JPH0837308A - Manufacture of thin film transistor - Google Patents

Abstract

PURPOSE:To prevent the generations of the cracks in the surfaces of a silicon nitride film, etc., which are caused by a heat treatment performed in a hydrogen gas. CONSTITUTION:A polycrystal silicon film 2 is formed on a quartz substrate 1, and by the implantation of ions thereinto, drain and source regions 5, 6 are formed. In an interlayer insulation film 7 covering extensively the regions 5, 6, contact holes 8 are bored, and further, by the etching of a conductive film formed extensively on the film 7, electrode wirings 9 are formed. Thereafter, a silicon nitride film is so formed that it has as its internal stress a compressive stress present in the range of 2.0$10<9>-5.0X10<9>, and it is heat-treated at a temperature present in the range of 400 deg.C-500 deg.C. Thereby, the generations of the cracks of the silicon nitride film which are caused by the excessively large tensile stress generated by the heat treatment are prevented, and as a result, the improvement of the reliability of a thin film transistor and the effective recovery of its characteristic are made possible.

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, and more particularly to a method of manufacturing a thin film transistor for driving a liquid crystal display used in a liquid crystal display device for displaying an image.

[0002]

2. Description of the Related Art CRTs, that is, cathode ray tubes, which have been put into practical use as displays for television receivers since about 1955, have been expanding their applications. As a display device, it has been unwavering in its leading role. However, in the 1980's, as the demand for portable electronic devices increased, the words of light, thin, short, and small became popular, leading to radios, radio-cassettes, headphone stereos, etc. The competition has become fierce.

On the other hand, the display is also characterized by being lightweight and thin, a plasma display (PDP) and an electrochromic display (EC) utilizing direct current gas discharge.
D), liquid crystal displays (LCDs) and others that utilize electrophoresis have been actively researched and developed for practical use. In particular, liquid crystal displays have rapidly solidified as desktop electronic calculators that have been put into practical use at the same time, that is, as display units of calculators and display panels of digital watches.
In addition, the TFT liquid crystal display that appeared in 1990 is thin with the progress of advanced manufacturing technology for color filters.
Not only is it lightweight and low in power consumption, but it is also close to a cathode ray tube in terms of display capacity such as the number of display colors, definition, and screen size.

Since then, the liquid crystal display has expanded its range of applications, and as a mainstream of thin and lightweight displays, various displays for portable small color television receivers, laptop computers, notebook personal computers, vehicle-mounted navigator systems, etc. It was used as a device and was put out. Further, recently, it is being applied to small-sized and high-definition displays such as viewfinders and projection-type displays (projectors) for small home video cameras.

In such a liquid crystal color television receiver and a liquid crystal viewfinder, an active matrix type liquid crystal display device using a thin film transistor (hereinafter referred to as a TFT) made of amorphous silicon or polycrystalline silicon or the like which can obtain high image quality is provided. Has been used,
These screens consist of tens of thousands to hundreds of thousands of pixels,
It must be manufactured in a nearly defect-free state by extremely advanced manufacturing technology.

In order to prevent ion contamination from the outside or contamination due to the penetration of water, which is the cause of leakage or corrosion disconnection of aluminum wiring or the like, in the TFT which constitutes hundreds of thousands of pixels formed without defects as described above. Requires a surface protection film. Conventionally, a film thickness of 500 is formed on the surface of the TFT for this purpose.
Vapor phase growth of a silicon nitride film having a thickness of up to 1000 nm is performed at a low temperature. On the other hand, the TFT for driving the pixel thus formed is required to have a large on-current and a small off-current in order to improve the display image quality. Therefore, in general,
The TFT characteristics were recovered by treating the T substrate in a hydrogen gas atmosphere at 380 ° C. for 30 minutes.

[0007]

However, this silicon nitride film has a problem that cracks occur at the temperature during the heat treatment in hydrogen gas, which is carried out for the purpose of recovering the characteristics of the TFT in the final step of the TFT manufacturing method. Was there. In particular, heat treatment in hydrogen gas at a high temperature is advantageous for recovering the characteristics of the TFT, and it is preferable to perform the heat treatment at a temperature of 400 ° C. or higher. There was a problem that it could no longer function as a protective film.

The present invention is intended to solve the above problems,
At the processing temperature at a relatively high temperature of the heat treatment in hydrogen gas, which is performed in order to further improve the characteristics of the TFT, T
It is an object of the present invention to provide a method of manufacturing a thin film transistor having a surface protective film capable of protecting from various external contaminations without causing damages such as cracks on the protective film formed on the surface of FT.

