JPH05217891A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a manufacturing method for a semiconductor device, in which a polysilicon film with sufficiently larger grain size can be obtained, by lowering the generating rate of a crystalline nucleus during the crystallization of an amorphous silicon film. CONSTITUTION:An amorphous silicon film 3 is formed on a substrate 3, and a thin oxide film 4 is formed on the amorphous silicon film 3. Then, the amorphous silicon film 3 is crystallized in a thermal treatment step so that a polysilicon film 5 with sufficiently large grain size is formed.

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 semiconductor device, and more particularly to a method for manufacturing a semiconductor device having a polycrystalline silicon film having a large crystal grain size.

[0002]

2. Description of the Related Art Conventionally, in the manufacturing process of semiconductor devices,
A polycrystalline silicon film is formed on a substrate for various purposes. As an example thereof, for example, a thin film transistor (Thin Film Transistor) in which a source / drain is formed on a polycrystalline silicon film formed on a substrate is used.
Hereinafter referred to as "TFT").

This TFT is generally used in a switching element of a liquid crystal display or an SRAM (Static Ra).
p-MOS (p-channel Metal Oxi) of a non-access memory memory cell.
de Semiconductor Transist
Or, it is used as a load and contributes to miniaturization and high integration of semiconductor devices.

In the TFT, for example, a channel is formed in a polycrystalline silicon film formed on a substrate made of glass or the like. This channel has electrons or positive electrons as the crystal grain size of the polycrystalline silicon film is larger. It is known that the mobility of holes increases and the leak current is suppressed (decreased). Therefore, as the crystal grain size of the polycrystalline silicon film is increased, the channel characteristics can be improved.

Therefore, in recent years, as a method of forming a polycrystalline silicon film having a large crystal grain size, an amorphous (amorphous) silicon film is formed on a substrate and heat-treated to form the amorphous silicon film. The method of crystallizing is introduced.

[0006]

However, in the above-mentioned conventional example, crystal nuclei generated when the amorphous silicon film is crystallized are actively generated from the early stage, especially on the surface of the amorphous silicon film. That is, the crystal nuclei are generated more rapidly and in large quantities on the surface of the amorphous silicon film than in the inside of the amorphous silicon film. This is because the atoms existing on the surface of the amorphous silicon film do not have atoms that can be bonded on top of them, so the atoms existing inside the amorphous silicon film (the entire number of atoms that can be bonded are This is because it is more likely to diffuse (move) and crystallize more easily than the atoms existing in ().

It is known that when the crystal nuclei collide with other crystal nuclei, the growth stops at that time.
Therefore, when a large amount of crystal nuclei are generated on the surface of the amorphous silicon film, the crystal nuclei collide with each other at a fast stage, and therefore the crystal nuclei cannot grow sufficiently and the crystal grain size is large. There is a problem that it is difficult to form a crystalline silicon film. In addition, since the crystal nuclei relatively slowly generated inside the amorphous silicon film also collide with the crystal nuclei generated on the surface of the amorphous silicon film, the growth thereof is hindered, and the polycrystal having a large crystal grain size is prevented. There is a problem that it becomes more difficult to form a silicon film.

An object of the present invention is to solve such a problem and to reduce the generation rate of crystal nuclei generated with the crystallization of an amorphous silicon film so that the crystal grain size is sufficient. An object of the present invention is to provide a method for manufacturing a semiconductor device, which is capable of forming a large polycrystalline silicon film.

[0009]

In order to achieve this object, the present invention provides a method for manufacturing a semiconductor device in which a polycrystalline silicon film is formed on a substrate, wherein the polycrystalline silicon film is formed on the substrate. A method of manufacturing a semiconductor device, comprising forming an amorphous silicon film, forming a thin oxide film on the amorphous silicon film, and then crystallizing the amorphous silicon film. is there.

[0010]

According to the present invention, an amorphous silicon film is formed on a substrate, a thin oxide film is formed on the amorphous silicon film, the amorphous silicon film is crystallized, and the amorphous silicon film is changed to a polycrystalline silicon film. By setting the above, a polycrystalline silicon film having a sufficiently large crystal grain size can be obtained.

