JPH06289424A - Transmission type display device - Google Patents

Abstract

PURPOSE:To improve productivity by using a c-Si substrate provided with recesses in the parts corresponding to pixel electrodes and connecting the sources of FETs to the pixel electrodes by the metallic films in the flank parts of the c-Si corresponding to the pixel electrode parts. CONSTITUTION:The c-Si (single crystal or polycrystalline silicon) substrate having (100) faces on its surfaces is subjected to anisotropic etching, by which tapered apertures are obtd. therein. Metal connecting the sources 4 of the FETs and the pixel electrodes 6 are deposited by evaporation on the flanks of the apertures. The drains 3 of the FETs and drain lines of a flush type are aligned in order to obtain a high opening rate. Auxiliary capacitance electrodes 11 are formed on the rear surface of the parts where the FETs are formed. Further, the drains 3 and sources 4 of the n<+> type layer of the FETs consisting of the c-Si are formed in a self-alignment manner. The recesses having about 54 deg. angle are obtd. on the substrate flanks by subjecting the c-Si substrate after the formation of the sources to anisotropic etching. This c-Si substrate 7 is adhered to a glass substrate 1 by an adhesive 8 to reduce the thickness. The pixel electrodes 6 are formed on the rear surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive display device,
In particular, the present invention relates to a novel structure of a FET of a liquid crystal display device using a c-Si substrate having an opening in a pixel electrode corresponding portion.

[0002]

2. Description of the Related Art A thin film transistor of a display device is formed by forming a silicon thin film on a glass substrate by a plasma CVD apparatus and then processing the silicon thin film on the glass substrate.

In the above-mentioned thin film transistor for forming a silicon thin film by using such a CVD apparatus, a large number of defects such as disconnection and short circuit occur due to dust or the like in the thin film forming process.

Further, when a silicon thin film is formed on a large-area substrate by a CVD device, the size of a display device is enlarged, so that a manufacturing device such as a CVD device is enlarged and the characteristic distribution of the silicon thin film is not uniform. Cause an increase.

As described above, since the silicon layer is formed by using the CVD apparatus, (1) it is difficult to obtain a defect-free thin film transistor matrix. (2) Non-uniformity of display increases as the area increases. (3) As the display device becomes larger, the manufacturing device becomes larger. There is a problem such as.

FIG. 5 is a sectional view of an active matrix substrate of a liquid crystal display device using an amorphous silicon (a-Si) film formed by a plasma CVD device.

As shown in FIG. 5, a thin film transistor is provided on a glass substrate 1 of an active matrix type liquid crystal display device, and although not shown, its driving circuit is externally attached.

The thin film transistor is a non-doped a-Si
2, a drain 3, a source 4 and a gate 5 each of which is a high-concentration layer.

A gate insulating film 10 made of silicon nitride and formed by plasma CVD is formed between the gate 5 and a-Si 2.

The source 4 is connected to the transparent ITO pixel electrode 6 through a contact hole provided in the silicon nitride film.

As described above, when amorphous silicon is used for the operating layer, disconnection or short circuit of the wiring frequently occurs due to peeling of the silicon film caused by dust in the plasma CVD process or the like and a step difference due to the insulating film, the metal film or the like.

Thus, it is difficult to form an active matrix substrate having no point defect or line defect.

On the other hand, an example in which single crystal silicon is used as a substrate material of an active matrix type liquid crystal display device is described in M. Hosokawa et al: SID '81
Digest (1981) pp114. Has been reported in.

However, since the liquid crystal display device of this report does not have holes in the silicon substrate below the pixel electrodes, only a reflective liquid crystal display device can be constructed.

[0015]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
A c-Si substrate on which a silicon substrate on which an ET matrix and a driving circuit are formed is adhered to a glass substrate, and then thinned to form pixel electrodes, thereby providing a highly productive transmissive display device. is there.

The c-Si of the present invention mainly means liquid phase grown silicon in contrast to conventional vapor phase grown silicon, but not only liquid phase grown single crystal silicon, It also means an ingot made of polycrystalline silicon, which is made by pouring molten metal into a mold and hardening it.

[0017]

In the transmissive display device of the present invention, the source electrode and the pixel electrode are formed on the upper surface and the lower surface of the c-Si substrate, respectively.

The c-Si substrate having a surface of (100) has a tapered opening of 35 ° to 85 ° with respect to the (100) face by anisotropic etching.

