JP3203459B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a substrate having a thin film portion including electric elements such as transistors.

[0002]

2. Description of the Related Art A method of manufacturing a liquid crystal display device by removing a part of a substrate having a thin film including an electric element such as a transistor and using an element substrate having a thin film surface portion made transparent only of the thin film. Is described, for example, in Japanese Patent Application Laid-Open No. 3-194115.
This is disclosed in Japanese Patent Publication No.

[0003] In such a liquid crystal display device, a driving circuit or the like including transistors and the like is formed on a single crystal silicon SOI substrate having a thermal oxide film, and a liquid crystal cell is formed using the silicon substrate and the glass substrate. The device configuration capable of transmissive display has been provided by etching the back surface only of the portion to be the display portion of the silicon substrate to remove the opaque silicon portion and forming a substantially transparent thin film including the circuit and the like.

[0004]

However, the thin film having the driving circuit and the like has a complicated geometrical structure and a dynamic structure, so that the mechanical state and the electric state tend to be unstable. As a result, there is a problem that the display quality of the liquid crystal display device is not stable.

Regarding the mechanical state of the thin film, for example, when the thin film shows a tensile stress (tensil) with respect to the substrate, the thin film in the portion to become a display portion is still taut after silicon is removed. State. However, when the tensile stress is very weak, it is difficult to keep the gap of the liquid crystal cell uniform, and the thin film after liquid crystal injection is sagging. On the other hand, if the tensile stress is too high, the cell gap becomes uniform, but the film breaking strength of the thin film is reduced as shown in FIG.

In the case where the thin film exhibits a compressive stress (compressive) with respect to the substrate, the thin film is wrinkled, cannot be bent, and a uniform cell gap cannot be realized. In this case, the thin film was broken by a large curvature.

[0007] Further, the electrical characteristics of the circuit element fluctuate in relation to the above-mentioned mechanical state. As a specific example,
Speed improvement of BJT due to tensile stress, MOSFE
A g _m , V _th shift of T has been reported.

An object of the present invention is to provide a liquid crystal display device in which a liquid crystal cell is formed using a substrate having a thin film surface portion including an electric element in view of the above-mentioned problems of the prior art. Another object of the present invention is to stabilize the state, and furthermore, to stabilize the characteristics of the electric elements in the thin film and improve the display quality and the yield.

[0009]

SUMMARY OF THE INVENTION The present invention, which has been made to achieve the above object, has a thin film including an electric element on a semiconductor substrate and a portion corresponding to an image display portion of the semiconductor substrate. In a liquid crystal display device using an element substrate on which the thin film surface portion is formed by removing the thin film ,
It has a large value of thermal expansion than the semiconductor substrate, a high temperature
In the film formation, the semiconductor by the temperature drop from the hot
To produce a tensile property stress to the body substrate in the liquid crystal display device characterized by having a stress control layer set to a sufficient film thickness.

[0010]

As described above, in a liquid crystal display device having a thin film surface portion including an electric element in a display portion, the stress of this thin film is a weak tensile force which can maintain a uniform cell gap and has a relatively large film breaking strength. (Approximately 3 × 10 ^{8 to} 3 × 10 ⁹ dyne / cm ² ). It is desirable that the stress control film according to the present invention should It is a thing to tighten.

That is, a stress control film having a larger coefficient of thermal expansion than the semiconductor substrate usually shows a tensile stress on the semiconductor substrate when the temperature is lower than the formation temperature. As a combination of such a semiconductor substrate and a stress control film, for example, a silicon substrate and a silicon nitride film,
Examples include a silicon substrate and an aluminum film, a silicon substrate and a polyimide film, a glass substrate and an aluminum film, and a glass substrate and a polyimide film. On the other hand, the stress control film having a smaller thermal expansion than the semiconductor substrate exhibits the same tensility to the semiconductor substrate when the temperature is higher than the formation temperature.
As a combination of such a semiconductor substrate and a stress control film,
For example, silicon substrate and silicon oxide film, silicon substrate and BPSG film, silicon substrate and ITO film, glass substrate and B
Examples include a PSG film, a glass substrate and an ITO film.

As described above, controlling the stress value of the thin film within a preferable predetermined range by the stress control film having a tensile stress at room temperature can be performed, for example, by using another film constituting the thin film. It can be easily performed by appropriately setting the film thickness of the stress control film in consideration of the film thickness .

