JPH04180268A - Liquid crystal display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to active matrix liquid crystal display devices.

[Prior Art] Up until now, driving transistors for active matrix liquid crystal display devices have been developed using
It was manufactured by depositing a semiconductor thin film on an insulating substrate such as glass and processing the thin film.

[Problems to be Solved by the Invention] However, since the semiconductor thin film forming the transistor is an amorphous or polycrystalline thin film, that is, a thin film with poor crystallinity, compared to a transistor formed on a single crystal substrate, Elements themselves have poor element characteristics such as low mobility and high leakage current.Furthermore, in the case of liquid crystal display devices, transistors are formed in each of over tens of thousands of pixels. It is necessary to make the device characteristics of the transistor uniform, but this is difficult to achieve as long as the above-mentioned semiconductor thin film with poor crystallinity is used. - On the other hand, when trying to make a liquid crystal driving transistor using a single-crystal silicon substrate with good crystallinity in order to improve the performance and integration of the device, the area of the PN junction is larger than that of a thin film transistor. In the case of liquid crystal drive devices where light incidence is unavoidable, leakage current is generated at the bonding interface due to the photoconductive effect.
The present invention is intended to solve these conventional problems, and aims to improve the characteristics of elements that drive liquid crystals, and to provide high-density, high-definition An object of the present invention is to provide a liquid crystal display device.

[Means for Solving the Problems] The liquid crystal display device of the present invention is a SIMO in which oxygen ions are implanted into a semiconductor substrate with good crystallinity as a substrate for forming liquid crystal driving elements, and an insulating layer is formed inside the semiconductor substrate.
X board (5 separation byIMplant
d OXygen).

[Example] FIGS. 2(a) and 2(b) are cross-sectional views showing a method for manufacturing a SIMOX substrate on which a thin film transistor is formed in an example of the present invention.

First, a method for manufacturing a SIMOX substrate on which thin film transistors are formed will be described. Silicon substrate 2 with good crystallinity
01, oxygen ions accelerated at 100-200kv 20
2 is implanted at a dose of approximately 1×101f101f1 (FIG. 2(a)), and a buried oxide film 203 is formed inside the silicon substrate (FIG. 2(b)). At this time, the crystals of the surface silicon layer 204 are implanted. In order to maintain the properties, the substrate is kept at a high temperature of approximately 500 degrees during ion implantation, and at the same time,
By applying heat treatment at about 1200 degrees after implantation, the crystallinity of the surface silicon layer is further improved. Thereafter, a pixel transistor for driving a liquid crystal and a driver element for controlling it are formed on this SIMOX substrate.

Next, the structure of the liquid crystal display device will be explained.

The liquid crystal display device of the present invention has the structure shown in FIG.

A liquid crystal cell constituting a pixel is formed by filling liquid crystal 104 that is oriented when no voltage is applied between a SIMOX substrate 105 on which a transistor is formed and a transparent substrate 101 on which a transparent electrode 102 is formed.

If the light 103 incident from above the transparent substrate 101 is not scattered within the liquid crystal cell, it will be directly reflected by the metal reflecting plate 110 made of aluminum as shown in FIG. When a certain voltage is applied, the incident light is scattered in the liquid crystal cell, reflected by a metal reflector, and then scattered once more in the liquid crystal cell, so that the emitted light is diffusely reflected. Therefore, if the incident light is observed while avoiding the directly reflected light, the contrast will be improved and a reflective liquid crystal display device will be obtained.

The manufacturing method will be explained below.

First, the surface silicon layer of the previous i1:sIMOX substrate is patterned, and an oxide film of about 1200 A is formed on the surface by thermal oxidation. Thereafter, a polycrystalline silicon thin film of 3,000 to 5,000 Å is laminated by vapor phase epitaxy, and after patterning, impurities to serve as donors and acceptors are implanted by ion implantation to form a gate electrode 106, a source region 107, and a drain region 10B. A channel MO8 and a p-channel MOS transistor are manufactured. At this time, at the same time as pixel transistors of the display section are formed, transistors to control them are also formed on the outer periphery of the display section.After forming an interlayer insulating film and opening a contact hole, aluminum is deposited by sputtering. Then, a source electrode 109 and a drain electrode that will become the metal reflective plate 110 are formed. After that, - transparent electrode 10 is placed on the main surface.
The transparent substrate 101 on which transistors 2 are formed is placed opposite to the SIMOX substrate 105 on which transistors are formed by the method described above, and liquid crystal is filled between them to complete the process.

It should be noted that the embodiment mentioned here is just one embodiment.

[Effects of the Invention] The liquid crystal display device of the present invention has the following excellent effects.

First, because the area of the PN junction is narrow, it is strong against light irradiation, and leakage current due to the photoelectric groove effect is significantly reduced. Suitable.

Second, in order to form the device on a substrate with good crystallinity,
A display device with improved element characteristics and uniformity without variations between elements can be formed. Furthermore, since high integration is easy, high-definition display is possible.

Third, by fixing the potential of the SIMOX substrate, capacitance can be easily formed between the pixel electrode and the substrate, so it is not possible to form a capacitive line on the substrate at the cost of sacrificing the aperture ratio to improve image quality, as in the past. This eliminates the need for a display that combines high definition and high image quality.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal display device in an embodiment of the present invention. FIGS. 2(a) and 2(b) are cross-sectional views of a SIMOX substrate forming a liquid crystal driving element according to an embodiment of the present invention. 101...Transparent substrate 102...Transparent electrode 103...Light 104...Liquid crystal 105105-8I substrate 106...Gate electrode 107...Source region 108...Drain region 109...Source electrode 110...Metal reflective plate 201...Silicon substrate 202...Oxygen ions 203...Buried oxide film 204...Surface silicon layer and above Applicant: Seiko Epson Co., Ltd. Representative Patent Attorney Kizobe Kisanbe (etc.) 1 person) (a) (b)

Claims (1)

[Claims] Active type with switching element for each pixel
A matrix liquid crystal display device, characterized in that the switching element is manufactured on a semiconductor substrate in which an insulating layer is embedded inside the substrate by ion implantation.