JPH02260456A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the number of processes and to reduce an irregularity in an electric characteristic of a MOS transistor by a method wherein a second polycrystalline silicon film is recrystallized and transformed into a second silicon film, it is used as a gate electrode and a thermal SiO2 film at its substratum is used as a gate insulating film. CONSTITUTION:A second polycrystalline silicon film 5 is formed, via a thermal SiO2 film 4, on an island composed of a first polycrystalline silicon film 3 which has been formed on an insulating film 2. After that, the first polycrystalline silicon film and the second polycrystalline silicon film 3, 5 are irradiated with an energy beam 6, are recrystallized at the same time and are transformed into a first silicon film and a second silicon film 7, 8. one part of the second silicon film 8 is used as a gate electrode 9, and the thermal SiO2 film 4 is used as a gate insulating film 10. Thereby, it is possible to reduce the number of processes used to form a MOS transistor; in addition, it is possible to reduce an irregularity in a film thickness of the gate insulating film 10 and to reduce an irregularity in an electric characteristic.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method of manufacturing a semiconductor device.

Conventional technology A conventional method of forming a silicon film with good crystallinity on an insulating film and forming a semiconductor device on this silicon film includes, for example, the 6th Diffraction Functional Element Technology Symposium Proceedings (1986
2013), pages 216 to 229.

FIG. 2 shows this conventional method for manufacturing a semiconductor device, in which 13 is a semiconductor substrate, and 14 is a first polycrystalline silicon film 16 which is sequentially formed on an insulating film 14 on the semiconductor substrate 13 using CVN or the like. 0.6μs, 5i02 film 16 0.2μm
A multilayer structure is formed in which the second polycrystalline silicon film 17 is o, epm, and the 5i02 film 18 is provided at the top layer at a thickness of 0.26 plM (FIG. 2a). Next, this multilayer structure is irradiated with a laser beam 19, and the polycrystalline silicon film 16 of the first cylinder 1 and the second
A polycrystalline silicon film 21 is formed (FIG. 2b). During this recrystallization process, the first polycrystalline silicon film 16 shown in FIG. 2a is melted by heat conduction from the second polycrystalline silicon film 17. At this time, the second polycrystalline silicon film 17 acts as a buffer layer L2 against the fluctuation of the laser beam, reduces the influence of the fluctuation of the laser beam 16 on the first polycrystalline silicon film 16, and The silicon film 16 undergoes highly stable crystal growth and is the first silicon film 2 with good crystallinity.
You can get 0.

After completing the second recrystallization step, the 5i02 film 16° and the second silicon film 21. The SiO2 film 18 is peeled off.

The first silicon film 20 exposed at the surface is used as an active layer, and a gate insulating film 22. Gate electrode 23. Source area 24. A drain region 25 is provided, and a MOS transistor is formed on the insulating film 14. The above is the conventional method for manufacturing a MOS type semiconductor device.

Problems to be Solved by the Invention However, in the above manufacturing method, in order to obtain the first silicon film 20 that will become the active layer of the MOS transistor, the 5102 film 16. Second polycrystalline Si film 21, f
In addition to the process of forming the Si02 film 18, a redundant process of removing each film is required, and the insulating film 14
This method has the problem of significantly increasing the number of steps required to form a MOS transistor on top.

Furthermore, although a thermally oxidized 5i02 film is normally used for the gate insulating film of a MOS transistor, if the gate insulating film 22 in FIG. It depends on the plane orientation of the first silicon film 20 in the region immediately below.

Generally, the surface orientation of the first silicon film 20 varies depending on the location, and this variation in surface orientation causes variations in the thickness of the gate insulating film of each MOS transistor formed on the same surface. . As a result, individual M
OS) had the problem of causing variations in electrical characteristics such as the threshold voltage of transistors.

In view of this point, the present invention maintains the advantages of the conventional technology of forming a silicon film with good crystallinity on an insulating film, while
To reduce the number of steps in forming a MOS (MOS) transistor on an insulating film, and to reduce variations in the thickness of the gate insulating film of each MO8) transistor formed on the same surface. It is an object of the present invention to provide a method for manufacturing a semiconductor device that achieves the above two points of reducing variations in electrical characteristics of transistors.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention applies heat 5i02 to an island made of a first polycrystalline silicon film provided on an insulating film.
After forming a second polycrystalline silicon film through the film, the first and second polycrystalline silicon films are simultaneously recrystallized by energy beam irradiation to form first and second silicon films, and A method of manufacturing a semiconductor device is used in which a part of the silicon film No. 2 is used as a gate electrode and the heat 5102 is used as a gate insulating film to form a MOS transistor on the insulating film.

Effect of the present invention By using the above-described means, the second polycrystalline silicon film used only as a buffer layer against fluctuations of laser light in the recrystallization process of the polycrystalline silicon film on the insulating film is recrystallized. After forming the second silicon film, it is used as a gate electrode (2, and in order to further use the underlying thermal 5io2 film as a gate insulating film, as shown in the conventional example, the second silicon film is used after the recrystallization process. Compared to the case where a new gate insulating film 22 and gate electrode 23 are formed after removing the silicon film 21 and the 5in2 films 16 and 18, the number of steps in forming a MOS transistor on the insulating film is significantly reduced. reduce Furthermore, by the means described above, the heat 5i02 M that coats the first polycrystalline silicon film is formed by thermally oxidizing the surface of the polycrystalline silicon film, but generally polycrystalline silicon films are (111) face centered (110) face centered. Since it is composed of crystal grains with a grain size of 0.03 to 0.3 μm distributed uniformly, the variation in the thickness of the thermal oxide film is due to recrystallization as shown in the conventional example. The variation in the thickness of the gate insulating film 22 formed by thermally oxidizing the surface of the first silicon film 20 is reduced, and the thermal 5i02 film formed by thermally oxidizing the first polycrystalline silicon film is MOS with less variation in electrical characteristics by being used as an insulating film
) A transistor is formed on the insulating film.

