JPS63101832A - Active matrix liquid crystal display device - Google Patents

Abstract

PURPOSE:To stably execute an operation even under an intense light irradiation by forming a light shielding layer on the surface of the opposite side of the surface on which a circuit of single crystal silicon has been formed. CONSTITUTION:As for an element substrate, a device layer consisting of single crystal silicon 3 and an insulator 4 which are adjacent to each other is stuck to a holding substrate 1. In the single crystal silicon 3, an active element consisting of a MOS transistor is formed at the substrate 1 side, and the same light shielding layer 24 is formed at the opposite side of the substrate 1. A connecting electrode 37 is formed by making a contact hole in the insulator 4, by which an electrical connection is taken. A source area 11 and a drain area 10 use a gate electrode 7 as a mask and generated as a self-alignment by an ion implantation. In such a MOS transistor, the light shielding layer 24 is formed so as to cover a channel part of a MOS-FET, and a malfunction under an intense light irradiation is prevented, and the device is operated stably.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an active matrix liquid crystal display device having a field effect transistor formed on a thick film single crystal silicon substrate.

(Prior art and its problems) In recent years, applications of liquid crystal display devices (LCDs), mainly twisted nematic type (TN type), have been developed and are being used in large quantities in the fields of wristwatches and calculators. In addition, information terminals,
Matrix types, which can display arbitrary characters, figures, etc. by combining dots, are also beginning to be used for applications such as word processors. The structure of a matrix type LCD is that two substrates each having striped electrodes are arranged facing each other with a liquid crystal interposed between them so that the electrode lines on each substrate intersect perpendicularly to each other. The x-y terminals of the LCD are called matrix terminals.

In order to expand the application fields of this matrix type LCD,
It is necessary to increase the display capacity. However, since the voltage transmittance change characteristic of conventional LCDs does not have a very steep rise, when the number of scans in multiplex drive is increased in order to obtain a large display capacity, the effective voltage applied to each selected pixel and non-selected pixel increases. ratio decreases. For this reason, the viewing angle at which good contrast can be obtained becomes significantly narrower, so that in conventional LCDs, the maximum number of scan lines was about 60 lines.

In order to significantly increase the display capacity of this matrix type LCD, an active matrix liquid crystal display device in which an active element for liquid crystal switching is arranged in each pixel of the LCD has been proposed. The active elements of prototype active matrix liquid crystal display devices announced in recent years include FET-structure thin film transistors (FETs) using amorphous silicon (a-Si) or polycrystalline silicon (p-8i) as semiconductor materials TPT), or single crystal silicon (s-8
Most of the FETs use i) as a semiconductor material. Hereinafter, a substrate on which such an active element is formed will be referred to as an element substrate.

Among these, the manufacturing process for A-8i and P-8i TPTs has not yet been established, so the yield is low, and the characteristics of good products are insufficient, and there is a limit to the number of scans. Furthermore, since the characteristics of TPT are insufficient and the characteristics are not uniform even within a single substrate, the halftones as seen on a television screen are not produced, the contrast is weak, and a contrast ring occurs within the screen.

On the other hand, since FETs on the 5-8i can be obtained by using the conventional silicon IC process as is, the yield is good, the characteristics of good products are sufficient, and there is no practical limit to the number of scans. However, since this 5-8i is opaque, it is difficult to produce full color, and it has essential drawbacks such as the inability to use the TN type, which can provide high contrast.

Regarding such conventional active matrix,
Ni Ai Lakatos (A, 1. Lakatos)
Magazine by author [Proceedings of SID (Monthly, 2nd issue)]
The article ``Promise and Challenge of Thin-Film Silicon Approaches to Active Matrix'' included in Volume 4, No. 2, Page 185 (published in 1982)
geof Thin-Film 5ilicon Ap
approaches to Active Matric
es).