That is, by forming a thin oxide film on the amorphous silicon film,
Atoms present on the surface of the silicon film can be bonded to atoms forming the oxide film. Therefore, it is possible to suppress the diffusion (movement) of atoms existing on the surface of the amorphous silicon film, which has conventionally been the cause of rapid and large-scale generation of crystal nuclei. As a result, crystal nuclei are not generated on the surface of the amorphous silicon film, and the crystal nuclei are mainly generated from the inside of the amorphous silicon film, which has a low generation rate. In addition, the amount of crystal nuclei generated and the rate of formation thereof can be reduced. Therefore, when the amorphous silicon film is crystallized, the crystal nuclei can be sufficiently grown, and as a result, a polycrystalline silicon film having a sufficiently large crystal grain size can be formed.

Further, since the thin oxide film does not interfere with various steps performed after the polycrystalline silicon film is formed, the step of removing the thin oxide film can be omitted.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 3 are sectional views showing a part of the manufacturing process of a semiconductor device according to an embodiment of the invention. In the step shown in FIG. 1, a base silicon oxide film 2 having a film thickness of about 6000Å is formed on the substrate 1 by a known method. Next, a film thickness of 50 is formed on the underlying silicon oxide film 2.
An amorphous silicon film 3 having a thickness of 0Å is formed.

Next, in the step shown in FIG. 2, the substrate 1 obtained in the step shown in FIG. 1 is oxidized in an oxygen atmosphere at 200 ° C. for 15 minutes to form a film having a thickness of 1 on the amorphous silicon film 3.
A thin silicon oxide film 4 of about 0Å is formed. By doing so, the atoms existing on the surface of the amorphous silicon film 3 are combined with the atoms existing on the thin silicon oxide film 4. The temperature at which the thin silicon oxide film 4 is formed is lower than the temperature at which the amorphous silicon film 3 is crystallized.

Next, in the step shown in FIG. 3, the substrate 1 obtained in the step shown in FIG. 2 is heat-treated at 600 ° C. in a nitrogen atmosphere for 15 hours to crystallize the amorphous silicon film 3 so that the crystal grain size becomes smaller. A large polycrystalline silicon film 5 is formed. At this time, the atoms existing on the surface of the amorphous silicon film 3 are bonded to the atoms existing on the thin silicon oxide film 4, so that the diffusion of the atoms existing on the surface of the amorphous silicon film 3 can be suppressed. it can. Therefore, crystal nuclei are less likely to be generated on the surface of the amorphous silicon film 3, and the crystal nuclei are mainly generated from the inside of the amorphous silicon film 3 having a low generation rate. Therefore, the amount and rate of generation of crystal nuclei can be reduced as a whole, and as a result of the crystal nuclei being sufficiently grown, the crystal grain size of the polycrystalline silicon film can be increased.

After that, desired steps are performed to complete the semiconductor device. Next, the number of crystal nuclei generated when the amorphous silicon film is crystallized in the above embodiment and the number of crystal nuclei generated when the amorphous silicon film is crystallized without forming the thin silicon oxide film (conventional example) A comparison was made with the number of crystal nuclei generated. The result is shown in FIG.

From FIG. 4, it was confirmed that the amount of crystal nuclei generated in this example was about 1/6 to 1/7 smaller than that in the conventional example. Further, the crystal grain size of the polycrystalline silicon film obtained in this example was compared with the crystal grain size of the polycrystalline silicon film obtained by the conventional method. The result is shown in FIG.

From FIG. 5, it was confirmed that the polycrystalline silicon film obtained in this example had a large crystal grain size of about 3 μm, whereas the conventional example had a small crystal grain size of about 0.3 μm. .. Next, an example of forming a TFT using the method for forming a polycrystalline silicon film according to the present invention will be described with reference to the drawings. 6 to 9 are sectional views showing a part of the manufacturing process of the semiconductor device (TFT) according to the present invention.

In the step shown in FIG. 6, the gate electrode 7 is formed on the substrate 1 by a known method through the interlayer insulating film 6 having a film thickness of about 6000 Å. Next, in a step shown in FIG. 7, a gate insulating film 8 having a film thickness of about 200 Å is formed on the substrate 1 obtained in the step shown in FIG. 6 by a known method.
Next, the amorphous silicon film 3 having a film thickness of about 500 Å is formed on the gate insulating film 8.

