JPH0310926B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image display device constructed by combining a semiconductor integrated circuit and a liquid crystal. The purpose is to remove.

One of the means to construct a flat display is to use two unit picture elements consisting of semiconductor switches and optical elements.
There is a way to arrange them into a matrix of dimensions. Figure 1 shows its equivalent circuit, where 1 is a MOS transistor;
2 is a liquid crystal cell, 3 is a scanning signal line, and 4 is a video signal line. MOS transistors can be integrated using single-crystal, polycrystalline, or amorphous silicon, but here we will use amorphous silicon, which is said to be relatively easy to reduce cost and increase in area. This is explained by quoting from the literature.

For example, a plan view and a sectional view of a unit picture element shown in Applied Physics Vol. 24, pages 357-362 (1981) are shown in FIGS. 2 and 3, and the manufacturing process thereof is as described below.

First, a transparent conductive film, such as ITO (Indium-Tin-
A transparent electrode 12 made of oxide) is selectively deposited. Next, a first metal layer 13 serving as a gate electrode and a scanning signal line is selectively deposited. Although chromium (Cr) is used in the above document, molybdenum (Mo) may also be used. Then, a transparent insulating film, for example, a silicon nitride (Si ₃ N ₄ ) film 14 is applied to the entire surface.
Then, an amorphous silicon film is deposited and left selectively on the gate metal layer 13 to form an island shape 15. Subsequently, an opening 16 is selectively formed in the silicon nitride film 14 using, for example, a hydrofluoric acid-based etching solution to expose a portion of the transparent electrode 12. At this time, although not shown, an opening is formed on the metal layer 13 at the end of the integrated circuit. Finally, video signal line 4 and MOS
A second metal layer 17 that also serves as the source or drain of the transistor and a second metal layer 18 that connects the drain or source of the MOS transistor and the transparent electrode 12 are selectively deposited. General aluminum A1 is used for the second metal layer 18, and the lead-out electrodes for the scanning signal lines are also formed at the same time through the above-mentioned openings. second metal layer 1
Since 7 and 18 also serve as the source and drain electrodes of the MOS transistor, they are arranged so as to partially overlap with the gate metal layer 13 to prevent an offset game.

Now, an image display device is constructed by filling liquid crystal 21 between the above-described amorphous silicon integrated circuit and a glass plate 20 having a second transparent electrode 19 deposited on one principal surface. The liquid crystal 21 has a phase transition type
When using TN (twisted nematic), two polarizing plates are required, upper and lower, but absorption type GH
(guest-host), a polarizing plate is not required.

The outline of the production process is as described above,
Upon detailed study by the present inventors, it was found that there were several problems in the formation of the opening 16. Photosensitive resin is used to form the openings, which is why the third
As is clear from the figure, when forming the opening 16 for partially exposing the transparent electrode 12, the silicon nitride film 14 and the transparent electrode 12 are used as the base of the photosensitive resin.
On the other hand, although not shown in the drawings, when forming an opening for partially exposing the gate metal layer 13 around the integrated circuit, the silicon nitride film 14 and the gate metal layer 13 are used as the base of the photosensitive resin. Therefore, the amount of exposure required to obtain transfer accuracy according to the mask dimensions naturally differs. As a result, when a negative resist is used, one of the openings is always smaller than the specified size in order to prevent pinholes due to insufficient exposure. Furthermore, when a positive resist is used, if one of the openings is made to have the specified dimensions, the other opening will become smaller or larger than the specified dimensions. This becomes a serious problem because when the unit picture element is made smaller in an attempt to downsize or increase the density of the image display device, the size of the aperture also becomes smaller. The reflection coefficient varies depending on the material of the gate metal layer 13, so it cannot be determined exactly, but if the minimum dimension of the opening is 10 μm or less, the situation becomes extremely severe.

Careful attention must also be paid to the removal of the photosensitive resin used to form the openings in the silicon nitride film 14. Since ITO12 is a metal oxide, it easily dissolves in both acids and alkalis. For example, if fuming nitric acid, which is often used to remove photosensitive resin, is used, not only the conductivity of the ITO 12 is impaired, but also the gate metal layer of Mo or Cr is lost. The safest method is to remove the photosensitive resin using oxygen gas plasma, but it cannot remove foreign substances and inflammable substances in the photosensitive resin and requires a post-treatment process such as surface treatment using a wafer scrubber. Furthermore, removal using oxygen gas plasma is not efficient as it takes 30 to 60 minutes depending on the equipment, which is approximately 10 times longer than processing using chemicals.

The present invention has been developed in view of the above-mentioned problems, and its key point is to leave a portion of the metal layer on the transparent electrode when forming the gate electrode.An embodiment of the present invention will be described with reference to FIG. 4. In FIG. 4, the same parts as in FIG. 3 are given the same numbers.

