JP3215409B2 - Light valve device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flat light valve device used for a direct-view display device, a projection display device, and the like. More specifically, the present invention relates to a light valve device such as an active matrix liquid crystal display device in which an integrated circuit in which a drive circuit is formed on a semiconductor thin film is integrally incorporated as a liquid crystal panel.

[Conventional technology]

The principle of an active matrix liquid crystal display device is very simple: a switching element is provided for each pixel, the corresponding switching element is turned on when a specific pixel is selected, and the switching element is turned off when not selected. It is something to keep. This switch element is formed on a glass substrate constituting a liquid crystal panel. Therefore, the technology for thinning the switch element is important. Usually, a thin film transistor is used as this element.

Conventionally, in an active matrix device, a thin film transistor is formed on the surface of an amorphous silicon thin film or polycrystalline silicon deposited on a glass substrate. Since these amorphous silicon thin films and polycrystalline silicon thin films can be easily deposited on a glass substrate using a chemical vapor deposition method, they are suitable for manufacturing an active matrix liquid crystal display device having a relatively large screen. A transistor element formed on an amorphous or polycrystalline silicon thin film is generally of a field effect insulated gate type. At present, an active matrix liquid crystal display device using amorphous silicon having an area of about 3 to 10 inches is commercially produced. Since the amorphous silicon thin film can be formed at a low temperature of 350 ° C. or less, it is suitable for a large-area liquid crystal panel. Further, in an active matrix liquid crystal display device using a polycrystalline silicon film, a small liquid crystal display panel of about 2 inches is currently commercially produced.

[Problems to be solved by the invention]

Conventional active matrix liquid crystal display devices using an amorphous silicon thin film or a polycrystalline silicon thin film are suitable for a direct-view display device requiring a relatively large screen image surface, while miniaturizing the device and increasing the pixel height. It is not necessarily suitable for densification. Recently, apart from the direct-view display device, there has been an increasing demand for an ultra-small display device or a light valve device having miniaturized high-density pixels. Such a micro light valve device is used, for example, as a primary image forming surface of a projection type image device, and can be applied as a projection type high vision television. 10μm by using fine semiconductor manufacturing technology
An ultra-small light valve device having a pixel size on the order and a size of about several cm as a whole is possible.

However, when a conventional amorphous or polycrystalline silicon thin film is used, a submicron-order transistor element cannot be formed by applying a fine semiconductor processing technique. For example, in the case of an amorphous silicon thin film, the mobility is about 1 cm ² / Vsec, so that a driving circuit requiring high-speed operation cannot be formed over the same substrate. In the case of a polycrystalline silicon thin film, the size of crystal grains is about several μm, so that miniaturization of an active element is necessarily limited. Further, even when the drive circuit is formed by a thin film transistor, at least ten or more terminals need to be electrically connected for a control signal for an image signal, a clock, synchronization, and the like or a power supply from outside. This is an obstacle to miniaturization of the micro light valve device. Further, the power supply circuit provided outside the light valve device increases the weight and volume of the entire system. As described above, in the conventional active matrix display device, there is a limit to miniaturization in consideration of electrical connection.

SUMMARY OF THE INVENTION In view of the above-described problems of the related art, it is a first object to provide a light valve device such as an active matrix liquid crystal display device that is miniaturized and miniaturized. In order to achieve this object, in the present invention, together with a driving circuit in a semiconductor single crystal layer formed on a carrier layer, to detect an optical signal,
A photovoltaic element capable of generating electric power from incident light is formed.

By the way, conventionally, various types of semiconductor laminated substrates in which a semiconductor layer is formed on such a carrier layer are known. This is a so-called SOI substrate. For example, an SOI substrate is formed by depositing a polycrystalline silicon thin film on the surface of a carrier made of an insulating material by chemical vapor deposition, etc., and then recrystallizing the polycrystalline film by laser beam irradiation etc. to convert it to a single crystal structure Had been obtained. However, in general, a single crystal obtained by recrystallization of a polycrystal does not always have a uniform crystal orientation and has a large lattice defect density. For these reasons, it has been difficult to apply a miniaturization technique to a SOI substrate manufactured by a conventional method, similarly to a silicon single crystal wafer, or to incorporate a high-performance photovoltaic element. In view of this point, the present invention uses a semiconductor thin film having the same crystal orientation uniformity and low-density lattice defect as a silicon single crystal widely used in a semiconductor process, and has a fine, high-resolution and photovoltaic power. A second object is to provide a light valve device having a built-in element.

