JPH03288474A - Active matrix type liquid crystal display - Google Patents

Abstract

PURPOSE:To offer an active matrix type liquid crystal display excellent in maintainability of image information without carriers, generated by the light entering the channel of a transistor, flowing into a drain, by providing an opposite conductivity of semiconductor layer on one conductivity of semiconductor substrate, and providing a transistor for driving a picture element on the semiconductor layer. CONSTITUTION:A p-well 2, which is formed by implanting boronic ions, is provided on an n-type silicon substrate 1, and in that p-well 2 is formed an active matrix type liquid crystal display wherein an n-channel transistor is used. In case that the light enters the p-well 2 and generates positive holes and electrons, the positive holes do not flow to the drain 3b due to the potential barrier existing between the p-well 2 and the drain 3b, and is accumulated in the p-well 2. Moreover, since the potential of the n-type silicon substrate 1 is higher than the drain 3b, most of the electrons generated flow to the n-type silicon substrate 1. According to this constitution, the currents generated by light can be reduced, and the maintainability of image information when the transistor is not supplied with currents can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an active matrix liquid crystal display device formed on a semiconductor substrate.

2. Description of the Related Art In recent years, the number of pixels in active matrix liquid crystal display devices has been increasing. In the active matrix method, one transistor is arranged per pixel to drive the pixel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pixel driving transistor formed on a semiconductor substrate, which is a main part of a conventional active matrix liquid crystal display device, will be described below with reference to the drawings.

FIG. 3 is a cross-sectional view of a conventional pixel driving transistor.

31 is a p-type silicon substrate, and 3a and 3b are n-type impurity layers forming a source 3a and a drain 3b, respectively. 4 is a gate oxide film, and 5 is a gate line, that is, a gate electrode, which constitutes an n-channel MO3 type transistor. 6 is an insulating film between the eyebrows, 7 is a data line, 8 is a pixel electrode, 9
is a silicon oxide film (SiO2) layer for isolation between elements,
10 is the p+ region of the channel stopper.

The operation of the pixel driving transistor configured as described above will be described below.

The video signal voltage sent through data n7 is transmitted to the pixel electrode 8 by applying an address signal to the gate line 5. After transmitting the video signal voltage to the pixel electrode 8,
Since the source 3a and drain 3b are cut off, the video signal voltage remains applied to the pixel until the next video signal voltage arrives.

Problems to be Solved by the Invention However, in the conventional configuration described above, when light enters the channel portion of the p-type silicon substrate while the transistor is non-conducting during the write-inhibited period to the pixel, the carriers generated by the light are transferred to the drain. A current flows by flowing into the source. As a result, the potential of the pixel electrode fluctuates, causing a problem in that pixel information is lost even when the transistor is non-conductive.

The present invention is intended to solve the above-mentioned conventional problems, and an object of the present invention is to provide an active matrix liquid crystal display device that can reduce photogenerated current.

Means for Solving the Problems In order to achieve the above object, an active matrix liquid crystal display device of the present invention includes a semiconductor layer of an opposite conductivity type on a semiconductor substrate of one conductivity type, and a pixel driving transistor on the semiconductor layer. The structure is as follows. Note that during use, the semiconductor layer is grounded to a ground potential, and a voltage is applied to the semiconductor substrate.

Effect: With this configuration, carriers generated when light enters the channel of the transistor can be flowed out by the electric field between the channel region and the semiconductor substrate, or can flow into the drain due to the presence of a potential barrier. do not have.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of a pixel driving transistor in one embodiment of the present invention. A p-well 2 formed by implanting boron ions is provided on an n-type silicon substrate 1, and an active matrix liquid crystal display device using n-channel transistors is formed within the p-well 2. In the manufacturing process, for example, the gate oxide film 4 and the isolation portion 5 are
Using the i02 layer 9 as a mask, an n-type impurity layer is formed by phosphorus ion implantation to form the source 3a and drain 3.
get b. Gate line 5, data line 7 and pixel electrode 8
is formed via the glabella insulating film 6. Further, 10 is a p+ region which serves as a channel stopper.

The n-channel transistor configured as described above is operated by grounding the p-well 2 to the ground potential and applying a positive voltage so that the n-type silicon substrate 1 has a higher potential than the drain 3a. FIG. 2 is a potential energy diagram from the drain 3b of the transistor toward the n-type substrate 1. When light enters the p-well 2 and generates holes and electrons, there is a potential barrier from the p-well 2 to the drain 3b, so the holes do not flow into the drain 3b and flow into the p-well 2. It can be stored. Furthermore, since the potential of the n-type silicon substrate 1 is higher than that of the drain 3b, most of the generated electrons flow to the n-type silicon substrate 1 side.

As described above, according to this embodiment, the photo-generated current can be reduced, and the pixel information retention characteristics when the transistor is non-conductive can be improved.

Note that the pixel driving transistor of the active matrix liquid crystal display device described in the above embodiment may be a p-channel transistor. In the case of a p-channel transistor, the p-channel transistor is formed on an n-well provided on a p-type silicon substrate, and is used by grounding the n-well to a ground potential and applying a negative voltage to the p-type silicon substrate.

Effects of the Invention As described above, the present invention provides a semiconductor layer of an opposite conductivity type on a semiconductor substrate of one conductivity type, and a pixel driving transistor is provided on the semiconductor layer, so that light incident on the channel of the transistor is It is possible to realize an active matrix liquid crystal display device in which generated carriers do not flow into the drain and have excellent pixel information retention characteristics.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a pixel driving transistor according to an embodiment of the present invention, FIG. 2 is a characteristic diagram of potential energy of the same transistor, and FIG. 3 is a sectional view of a conventional pixel driving transistor. 1... n-type silicon substrate (semiconductor substrate), 2.
...P well (semiconductor layer), 3b...Drain, 5...Gate line, 7...Data line, 8...Pixel electrode .

Claims (1)

[Claims] A pixel consisting of transistors arranged in a one-dimensional or two-dimensional matrix and a pixel electrode connected to the drain thereof, a gate line that controls conduction or non-conduction of the transistor, and a data line that applies a video signal voltage to the pixel. An active matrix liquid crystal display device comprising: a semiconductor layer of an opposite conductivity type provided on a semiconductor substrate of one conductivity type; and the transistor formed on the semiconductor layer of the opposite conductivity type.