JPH01196116A - Manufacture of polycrystalline silicon thin film - Google Patents

Abstract

PURPOSE:To assure the use of a blue glass which is inexpensive as a substrate by irradiating an amorphous silicon thin film formed on the substrate with light while heating the substrate. CONSTITUTION:An amorphous silicon thin film formed on a substrate is irradiated with a light while heating the substrate. Hereby, a polycrystalline silicon thin film can be formed at a high speed from the amorphous silicon thin film at a substrate temperature lower than 600 deg.C. Visible and ultraviolet laser lights, which have high photon density, are preferably employed, and heating temperature for the substrate is enough to be 600 deg.C or below. Although the substrate is not limited in particular, a glass substrate, preferably a blue glass of a low melting point, which is low in deformation temperature and heat-resistance and is low priced, is useable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing polycrystalline silicon thin films, and particularly to the formation of polycrystalline silicon thin films at low temperatures.

[Background Art] Crystalline and amorphous semiconductor thin films are used as thin film semiconductor devices. Many single crystal thin films and polycrystalline thin films are used as crystalline semiconductor thin films. Polycrystalline thin films are used by being formed on various substrates, but there is a problem in that the substrate temperature must be raised to a high temperature when forming the polycrystalline thin film to promote crystallization, or After that, a high-temperature annealing process was required. For this reason, materials that can withstand high temperatures have been required for the substrate. High-temperature resistant substrates are costly, and the types of substrates available are also limited.

However, among the inexpensive and practical glass substrates,
Although blue plate glass has the lowest cost and is produced in large quantities, it has until now been unable to be used as a substrate for forming polycrystalline thin films because of its poor durability at high temperatures.

As a result of intensive investigation into this point, the present inventors have discovered an effective method for promoting crystal growth at low temperatures that also enables the use of soda-lime glass.The present inventors hereby disclose the technical content in detail. At the same time, it requests the granting of patent rights, which are exclusive and exclusive rights, in return.

[Disclosure of the Invention] The present invention is characterized in that an amorphous silicon thin film formed on a substrate is irradiated with light while heating the substrate.

The light used in the present invention may be light with a narrow spectrum width such as a laser beam or light with a wide spectrum width. Preferably, 1 has a large absorption coefficient of amorphous silicon.
It is light having a wavelength of μm or less. In particular, visible light and ultraviolet lasers, which can increase the number of photons of irradiated light, are preferably used. Specifically, argon ion laser, Nd\AC laser, etc. are preferable.

In the present invention, it is sufficient to heat the substrate at a temperature of 600'C or less. Preferably, it is heated to a temperature of about 400 to 600°C. In this temperature range, blue plate glass can also be used satisfactorily. The substrate is heated using a far-infrared cotton heater, a sheath heater, a lamp heater, etc. alone or in combination. Since the lamp heater includes the visible light spectrum, the absorption coefficient of amorphous silicon is large, and it is effective in raising the temperature of the substrate and the amorphous silicon thin film, and is therefore preferably used.

The amorphous silicon thin film that can be used in the present invention is formed by a plasma CVD method, a microwave CVD method, a sputtering method, a thermal CVD method, etc. What is specified is used. The amorphous silicon may contain impurities, or may not contain any impurities intentionally. Polycrystalline thin films obtained by using an amorphous silicon thin film containing group ■ or group ■ impurities as impurities are as follows:
Shows P-type and N-type electrical conductivity. Amorphous silicon to which impurities are not intentionally introduced provides a polycrystalline thin film exhibiting weak P-type or weak N-type electrical conductivity. Amorphous silicon-germane alloys and amorphous solicon carbon alloys can also be used as raw materials for the present invention.

Another feature of the present invention is that it can effectively increase the growth rate of polycrystalline thin films at low temperatures. In the temperature range used in the present invention, if a silicon thin film is deposited and grown at a high rate of 5 people/second or more, the resulting silicon thin film will become amorphous, and the polycrystalline thin film will become amorphous. It is difficult to do so. However, by using the present invention, this problem is easily solved. That is, since amorphous silicon can be formed at a high rate, by applying the present invention thereto, factors that inhibit the growth rate can be eliminated. Although the growth rate is also affected by the intensity of the irradiated light, it is easy to achieve a growth rate of 5 or more people/second.