Embodiment FIG. 1 shows a method of manufacturing a semiconductor device according to an embodiment of the present invention. In FIG. 1a, 1 is a silicon semiconductor substrate, on which a first layer of semiconductor elements may be formed. 2 is an insulating film such as 8102 formed by CvD or the like and has a thickness of 1 μm.

3 is a polycrystalline silicon film processed into an island shape with a film thickness of O.S.mu.m, into which P-type impurities are implanted.

Next, the surface of the polycrystalline silicon film 3 is thermally oxidized to have a film thickness of 0.0
A thermally oxidized 8102 film 4 of 3μ thick is coated, and a polycrystalline silicon film 6 is further deposited to a thickness of O and S2 layers to form a polycrystalline silicon film 3. Thermal oxidation 5102 film 4. Polycrystalline silicon film 6
(Fig. 2b). The polycrystalline silicon film 3 is composed of crystals having (111) planes and (110) planes with a grain size of 0.03 to 0.3 μm distributed uniformly, and is therefore thermally oxidized. Formed heat 5102 film 4
The variation in film thickness within the wafer surface is smaller than that of an 8i02 film formed by thermally oxidizing a recrystallized single crystal silicon surface, resulting in a high quality film.

This multilayer structure is irradiated with laser light 6 to simultaneously recrystallize polycrystalline silicon film 3 and polycrystalline silicon film 6. At this time, the polycrystalline silicon film 3 melts due to heat conduction from the polycrystalline silicon film 6, but since the polycrystalline silicon film 6 acts as a buffer layer against fluctuations in the laser beam 6, the polycrystalline silicon film 3 becomes a highly stable crystal. Growth takes place. Through the above recrystallization process, silicon film 7 and silicon film 8 are formed (FIG. 2O). Hereafter, silicon film 8. Thermal oxidation 8i (
), the film 4 is selectively removed, the silicon film 7 is used as an active layer, the silicon film 8 is used as a gate electrode material, and the thermally oxidized 5102 film 4 is used as a gate insulating film material, according to a standard Nd MOS transistor formation method. , gate insulating film 10. Gate electrode 9
．． An n+ source region 11°n and a drain region 12 are provided, and a 1 cNch MOS transistor is formed on the insulating film 2 (FIG. 2d).

As described above, according to this embodiment, the silicon film 8 obtained by recrystallizing the polycrystalline silicon film 3 used as a buffer layer against fluctuations of laser light is used as the gate electrode material, and the thermally oxidized 5io2 film 4 underlying the silicon film 8 is used as the gate electrode material. Since MOS transistors are used as the gate insulating film material, the number of steps in forming a MOS transistor on the insulating film can be significantly reduced compared to the conventional method. In addition, since the SiO2 film 4 is formed by thermally oxidizing the polycrystalline silicon film 3, the uniformity of the crystal grains of the polycrystalline silicon film 3 may cause variations in the film thickness of the thermally oxidized film 5i021[14] within the wafer surface. is smaller than before. As a result, each MO using the thermally oxidized 8i02 film 4 as the gate insulating film material
5) Variation in the gate capacitance of transistors within the wafer surface is reduced compared to the conventional method, and a MOS transistor with less variation in electrical characteristics compared to the conventional method can be formed on an insulating film.

Although the embodiment shown in FIG. 1 is a method for forming an Nch MOS transistor, a Pch MOS transistor may also be formed.

As described in detail, according to the present invention, the number of steps for forming a MOS transistor on an insulating film can be significantly reduced compared to the conventional method, and variations in the thickness of the gate insulating film can be reduced. Especially MO with small variation in stain resistance properties.
S) A transistor can be formed on an insulating film, which greatly contributes to the realization of a high-performance semiconductor device with a stacked structure.

Ru.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a conventional method for manufacturing a semiconductor device. 1... Semiconductor substrate, 2... Insulating film, 3
...Polycrystalline silicon family, 4...Heat 51
02 film, 6... curved polycrystalline silicon film, 6... laser light, 7... silicon film, 8... silicon film, 9... gate insulating film, 10... Gate electrode, 11... Source region, 12...
...Drain region. Name of agent: Patent attorney Shigetaka Awano #1 is one person
・-Half S salary board 2...$1! Abbreviation s, s-4 arc 11 police officer shizokon 挎J112 prisoner 13...-hand 4 yen saka/4-ichizetsu hemorrhoid hou lko 17..., book 9 kan shizokon dwarf/6. /1h-3u)zFi$

Claims (1)

[Claims] An island made of a first polycrystalline silicon film is formed on an insulating film provided on a semiconductor substrate, the surface of the island is covered with a thermal oxide film having a desired thickness, and a second polycrystalline silicon film is formed on the thermal oxide film. After depositing the polycrystalline silicon film, the first and second polycrystalline silicon films are simultaneously recrystallized by an energy beam to form a first silicon film and a second silicon film, and the second polycrystalline silicon film is deposited. By using a partial region of the silicon film as a gate electrode, using the thermal oxide film as a gate insulating film, and providing a source region and a drain region on the island made of the first silicon film,
A method of manufacturing a semiconductor device, comprising forming a MOS transistor on the insulating film.