JPH09230375A - Liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal panel having a sure light shielding structure to MOS transistors by devising a reflection electrode structure. SOLUTION: A low reflection layer 150a, a high melting metallic layer 150b and a high reflection layer 150c are formed as reflection electrode layers 150 on a lower electrode substrate P1. Grooves G are formed over the three layers of these reflection electrode layers 150 and the respective reflection electrodes H are segmented and formed to a matrix form. These reflection electrodes H are respectively connected to plural MOS transistors (90a to 90d) formed in the matrix form on the one main surface 61 of a semiconductor substrate 60 via interlayer insulating films. An upper electrode substrate P2 is disposed via high-polymer dispersed liquid crystals P3 to face the electrode substrate P1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal panel used in an image display device, and more particularly to a reflection type liquid crystal panel having a plurality of MOS transistors and reflection electrodes arranged in a matrix.

[0002]

2. Description of the Related Art Conventionally, this type of reflection type liquid crystal panel is constructed by enclosing a liquid crystal between both electrode substrates. Here, one of the electrode substrates is formed by sequentially forming a plurality of matrix-shaped MOS transistors, an interlayer insulating film, and a plurality of matrix-shaped reflective electrodes on the inner surface of the semiconductor substrate.

The display by the reflection type liquid crystal panel is performed by reflecting the light incident from the other electrode substrate through the liquid crystal by each reflection electrode.

[0004]

By the way, in such a liquid crystal panel, since the reflective electrodes are formed in a matrix as described above, it is inevitable that the reflective electrodes are adjacent to each other. A gap is formed in the. Therefore, the light incident on the liquid crystal panel from the other electrode substrate is
Leakage through the gap between both reflective electrodes and through the interlayer insulating film
It reaches the OS transistor.

Therefore, the MOS transistor generates a leak current due to the photoconductive effect of the leaked light. As a result, the leak current changes the voltage applied to the liquid crystal, which causes a decrease in display contrast of the liquid crystal panel and the occurrence of flicker, which deteriorates the display quality. To solve this, as disclosed in Japanese Patent Laid-Open No. 57-20778, an interlayer insulating film is formed by sandwiching a metal light-shielding film between both insulating films, and the two reflective electrodes adjacent to each other are formed. There is an attempt to block light leaking to the MOS transistor side through the gap between them by a metal light shielding film.

However, as in this publication, in the structure in which the metal light-shielding film is provided in the interlayer insulating film, this metal light-shielding film is used for both the reflective electrode and the MOS transistor, that is, the interlayer insulating film for connecting the reflective electrode and the MOS transistor. It must be electrically isolated from the via hole inside. Therefore, a region where the metal light shielding film does not exist, that is, a non-contact region between the via hole and the metal light shielding film is formed around the via hole.

Therefore, as described above, the light incident on the liquid crystal panel leaks through the non-contact region and reaches the MOS transistor. Therefore, the above publication cannot block the light leaking to the MOS transistor. Therefore,
SUMMARY OF THE INVENTION It is an object of the present invention to provide a reflective liquid crystal panel having a reliable light shielding structure for MOS transistors by devising a reflective electrode structure in order to deal with the above problems.

[0008]

In order to achieve the above object, according to the invention described in any one of claims 1 to 7, of the plurality of reflective electrodes arranged in a matrix of the reflective liquid crystal panel, both reflective electrodes adjacent to each other. The gap formed between the two has a width that causes diffraction of light leaking into the gap. Also,
Each of these reflective electrodes is formed on the interlayer insulating film with a material having a low reflectance having a large absorption coefficient for visible light and is connected to each MOS transistor through the interlayer insulating film. The low-reflection electrodes are provided with high-reflection electrodes made of a material having a high reflectance from the liquid crystal side.

As a result, even if light leaks into the gap between the reflective electrodes, the light is diffracted in the gap and is absorbed by the side wall portion of the low reflection electrode forming the side wall of the gap. As a result, the leaked light does not reach the MOS transistor without passing through the gap and the inter-layer insulating film, and the leak light is reliably transmitted to the MOS transistor.
It is cut off from the transistor. Therefore, no leak current is generated in the MOS transistor.