[0009]

To achieve the above object, the present invention selectively forms a polycrystalline silicon film to be a thin film transistor forming region after forming a polycrystalline silicon film on a transparent insulating substrate such as a quartz substrate. , A step of forming a gate electrode made of a gate oxide film and a polycrystalline silicon film, a step of forming a drain region and a source region of a thin film transistor by ion implantation, and an interlayer insulating film such as a silicon oxide film over the entire surface. Forming step, forming a contact hole reaching the drain region and the source region in the interlayer insulating film, forming a conductive film containing aluminum as a main component on the entire surface, and then selectively etching to form an electrode wiring And the internal stress of the silicon nitride film for protecting the thin film transistor constituent part including the electrode wiring is 2.0 × 10 ^{9 to} 5. After being formed so as to have a compressive stress within the range of 0 × 10 ⁹ , it is subjected to a heat treatment in hydrogen gas at a temperature within the range of 400 to 500 ° C.

[0010]

Therefore, according to the present invention, the polycrystalline silicon film formed on the transparent insulating substrate is used as the active region, and the internal stress is 2.0 × 10 ⁹ to 5.0 on the TFT provided with the electrode wiring.
After forming a silicon nitride film having a compressive stress in the range of × 10 ⁹ by a plasma CVD device, this TFT is
Since the compressive stress generated inside the silicon nitride film is changed to an appropriate tensile stress by heat treatment in hydrogen gas at a temperature within the range of 00 to 500 ° C., the conventional excessive tensile stress is applied. No stress is generated inside the silicon nitride film, and thus the function as the surface protective film can be maintained without causing cracks in the silicon nitride film. Further, since the heat treatment can be performed at a higher temperature than the conventional one, the characteristic recovery of the TFT can be carried out more effectively than the conventional one.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method of manufacturing a thin film transistor according to the present invention will be described below with reference to the drawings.

FIG. 1 is a process sectional view showing a manufacturing method of the present embodiment. As shown in FIG. 1A, after a polycrystalline silicon film having a film thickness of about 100 nm is formed on a transparent insulating substrate 1 made of quartz or the like, the polycrystalline silicon film 2 to be a TFT formation region is selectively dried. Leave by etching.

Next, as shown in FIG. 1B, a gate electrode 4 made of a gate oxide film 3 and a polycrystalline silicon film is formed. Next, as shown in FIG. 1C, the drain region 5 and the source region 6 on the polycrystalline silicon film 2 are formed by ion implantation.

Next, as shown in FIG. 1D, after the entire surface is covered with an interlayer insulating film 7 such as a silicon oxide film,
As shown in (e), a contact hole 8 reaching the drain region 5 and the source region 6 is provided in the interlayer insulating film 7, and then a conductive film containing aluminum as a main component is formed on the entire surface and then selectively etched. To form the electrode wiring 9.

Next, the TFT thus constructed
As shown in FIG. 1 (f), a silicon nitride film 10 is formed as a surface protection film on the entire surface of. Inside the silicon nitride film formed at this time, a compressive stress of 2.0 × 10 ⁹
Internal stresses in the range of ˜5.0 × 10 ⁹ are formed. A silicon oxide film may be formed under the silicon nitride film 10.

Next, as shown in FIG. 1 (g), this TF
By subjecting the quartz substrate 1 on which T is formed to a heat treatment in a hydrogen gas at a temperature in the range of 400 to 500 ° C., the TFT in this embodiment is completed.

Next, the internal stress of the silicon nitride film in this embodiment will be described. The internal stress was measured by measuring the deformation amount (warpage amount) of the quartz substrate 1 with a flat nest tester and calculating from the following equation (1).

Δ _f = 4 · E · D ² · δ / 3 (1-ν) · d · L ² (1) Here, the equation (1) is the deformation amount δ and the internal stress δ _f In the relational expression, L is the interval at which the deformation amount δ is measured, d is the thickness of the silicon nitride film, D is the thickness of the quartz substrate, ν is the Poisson's ratio, and E
Is Young's modulus. The numerical value of the material used for the measurement was substituted into the formula (1) to obtain the following relational formula (2).

Δ _f = 3.69 × 10 ¹¹ · δ (2) Next, after forming the silicon nitride film 10 and at a temperature of 450
Silicon nitride film 10 after heat treatment in hydrogen gas at ℃
Table 1 shows the measurement results of the internal stress of the above, and Table 2 shows a conventional example as a reference. The negative deformation amounts in Tables 1 and 2 indicate concave deformation, and the negative internal stresses indicate compressive stress.