[Means for solving the problem]

Means taken to achieve the objects of FIGS. 1 and 2 will be described with reference to FIG. Fig. 1 (A)
1 shows the plan shape of the substrate 1 used in the present invention, and FIG. 1 (B) shows the same cross-sectional structure. As shown, the substrate 1 has, for example, a wafer shape with a diameter of 6 inches. Substrate 1
Has a two-layer structure composed of a carrier layer 2 made of, for example, quartz and a single crystal semiconductor layer 3 made of, for example, silicon formed thereon. A miniaturized semiconductor manufacturing technique is applied to the single crystal semiconductor layer 3 of the substrate 1 to form, for example, a drive circuit, a photovoltaic element, and a pixel electrode of an active matrix display device for each chip section.

FIG. 1 (C) is an enlarged plan view of the integrated circuit chip thus obtained. As shown, the integrated circuit chip 4 has a length of, for example, 1.5 cm per piece, and is significantly smaller than a conventional active matrix display device.
The integrated circuit chip 4 has a pixel region 5 in which fine pixel electrodes arranged in a matrix and insulated gate field-effect transistors corresponding to individual pixel electrodes are formed, and an image signal for supplying an image signal to each transistor. A driving circuit, that is, an X driver region 6 in which an X driver is formed, a scanning circuit that scans each transistor line-sequentially, that is, a Y driver region 7, and a solar cell in which a solar cell that generates photovoltaic power from incident light is formed It has a battery area 8 and an optical signal detection area 9 for generating a control signal such as clock and synchronization or an image signal from an incident optical signal. According to the present invention, since a single crystal thin film having extremely high charge mobility and less crystal defects is used as compared with an amorphous thin film or a polycrystalline thin film, an X and Y driver requiring high-speed response and a high photoelectricity are used. A solar cell having conversion efficiency and an optical signal detection element having high speed and high photodetection sensitivity can be formed on the same plane as the pixel region. The output from the solar cell is connected to the X and Y driver power supplies, the image signal from the optical signal detector is sent to the X driver,
Control signals such as clock and synchronization are connected to X and Y drivers.

FIG. 1 (D) is a sectional view showing an active matrix type light valve device which inputs signals and power with light at a very small size and at a very high density assembled using the integrated circuit chip 4 described above. As shown in the figure, the light valve device includes an opposing substrate 10 that is arranged to face the integrated circuit chip 4 with a predetermined gap therebetween, and an electro-optical material layer, for example, a liquid crystal layer 11 that fills the gap. The surface of the integrated circuit chip 4 is covered with an alignment film 12 for aligning liquid crystal molecules contained in the liquid crystal layer 11. Each pixel electrode formed in the pixel region 5 of the integrated circuit chip 4 is selectively excited by the conduction of the corresponding transistor element, acts on the liquid crystal layer 11, controls its light transmission characteristics, and functions as a light valve. Since the size of each pixel electrode is about 10 μm, an extremely fine active matrix liquid crystal light valve device can be obtained.

FIG. 1E is a partially enlarged plan view of the pixel region 5 shown in FIG. 1C, and shows one pixel. Fig. 1 (F)
Is a schematic cross-sectional view of one pixel. As shown, the pixel 13 has a pixel electrode 14, a transistor 15 for exciting the pixel electrode 14 according to a signal, and the transistor
It comprises a signal line 16 for supplying a signal to 15 and a scanning line 17 for scanning the transistor. The signal line 16 is connected to an X driver, and the scanning line 17 is connected to a Y driver. The transistor 15 includes a drain region and a source region formed in the single crystal thin film layer 3, and a gate electrode 18 formed on a channel region via a gate insulating film. That is, the transistor 15 is an insulated gate field effect type. The gate electrode 18 is composed of a part of the scanning line 17, the pixel electrode 14 is connected to the source region, and the drain electrode 19 is connected to the drain region. The drain electrode 19 forms a part of the signal line 16.

[Action]

As described above, according to the present invention, a substrate having a two-layer structure including an insulating carrier layer and a semiconductor single crystal thin film layer formed thereon is used, and the semiconductor single crystal thin film layer is formed of a semiconductor. It has the same quality as a single crystal bulk wafer. Therefore, a switching element for driving the pixel electrode and the pixel, a solar cell, an optical signal detecting element, and the like can be integratedly formed on the semiconductor single crystal thin film layer by making full use of the miniaturization technology. The resulting integrated circuit chip has an extremely high pixel density and an extremely small pixel size, and can constitute a microminiature light valve device such as an active matrix liquid crystal display with no or very few external electrical connection terminals.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a schematic exploded perspective view showing one embodiment of the light valve device according to the present invention. As shown in the figure, the light valve device includes a driving substrate 1, an opposing substrate 10 disposed opposite to the driving substrate, and an electro-optical material layer such as a liquid crystal layer disposed between the driving substrate 1 and the opposing substrate 10. It consists of eleven. The drive substrate 1 includes a pixel electrode or a drive electrode 14 for defining a pixel, a drive circuit for exciting the drive electrode 14 according to a predetermined signal, a solar cell 8 for supplying power to the drive circuit, and an incident light signal. And an optical signal detecting element 9 for converting the optical signal into an electric signal and supplying the electric signal to the drive circuit.