A metal is deposited on the side surface of the tapered opening to connect the source of the FET and the pixel electrode of the transmissive display device.

Further, in order to obtain a high aperture ratio, the drain and the drain line are made to coincide with each other, the auxiliary capacitance is formed on the back surface of the FET formation portion, and the drain line is a buried type with a structure having a small step.

In addition, the source and drain of the FET are formed by self-alignment.

[0022]

[Operation] 1. When the silicon substrate on which the source has been formed is anisotropically etched with a KOH solution, recesses (recesses) whose side surfaces have an average angle of about 54 ° are obtained.

A metal film connected to the source is formed on the side surface having this angle.

The surface of the silicon substrate thus recessed is bonded to the glass substrate, and the back surface is lapped and polished to form a thin plate.

An insulating film is formed on the back surface, the bottom surface of the side surface of the opening of the silicon substrate is exposed, and then the pixel electrode is formed.

In this way, the source electrode on the upper surface is connected to the pixel electrode on the lower surface via the metal film on the side surface of the opening.

2. Although it is necessary to minimize the area of the FET portion in order to increase the aperture ratio, the area was reduced by sharing the drain and the drain line in common.

Further, the auxiliary capacitance is also formed on the back surface of the FET formation portion to eliminate the reduction of the opening area due to the auxiliary capacitance electrode.

3. Disconnection on the active matrix substrate,
Most of the short circuits occur at the intersection of the drain line and the gate line or at the gate electrode part.

One factor is the step due to the thickness of the insulating film and the metal film. In order to eliminate this step, the drain line was formed simultaneously with the source and drain by diffusion or ion implantation to form a buried layer. This eliminated the step at the intersection.

The gate is also made of polycrystalline silicon (polysilicon).
-Si) and thermally oxidized to form a strong and stable insulating film.

[0032]

EXAMPLE FIG. 1 shows a cross-sectional view of an active matrix substrate in which a c-Si substrate on which an FET matrix of the present invention is formed is attached to a glass substrate.

In FIG. 1, a thin c-Si 7 having an opening and an FET is fixed on a glass substrate 1 with an adhesive 8 having a high light transmittance.

While the c-Si acts as a black matrix of the transmissive display device, the opening where c-Si does not exist serves as a light passage.

Although not shown, a peripheral drive circuit for driving the FET matrix is provided in the peripheral portion of the c-Si 7.

Further, in the case of a liquid crystal display device, c-S
The glass substrate to which i is bonded and the counter glass substrate are about 15
It is sealed with a sealing agent with a gap of μm, and a liquid crystal having a thickness of about 5 μm is sealed therein.

In FIG. 1, the FET made of c-Si is formed in a self-aligned manner and has an impurity density 10 ^{13 of} 10 μm in thickness.
Drain 3 and source 4 of an n ⁺ -type layer having an impurity density of 10 ¹⁸ to 10 ²⁰ cm ^-3 in which an impurity P (phosphorus) is added at a high concentration to an n-type layer of -10 ¹⁴ cm ^-3 and side surfaces of the opening. The source electrode 9 made of Au provided, the gate insulating film 10 made of silicon dioxide having a thickness of 500 Å formed by thermal oxidation of c-Si, and the thickness 0.4 μ further formed on the gate insulating film.
The gate 5 is made of n ⁺ -type polycrystalline silicon having a sheet resistance of 20 m / square.

The metal source electrode 9 of the FET is formed not only on the surface of the c-Si having the gate but also on the side surface of the opening of the c-Si, and is an ITO pixel electrode covering the back surface of the c-Si and the opening. It is connected to the.

Although the thickness of c-Si is several tens of μm, when the source electrode is made of metal, the resistance between the source of the FET and the pixel electrode becomes 0.1Ω or less,
Almost no voltage loss occurs.

The drain line of the FET is formed integrally with the drain 3 of the n ⁺ type layer on the c-Si.

Therefore, since the pixel electrode area occupied on the active matrix substrate can be increased, the light utilization rate of the light source is increased and a high-brightness liquid crystal display device can be obtained.

Since the auxiliary capacitance electrode 11 is formed on the back surface of the originally opaque c-Si 7, the light transmittance of the pixel electrode 6 in the opening does not decrease, and even if the auxiliary capacitance electrode is opaque. It is possible to use a metal having low resistance.