The thickness of the amorphous silicon thin film in the present invention is not limited in principle, but from a practical standpoint it is 20 μm.
It is possible to process up to IU thickness. Furthermore, it was confirmed that the present invention is effective even in ultra-thin films containing about 100 people.

The substrate used in the present invention is not particularly limited, such as single-crystal or non-single-crystal, transparent or opaque materials, but from a practical standpoint, glass substrates are preferred because of their low deformation temperature and poor heat resistance. Even soda-lime glass, which is a low-melting glass that is inexpensive, can be suitably used as the substrate. This point is the most distinctive feature of the present invention, and is in marked contrast to conventional techniques that use silicon wafers as substrates.

[Preferred Modes for Carrying Out the Invention] Next, embodiments of the present invention will be described. The glass substrate on which the amorphous silicon thin film is formed is heated to 400 to 600° C. using a lamp heater and a hot wire heater, and irradiated with visible light or ultraviolet laser. Since visible light passes through the glass substrate, the direction of irradiation is not limited. Amorphous silicon can also be irradiated directly or indirectly through glass. Of course, since the absorption coefficient of glass is large for ultraviolet rays, it is effective to directly irradiate the amorphous silicon thin film.

[Effects and industrial applicability of the invention] In the present invention, the polycrystalline silicon thin film is made from a non-quality silicon thin film.
The substrate is formed at a low temperature of 600° C. or less at high speed.

In the present invention, since a glass substrate with a low melting point can be used, it can be effectively used as a material for a large area semiconductor device. In particular, it provides high-performance, inexpensive, and practical materials for solar cells and liquid crystal driving transistors.

[Example 1] A blue plate glass on which a 1 μm thick amorphous silicon thin film was formed was prepared, and while it was heated to 400° C. with a lamp heater, it was irradiated with a 514 nm argon ion laser. A laser beam with a diameter of 0.2 cm was scanned over the amorphous silicon to obtain a polycrystalline silicon thin film with a size of 10 cm square.

The scanning speed is 1 cm/sec, which is converted to a film formation speed of 2
Polycrystalline silicon could be obtained at a high speed comparable to 0 person/second or higher. The conductivity of this polycrystalline silicon thin film is I
It was Xl0-7S 7 cm and could be sufficiently used as a substrate for solar cells. The particle size estimated by X-ray diffraction (XRD) was 0.1 μm.

[Example 2] A blue plate glass on which 1 μm of N-type amorphous silicon was formed was prepared, and while it was heated to 400° C. with a lamp heater, it was irradiated with a 514 nm argon ion laser. The laser beam diameter was Q and the amorphous silicon was scanned with a diameter of 2 cm to obtain a polycrystalline silicon thin film having a size of 10 cm square.

The scanning speed is 2 cm/sec, which is converted into a film formation speed of 4.
Polycrystalline silicon could be obtained at a high speed comparable to 0 person/second or higher. The conductivity of this N-type polycrystalline silicon thin film was 600 S/cm, and it could be sufficiently used as a substrate for solar cells.

[Example 3] A blue plate glass on which 1 μm of P-type amorphous silicon was formed was prepared, and while it was heated to 400°C with a lamp heater,
It was irradiated with a 514 nm argon ion laser. A polycrystalline silicon thin film having a size of 10 cm square was obtained by scanning amorphous silicon with a laser beam diameter of 0.2 cm. The scanning speed was 0.5 cm 2 /sec, and polycrystalline silicon could be obtained at a high speed equivalent to 10/sec or more when converted into a film deposition rate. The conductivity of this P-type polycrystalline silicon thin film was 300 S/cm, and it could be sufficiently used as a substrate for solar cells.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] (1) A method for producing a polycrystalline silicon thin film, which is characterized by irradiating light onto an amorphous silicon thin film formed on a substrate while heating the substrate. (2) The method for producing a polycrystalline silicon thin film according to claim 1, wherein the amorphous silicon thin film is irradiated with visible light or ultraviolet laser. (3) The method for producing a polycrystalline silicon thin film according to claim 1, wherein the substrate is a low melting point glass substrate. (4) The method for producing a polycrystalline silicon thin film according to claim 3, wherein heating is performed at a temperature below the melting point of the glass substrate.