In general, methods for forming semiconductor devices on insulating substrates include epitaxial growth of single crystal silicon on crystalline insulators such as sapphire or spinel, in addition to methods using A-8I and P-8I. element in the epitaxial layer (this element is formed on sapphire, SO8
There is also a method of forming a This SO8 is 5
Although the performance equivalent to the number of elements on -8i can be obtained, the cost of the substrate made of sapphire or the like is very high, and there are drawbacks that a large-area substrate cannot be obtained.

In recent years, in addition to the SO8 described above, a transferred semiconductor device (hereinafter abbreviated as PTD) using boring has appeared as an active device made of single crystal silicon on an insulating substrate. Regarding this element, Rikuguchi et al. [Proceedings of the 45th Autumn 1981 Academic Conference of the Japan Society of Applied Physics] (Lecture No. 12a-c-
2) and “Japanese Society of Applied Physics European Journal”
Journal of Applied Ph5ic
This is disclosed in the article published in 1984, Vol. 23, p. 5815, and in Japanese Patent Application No. 137606/1983.

The method for manufacturing this PTD element is approximately as follows.

First, a device isolation region made of oxide with a controlled depth is provided on a 5-8i substrate, and a desired device is formed in the semiconductor portion between the device isolation regions, and then the device formation surface is glued to the holding substrate. The semiconductor substrate is removed while being polished from the back side until the element isolation region is exposed, and the surface exposed by the removal is fixed to a support substrate via an adhesive made of an insulating polymeric material. It is formed by removing the holding substrate.

The transferred semiconductor element thus obtained has excellent performance comparable to that of a normal silicon device because the device is formed on single crystal silicon, and is inexpensive and formed on a transparent insulator. , there is a possibility that an element substrate suitable for a liquid crystal substrate can be obtained at low cost. However, liquid crystal display devices are usually used in the presence of a certain amount of light. for example,
It is not uncommon for devices to be required to operate stably under direct sunlight and under intense light irradiation, such as from projection optical systems. Well-known semiconductor devices generally do not operate stably under light irradiation, so
This problem of light irradiation is a big problem.

Apart from this problem, there is another problem with flat displays in general: terminals. For example, 400 x 640
A pixel display has 400 vertical and 640 horizontal terminals, so 1040 connections and 1040 drivers are required. Although it has become possible to solve this problem in recent years due to the use of IC drivers and improvements in terminal connection technology, this problem still requires a considerable amount of cost.

(Object of the Invention) An object of the present invention is to eliminate such conventional drawbacks and provide a high-yield, high-performance active matrix liquid crystal display device. In particular, it is an object of the present invention to provide an active matrix liquid crystal display device that operates stably even under intense light irradiation and has a significantly reduced number of lead-out terminals from the panel.

(Means for Solving the Problems) In the active matrix liquid crystal display device of the present invention, an element substrate in which an active element is provided at a position determined by a data signal electrode and a scanning signal electrode, and a counter substrate in which a counter electrode has a counter electrode display a liquid crystal display device. In an active matrix liquid crystal display device in which the element substrate is disposed facing each other through a holding substrate, a device layer is formed on the holding substrate by adhesive polishing, and the device layer is made of single crystal silicon and an insulator, In addition to the active element, at least a scanning side driving circuit and a data side driving circuit of the liquid crystal driving circuit are formed on the device layer, and light is formed on the surface of the single crystal silicon opposite to the surface on which the above is formed. It has a structure in which a shielding layer is formed.

The light shielding layer needs to cover at least the transistor portion of the drive circuit around the liquid crystal panel. Furthermore, it is desirable to cover the active elements of the liquid crystal pixel drive circuit in the pixel portion of the liquid crystal panel with a light shielding layer in order to prevent malfunctions. However, the portion of the pixel electrode that turns on and off light transmission is not covered with the light shielding layer.

(Function) In addition to the active elements, a scanning side drive circuit and a data side drive circuit are formed on the device layer, and matrix terminals are connected to each drive circuit, so the number of terminals taken out from the panel can be significantly reduced. Further, by providing a light shielding layer on the surface opposite to the surface on which the transistor is formed, the device operates stably even under intense light irradiation.