Next, in the step shown in FIG. 8, the substrate 1 obtained in the step shown in FIG. 7 is oxidized in an oxygen atmosphere at 200 ° C. for 15 minutes to form a film having a thickness of 1 on the amorphous silicon film 3.
A thin silicon oxide film 4 of about 0Å is formed. Next, in the step shown in FIG. 9, the substrate 1 obtained in the step shown in FIG.
The amorphous silicon film 3 is crystallized by heat treatment at 00 ° C. in a nitrogen atmosphere for 15 hours to form a polycrystalline silicon film 5 having a large crystal grain size. Next, desired impurity ions are introduced into the source 9 and drain 10 regions of the polycrystalline silicon film 5 having a large crystal grain size to form the source 9 and drain 10. In this way, a channel was formed in the polycrystalline silicon film 5 having a large crystal grain size.

Thereafter, desired steps are performed to complete the TFT, but the thin silicon oxide film 4 does not support the various steps performed after forming the polycrystalline silicon film 5 having a large crystal grain size. Therefore, it need not be removed. Through the above steps, a TFT having a channel portion formed of the polycrystalline silicon film 5 having a large crystal grain size was obtained.

The channel of the TFT thus obtained is
Mobility of electrons and holes increases, leakage current is suppressed,
The channel characteristics were improved. In this embodiment, the TFT in which the source / drain portion and the channel portion are formed on the polycrystalline silicon film having a large crystal grain size has been described.
Not limited to this, it goes without saying that a polycrystalline silicon film having a large crystal grain size may be formed for use in other portions (elements).

[0023]

As described above, according to the present invention,
By forming a thin oxide film on the amorphous silicon film formed on the substrate, the atoms existing on the surface of the amorphous silicon film can be bonded to the atoms forming the oxide film. .. Therefore, when the amorphous silicon film is crystallized, it is possible to suppress the diffusion of atoms existing on the surface of the amorphous silicon film, which has conventionally been a cause of rapid and large-scale generation of crystal nuclei. Therefore, in addition to the fact that crystal nuclei are not generated on the surface of the amorphous silicon film, the crystal nuclei are mainly generated from the inside of the amorphous silicon film whose generation rate is slow. Therefore, the amount and rate of generation of crystal nuclei can be reduced as a whole, so that the crystal nuclei can be sufficiently grown. As a result, a polycrystalline silicon film having a sufficiently large crystal grain size can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a part of a manufacturing process of a semiconductor device according to an embodiment of the invention.

FIG. 2 is a sectional view showing a part of the manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 3 is a sectional view showing a part of the manufacturing process of the semiconductor device according to the example of the invention.

FIG. 4 is a comparison diagram of the number of generated crystal nuclei in this example and the number of generated crystal nuclei in the conventional example.

FIG. 5 is a comparison diagram of the crystal grain size of the polycrystalline silicon film obtained in this example and the crystal grain size of the polycrystalline silicon film obtained by the conventional method.

FIG. 6 is a cross-sectional view showing part of a process for manufacturing a semiconductor device (TFT) according to the present invention.

FIG. 7 is a cross-sectional view showing a part of a manufacturing process of a semiconductor device (TFT) according to the present invention.

FIG. 8 is a cross-sectional view showing a part of a manufacturing process of a semiconductor device (TFT) according to the present invention.

FIG. 9 is a cross-sectional view showing a part of the manufacturing process of the semiconductor device (TFT) according to the present invention.

[Explanation of symbols]

 1 Substrate 2 Base Silicon Oxide Film 3 Amorphous Silicon Film 4 Thin Silicon Oxide Film 5 Polycrystalline Silicon Film with Large Crystal Grain Size 6 Interlayer Insulation Film 7 Gate Electrode 8 Gate Oxide Film 9 Source 10 Drain

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device in which a polycrystalline silicon film is formed on a substrate, the amorphous silicon film is formed on the substrate, and the amorphous silicon film is formed on the amorphous silicon film.
A method of manufacturing a semiconductor device, comprising forming a thin oxide film and then crystallizing the amorphous silicon film.