The drive substrate 1 has a two-layer structure including a carrier layer 2 made of quartz glass and a single-crystal silicon semiconductor film layer 3. In addition, a polarizing plate 20 is adhered to the back side of the quartz glass carrier layer 2. The driving circuit and the photovoltaic element such as a solar cell and an optical signal detecting element are formed of an integrated circuit formed on the single crystal silicon semiconductor film layer 3. This integrated circuit includes a plurality of field effect insulated gate transistors 15 arranged on a matrix. The source electrode of the transistor 15 is connected to the corresponding pixel electrode 14, the gate electrode is connected to the scanning line 17, and the drain electrode is also connected to the signal line 16. The integrated circuit further includes an X driver 6 and is connected to a column-shaped signal line 16.
Further, it includes a Y driver 7 and is connected to a row-shaped scanning line 17. The counter substrate 10 includes a glass carrier 21, a polarizing plate 22 formed on the outer surface of the glass carrier 21, and a counter electrode or common electrode 23 formed on the inner surface of the glass carrier 21.

Next, the operation of the above-described embodiment will be described in detail with reference to FIG. The gate electrode of each transistor element 15 is connected to the scanning line 17, and a scanning signal is applied by the Y driver 7 to control the conduction and interruption of each transistor element 15 line by line. The display signal output from the X driver 6 is applied via a signal line 16 to a selected transistor 15 in a conventional body. The applied display signal is transmitted to the corresponding pixel electrode 14, and the pixel electrode acts on the excitation display liquid crystal layer 11 to make the transmittance substantially 100%. On the other hand, at the time of non-selection, the transistor element 15 becomes a non-conductive normal body, and maintains the display signal written to the pixel electrode as electric charge.
The liquid crystal layer 11 has a high specific resistance and normally operates as a capacitive element. The on / off current ratio is used to express the switching performance of these drive transistor elements 15. The current ratio required for the liquid crystal operation can be easily obtained from the writing time and the holding time. For example, when the display signal is a television signal, 90% or more of the display signal must be written during about 60 μsec of one scanning period. On the other hand, 90% or more of the electric charge must be held in one field period of about 16 msec. As a result, the current ratio needs to be 5 digits or more. At this time,
Since the driving transistor element is formed on the single crystal silicon semiconductor thin film layer 3 having extremely high charge mobility, an on / off ratio of 6 digits or more can be secured. Accordingly, it is possible to obtain an active matrix type light valve device having an extremely high-speed signal response. Further, the peripheral circuits 6 and 7 can be formed on the same silicon single crystal semiconductor thin film at the same time by utilizing the high mobility of the single crystal thin film. Furthermore, since a single crystal silicon semiconductor thin film has very few crystal defects, it is possible to form a highly efficient solar cell 8 and an optical signal detecting element 9 having excellent response speed and detection sensitivity on the same silicon single crystal thin film. it can. As shown in FIG. 3, in the solar cell 8, a plurality of PN junction diodes 24 are connected in series according to a required voltage, and the area is increased or connected in parallel according to a required current. . The electric power extracted from the PN junction diode 24 is stabilized through the constant voltage circuit 25 and then supplied to the drive circuits 6 and 7. The optical signal detection element 9 also supplies a photocurrent detected using the PN junction diode 26 to the load through the resistance element 27, amplifies the voltage generated by the amplifier 28, and supplies the amplified voltage to the drive circuits 6, 7. The signals required in the normal drive circuit include an image signal, a synchronizing signal of each of the X driver and the Y driver, a clock signal, and the like, so that a corresponding number of photodetectors are provided. Since light valves are generally used in the presence of light incidence, if a solar cell is provided in an area excluding pixels or drive circuits, a part of the light incident on the light valve device will be used as a light source for the solar cell. Can be used. The optical signal input to the optical signal detection element is introduced into each light detection element by narrowing down the light modulated by a laser diode or photodiode by an optical system using a lens, or by passing through an optical fiber. You. By providing an optical filter suitable for incident light on the light detection element, extra light due to disturbance such as stray light can be removed, and the light detection ability can be improved. In order to minimize the number of optical inputs, only an image signal is used as an input, and an image signal is passed through an image signal processing circuit to generate a synchronizing signal of the X driver and the Y driver, a clock, and the like. it can. In this case, the optical input may be one image signal.