(Example) Next, the present invention will be described in detail based on an example. FIG. 1 is a cross-sectional view of a layered transistor of a liquid crystal drive circuit on an element substrate 38 in an embodiment of an active matrix liquid crystal display device according to the present invention.

In this embodiment, as shown in FIG. 3, active elements for liquid crystal pixel switching are provided at the intersections of data signal electrodes 21 and scanning signal electrodes 20, and matrix terminals 19 to be taken out are fabricated on the element substrate. The scanning side drive circuit 22 and the data side drive circuit 23 are connected to each other.

The transistor according to the present invention is formed on an element substrate 38 as shown in FIG. The element substrate is formed by adhering a device layer consisting of a single crystal silicon 3 and an insulator 4 adjacent to each other to a holding substrate 1, and an active element consisting of a MOS transistor 18 is formed on the single crystal silicon on the holding substrate side. , the same light-shielding layer 24 is formed on the side opposite the holding substrate, contact holes are drilled in the insulator 4,
A connection electrode 37 is formed to establish electrical connection. The source region 11 and the drain region 10 are formed in a self-implanted manner by ion implantation using the gate electrode 7 as a mask.

In such a MOS) transistor, the light shielding layer 2
4 is formed to cover the channel portion of the MOS-FET to prevent malfunction under intense light irradiation.

As the light shielding layer used in the present invention, any material that has a light shielding effect can be used. Typical materials include:
There are metal films or multilayer films of metals and metal compounds, and polymer films containing dyes.

The metal film includes vapor deposited films of chromium Cr, molybdenum Mo, tungsten W, aluminum Al, nickel Ni, etc. Nickel and the like can also be produced by electroless plating. The multilayer film has a structure such as chromium oxide Cr2O3/chromium/chromium oxide. The polymer membrane containing the dye contains gelatin,
There are polymers such as casein and other synthetic polymers, and dyes such as cationic dyes and acidic dyes. Furthermore, in order to prevent contamination of the single crystal silicon and prevent electrical short circuits, an intermediate layer is often provided between the single crystal silicon and the light shielding layer, but this intermediate layer is not essential, so see Figure 1. I omitted it.

The basic circuit of the liquid crystal drive circuit will be explained. Scanning side drive circuit 2
2 and the data side drive circuit 23 are constructed using the above-mentioned MOS transistors, and representative conceptual circuit diagrams of each are shown in the fourth section.
It is shown in Fig. and Fig. 5. The scanning side drive circuit has shift registers 36 equal to the number of scanning electrodes, a vertical synchronizing signal 26 is input to each of these shift registers, and the output scanning signal is input to a driver 25a, where it is converted into a voltage suitable for driving the liquid crystal. and outputs it as a scanning signal 27. The data side drive circuit is
It has sample and hold circuits 28 as many as the number of data signals,
Each of these sample and hold circuits holds the video signal 29 by closing the gate with the horizontal synchronization signal 30, inputs this value to the driver 256, and outputs it as a data signal 31. In this embodiment, a case has been described in which the drive circuit is configured using MOS transistors, but the drive circuit is not limited to this, and may also be configured using bipolar transistors. This case is also basically the same as this embodiment.

The cross-sectional structure of the liquid crystal panel is as shown in FIG. The element substrate 38 and the counter substrate 15 having the counter electrode 14 are
They are arranged facing each other with the liquid crystal 13 interposed therebetween. As shown in this figure, the active elements for driving liquid crystal pixels are also M
It has an OS structure and is manufactured in the same way as the drive circuit.

The manufacturing method of this example is roughly as shown in FIGS. 6 to 8. These figures are cross-sectional views of the main parts of the element substrate arranged in the order of steps for explaining the method of manufacturing the active matrix liquid crystal display device of the present invention. In particular, a method for manufacturing a drive circuit and an active element for driving a pixel has been described.