After forming the transparent electrode 12, a part of the metal layer 13' of the metal layer 13 is left on the transparent electrode 12 when forming the gate metal layer 13, and an opening 16 is formed in the silicon nitride film 14 on the metal layer 13'. A feature of the present invention is that the transparent electrode 12 and the source or drain wiring 18 are connected via a metal layer 13'.

As is clear from the above explanation, the transparent electrode 12
The opening necessary for connection to the gate metal wiring 13
Since the openings required for connection to both have the same photosensitive resin base, the exposure index is the same.
The transfer accuracy of the two openings is significantly improved compared to the conventional example. Also, when removing photosensitive resin, it is possible to use strong removal chemicals such as J-100, a weak alkali, if the gate metal wiring material is Mo, or hot sulfuric acid, a strong acid, if the material is _MoSi2 . As a result, processing time is shortened. Furthermore, during etching of the silicon nitride film 14, which is the gate insulating film, there are many problems such as over-etching, which reduces the polarity of the transparent electrode and increases the contact resistance with the source or drain wiring. Excellent effects can be obtained.

FIG. 5 shows an equivalent circuit of another embodiment of the invention. This structure is obtained by using a glass plate having a transparent conductive layer or a metal layer and a transparent insulating layer deposited on one principal surface in place of the glass plate 11 in FIG. The capacitance formed by the layer or metal layer and the transparent electrode 12 via the transparent insulating layer is used as the auxiliary capacitor 5. It is extremely easy to set the auxiliary capacitor 5 to 10 times or more the capacitance of the liquid crystal cell 2, and as a result, it is possible to increase the conductivity of the liquid crystal in order to increase the response speed of the liquid crystal.
In addition, there is no problem even if the leakage current when the MOS transistor 1 is turned off is about 10 times larger than when the MOS transistor 1 operates without the auxiliary capacitor 5, so the restrictions on the film quality of the amorphous silicon are relaxed. Furthermore, the overlapping capacitance between the gate and the source or drain suppresses fluctuations in the source or drain potential due to the presence of a gate pulse, making it suitable for non-self-aligned amorphous silicon MOS transistors as shown in Figure 2. It is extremely effective. It goes without saying that if a metal layer is used for one electrode of the auxiliary capacitor 5 and the liquid crystal is of the DSM type, a reflective liquid crystal image display device having the above-mentioned features can be obtained.

In addition, 6 is a common transparent electrode 19, which is fixed at 6V in the present invention, and the video signal is connected to 0 to 6V and 6 to 6V.
By inverting the polarity at 12V, the liquid crystal cell 2 is designed to be AC driven.

As described above, the present invention allows openings to be formed with high precision and without any inconvenience, and greatly contributes to the realization of a high-density, high-performance liquid crystal image display device.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit diagram of a conventional liquid crystal image display device, FIGS. 2 and 3 are a schematic plan view and a sectional view of essential parts of the device shown in FIG. 1, and FIG. 4 is an embodiment of the present invention. FIG. 5 is an equivalent circuit diagram of the same display device according to another embodiment of the present invention. 1...MOS transistor, 2...liquid crystal cell,
3...Scanning signal line, 4...Video signal line, 5...Auxiliary capacitor, 11...Insulating transparent substrate, 12...Transparent electrode, 13...Gate, 14...Gate insulating film,
14...Silicon nitride film, 15...Amorphous silicon layer, 16...Opening, 17, 18...Source
drain wiring.

Claims (1)

[Claims] 1. A first transparent conductive layer is selectively deposited on a first insulating transparent substrate, and the same layer is formed on the first transparent conductive layer and the first insulating transparent substrate. First and second metal layers made of the same material are selectively deposited, and an island-shaped amorphous silicon layer for a semiconductor device is selectively formed on the first metal layer with an insulating layer interposed therebetween. an opening is formed in the insulating layer on the second metal layer, and the insulating layer is selectively deposited on the amorphous silicon layer so as to overlap a part of the first metal layer. a second insulating transparent substrate on which a part of the third metal layer made of metal is in contact with the second metal layer through the opening, and a second transparent conductive layer is deposited on one main surface; A liquid crystal image display device, characterized in that a liquid crystal is filled between the semiconductor device and the semiconductor device. 2. Claim 1, characterized in that the first insulating transparent substrate is an insulating transparent substrate having a transparent conductive layer or a metal layer and a transparent insulating layer deposited on one principal surface. LCD image display device. 3. The liquid crystal image display device according to claim 1, wherein the first and second metal layers are molybdenum or molybdenum silicide.