JPH08167719A - Thin film transistor and manufacture thereof - Google Patents

Abstract

PURPOSE: To completely shade light without deteriorating the display performance of a liquid crystal display unit due to the influence of the light. CONSTITUTION: A thin film transistor has a shading film 2 formed on a transparent substrate 1 to form the transistor on the film 2, wherein the film 2 has a semiconductor film 4 for forming the transistor and an insulating film formed at the periphery and pattern-formed in a self-aligning manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor used as a pixel selection switching element or a liquid crystal driving driver element of a liquid crystal display device, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A thin film transistor is generally used as a driver element for switching pixels or driving a liquid crystal in a conventional liquid crystal display device. In this thin film transistor, its active film is made of amorphous silicon, microcrystalline silicon or polysilicon. Is formed by. A liquid crystal display panel is often of a transmissive type, so that external light illuminates the silicon film. When the thin film transistor receives strong light, the off current increases, so that the transistor characteristics are deteriorated and the display performance of the liquid crystal display device is deteriorated.

Conventionally, in order to solve the above-mentioned problems, as disclosed in Japanese Patent Publication No. 3-52611, a light-shielding film is provided between a transistor and a substrate in order to block light from the substrate side. A liquid crystal display device provided with is proposed. FIG. 4 is a sectional view of a main part of a thin film transistor including such a light shielding film.

In the manufacturing process of the thin film transistor shown in FIG. 4, the light shielding film 22 made of metal or metal silicide is first deposited on the glass substrate 21, and the area of the active region of the thin film transistor formed later by the photolithography process becomes larger than that of the thin film transistor. In this way, the insulating film 23 and the semiconductor film 24 are sequentially deposited thereon, and the semiconductor film 24 is patterned by photolithography so that the semiconductor film 24 overlaps the light shielding film 22.

A gate insulating film 25 such as a silicon oxide film (SiO ₂ ) and a gate electrode 2 are formed on the semiconductor film 24.
6 are sequentially formed, and an insulating film 27 is further deposited. Then, a source contact 28 and a drain contact 29 are opened in the insulating film 27 overlapping the semiconductor film 24, and the source electrode 30 and the drain contact 28 are formed in the source contact 28. A drain electrode 31 is formed on the insulating film 27.
The drain electrode 31 formed on the upper surface is connected to one end of the pixel electrode 32, and finally, the passivation film 3 is formed as a protective film.
3 is deposited to complete a thin film transistor as shown in FIG.

In the thin film transistor configured as described above, the light shielding film 22 blocks the light from the glass substrate 21 side from irradiating the transistor portion, and the channel is not exposed to light, so that the same contrast ratio as in the dark is obtained. It can be achieved.

[0007]

However, in the conventional thin film transistor and the method of manufacturing the same configured as described above, irradiation of light from the glass substrate 21 side to the transistor portion is blocked, and the influence of light is affected. This makes it possible to prevent the display performance of the liquid crystal display device from deteriorating. However, since the connection portion between the drain electrode 31 and the pixel electrode cannot be wide, it is possible to ensure the conduction between the drain electrode and the pixel electrode 32. There was a problem that it could not be done.

Further, the glass substrate 21 is arranged so that the respective semiconductor films 24 are collectively overlapped with each other within the area on the respective light shielding films 22.
Since the mask and the mask are overlapped and aligned with each other, an error is likely to occur in the overlay of the light shielding film 22 and the semiconductor film 24, and the overlay error causes the display quality of the liquid crystal display device to be deteriorated. There is a problem that it is difficult to superimpose it on the film 24.

Further, since the light shielding film 22 is patterned on the glass substrate 21 by the photolithography process, a mask for the patterning must be formed, and ashing and resist stripping must be performed after etching. There is a problem that it takes time to form the light shielding film 22 which is slightly larger than 24.

The thin film transistor and the method of manufacturing the same according to the present invention have solved the above problems, and can completely block light without degrading the display performance of the liquid crystal display device due to the influence of light. Further, conduction between the drain electrode and the pixel electrode becomes more reliable, and further, no error occurs in superimposing the light shielding film and the semiconductor film,
A mask for preventing deterioration of display quality of a liquid crystal display device caused by an overlay error, easily and surely superimposing a light-shielding film and a semiconductor film on each other, and for patterning the light-shielding film on a transparent substrate. It is an object of the present invention to provide a thin film transistor and a method for manufacturing the same, which can simplify the manufacturing process without forming a film, ashing after etching, and resist stripping.

[0011]

In order to achieve the above object, a thin film transistor and a method for manufacturing the same according to the present invention are: a light shielding film formed on a transparent substrate; and a light shielding film formed on the light shielding film. In the thin film transistor described above, the light shielding film is formed in a self-aligned pattern by a semiconductor film that constitutes the thin film transistor and an insulating film formed around the semiconductor film.

The invention according to claim 2 is the above-mentioned claim 1.
In the invention described above, the light shielding film is formed of a metal or a metal silicide, and a pixel electrode made of a transparent thin film that is in contact with the back surface of the light shielding film is formed.