The opening is about 15 μm on the surface of the c-Si substrate,
It is obtained by etching and forming a recess, then adhering it to a glass substrate with an adhesive, and mechanically and chemically polishing from the back surface to make the thickness of the c-Si substrate about 10 μm.

Since the opening is filled with the adhesive 8 made of transparent polyimide resin, unlike the prior art,
The present invention can form a transmissive display device.

C-Si whose entire surface is covered with the source electrode 9
The side surface of 7 is tapered, and as a result, the contact area between the glass substrate 1 and the c-Si 7, which is a transparent substrate, and the adhesive 8 is widened, and the bond between the two is made more solid.

FIG. 2 is a plan view of an active matrix substrate in which the c-Si substrate on which the FET matrix of the present invention is formed is attached to a glass substrate.

The highly conductive Au source electrode 9 of the FET of FIG. 2 is connected to the pixel electrode in a single connection region such as a hollow quadrangular pyramid around the pixel electrode 6, so that the source and the pixel electrode are electrically connected. Therefore, the charging and discharging of the AC signal peculiar to the liquid crystal display device can be speeded up.

On the c-Si surface side to which the pixel electrode is connected, c-
An auxiliary capacitance electrode 11 made of Al is formed so as to substantially cover the surface of Si.

Further, since the pixel electrode is extended to cover the c-Si, an auxiliary capacitance for increasing the amount of charge to the liquid crystal is formed between the pixel electrode and the auxiliary capacitance electrode.

FIG. 2 shows a plan view of an embodiment of the present invention in which a single crystal silicon substrate is used as a c-Si substrate and a MOS-FET matrix is formed on the surface thereof.

In FIG. 2, the drain is included in the drain line, and has a drain electrode 13 made of Au immediately above.

Then, the drain electrode 13 and the source electrode 9 made of metal having a low resistance of the FET matrix are formed at the same time.

The pixel electrode 6 surrounded by the source electrode 9
The inside of the pixel functions as one pixel of the display device.

Here, the pixel electrode 6 not only covers the source electrode 9, but also covers the drain line as a planar region and the auxiliary capacitance electrode on c-Si on the back surface as a vertical position.

As a matter of course, since the drain line is formed on the c-Si, the overlapping area of the auxiliary capacitance electrode and the pixel electrode on the c-Si covers the area of the FET and the drain line for a maximum of one pixel. Can be adjusted.

In FIG. 2, the pixel size is 50 μm × 50 μm,
When the line width of the gate line and the drain line is 5 μm, an active matrix substrate for a liquid crystal display device having an aperture ratio of about 70% (about twice that of the conventional method) can be formed.

FIG. 3 is a sectional process diagram for explaining a wafer process for a single crystal silicon substrate, and FIG. 4 is a sectional process diagram for explaining a process of thinning it to form openings and pixel electrodes.

First, FIG. 3 shows a manufacturing cross-sectional process diagram in which an FET matrix and a recess are provided on a silicon substrate.

First, FIG. 3A shows a state in which a dense gate insulating film 10 is formed on a (100) plane silicon substrate 15 made of single crystal by wet thermal oxidation at 1100 ° C.

Next, the poly-Si gate 5 to which impurities are added is formed on the gate insulating film 10 (FIG. 3).
b).

Subsequently, the silicon substrate (or c-Si) on which the gate is formed is again thermally oxidized to grow an insulating film and activate to lower the gate resistance (FIG. 3).
c). Further, to form a FET, self-alignment is performed on both sides of the gate to form a drain 3 and a source 4 having a depth of about 500 Å (FIG. 3d).

In order to obtain a transmissive display device, FE
A rectangular recess 16 is formed on the T-formed c-Si by anisotropic etching using an alkaline aqueous solution (FIG. 3e).

When the recess is formed after the FET matrix is formed, it is useful because diffusion of alkali metal or inorganic impurities accompanying etching into the silicon substrate can be avoided.

The recess 16 is formed in a forward taper with respect to the surface of the silicon substrate on which the FET is formed.

In addition, in order to transmit a pixel signal from the front surface to the back surface of the silicon substrate, a contact hole is formed in the thermal oxide film, and then the source electrode is formed by Au so as to cover from the source to the side surface of the recess (FIG. 3f). ).

Since the FET matrix manufacturing process of FIG. 3 is performed on a semiconductor substrate, fine processing down to submicron is possible.

