JPH09283439A - Method for manufacturing polycrystal silicon substrate and method for manufacturing thin film transistor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a polycrystal silicon substrate at a high speed using a low-cost substrate not through a dehydrogenizing step by a method wherein, after amorphous silicon is formed on the substrate by a sputtering method, this amorphous silicon is continuously heated to by polycrystalized. SOLUTION: A shield film 2 composed of a-Si is formed on a glass substrate, an undercoat film 3 is coated thereon, and an a-Si film is formed by a sputtering method. Thereafter, a polycrystal silicon 4 is formed by laser annealing to be patterned. A gate insulation film 5 is formed thereon, and further a gate electrode 6 is formed to be patterned, and with the use of the gate electrode 6 as a mask, an ion doping is performed to the polycrystal silicon, a source region 4a and a drain region 4b are formed, and besides an insulation film 7 is formed on the entire face. Further, a through hole is opened on the source region 4a and drain region 4b of the insulation film, and a source electrode 8a and a drain electrode 8b are formed to obtain a thin film transistor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polycrystalline silicon substrate and a method for manufacturing a thin film transistor substrate.

[0002]

2. Description of the Related Art Polycrystalline silicon is formed by forming amorphous silicon (hereinafter referred to as a-Si) and then forming the a-Si.
Is annealed to obtain polycrystalline silicon (hereinafter referred to as p-Si). Here, when a-Si contains a large amount of hydrogen when annealing a-Si, there is a problem that the film quality deteriorates.

Conventionally, low pressure CVD (Chemical)
The a-Si film was formed by the Vapor Deposition) method or the plasma CVD method. Although the a-Si film formed by the low pressure CVD method has a low hydrogen content and can be formed at high speed, it has a problem that an expensive substrate having high purity and high heat resistance must be used because of high temperature.

On the other hand, as shown in FIG. 3, plasma CVD
The method does not require the use of an expensive substrate because it can form a film at a low temperature and at a high speed, but since the formed a-Si contains a large amount of hydrogen, the above problems occur if it is annealed as it is. There is a problem that a dehydrogenation process is required for dehydrogenating.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a method for manufacturing a polycrystalline silicon substrate which uses an inexpensive substrate, is high-speed, and does not require a dehydrogenation step, and a thin film transistor substrate. It is intended to provide a manufacturing method.

[0006]

The present invention comprises a step of forming amorphous silicon on a substrate by a sputtering method,
And a step of heat-treating the amorphous silicon to polycrystallize it without performing a dehydrogenation step.

Further, according to the present invention, a step of forming amorphous silicon on a substrate by a sputtering method, a step of subsequently polycrystallizing the amorphous silicon by heat treatment to form polycrystalline silicon, and a step of patterning the polycrystalline silicon. A step of forming a first insulating film on the polycrystalline silicon, a step of forming a gate electrode on a region of the insulating film corresponding to a part of the polycrystalline silicon, the polycrystalline silicon Forming a source region and a drain region in a predetermined region of silicon; forming a second insulating film covering the gate electrode; and connecting the source electrode to the drain region so as to connect to the source region. And a step of respectively forming drain electrodes so that the thin film transistor substrate is manufactured.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below. FIG. 1 shows a- in the embodiment of the present invention.
It is a process from Si film formation to polycrystallization. First, an a-Si film, which will later become polycrystalline silicon, is formed by a sputtering method using a silicon target. For example, the base pressure is 1.0 × 10 ⁻⁴ Pa, and RF (R
Radio frequency) power is used, and Ar gas is used. The deposition pressure is 0.6 Pa, and the substrate temperature is 150 ° C. The film forming rate is appropriately selected by adjusting the RF power.

According to this method, the substrate temperature is about 150 ° C., and a-Si can be formed into a film at a temperature that can sufficiently withstand an inexpensive glass substrate. It is desirable that the substrate temperature does not exceed about 400 ° C., but it is even more preferable if it is lower. According to the sputtering method of the present invention, the temperature is about 150 ° C., which is much lower than 400 ° C., so that even if an inexpensive substrate is used, there is no problem due to precipitation of impurities or distortion.

Moreover, a
-Si is deposited. In the plasma CVD, the hydrogen content was about 20%, but according to the sputtering method, it was about 5%.
It can be suppressed to the following. It has been found that if the content is 5% or less, the film quality is not adversely affected even if polycrystallization is performed without performing the dehydrogenation step.

