storage capacitor for each pixel is formed below the reflective electrode, and the other of the storage capacitor is formed below or above the conductive layer via an insulating film. Is formed, and the conductive layer is electrically connected to the transistor, applies a potential to the other conductive layer, and supplies a potential to a well region where the transistor is formed. A liquid crystal panel substrate having a conductive layer formed thereon. 11. A concave portion is formed in a reflection electrode forming portion of an insulating film formed so as to cover the transistor and the storage capacitor, and a metal layer is formed thereon, and the metal layer and the insulating film are chemically formed. A reflective electrode made of the metal layer is formed in the concave portion by being polished by a mechanical polishing method,
11. The substrate for a liquid crystal panel according to claim 1, wherein the surface is flattened from the reflective electrode to the surrounding insulating film. 12. A semiconductor device according to claim 1, wherein a support base for reinforcement is joined to a back surface of said semiconductor substrate.
2. The liquid crystal panel substrate according to 1. 13. The liquid crystal panel substrate according to claim 1 and an incident side transparent substrate having a counter electrode are arranged at an appropriate distance, and the liquid crystal panel substrate and the transparent substrate are arranged. A liquid crystal panel characterized in that liquid crystal is sealed in a gap between the liquid crystal panel and the liquid crystal panel. 14. A light source, a liquid crystal panel configured to modulate and reflect light from said light source, and projection optical means for condensing and modulating and projecting light modulated by these liquid crystal panels. And a projection-type display device.