First, as shown in FIG. 6, a silicon oxide film 5i02 with a thickness of 211 m is formed on a single crystal silicon substrate 16 by thermal oxidation.
This silicon oxide film is removed by reactive ion etching except for the portions corresponding to each display pixel. This remaining silicon oxide film portion becomes the insulator 4. 5iH2C is applied to the exposed part of the single crystal silicon substrate 16.
Using I2-H2-HCl system, silicon is selectively epitaxially grown to the same height as the insulator 4 to form single crystal silicon 3. A FET type transistor is formed thereon in the same manner as in a normal MOS process. That is, as shown in FIG. 7, a gate insulating film 9 made of silicon oxide, a gate electrode 7 made of a metal electrode,
After forming interlayer insulating films 12 made of silicon oxide, source region 1 and drain region 1 are formed by ion implantation.
form 0. Metals such as aluminum, molybdenum, and tungsten are used for the metal electrode used as the gate electrode, but metal silicide, polysilicon, and the like can also be used in addition to these metals.

Further, contact holes 17 are formed in the insulator 4 made of silicon oxide at two locations per pixel, deeper than the insulator, by using ordinary photoetching techniques. A drain electrode 6 is formed by vapor deposition of a metal such as chromium, molybdenum, tungsten, etc., and wiring is provided from the MOS transistor (active element) to the contact hole. Similarly, a source electrode 8 is formed by metal vapor deposition, and wiring is provided from the MOS transistor to the contact hole.

Next, as shown in FIG. 8, the MOS element forming surface of the single crystal silicon substrate 16 on which this MOS transistor is formed is covered with an adhesive layer 2 made of an insulating polymeric material such as epoxy or polyimide. borosilicate glass, pyrex glass, soda glass, silicon wafer,
It is attached to a holding substrate 1 such as the like.

Next, the single crystal silicon substrate 16 excluding the MOS forming portion is removed by mechanochemical boring. In this case, polishing uses an organic amine as the chemical solution, so
Since the processing speed of silicon oxide, which is a component of the insulator layer 4, is much slower than that of single crystal silicon, the polishing process can be stopped at the depth of the insulator layer 4. In this way, the device layer composed of the single crystal silicon region 3 and the insulator region 4 in which the element is formed can be easily left.

Next, in the case of an MO8 element for a drive circuit, a connection electrode 37 is formed on the polished insulator 4 as shown in FIG. 1, and conduction is established between the drain electrode 6 and the source electrode 8 through the contact hole 17. Another transistor using this connection electrode,
Connect with resistor, etc. Further, the connection electrode can also be formed on the same surface as the MO8 element.

In the case of a MOS (MOS) transistor active element for pixel driving, as shown in FIG. Take. The data signal electrode is usually the same metal electrode as the drain electrode and the like. Next, a pixel electrode 5 is formed on the polished surface and electrically connected to the drain electrode 6 through the contact hole 17. The pixel electrode 5 is usually a transparent electrode such as indium-tin oxide (ITO) or tin oxide (NESA). Through this step, the pixel electrode 5 is formed on the surface of the element substrate. Also, in this manner, scanning signal electrodes and data signal electrodes were formed on both sides of the device layer.

Next, silicon oxide was formed on the device layer made of single crystal silicon 3 and insulator 4 by a sputtering method to form an intermediate layer. Chromium was further formed on this by a sputtering method and patterned to cover the channel portion of the MOS-FET to form a light shielding layer 24.

The MOS transistors of the scanning side drive circuit 22 and data side drive circuit 23 manufactured as described above, and the scanning signal electrodes 2
0 and the data signal electrode 21 at the intersection of the liquid crystal pixel electrode 5
The driving active element (MOS) transistor 18 is connected to the periphery of the liquid crystal panel via a matrix terminal 19, as shown in FIG.

The element substrate thus produced is combined with a counter substrate 15 on which a counter substrate 14 of ITO or the like is formed on its entire surface via a spacer such as a glass fiber to form a liquid crystal cell. A liquid crystal is injected into this liquid crystal cell to form a liquid crystal layer 13, and an AM-LCD is obtained by sealing using an ordinary epoxy organic seal (FIG. 2).