After the a-Si film is formed, the a-Si is subjected to laser annealing. In laser annealing, shots are made for each part in a very short time, for example, 24 ns. Since the time is extremely short and is partial as described above, the substrate does not change. By forming the a-Si film at a low temperature by the sputtering method and further using the laser annealing for the heat treatment, the stress applied to the substrate is significantly reduced. Therefore, by combining the film formation by the sputtering method and the heat treatment by the laser annealing, The present invention is even more effective.

For this laser annealing, for example, XeCl
Use a laser. This energy density is 200-40
A range of 0 mJ / cm ² is preferred. If the energy density is 200 mJ / cm ² or less, the crystallization will not be complete, resulting in incomplete polycrystalline silicon. On the other hand, when the energy density is 400 mJ / cm ² or more, undesired irregularities are formed on the film surface and the film quality deteriorates. When laser annealing is performed with an energy density in the range of 200 to 400 mJ / cm ² , a polycrystalline silicon film having a completely crystallized and uniform surface can be obtained.

Further, in the above embodiment, the sputtering was performed by RF power, but DC power can also be applied. However, since the silicon target is not very conductive, RF
Seems to be preferable. Furthermore, the annealing method is not limited to laser annealing, and RTA (Rapid Th
ermal Annealing) and FA (Furn
ace Annealing).
Further, the laser gas is not limited to XeCl, and various modifications such as ArF and KrF can be considered.

The polycrystalline silicon obtained by such a method can be used to form, for example, a thin film transistor. As shown in FIG. 2, the substrate 1 made of glass
A light-shielding film 2 made of a-Si or the like is formed on top of which S is formed.
The undercoat film 3 made of iN _x or the like is coated. Then, after the a-Si film is formed by the sputtering method by the method described above, the polycrystalline silicon 4 is formed by laser annealing and patterned.

A gate insulating film 5 is formed thereon, and a gate electrode 6 made of MoW or the like is further formed and patterned. Then, using the gate electrode 6 as a mask, the polycrystalline silicon is ion-doped to form a source region 4a and a drain region 4b. Furthermore, for example, S on the whole surface
An insulating film 7 made of iO _x is formed.

Further, through holes are opened on the source region 4a and the drain region 4b of the insulating film. Then, a source electrode 8a and a drain electrode 8b are formed and connected to the source region and the drain region by through holes, respectively. Thus, a thin film transistor is formed.

In the case of a thin film transistor for pixel switching of a liquid crystal display device, it may be formed by connecting a pixel electrode made of, for example, indium tin oxide to a source electrode. At this time, indium tin oxide can be directly connected to the source region to replace the source electrode.

[0018]

According to the present invention, a- which is later polycrystallized
Since Si is formed by the sputtering method, an a-Si film having a low hydrogen content can be obtained, and since it can be formed at a low temperature, an inexpensive substrate can be used. Since the hydrogen content of a-Si is low, the dehydrogenation step becomes unnecessary before the heat treatment for polycrystallization. That is, since an inexpensive substrate is used and the number of steps can be reduced, it is possible to significantly reduce the cost.

[Brief description of drawings]

FIG. 1 is a process flowchart in an embodiment of the present invention.

FIG. 2 is a sectional view of a thin film transistor according to an example of the present invention.

FIG. 3 is a conventional process flowchart.

[Explanation of symbols]

 4 ... Polycrystalline silicon

Claims (6)

[Claims] 1. A method for producing a polycrystalline silicon substrate, comprising: a step of forming amorphous silicon on a substrate by a sputtering method; and a step of subsequently polycrystallizing the amorphous silicon by heat treatment. 2. A polycrystalline silicon substrate comprising a step of forming amorphous silicon having a hydrogen content of 5% or less on the substrate, and a step of subsequently polycrystallizing the amorphous silicon by heat treatment. Manufacturing method. 3. The method for producing a polycrystalline silicon substrate according to claim 1, wherein the sputtering method uses silicon as a target and forms amorphous silicon by RF power. 4. The method for producing a polycrystalline silicon substrate according to claim 1, 2 or 3, wherein the heat treatment is performed by laser annealing. 5. The method for producing a polycrystalline silicon substrate according to claim 4, wherein the energy density of the laser annealing is in the range of 200 to 400 mJ / cm ² . 6. A step of forming amorphous silicon on a substrate by a sputtering method, a step of subsequently polycrystallizing the amorphous silicon by heat treatment to form polycrystalline silicon, and a step of patterning the polycrystalline silicon. Forming a first insulating film on the polycrystalline silicon; forming a gate electrode on the insulating film in a region corresponding to a part of the polycrystalline silicon; and a predetermined region of the polycrystalline silicon. A source region and a drain region, a step of forming a second insulating film to cover the gate electrode, a source electrode connected to the source region, and a drain connected to the drain region. And a step of forming electrodes, respectively.