Second, FIG. 4 shows F on a single crystal silicon substrate.
FIG. 6 is a cross-sectional process diagram of a process of forming display electrodes in the liquid crystal display device of the present invention which is attached to a transparent substrate after providing ET.

First, FIG. 4A is a sectional view showing a state in which the processed silicon substrate 15 is adhered to the glass substrate 1 by the transparent adhesive 8.

The thermosetting adhesive 8 is a transparent polyimide resin.

Alternatively, instead of the adhesive, the glass substrate and the silicon substrate are fixed by electrostatic welding (anodic bonding) at 1000 V and 350 ° C. in vacuum with the glass substrate as − and the silicon substrate as +.

Next, the silicon substrate 15 bonded to the glass substrate 1 is mechanically and chemically polished from the side opposite to the gate so that the recess formed previously becomes an opening through which light can pass, so that the thickness of the silicon substrate 15 becomes about 10 μm. It is thinned (Fig. 4b).

The bottom surface of the concave portion of the silicon substrate 15 is removed, and the opening 17 filled with the adhesive 8 is exposed on the surface opposite to the surface of the FET having the gate.

Then, silicon nitride (SiNx) is formed on the entire surface.
A protective film 18 made of is provided (FIG. 4c).

Then, after forming a contact hole in the protective film 18, a metal having good contact with the source electrode is formed on the source electrode (FIG. 4d).

Further, an auxiliary capacitance electrode made of metal such as Al is formed on the protective film. The formed auxiliary capacitance electrode is extracted to the outside of the transmissive display device through the back side of the gate line portion where light is difficult to pass.

Finally, after forming the protective film again,
An ITO film having a thickness of 0.1 μm is formed on the surface on the opposite side to the surface of the protective film, and the transparent pixel electrode 6 is formed on the protective film so as to be electrically connected to the source electrode 9 (FIG. 4).
e).

By forming the active matrix substrate thus formed into a panel by an ordinary method for manufacturing a liquid crystal display device, an active matrix type liquid crystal display device integrated with a drive circuit can be obtained with almost no defects.

[0078]

【The invention's effect】

1. Instead of forming a thin film transistor after forming a thin film semiconductor film on a glass substrate by a CVD method or the like, an active matrix and a peripheral drive circuit are formed on a solid (single crystal or polycrystal) semiconductor substrate in advance, and then,
Since the thin plate is formed, it is possible to form an active matrix without defects, and the manufacturing yield of the liquid crystal display device is dramatically improved.

2. FET is formed by self-alignment,
Since the drain is included in the drain line and the auxiliary capacitance electrode is formed on opaque c-Si, the aperture ratio can be increased.

3. Even c-Si, which has a large photoelectric effect, does not cause any difficulty as a liquid crystal display device exposed to light because the surface is covered with the metal film.

4. Since the glass substrate and the liquid crystal are in contact with each other through the polyimide layer of about 10 μm, they are hardly affected by the alkali ions from the glass.

Therefore, there is also an advantage that low-priced soda lime glass can be used.

5. An ultrahigh-definition display of 2000 × 2000 pixels can be realized.

As described above, the present invention greatly contributes to the manufacture of the active matrix type liquid crystal display device.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an active matrix substrate of a liquid crystal display device of the present invention.

FIG. 2 is a plan view of an active matrix substrate of a liquid crystal display device of the present invention.

FIG. 3 is a manufacturing process diagram of an FET of the present invention using a semiconductor substrate.

FIG. 4 is a process diagram of adhering the FET of the present invention to a glass substrate.

FIG. 5 is a sectional view of a conventional a-Si TFT.

[Explanation of symbols]

 1 Glass Substrate 2 a-Si 3 Drain 4 Source 5 Gate 6 Pixel Electrode 7 c-Si 8 Adhesive 9 Source Electrode 10 Gate Insulating Film 11 Auxiliary Capacitance Electrode 12 Drain Line 13 Drain Electrode 14 Gate Line 15 Silicon Substrate 16 Recess 17 Opening Part 18 Protective film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 29/784

Claims (13)