Here, according to the invention of claim 7,
A barrier layer made of a refractory metal is formed between each pair of low-reflecting electrodes and high-reflecting electrodes corresponding to each other. As a result, mutual diffusion between the low-reflection electrode and the high-reflection electrode due to heat is blocked by the barrier layer, so that the reflectance of the high-reflection electrode does not decrease.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic configuration of an image display device to which the present invention is applied. In this image display device, the light from the light source 10 is converted into parallel light by the concave reflecting mirror 20, the parallel light is reflected by the reflective liquid crystal panel P, and the reflected light is collected by the condenser lens 30 and the Schlieren diaphragm plate 40. The image is projected as a projection image on the screen S through the diaphragm hole 41 and the projection lens 50.

The liquid crystal panel P includes a polymer dispersed liquid crystal P between a lower electrode substrate P1 and an upper electrode substrate P2 which face each other.
3 is inserted together with a large number of spacers (not shown), and is manufactured as follows (see FIGS. 1 to 7). First, the manufacturing process of the electrode substrate P1 will be described. Inner surface 61 of semiconductor substrate 60 made of silicon or the like
Channel stop regions 70a to 70c are formed on (hereinafter, referred to as one main surface 61) as shown in FIG. Then, local oxide films 80a to 80c are formed on the channel stop regions 70a to 70c, respectively.

After that, a gate oxide film 90a is formed on the main surface 61 of the semiconductor substrate 60 between the local oxide films 80a and 80b, and the gate routing wiring 100 (hereinafter referred to as the scanning line 100) is formed. Are formed on the local oxide film 80c. After forming the scanning line 100 in this way, the insulating film 1 is formed.
20 together with the gate electrode 90b and the storage capacitor electrode 110 together with the local oxide films 80a to 80c and the gate oxide film 90.
a on the scanning line 100. Here, the gate electrode 90b is located between the two local oxide films 80a and 80b,
The storage capacitor electrode 110 includes both local oxide films 80b and 80b.
Located between.

However, before forming the insulating film 120, a low concentration source region 90c and a drain region 90d are formed on the main surface 61 of the semiconductor substrate 60 between the local oxide films 80a and 80b. Keep it. In addition, these source regions 9
A high-concentration n region for contact with an electrode is formed in each specific region of 0c and the drain region 90d. Here, the gate oxide film 90a, the gate electrode 90b, the source region 90c, and the drain region 90d form a MOS transistor for one reflective electrode H described later.

When the polymer-dispersed liquid crystal P3 is driven at a sufficiently low voltage of about 5 V, the MOS transistor is not required to have a high breakdown voltage, and therefore the source region 90c and the drain region 90d may be omitted. After forming the insulating film 120 as described above, a predetermined mask pattern etching process is performed under a photoresist process to perform the source region 90c, the drain region 90d, and the storage capacitor electrode 110.
The openings 121 to 122 are formed in the respective portions of the insulating film 120 corresponding to the respective upper portions.

Next, the wiring layer 130 made of AlSi is formed on the insulating film 120. After that, this wiring layer 130
Then, a predetermined mask pattern etching process is performed under a photoresist process to form a source line 131 (hereinafter referred to as a signal line 131) and a line 132 for a storage capacitor electrode which also serves as a drain electrode. Next, after heat-treating these wirings at about 450 ° C., the signal line 1
31, the wiring 132 and the insulating film 130 on the interlayer insulating film 14
Form 0.

Then, a part of the interlayer insulating film 140 corresponding to the drain electrode 132 is removed to open the opening 141.
Then, the low-reflectivity layer 150a that forms the reflective electrode layer 150 together with the refractory metal layer 150b and the high-reflectance layer 150c described later is formed with a low reflectance of chromium oxide, titanium, or silicon, and a high absorption rate for visible light. Depending on the material
It is formed on the interlayer insulating film 140. At this time, the low reflection layer 1
Since 50a is also formed in the opening 141, the low reflection layer 150a is formed in the drain electrode 13 through the opening 141.
2 is connected.

The material used here may have a high series resistance as long as contact with the silicon in the source region and the drain region can be obtained without rectification. The surface of the reflective electrode layer is
It is desirable that the surface is optically flat, but the surface after the formation of the reflective electrode layer is the MOS formed under the reflective electrode layer.
There are a large number of steps inside and outside 1 μm due to transistors, storage capacitors, wirings, and the like.

