JP2002246605A - Method of manufacturing thin film transistor for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a thin film transistor which can increase the throughput while maintaining a sufficient electron mobility at the time of manufacturing a large-sized highly precise liquid crystal display device. SOLUTION: In this method, a gate insulating film, an i-type a-Si film, and an n+-type a-Si film are continuously formed by the plasma chemical vapor deposition method. In addition, the i-type a-Si film is formed in two layers having different deposition rates.

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, and more particularly, to a method for manufacturing a thin film transistor for a liquid crystal display used as a switching element in a liquid crystal display.

[0002]

2. Description of the Related Art A display device using a liquid crystal has features such as low power and light weight which cannot be seen in a conventional display device. Among them, a thin film transistor (hereinafter, referred to as a TFT) is used as a switching element for each pixel. The placed liquid crystal display device
Since crosstalk is small and a high-resolution image can be obtained, it is used for a notebook computer, a car navigation display, and the like. In recent years, it has been rapidly used as a large display monitor.

As shown in FIG. 2, in a conventional TFT, a gate electrode 2 is generally formed on a glass substrate 1, and a gate insulating film 3 is formed on the glass substrate 1 while covering the gate electrode 2. ing. An i-type a-Si film 4 is formed on the upper surface of the gate insulating film 3 above the gate electrode 2, and a channel protective film 5 is formed at the center of the upper surface of the i-type a-Si film 4. ing. Further, the n + type a-S is formed while covering the end of the channel protection film 5 and a part of the i-type a-Si film 4 and being divided by the channel protection film 5.
The i films 6a and 6b are formed so as to be sandwiched between a source electrode 7a and a drain electrode 7b made of metal, and a pixel electrode 8 is formed on the drain electrode 7b.

In the TFT having the above-described structure, a method of forming a microcrystalline Si film instead of the i-type a-Si film 4 as a semiconductor layer is also known.

[0005]

However, although the microcrystalline Si film has a high electron mobility and is effective in improving the TFT characteristics, it takes a lot of time to form the film. When a film is tried, there is a problem that the throughput is extremely reduced.

[0006] The present invention has been made in view of the above-mentioned problems of the prior art, and while maintaining a sufficient electron mobility for manufacturing a large-sized, high-definition liquid crystal display,
It is an object of the present invention to provide a method of manufacturing a thin film transistor for a liquid crystal display capable of increasing throughput.

[0007]

Means for Solving the Problems In order to achieve the above object, of the present invention, the invention according to claim 1 includes a first electrode, an insulating film, an i-type a-Si film, n + type a-
A method for manufacturing a thin film transistor for liquid crystal display, comprising a Si film and a second electrode laminated, wherein the insulating film, i-type a-S
An i-film and an n + -type a-Si film are continuously formed by a plasma enhanced chemical vapor deposition method, and the i-type a-Si film is composed of first and second i-type a-Si films. The first and second i-type a-Si films are formed at different deposition rates.

[0008] The invention described in claim 2 is the first invention.
The i-type a-Si film 600 × ^{10 - 10} m / min under the following deposition rate while forming on said insulating film, said second i-type a-Si film of 1300 × ¹⁰ -10 m / min It is characterized in that the film is formed on the first i-type a-Si film at the above film forming speed.

Further, in the invention according to claim 3, the total thickness of the first and second i-type a-Si films is 2000 × 10
It is characterized by being set to ^-10 m or more.

The invention according to claim 4 is characterized in that a microcrystalline Si film is formed between the insulating film and the first i-type a-Si film.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a TFT structure for a liquid crystal display according to the present invention.
A gate electrode 2 is selectively formed thereon, and a gate insulating film 3 is formed on a glass substrate 1 so as to cover the gate electrode 2.

On the upper surface of the gate insulating film 3 above the gate electrode 2, a microcrystalline Si film 11 and a first i-type a-Si film 12
And the second i-type a-Si film 13 are sequentially formed in this order. On the upper surface of the second i-type a-Si film 13, n + -type a-Si films 6 a and 6 b are formed while being separated by the second i-type a-Si film 13. + Type a-Si
The films 6a and 6b are covered with a source electrode 7a and a drain electrode 7b made of metal, respectively. The picture element electrode 8 is formed on the upper surface of the drain electrode 7b.

In the TFT according to the present invention having the above structure, the gate insulating film 3, the microcrystalline Si film 11, the first and second
I-type a-Si films 12 and 13 and n + -type a-Si film 6
a and 6b are continuously formed using a plasma enhanced chemical vapor deposition method.

Further, in the TFT having the above structure, FIG.
Unlike the TFT having the conventional structure shown in FIG. 1, the channel portion is formed by the i-type a-Si films 12 and 13 without forming the channel protective film 5.