According to the third aspect of the present invention, a light-shielding film, an insulating film, and a semiconductor film are sequentially deposited on a transparent substrate, the insulating film and the semiconductor film are patterned into the same shape, and the pattern and the light-shielding film are formed. An insulating film is formed on the substrate, and a sidewall is formed on the side surface of the pattern by etching back the insulating film, and the light shielding film is etched using the sidewall and the semiconductor film as a mask.

[0014]

The present invention has the above-described structure. According to the invention of claim 1, the light-shielding film is formed in a self-aligned pattern by a semiconductor film forming a thin film transistor and an insulating film formed around the semiconductor film, thereby forming a transparent substrate. Irradiation of light from the side to the transistor portion can be reliably blocked, and deterioration of display performance of the liquid crystal display device due to the influence of light can be prevented.

The invention according to claim 2 is the above-mentioned claim 1.
In the structure described above, the light-shielding film is made of metal or metal silicide, and the pixel electrode made of a transparent thin film that is in contact with the light-shielding film is formed. Conduction between the pixel electrode and the drain electrode becomes more reliable via the.

Further, in the invention as set forth in claim 3, a light-shielding film, an insulating film and a semiconductor film are sequentially deposited on a transparent substrate, the insulating film and the semiconductor film are patterned in the same shape, and on the pattern and the light-shielding film. An insulating film is formed on the insulating film, and a sidewall is formed on the side surface of the pattern by etching back the insulating film. There is no error and it is possible to prevent the deterioration of the display quality of the liquid crystal display device caused by the overlay error, and it is possible to easily and surely overlay.

Moreover, a mask for patterning the light-shielding film is not formed on the transparent substrate, and neither ashing nor resist peeling after etching is performed, so that the manufacturing process can be simplified.

[0018]

Embodiments of a thin film transistor and a method of manufacturing the same according to the present invention will be described below in detail with reference to FIGS.
1A to 1F are cross-sectional views of a main part of a manufacturing process showing a first embodiment of a thin film transistor and a manufacturing method thereof according to the present invention.

First, in FIG. 1A, a tantalum (Ta) film having a thickness of 150 [nm] is formed as a light shielding film 2 on a transparent substrate 1.
Pile up. As the light shielding film 2, in addition to refractory metal or refractory metal silicide (for example, tantalum (Ta), titanium (Ti), tungsten (W), titanium tungsten (TiW), tantalum silicide (TaS).
i), titanium silicide (TiSix) is used, and a film thickness (100 to 150 [n
m]) The above may be deposited.

Then, a silicon oxide film (SiO ₂ ) is deposited on the light-shielding film 2 as the insulating film 3 to a film thickness of 300 nm, and amorphous silicon or microcrystalline silicon is formed as the semiconductor film 4 on the insulating film 3. Polysilicon is deposited, followed by a photolithography process.

The deposited thickness of the insulating film 3 is thicker than the width of the sidewall 6 formed in a later step. Eg 3
When the side wall 6 of 00 [nm] is formed, 30
A silicon oxide film of 0 [nm] is deposited.

In the photolithography process, first, a resist (not shown) is applied on the semiconductor film 4, and a mask (not shown) formed in a shape for patterning the insulating film 3 and the semiconductor film 4 is used as a semiconductor. Exposure is performed through the mask from above the film 4 in accordance with the position to be patterned, the exposed resist is peeled off by developing, and the insulating film 3 and the semiconductor film 4 from which the resist is peeled off are continuously dry-etched. As shown in FIG. 1B, the insulating film 3 and the semiconductor film 4 are processed into the same shape and perpendicular to the transparent substrate 1. After dry etching, ashing,
A resist removing process such as organic cleaning is performed.

Further, as shown in FIG. 1C, a silicon oxide film (SiO ₂ ) 5 having a film thickness of 300 [nm] is formed on the entire surface with good step coverage, for example, by CVD or TEOS (tetraethoxysilane) CVD process. Pile up. This film thickness may be the same as the width of the sidewall 6 to be formed. For example, when forming the sidewall 6 of 300 [nm], the silicon oxide film 5 of 300 [nm] is deposited.

Then, the entire surface of the silicon oxide film 5 is etched back to form side walls 6 having a width of 300 nm on the side surfaces of the insulating film 3 and the semiconductor film 4 as shown in FIG. 1D. . Thereafter, as shown in FIG. 1E, the light shielding film 2 is etched using the semiconductor film 4 and the sidewalls 6 as a mask. Thereby, the light shielding film 2 larger than the semiconductor film 4 by the width of the sidewall 6 can be formed in a self-aligned manner.

After that, a gate insulating film 7 and a gate electrode 8 are sequentially formed on the semiconductor film 4, an insulating film 9 is deposited, and then a source contact 10 and a drain contact 11 are formed in the insulating film 9 overlapping the semiconductor film 4. 1F is formed by forming a source electrode 12 on the source contact 10 and a drain electrode 13 on the drain contact 11 and finally depositing a passivation film 14 as a protective film.
A thin film transistor as shown in is completed.