Therefore, in order to maintain the flatness of the reflective electrode layer surface, in this embodiment, the low reflective layer 150a of the reflective electrode layer is used.
As shown in FIG. 4, 1.0 μm to 2.0 μm
A chemical mechanical polishing (CMP) process of about μm was performed to flatten a step of about 1 μm on the surface of the low reflection layer 150a. Since it is desirable to form a gap between both reflection electrodes described later as deep as possible, the low reflection layer 150a formed by CMP.
In anticipation of the decrease in the film thickness, chromium oxide, titanium, etc., which will become the reflective electrode layer, can be formed by a method such as electron beam evaporation or sputtering.
It is desirable to form it to a thickness of about 4 μm to 5 μm.

Next, as shown in FIG. 4, the low reflection layer 15 is formed.
Layer of refractory metal such as titanium or molybdenum on the surface of 0a
50b is formed as a barrier layer with a thickness of about 100 nm. Then, as shown in FIG. 5, the highly reflective layer 150c constituting the outermost surface of the reflective electrode layer is made of a highly reflective material such as aluminum, silver or a dielectric multilayer film mirror at a thickness of about 1 μm.
It is formed on the surface of the refractory metal layer 150b. Accordingly, it is possible to prevent the high reflection layer 150c and the low reflection layer 150a from interdiffusing during the heat treatment of the subsequent process, thereby preventing the reflectance of the high reflection layer 150c from decreasing.

When the low reflection layer 150a is formed of a high melting point metal, the high reflection layer 150c is directly formed on the surface of the low reflection layer 150a without using the high melting point metal layer 150b. Next, the reflective electrode layer 150 is subjected to anisotropic etching treatment such as photolithography using g-line and i-line and dry etching to form a plurality of matrix-shaped reflective electrodes H as shown in FIG. . This means that a plurality of the MOS transistors are formed in a matrix corresponding to each reflection electrode H.

At this time, the low-reflection layer 150a, the high-melting-point metal layer 150b and the high-reflection layer 150c respectively have a low-reflection electrode Ha, a high-melting-point metal portion Hb and a high-reflection electrode Hc.
Is formed into compartments. In addition, low reflection electrodes H corresponding to each other
The reflective electrode H is formed for each of the high melting point metal portion Hb and the high reflective electrode Hc. Here, a gap G having a width of 1 μm or less is provided between the adjacent reflective electrodes of the plurality of reflective electrodes H, and the high reflective layer 150c, the high melting point metal layer 150b, and the low reflective layer 15 are provided.
It is formed all over 0a at once.

Here, the width of the gap G is set to 1 μm or less. However, the width of the gap G is not limited to this, and the width of the gap G may be set to an appropriate value as long as light leaking into the gap G causes diffraction within the gap G. You may change. The depth of the gap G, that is, the reflective electrode layer 15
The total thickness of 0 is preferably 1 μm or more in order to more effectively cause the diffraction of the leaked light.
Further, as described above, the low reflection layer 150a, the high melting point metal layer 150b, and the high reflection layer 150c are formed in the same manufacturing process to form the reflection electrode layer 150, and three layers of the reflection electrode layer 150 are formed as described above. Since the grooves G are formed at one time to partition the reflective electrodes H, the reflective electrodes can be easily formed by a simple manufacturing process.

Next, heat treatment is performed at about 450.degree. C. in order to remove damage caused to the gate oxide film 90a of the MOS transistor by the electron beam or plasma during the film formation and patterning of the reflective electrode layer 150. here,
Since the refractory metal layer 150b exists below the high reflection layer 150c, the high reflection layer 150b is not formed by heat treatment at about 450 ° C.
The light-reflecting material forming c does not cause mutual diffusion with the low-reflecting material forming the low-reflecting layer 150a. Therefore, the reflectance of the surface of the reflective electrode layer, that is, the high reflective layer 150.
The reflectance of c does not decrease.