However, in order to enable the formation of a channel portion using an i-type a-Si film, the amount of etching must be controlled when performing channel etching. It is necessary to secure an etching margin depending on the film thickness. Further, in order to prevent the etching characteristics of the i-type a-Si film from affecting the TFT characteristics, the i-type a-Si film has a size of 2000 × 10 ⁻¹⁰ m (20 μm).
00 °) or more.

As a result of various examinations of the production conditions that make this possible, it is necessary to increase the film forming speed in order to increase the throughput, and the film forming speed is 1300 × 10 ⁻¹⁰ m / m
min (1300Å / min) or more and high rate i-type a
This was achieved by forming the -Si film 13.

Furthermore, in order to increase the throughput and to secure a predetermined electron mobility (at least 0.3 cm ² / V · s) in the TFT saturation region, the film forming speed is set to 600 × 10 ⁻¹⁰ m / m. This was achieved at the same time by forming a dense low-rate i-type a-Si film 12 having a thickness of not more than min (600 ° / min) below the high-rate i-type a-Si film 13.

Note that, for the reasons described above, the low rate i
The total thickness of the type a-Si film 12 and the high-rate i-type a-Si film 13 is set to 2000 × 10 ⁻¹⁰ m (2000 ^° ) or more.

The microcrystalline Si film 11 is formed only for the purpose of maintaining the adhesiveness or consistency at the interface with the underlying gate insulating film 3 and is formed extremely thin.

[0020]

Since the present invention is configured as described above, it has the following effects. According to the first aspect of the present invention, an insulating film,
An i-type a-Si film and an n + -type a-Si film are continuously formed by a plasma enhanced chemical vapor deposition method, and an i-type a-Si film is formed.
First and second i-type a-Si having different Si film formation rates
Since it is composed of a film, it is possible to increase the throughput while maintaining a sufficient electron mobility for manufacturing a large and high-definition liquid crystal display device.

According to the second aspect of the present invention,
1 i-type a-Si film is 600 × 10 ^-10m / min or less
Since a dense film is formed at the lower film formation rate,
0.3cm in transistor saturation region²/ V · s or less
The above electron mobility can be secured. On the other hand, the second
1300 × 10 i-type a-Si film^-10m / min or more
Because the film was formed at a film formation rate of
Channel, and channel edge
Sufficient to secure the etching margin during
The film thickness can be formed quickly.

Further, according to the third aspect of the present invention,
The total thickness of the first and second i-type a-Si films is 2000 × 1
0 ^-10 Because set above m, TFT characteristics are not adversely affected by the etching damage i-type a-Si film is subjected.

According to the fourth aspect of the present invention, since the microcrystalline Si film is formed between the insulating film and the first i-type a-Si film, the predetermined adhesion at the interface with the insulating film is achieved. Character or consistency can be ensured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a TFT structure for a liquid crystal display according to the present invention.

FIG. 2 is a cross-sectional view illustrating a conventional liquid crystal display TFT structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Gate electrode 3 Gate insulating film 4 i-type a-Si film 5 Channel protective film 6a, 6b n + type a-Si film 7a Source electrode 7b Drain electrode 8 Pixel electrode 11 Microcrystalline Si film 12 First i-type a-Si film 13 Second i-type a-Si film

 ──────────────────────────────────────────────────続 き Continued on front page F-term (reference) 2H092 JA26 JA28 JA33 KA04 KA05 KA07 MA08 NA25 NA27 5F045 AB03 AB04 AF07 BB08 BB16 CA15 DA52 GB09 GB19 5F110 BB01 CC07 GG02 GG14 GG15 GG19 GG24 GG35 GG45 HK16 HK21 HK16

Claims (4)

[Claims] A first electrode, an insulating film, and an i.
A method for manufacturing a thin film transistor for liquid crystal display, comprising laminating a type a-Si film, an n + type a-Si film, and a second electrode, wherein the insulating film, the i-type a-Si film, and the n + type a -Si film is continuously formed by plasma enhanced chemical vapor deposition, and the i-type a-Si film is composed of first and second i-type a-Si films. A method for manufacturing a thin film transistor for a liquid crystal display, wherein i-type a-Si films are formed at different film forming rates. 2. The method according to claim 1, wherein the first i-type a-Si film is 600 × 1
0 ^-10 m / min while formed on the insulating film in the following deposition rate, the second i-type a-Si film of 1300 × 1
0 ^-10 m / above min or more deposition rate first i-type a
2. The method according to claim 1, wherein the thin film transistor is formed on a -Si film. 3. The method according to claim 2, wherein the total thickness of the first and second i-type a-Si films is set to 2000 × 10 ⁻¹⁰ m or more. Method. 4. The method according to claim 2, wherein a microcrystalline Si film is formed between the insulating film and the first i-type a-Si film. .