2 (a) to 2 (f) are sectional views of the essential part of the manufacturing process showing the thin film transistor of the present invention and the second embodiment of the manufacturing method thereof, and FIG. 3 is the positions of the light shielding film, the semiconductor film and the contact. It is a block diagram which shows a relationship. It should be noted that the same parts of the first and second embodiments of the present invention are designated by the same reference numerals,
The description is omitted.

In FIG. 2A, ITO (Indium.Tin.Oxid) is used as the pixel electrode 15 on the transparent substrate 1.
e) is deposited to a thickness of 100 nm and patterned by a photolithography process.

Thereafter, until the insulating film 9 is deposited, as shown in FIG.
A thin film transistor having a light-shielding film 2 formed in a self-aligning manner is formed similarly to the first embodiment shown in (a) to (e).

In the second embodiment, FIG. 2 (f) and FIG.
As shown in, the positional relationship between the semiconductor film 4 and the pixel electrode 15 is
The semiconductor film 4 and the pixel electrode 15 are arranged so as to overlap each other such that the end of the semiconductor film 9 on the drain side is located on the pixel electrode 15.

After depositing the insulating film 9, the source contact 10 is opened on the semiconductor film 4 and the drain contact 11 is opened on the position where the edge of the semiconductor film 4 and the light-shielding film 2 overlap with each other, as shown in FIG. A source electrode 12 is formed on the source contact 10, a drain electrode 13 is formed on the drain contact 11, and a passivation film 1 is formed on the drain electrode 13.
4 is deposited to complete a thin film transistor as shown in FIG.

According to the second embodiment, the light shielding film 2 is made of metal or metal silicide, so that the light shielding film 2 and the pixel electrode 15 are in contact with each other over a wide area. Drain electrode 13 and pixel electrode 1
It becomes more reliable than the connection with 5.

[0032]

Since the thin film transistor and the method for manufacturing the same according to the present invention have the above-described structure, the invention according to claim 1 is such that the light-shielding film is formed of the semiconductor film forming the thin film transistor and the insulating film formed around the semiconductor film. By patterning in a self-aligned manner, it is possible to reliably block the light from the transparent substrate side from irradiating the transistor portion, and prevent the display performance of the liquid crystal display device from being deteriorated by the influence of light. be able to.

The invention according to claim 2 is the above-mentioned claim 1.
In addition to the effects described above, the light-shielding film is formed of metal or metal silicide, and the pixel electrode made of a transparent thin film that contacts the light-shielding film is formed. Conduction between the pixel electrode and the drain electrode becomes more reliable through the light shielding film.

Further, in the invention of claim 3, a light shielding film, an insulating film and a semiconductor film are sequentially deposited on a transparent substrate, the insulating film and the semiconductor film are patterned into the same shape, and the pattern and the light shielding film are formed. An insulating film is formed on the insulating film, and a sidewall is formed on the side surface of the pattern by etching back the insulating film, and the light shielding film is etched by using the sidewall and the semiconductor film as a mask, so that the light shielding film and the semiconductor film can be superposed. There is no error, it is possible to prevent the deterioration of the display quality of the liquid crystal display device caused by the overlay error, and it is possible to easily and surely overlay.

Moreover, a mask for patterning the light-shielding film is not formed on the transparent substrate, and neither ashing nor resist peeling after etching is performed, so that the manufacturing process can be simplified.

[Brief description of drawings]

1A to 1F are cross-sectional views of a main part of a manufacturing process showing a first embodiment of a thin film transistor and a manufacturing method thereof according to the present invention.

2A to 2F are cross-sectional views of the essential part of the manufacturing process showing the second embodiment of the thin film transistor and the manufacturing method thereof according to the present invention.

FIG. 3 is a configuration diagram showing a positional relationship among a light-shielding film, a semiconductor film, and a contact showing a second embodiment of the thin film transistor and the manufacturing method thereof according to the present invention.

FIG. 4 is a cross-sectional view of an essential part showing a conventional thin film transistor.

[Explanation of symbols]

 1 transparent substrate 2 light-shielding film 3 insulating film 4 semiconductor film 5 silicon oxide film 6 sidewall 15 pixel electrode

Claims (3)

[Claims] 1. A light-shielding film formed on a transparent substrate and a thin film transistor formed on the light-shielding film, wherein the light-shielding film is self-aligned by a semiconductor film forming the thin film transistor and an insulating film formed around the semiconductor film. A thin film transistor, which is formed by patterning. 2. The thin film transistor according to claim 1, wherein the light-shielding film is formed of metal or metal silicide, and a pixel electrode made of a transparent thin film that contacts the back surface of the light-shielding film is formed. 3. A light-shielding film, an insulating film, and a semiconductor film are sequentially deposited on a transparent substrate, the insulating film and the semiconductor film are patterned into the same shape, and an insulating film is formed on the pattern and the light-shielding film. A method for manufacturing a thin film transistor, characterized in that a side wall is formed on the side surface of the pattern by etching back this, and the light shielding film is etched using the side wall and the semiconductor film as a mask.