[0020]

[Table 1]

[0021]

[Table 2]

As can be seen in Table 1, silicon nitride film 1
Immediately after forming 0, the internal stress is 3.0 × 10 ^{9 to} 4.2 ×.
It has a compressive stress of 10 ⁹ dynes / cm ² , but the polarity of the stress is reversed after heat treatment in hydrogen gas, and 1.6 × 1
The tensile stress has changed to 0 ^{9 to} 2.7 × 10 ⁹ dynes / cm ² .

On the other hand, in the conventional example shown in Table 2, the internal stress after forming the silicon nitride film is 2.7 × 10 ⁹ to 2.
A tensile stress of 8 × 10 ⁹ dynes / cm ² is generated,
This is because the tensile stress is further increased by heat treatment in high temperature hydrogen gas, and 9.2 × 1 after heat treatment in hydrogen gas.
It has reached 0 ^{10 to} 11.1 × 10 ¹⁰ dynes / cm ² . This large tensile stress causes cracks in the conventional silicon nitride film.

As described above, according to the above-mentioned embodiment, the internal stress during the formation of the silicon nitride film is 2.0 × 10 ^{9 to} 5.0 ×.
By controlling so that the compressive stress in the range of 10 ⁹ is provided, even if the heat treatment in hydrogen gas at a temperature in the range of 400 to 500 ° C. is performed, excessive tensile stress as in the conventional case is not generated inside. Therefore, the TFT can be protected from damage such as cracking.

When the compressive stress after forming the silicon nitride film is less than 2.0 × 10 ⁹ dynes / cm ² , the tensile stress after the heat treatment in hydrogen gas becomes excessive and causes the cracking of the silicon nitride film. Becomes When the compressive stress exceeds 5.0 × 10 ⁹ dynes / cm ² , the silicon nitride film is not cracked, but the transparent insulating substrate such as a quartz substrate is excessively warped, and during the automatic transfer and the exposure process. Problems may occur, and in extreme cases, the transparent insulating substrate may crack.

Further, when the heat treatment temperature during the heat treatment in hydrogen gas is less than 400 ° C., the characteristic recovery of the TFT is insufficient.
If the temperature exceeds 00 ° C, the silicon nitride film is cracked.

Although the example of the silicon nitride film has been described in the present embodiment, the present invention is not particularly limited to this range, and the same effect can be expected in the silicon oxynitride film.

[0028]

According to the present invention, a polycrystalline silicon film formed on a transparent insulating substrate is used as an active region, and a T electrode having an electrode wiring is provided.
Internal stress is 2.0 × 10 on a FT ⁹ ~5.0 × 10 ⁹ plasma CV silicon nitride film having a compressive stress in the range of
After forming by D device, this TFT is 400-500
Due to the heat treatment in hydrogen gas at a temperature within the range of ℃,
The function as a surface protection film can be maintained without causing cracks in the silicon nitride film, and since it is possible to perform heat treatment at a higher temperature than before, the effect of recovering TFT characteristics is further improved than before. Can be made.

[Brief description of drawings]

1A to 1G are process cross-sectional views showing a method of manufacturing a thin film transistor according to an embodiment of the present invention.

[Explanation of symbols]

 1 quartz substrate (transparent insulating substrate) 2 polycrystalline silicon film 3 gate oxide film 4 gate electrode 5 drain region 6 source region 7 interlayer insulating film 8 contact hole 9 electrode wiring 10 silicon nitride film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/336 9056-4M H01L 29/78 311 Y

Claims (1)

[Claims] 1. A step of selectively leaving a polycrystalline silicon film to be a thin film transistor forming region after forming a polycrystalline silicon film on a transparent insulating substrate such as a quartz substrate, and a gate made of a gate oxide film and a polycrystalline silicon film. Forming an electrode, forming a drain region and a source region of the thin film transistor by ion implantation, forming an interlayer insulating film such as a silicon oxide film on the entire surface, and forming the drain region and the source region in the interlayer insulating film. To form a contact hole reaching up to, a step of forming a conductive film containing aluminum as a main component and then selectively etching to form an electrode wiring, and for protecting the thin film transistor constituent portion including the electrode wiring. silicon nitride film inside stress comprises a compressive stress in the range of 2.0 × 10 ⁹ ~5.0 × 10 ⁹ of After forming by plasma CVD apparatus, a thin film transistor fabrication method of comprising the step of heat treatment in the temperature of the hydrogen gas in the range of 400 to 500 ° C..