Here, the element substrate and the counter substrate were subjected to alignment treatment by rubbing. In this case, an alignment treatment film of polyimide or the like is often applied, but it is not essential, so it is omitted in FIG. In addition, the liquid crystal is ZLI-1, which is a TN type liquid crystal.
565 (manufactured by Merck & Co., Ltd.), the cell thickness was 8 pm, and the deflection plate was NPF-1100H manufactured by Nitto Denko. When an LCD using this TN type liquid crystal and this polarizing plate was statically driven, a viewing angle of ±50° was obtained that provided a contrast ratio CR of 5:1.

In this example, selective epitaxial growth was performed after selectively removing the silicon oxide film after thermal oxidation, but selective epitaxial growth may not be performed if the single crystal silicon substrate is selectively oxidized.

In that case, a slight difference in level will occur between the single crystal silicon and the insulator, but in terms of performance, comparable performance can be obtained.

A prototype active matrix liquid crystal display with 400 x 640 pixels and a pitch of 0°05 mm was fabricated using this element configuration, and this active matrix liquid crystal display device showed almost the same display performance as when statically driven. Furthermore, even though a signal equivalent to 2000 lines of scanning was applied as a simulated signal, almost the same display performance as in static driving was obtained. For the drive signal, a conventional MOS transistor or T
A signal similar to that used in an active matrix liquid crystal display device in which PTs are stacked was used. When a television screen containing halftones was displayed on this display device, the gradations were expressed very faithfully, the contrast was high, and contrast salts did not occur within the screen. Furthermore, T of a-8i or p-8i
The yield was also significantly improved compared to that using PT. Since the panel according to this example has drive circuits laminated,
The number of terminals has been significantly reduced from 1040 to 7 for tarok signal, vertical synchronization signal, horizontal synchronization signal, video signal, power supply (2 power supplies), and ground, and the terminal connection process has been significantly simplified. Since this panel is small, it is suitable for viewfinders of video cameras and the like. Further, by applying the present invention to a projection type display described later, a good projection screen of 1 m x 1 m square was obtained. Halftone display was also good.

The second embodiment of the active matrix liquid crystal display device according to the present invention has the following features except that the pixel pitch is 0.2 mm.
A prototype was manufactured in the same manner as the first example. This panel had good contrast, gradation, and viewing angle even when viewed directly.

FIG. 9 is a schematic plan view of an element substrate for explaining the third embodiment of the active matrix liquid crystal display device of the present invention. In this embodiment, the control circuit 32 and the television signal processing circuit 33 are connected to a MOS transistor connected to the pixel electrode 5.
) It is the same as the first embodiment except that it is provided in a predetermined single crystal silicon region simultaneously with the formation of the transistor 18 and the formation of the scanning side drive circuit 22 and the data side drive circuit 23.

These control circuits and television signal processing circuits are also constructed from MOS transistors like ordinary MOS-ICs. A television signal processing circuit is connected to an antenna terminal 34 and a speaker terminal 35, and a television is configured by this panel and a few external passive elements. The number of pixels in this example is 400 x 640 pixels, and the pitch is 0.05
mm, and showed good characteristics as a viewfinder and a projection side display like the first example. The active matrix liquid crystal display device according to this embodiment can be used not only for ordinary televisions but also as displays for personal computers, word processors, information terminals, and the like.

Next, application examples of the AM-LCD of the present invention will also be described. The above-mentioned embodiments can be used both as a direct view type display and as a projection type display as described below. In contrast to the direct view type, a projection type display that projects strong light from a xenon lamp or the like onto a liquid crystal panel is suitable for displaying a super large screen of approximately 1 m x 1 m square. By replacing the liquid crystal panel of a projection type display using a conventional laser thermal writing liquid crystal panel with the liquid crystal panel of the present invention, a laser and its driving circuit are not required, so a small projection type display can be realized. A conventional projection optical system can be used. For example, as a liquid crystal panel, 400 x 640 pixels, pitch 0
．． If the AM-LCD of the present invention with a diameter of 0.05 mm is used, the liquid crystal panel will be significantly smaller, so a significantly smaller projection optical system can be realized. Further, a normal overhead projector (so-called 0HP) can also be used as the projection system.