〔The invention's effect〕

As described above, according to the present invention, a pixel electrode, a driving circuit, a power supply circuit using a solar cell, and incident light signal detection are applied to a semiconductor single crystal thin film formed on a carrier layer by using a semiconductor miniaturization technique. A light valve device is formed using an integrated circuit chip substrate obtained by integrally forming elements. Therefore, there is an effect that a light valve device having an extremely high pixel density can be obtained. In addition, since the light valve device can be made as small as an integrated circuit chip, an extremely small light valve device can be obtained. Since the integrated circuit technology can be used for the single crystal thin film layer, there is an effect that circuits having various functions comparable to LSI can be easily added. Further, there is an effect that not only a switching transistor but also a driving circuit, a solar cell for a power supply, and a photodetector for signal input can be simultaneously built in using a single crystal thin film. Finally, there is the effect that the light valve device can be driven with no or very little electrical connection to the light valve device.

[Brief description of the drawings]

1 (A) is a plan view of a substrate, FIG. 1 (B) is a schematic cross-sectional view of the same substrate, FIG. 1 (C) is an enlarged plan view of an integrated circuit chip formed on the substrate, FIG. FIG. 1D is a schematic sectional view of a light valve device using an integrated circuit chip as a substrate, FIG. 1E is a partially enlarged plan view of a pixel region of the integrated circuit chip,
1 (F) is a schematic sectional view of a pixel, FIG. 2 is a schematic exploded perspective view showing one embodiment of a light valve device, FIG. 3 is one embodiment of a solar cell circuit, and FIG. 5 is an embodiment of a signal detection circuit. DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Carrier layer 3 ... Semiconductor single crystal thin film 4 ... Integrated circuit chip substrate 5 ... Pixel region 6 ... X driver 7 ... Y driver 8 ... Solar cell 9 ... Optical signal detection element 10 counter substrate 11 liquid crystal layer 13 pixel 15 transistor 16 signal line 17 scanning line

 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-64-38727 (JP, A) JP-A-56-88111 (JP, A) JP-A-2-3286 (JP, A) JP-A-2-38 191321 (JP, A) JP-A-59-200288 (JP, A)

Claims (8)

(57) [Claims] A drive substrate on which a drive electrode and a drive circuit for exciting the drive electrode according to a predetermined signal are formed;
In a light valve device including an opposing substrate disposed opposite to the driving substrate and an electro-optical material layer disposed between the driving substrate and the opposing substrate, the driving substrate includes a carrier layer and a semiconductor single crystal thin film layer. Wherein the drive circuit comprises an integrated circuit formed on the semiconductor single crystal thin film layer, and the drive electrode is integrated on the semiconductor single crystal thin film layer and excited by the drive circuit. When acting on the electro-optical material layer to control its light transmittance, the semiconductor single crystal thin film layer, a photovoltaic element for supplying power generated by incident light as a power supply of the drive circuit, A light valve device comprising: a light signal detecting element for controlling an electric signal generated by incident light and supplying the electric signal to the drive circuit as an input signal. 2. The integrated circuit includes a plurality of driving elements arranged in a matrix, wherein the driving electrodes include a plurality of pixel electrodes arranged in a matrix, and are selectively excited by individual driving elements. The light valve device according to claim 1, wherein the light valve device is used. 3. The light valve device according to claim 2, wherein the integrated circuit includes a scanning circuit for scanning the plurality of driving elements arranged in the matrix. 4. The light according to claim 3, wherein the integrated circuit includes an image processing signal processing circuit for processing an externally input image signal and transferring the processed image signal to the scanning circuit. Valve device. 5. The driving substrate is provided with a spacer for maintaining a predetermined gap with respect to the counter substrate, and the gap is filled with an electro-optical material layer made of liquid crystal. The light valve device according to claim 1. 6. A substrate having a two-layer structure comprising a carrier layer and a semiconductor single crystal thin film layer formed thereon, a plurality of pixel electrodes formed in a matrix on the semiconductor single crystal thin film layer, An integrated circuit formed integrally with the semiconductor single crystal thin film layer and including a plurality of drive circuits formed in a matrix for exciting the plurality of pixel electrodes; and A photovoltaic element for supplying power to an integrated circuit, and an optical signal detection element for supplying a control signal or an image signal, wherein the integrated circuit includes an insulated gate transistor formed on a surface of the semiconductor single crystal thin film. A light valve device having a gate electrode on a surface of the semiconductor single crystal thin film opposite to the carrier layer, and a channel formation region formed in the semiconductor single crystal thin film layer. 7. The light valve device according to claim 6, wherein the carrier layer is made of quartz and the semiconductor single crystal thin film layer is made of silicon. 8. The light valve device according to claim 6, wherein the photovoltaic element is a PN junction type diode formed on a surface of the semiconductor single crystal thin film layer.