[0014]

EXAMPLES The following provides a detailed explanation of the present invention through examples, not intended that the present invention is limited to these Examples needless to say, it is applicable Yichun possible deformation in the scope of the gist of the present invention .

Embodiment 1 The liquid crystal display of this embodiment will be described with reference to the manufacturing process diagram of FIG.

First, a single crystal silicon SOI substrate 10 having a buried silicon oxide film 12
The active layer 13 having a thickness of about 2,000 mm is PMOSFE
T was formed (FIG. 1A).

Next, a low pressure CVD method at about 800 ° C.
Stress control film 1 made of a silicon nitride film having a thickness of 6000 mm
4 was formed (FIG. 1B). The thermal expansion coefficient of this stress control film is about 3.0 × 10 ⁻⁶ , which is larger than the thermal expansion coefficient of the silicon substrate 11 of 2.6 × 10 ⁻⁶ .

Next, a pixel electrode for liquid crystal display (not shown) and a protective film 15 were formed, and an element substrate was formed (FIG. 1C) .

Next, a glass substrate 16 on which a counter electrode and the like are formed and the above-mentioned element substrate are bonded together using a sealing material 17 (FIG. 1 (d)). 18 was injected (FIG. 1 (e)).

Finally, a portion corresponding to the display portion 19 of the silicon substrate 11 is etched away from the back surface, and the PMO is removed.
The thin film 20 containing the SFET or the like is exposed. Thereby, the display portion of the liquid crystal cell was made transparent, and a liquid crystal display device capable of transmissive display was obtained. In this embodiment, the display unit 19
Was made 14 mm × 10 mm.

The silicon nitride film having a thickness of 6000Å was formed under the high temperature as a stress control film 14 in the present embodiment, at room temperature in a single layer 5 × 10 ⁹ dyne / cm ² about a relatively large tensile of stress However, due to the stress of other compressive films constituting the thin film 20, the thin film finally shows a weak tensility in a normal operating temperature range (−15 to + 60 ° C.).

Although the stress of the film naturally changes depending on the patterning applied to the film, in this embodiment, the patterning applied to the stress control film 14 is only for the contact hole portion, and the aperture ratio is 10%. Because of the following, the rate at which the tensile stress of the stress control film was reduced by this patterning was very small. In the case where the stress control film requires patterning that is not taken into account in the stress design in the manufacturing process of the element substrate as in the present embodiment, the aperture ratio due to the patterning should be about 30% or less. desirable.

In the liquid crystal display device of the present embodiment manufactured as described above, the thin film 20 did not hang down in the display portion 19 and a uniform cell gap could be maintained. Further, there were no defects such as cracks in the thin film, and the electrical characteristics of the circuit element constituted by the PMOSFET were stable.

[0024]

[0025]

[0026]

[0027]

[0028]

As described above, in the liquid crystal display device of the present invention in which a stress control film is formed in a thin film containing an electric element, the stress of the thin film can be easily controlled within a suitable range. By being able to stabilize the characteristics of the electric elements, the display quality could be improved and the yield could be improved.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of the liquid crystal display device of the present invention shown in Example 1.

FIG. 2 is a diagram showing an example of a tensile stress-film breaking strength characteristic of a thin film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 SOI substrate 11 Silicon part 12 Embedded silicon oxide film 13 Active layer 14 Stress control film 15 Protective film 16 Glass substrate 17 Sealing material 18 Liquid crystal 19 Display part 20 Thin film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI H01L 29/786 (58) Investigated field (Int.Cl. ⁷ , DB name) G02F 1/1333 500 G02F 1/1368 H01L 21 / 822 H01L 27/04 H01L 27/12 H01L 29/786

Claims (3)

(57) [Claims] 1. A liquid crystal display using an element substrate having a thin film including an electric element on a semiconductor substrate and removing a portion corresponding to an image display portion of the semiconductor substrate to form the thin film surface portion. In the apparatus, the thin film has a larger coefficient of thermal expansion than the semiconductor substrate.
Has been film formed at high temperature, due to temperature drop from the hot
A liquid crystal display device having a stress control film set to a thickness sufficient to generate a tensile stress on the semiconductor substrate . 2. The liquid crystal display device according to claim 1, wherein said semiconductor substrate is a silicon substrate. 3. The liquid crystal display device according to claim 1, wherein the stress control film is a silicon nitride film.