All of the above explanations were for monochrome screens, but as is usually done, each pixel is displayed on the opposite substrate.
By forming color filters of each dot of RGB, a color screen can be easily obtained for both direct view type and projection type. In addition, in the case of a projection type, an AM-LCD according to the present invention
It is also possible to use three images, combine one of the three RGB images with each image, and synthesize them to obtain a color screen.

(Effect of the invention) As explained above, conventionally, a-8i or p-8i is formed on a transparent substrate and TPT is formed on it, so the characteristics are poor and the number of scanning lines is about 500, which is equivalent to static drive. However, according to the present invention, since the MOS formed in A-8I can be transferred onto a transparent substrate, good characteristics can be obtained, and 2000 lines can be scanned.
Furthermore, the manufacturing yield is significantly improved. Furthermore, according to the present invention, an active lens that operates stably even under direct sunlight and under intense light irradiation such as from a projection optical system, etc.
A matrix liquid crystal display device is obtained.

By combining a large number of AM-LCDs according to the present invention, it is possible to increase the area, and by manufacturing the peripheral drive circuit on the same substrate as the active element of each pixel, the number of terminals can be significantly reduced, and the projection type By applying this method, an ultra-small projection display can also be obtained. Furthermore, by manufacturing the control circuit and signal processing circuit on the same board,
A television set or an information terminal device can be configured with only a few external passive components.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a transistor portion of a liquid crystal drive circuit of a first embodiment of an active matrix liquid crystal display device of the present invention, and FIG. 2 is a cross-sectional view of a pixel portion of a first embodiment of the present invention. It is a diagram. FIG. 3 is a schematic plan view of the element substrate in this example. 4 and 5 are representative conceptual circuit diagrams of a scanning side drive circuit and a data side drive circuit, respectively. Figures 6 to 8 are
FIG. 9 is a cross-sectional view of the main parts of the element substrate arranged in the order of steps to explain the manufacturing method of the active matrix liquid crystal display device of the present invention, and FIG. 9 shows a third embodiment of the active matrix liquid crystal display device of the present invention. FIG. 2 is a schematic plan view of an element substrate for explanation. 1.0. Holding substrate, 2... Adhesive layer, 3... Single crystal silicon, 4... Insulator, 5... Pixel electrode, 6...
drain electrode, 70. . Gate electrode, 8... Source electrode, 9... Gate insulating film, 10... Drain region, 11... Source region,
12... interlayer insulating film, 1310. Liquid crystal layer, 14...
Counter electrode, 15... Counter substrate, 16... Single crystal silicon substrate, 17... Contact hole, 18... MOS
) transistor, 19...matrix terminal, 20...
・Scanning signal electrode, 21...Data signal electrode, 22...
・Scanning side drive circuit, 23...Data side drive circuit, 24
...Light shielding layer, 25a. 25b... Driver, 26... Vertical synchronization signal, 27
...Scanning signal, 28...Sample hold circuit, 2
9...Video signal, 30...Horizontal synchronization signal, 31.
...Data signal, 32...Control circuit, 33.
...TV signal processing circuit, 34...Antenna terminal, 3
5...TV signal processing circuit, 3609. Shift register Figure 1 3 Single crystal silicon 38 element basis 8 source lightning pole 7 gate Yukion
M Fig. 3 19 Matrix terminal Fig. 4 36 Shift register Fig. 6 Fig. 7 Fig. 8 3 Single crystal silicon Fig. 9 32 Control UO

Claims (1)

[Claims] In an active matrix liquid crystal display device, an element substrate in which an active element is provided at a position determined by a data signal electrode and a scanning signal electrode, and a counter substrate having a counter electrode are arranged to face each other with a liquid crystal interposed therebetween. A device layer is formed on a holding substrate via an adhesive layer, the device layer is made of single crystal silicon and an insulator, and the device layer includes at least a scanning side drive circuit of the liquid crystal drive circuit in addition to the active element. and a data-side drive circuit, and a light shielding layer is formed on a surface of the single crystal silicon opposite to the surface on which the circuit is formed.