Through the above steps, formation of the electrode substrate P1 of the liquid crystal panel P is completed. Next, as shown in FIG. 6, one transparent electrode 170 is formed of ITO or the like on the inner surface of the glass substrate 160 to form an electrode substrate P2. Then, the electrode substrate P2 is opposed to the electrode substrate P1 through a spacer so that the transparent electrode 170 faces each of the matrix-shaped reflective electrodes H, and both electrode substrates P1 and P2 are arranged.
In the meantime, a uniform solvent for the liquid crystal and the prepolymer for forming the polymer dispersed liquid crystal P3 is injected. Then, the uniform solvent of the prepolymer is polymerized by irradiating the outer surface of the electrode substrate P1 with ultraviolet rays to form a polymer dispersed liquid crystal P3.

As a result, the manufacture of the liquid crystal panel P having the cross section shown in FIG. 6 and the plane shown in FIG. 7 is completed. Note that, in FIG. 7, in order to facilitate understanding of the planar structure of the electrode substrate P1, constituent elements located inside the electrode substrate P1 are indicated by solid lines. According to the liquid crystal panel manufactured in this manner, as described above, the width of the gap G is 1 μm or less, or is formed to a value that can cause light diffraction,
The light leaking into the gap G is diffracted in the gap G, and is absorbed and attenuated by the side wall portion of the low reflection layer 150a forming the side wall of the gap G.

Therefore, the leaked light into the gap G can be reliably cut off from the MOS transistor by the gap G without reaching the MOS transistor side through the interlayer insulating film 140. As a result, the MOS transistor does not generate a leak current due to the photoelectric effect, and it is possible to provide a reflective liquid crystal panel with good display quality. In this case, by setting the depth of the gap G to 1 μm or more as described above, it is possible to more effectively generate the diffraction of the leaked light.
It is possible to further improve the leakage light blocking effect on the S-transistor.

Even if the width of the gap G is narrow and deep, the gap G
Because the polymer of polymer dispersed liquid crystal is filled in the inside,
Short-circuiting between the reflective electrodes on the side wall of the gap due to aging does not occur. FIG. 8 shows the main parts of the first modification of the above embodiment. In the first modified example, as described in the above embodiment, CMP is performed on the surface of the low reflection layer 150a.
Instead of performing CMP, the surface of the high reflection layer 150c is modified by CMP to be planarized.

By thus performing CMP at the end of the step of forming the reflective electrode layer 150, the low reflective layer 150a, the refractory metal layer 150b and the high reflective layer 150c can be continuously formed. Therefore, the manufacturing process of the reflective electrode layer 150 is simplified. Other configurations and operational effects are similar to those of the above embodiment. FIG. 9 shows the main parts of the second modification of the above embodiment.

In the above embodiment or the first modification, the low reflection layer 150a of the reflection electrode layer 150 or the light reflection layer 15 is used.
Since the surface of 0c is only subjected to the CMP process, the surface of the interlayer insulating film 140 has a portion that intersects the source line 131 of the gap G (see FIG. 9B) and a portion that does not intersect. There is a step between them. Therefore, at the intersection of the gap G and the source line 131, the depth of the gap G is
Is shallower than the portion that does not intersect with the source line 131.
Therefore, the light blocking effect due to the diffraction of light at the intersection of the gap G and the source line 131 may be reduced.

In particular, when the surface area of the reflective electrode H is reduced in order to obtain a high-definition image, the area of the shallow portion of the gap G increases as the line density of the source line 131 increases. Therefore, in the second modified example, in order to cope with the above, as shown in FIG. 9A, the surface of the interlayer insulating film 120 is planarized in advance, and then the reflective electrode layer 150 is formed.
Was formed.

In this case, after forming the interlayer insulating film 140 as in the above-described embodiment, the surface of the interlayer insulating film 140 is subjected to CMP treatment to flatten the surface of the interlayer insulating film 140. Then, after that, the reflective electrode layer 150 is formed. According to this, as shown in FIG. 9A, the thickness of the reflective electrode layer 150 becomes uniform by flattening the surface of the interlayer insulating film 140.

Therefore, the depth of the gap G between the reflective electrodes H formed by the reflective electrode layer 150 is determined by the source line 1
It becomes uniform regardless of the presence or absence of 31. Therefore, the gap G
The light-shielding effect due to the diffraction of light does not deteriorate even if there is the source line 131. Further, such an effect can be similarly secured even if the line density of the source line 131 is high.