[Claims] 1. A FE in a transmissive display device, which uses a c-Si substrate having a FET matrix formed in advance on a surface thereof and having a recess in a portion corresponding to a pixel electrode.
A transmissive display device, wherein a source of T is connected to the pixel electrode by a metal film on a side surface of the c-Si corresponding to the pixel electrode portion. 2. In a transmissive display device, which uses a c-Si substrate having a FET matrix formed in advance on its surface and having a recess in a portion corresponding to a pixel electrode, an auxiliary capacitance is formed on the back surface of the c-Si substrate. A transmissive display device characterized by being provided. 3. A FE in a transmissive display device, which uses a c-Si substrate having a FET matrix formed on its surface in advance and having a recess in a portion corresponding to a pixel electrode.
A transmissive display device characterized in that the drain electrode portion of T is included in the drain line. 4. A transmissive display device using a c-Si substrate having a FET matrix formed on its surface in advance and having a recess in a portion corresponding to a pixel electrode, wherein a pixel electrode portion having an opening of the c-Si substrate. A transmissive display device, which is characterized in that: 5. A transmissive display device using a c-Si substrate having a FET matrix formed on its surface in advance and having a recess in a portion corresponding to a pixel electrode.
A transmissive display device characterized in that a recess is formed in a c-Si substrate of (00) plane. 6. A transmissive display device using a c-Si substrate having a FET matrix formed on the surface in advance and having recesses in the portions corresponding to the pixel electrodes, wherein the opening is formed in a forward taper with respect to the surface. A transmissive display device characterized by being provided. 7. A transmissive display device using a c-Si substrate having a FET matrix formed on the surface in advance and having a recess in a portion corresponding to a pixel electrode, wherein an opening is formed on the surface of the c-Si substrate. A transmissive display device characterized by having a taper. 8. In a transmissive display device using a c-Si substrate having a FET matrix formed in advance on its surface and having a recess in a portion corresponding to a pixel electrode, a source electrode is annularly arranged around the pixel electrode. A transmissive display device characterized by being provided. 9. A transmissive display device using a c-Si substrate having a FET matrix formed on the surface in advance and having a recess at a portion corresponding to a pixel electrode, wherein the source electrode is from the front surface to the back surface of the c-Si substrate. A transmissive display device, which is characterized by being extended to. 10. A transmissive display device using a c-Si substrate having a FET matrix formed on the surface in advance and having a recess in a portion corresponding to a pixel electrode, in which a drain line is embedded in the surface of the c-Si substrate. A transmissive display device characterized by being provided. 11. A recess and an FE on the surface of a c-Si substrate.
The step of forming the T matrix and the source electrode of c-Si
The step of forming from the FET source of the substrate to the slope of the recess of the c-Si substrate, and c using the transparent adhesive on the transparent substrate
A step of pasting the front surface of the -Si substrate, a step of thinning the c-Si substrate from the back surface to form a recess on the front surface of the c-Si substrate as an opening, and a step of forming an auxiliary capacitance electrode on the back surface of the c-Si substrate A step of forming an auxiliary capacitance insulating film on the back surface of the c-Si substrate, a step of forming a pixel electrode so as to cover the auxiliary capacitance electrode, the source electrode and the opening, and a step of covering the pixel electrode with an alignment film. And a step of pasting a counter transparent substrate having a counter electrode and a counter alignment film on the transparent substrate, and a step of enclosing a liquid crystal between the counter transparent substrate and the transparent substrate, and manufacturing the liquid crystal display device. Method. 12. A recess and FE on the surface of a c-Si substrate.
The step of forming the T matrix and the source electrode of c-Si
The process of forming from the FET source of the substrate to the slope of the recess of the c-Si substrate and c- by electrostatic welding on the transparent substrate
A step of fixing the front surface of the Si substrate, a step of thinning the c-Si substrate from the back surface to form a recess on the front surface of the c-Si substrate as an opening, and a step of forming an auxiliary capacitance electrode on the back surface of the c-Si substrate. A step of forming an auxiliary capacitance insulating film on the back surface of the c-Si substrate, a step of forming the pixel electrode so as to cover the auxiliary capacitance electrode, the source electrode and the opening, and a step of covering the pixel electrode with an alignment film. A method for manufacturing a liquid crystal display device, comprising: a step of pasting a counter transparent substrate having a counter electrode and a counter alignment film on a transparent substrate; and a step of enclosing a liquid crystal between the counter transparent substrate and the transparent substrate. . 13. The method of manufacturing a liquid crystal display device according to claim 11, wherein the recess formation is a step after the formation of the FET matrix.