In the second modification, as described above,
Since the interlayer insulating film 140 has already been subjected to CMP processing,
The CMP process on the reflective electrode layer 150 is unnecessary. In implementing the present invention, the liquid crystal used in the liquid crystal panel is not limited to the polymer dispersed liquid crystal, and various liquid crystals such as TN liquid crystal and smectic liquid crystal may be adopted.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image display device that provides a reflective liquid crystal panel according to the present invention.

2 is a sectional view taken along line AA in FIG. 7 for explaining a process up to forming a low reflection layer on the semiconductor substrate of the lower electrode substrate of FIG.
It is sectional drawing which follows a line.

3 is a cross-sectional view showing a state where the surface of the low reflection layer in FIG. 2 is subjected to CMP treatment.

4 is a cross-sectional view showing a state in which a refractory metal layer is formed on the surface of the low reflection layer in FIG.

5 is a cross-sectional view showing a state in which a high reflection layer is formed on the refractory metal layer of FIG. 4 and a reflection electrode layer is formed by partitioning each reflection electrode.

6 is a cross-sectional view showing a state in which an upper electrode substrate is arranged on the lower electrode substrate of FIG. 5 with a polymer dispersed liquid crystal interposed therebetween to form a liquid crystal panel.

FIG. 7 is a schematic plan view of the liquid crystal panel of FIG. 6 viewed from the upper electrode substrate.

FIG. 8 is a cross-sectional view showing the main parts of a first modification of the above embodiment.

9A is a cross-sectional view showing a main part of a second modified example of the above-described embodiment, and FIG. 9B is a schematic partial plan view of the main part.

[Explanation of symbols]

G ... Gap, H ... Reflective electrode, Ha ... Low reflective electrode, Hb ... Refractory metal part, Hc ... High reflective electrode,
P ... Liquid crystal panel, P1, P2 ... Electrode substrate, P3
... Polymer dispersed liquid crystal, 60 ... Semiconductor substrate, 60 ...
..One main surface, 140 ... Interlayer insulating film, 90a ... Gate oxide film, 90b ... Gate electrode, 90c ... Source region, 90d ... Drain region, 150 ... Reflective electrode layer , 150a ... Low reflection layer, 150b ... High melting point metal layer, 150c ... High reflection layer.

Claims (6)

[Claims] 1. A semiconductor substrate (60) and a plurality of MOs formed in a matrix on one main surface (61) of the semiconductor substrate.
S transistors (90a to 90d) and these MOS
A first electrode substrate (P1) comprising an interlayer insulating film (140) formed on the one main surface so as to cover the transistor, and a plurality of reflective electrodes (H) formed in a matrix on the interlayer insulating film. A second electrode substrate (P) having a transparent electrode (170) arranged in parallel with the first electrode substrate and facing the plurality of reflection electrodes.
2) and a liquid crystal (P) interposed between the first and second electrode substrates.
3) and the gap (G) formed between the two adjacent reflection electrodes of the plurality of reflection electrodes has a width that causes incident light to the gap to be diffracted, Each of the reflective electrodes is formed of a material having a low reflectance having a large absorption coefficient for visible light on the interlayer insulating film and is connected to each MOS transistor through the interlayer insulating film. A reflective liquid crystal panel comprising electrodes (Ha, 150a) and high reflection electrodes (Hc, 150c) formed of a material having high reflectance from the liquid crystal side on the low reflection electrodes. 2. The liquid crystal panel according to claim 1, wherein the gap has a width of 1 μm or less. 3. The liquid crystal panel according to claim 2, wherein the depth of the gap is 1 μm or more. 4. The low reflection electrode is made of polysilicon, chromium oxide or titanium.
4. The liquid crystal panel according to any one of items 1 to 3. 5. The liquid crystal panel according to claim 1, wherein each of the high reflection electrodes is made of aluminum, silver or a dielectric multilayer mirror. 6. A barrier layer (150b) made of a refractory metal is provided between each pair of low reflection electrodes and high reflection electrodes corresponding to each other among the plurality of low reflection electrodes and high reflection electrodes.
Hb) is formed, The liquid crystal panel as described in any one of Claim 1 thru | or 5 characterized by the above-mentioned.