JPH07187891A - Crystal silicon thin film and its production - Google Patents

Abstract

PURPOSE:To grow crystal thin films having good quality to a large area on a foreign matter type substrate by arranging heat resistant fibers coated with silicon on the heat resistant substrate and recrystallizing the coating silicon while moving the fibers in a melting zone. CONSTITUTION:First, the heat resistant fibers 1 are passed in a reaction chamber 2 and the silicon layers 3 are formed by a CVD method, etc., thereon in order to form the silicon 3 around the heat resistant fiber 1. The fibers are taken up on a drum 4 where the fibers emerge from this reaction chamber 2. The fibers coated with the silicon are thus continuously produced. The fibers 6 coated with the silicon are arrayed on, for example, the insulating substrate 8 and a straight heater 7 is arranged perpendicularly in the axial direction of the fibers 7 in order to convert the silicon to the crystal thin films. The silicon is then melted and recrystallized gradually from one end of the fiber array. The ends where the melting and recrystallization begin are formed as fine crystals. The crystals having the same crystal direction (100) are selected and are made into single crystals owing to the restriction in the growth direction in the recrystallization by the small spaces made among the arranged fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystalline thin film of semiconductor silicon and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, as a method for growing a crystalline silicon thin film, particularly a single crystalline thin film on a substrate, an epitaxial method is used in which the same axial orientation is grown on the single crystalline silicon substrate. However, with this method, the substrate must be made of single-crystal silicon, which is expensive, and it is almost impossible to grow a silicon single-crystal thin film on a substrate other than single-crystal silicon. , Are subject to various restrictions.

Therefore, as a technique for growing a silicon crystal thin film, particularly a single crystal thin film on a substrate of a different material, grapho-epitaxy and ZMR method (linear heating zone melting recrystallization method) have been studied. There is. (See Sangyo Tosho Co., Ltd., SOI structure formation technology, pages 11 to 34)
In graphoepitaxy, it is necessary to artificially form regular grooves (gratings) on the substrate, and the substrate is easily damaged because it is recrystallized by laser light, and the grown silicon thin film only obtains mosaic-like polycrystals. Has not been done. On the other hand, also in the ZMR method, since microcracks are generated in the grown single crystal thin film and grain boundaries and dislocations are present,
There is a drawback that a film having an extremely small area (250 × 500 µm ² or less) can be formed only in an island shape.

[0004]

The problem to be solved by the present invention is to solve the above-mentioned problems of the prior art by using a foreign substance substrate (even if the substrate is silicon, its surface layer is a substance other than silicon). In addition, the purpose is to grow a good quality thin crystal film over a large area.

[0005]

The present invention comprises a step of forming a silicon film around a heat resistant fiber and a step of arranging the silicon film on a heat resistant substrate and melting and recrystallizing the coated silicon. Become. Further, if necessary, a step of etching or polishing the surface of the grown thin film is added.

An embodiment of the present invention will be described below with reference to the drawings. First, the silicon 3 around the heat resistant fiber 1
For example, as shown in FIG. 1, the heat resistant fiber 1 is passed through the reaction chamber 2 and the silicon layer 3 is formed by a general method such as a CVD method. If it is wound around the drum 4 when it leaves the reaction chamber 2, it can be continuously manufactured. Alternatively, the silicon layer may be coated by immersing the heat resistant fiber in a silicon melt and pulling it out. If the diameter of the heat-resistant fiber is too thin, the productivity will decrease, and if it is too thick, the space between the heat-resistant fibers used in the next step will become large and it will not be possible to obtain good quality crystals, especially single crystals. Ranges are preferred. The thickness of the produced silicon crystal thin film can be adjusted by adjusting the thickness of the silicon to be coated and the diameter of the heat resistant fiber. In this case, various types of heat resistant fibers can be used, but when it is necessary to prevent contamination of impurities, glass fibers are preferable, and silica glass fibers are particularly preferable.

In order to make this into a crystal thin film, for example, as shown in FIG. 2, fibers 6 coated with silicon are arranged on an insulating substrate 8, and then a linear heater 7 is perpendicular to the axial direction of the fibers. And gradually melt and recrystallize from one end of the fiber array. The end where melt recrystallization starts is a fine crystal, but due to the small space created between the arranged fibers, those with the same crystal orientation (100) gradually become due to the restriction of the growth direction in recrystallization. A single crystal is selected.

In this case, if the fiber end is an open system, the specific relationship between the silicon and the fiber material determines the vertical relationship in the cross section of the produced thin film and the fiber. That is, when it is necessary to remove the fiber after growing the single crystal silicon thin film, a fiber having a smaller specific gravity than silicon is used. Since the specific gravity of glass fiber is smaller than that of silicon, when the fiber end is made open and a thin film is grown, it will float on the surface. After the film growth, the fibers can be removed by etching with an acid that dissolves only the fibers. Glass fibers can be etched with hydrofluoric acid. On the other hand, if the fiber may be embedded in the thin film and remain (for example, a silicon thin film for solar cells), the fiber end may be thickened by fixing the fiber end in advance by welding or the like. It is easy to obtain a single crystal that is dense and has no microcracks in a large area.

The obtained crystalline silicon thin film may be used as it is or may be surface-etched depending on the purpose. Furthermore, the surface may be mirror-polished and used according to a general method together with the substrate so that it can be used for a semiconductor device. In this case, the substrate used must have a high flatness.

[0010]

[Examples] Glass fibers having a diameter of 125 μm and a length of 10 m were wrapped around a frame made of square quartz rods so as not to overlap or intersect each other, placed in a vacuum reactor, and treated for 12 hours at 650 ° C. in a silane gas atmosphere of 100 Pa. Silicon was deposited on the surface of the glass fiber. The deposited silicon was polysilicon having a thickness of 14 μm and a grain size of about 10 μm. This is cut into 5 cm pieces and 120 pieces are prepared, and a quartz glass substrate (high flatness used for mirror polishing)
Arrayed parallel to the 2 cm x 5 cm area above. Put this in a vacuum furnace, melt the silicon on the side formed by the end of the fiber with a rod-shaped heater, and perform melting and recrystallization in order while moving the heater in the axial direction of the fiber at a speed of 0.2 cm per minute. Around 17mm from the side where melting and recrystallization started
After that, it became a single crystal. That is, a silicon single crystal thin film having a large area of about 3 cm × 2 cm could be obtained on the quartz plate.

The surface of the obtained thin film was treated with hydrofluoric acid to remove the fibers, and then the orientation was examined by X-ray diffraction.
0) surface. In addition, the film surface is selectively etched (HF: HN
O ₃ : CH ₃ COOH = 1: 50: 50), no microcracks or grain boundaries were observed.

Further, when the single crystal thin film on the quartz substrate was polished under exactly the same conditions as when manufacturing a normal silicon single crystal mirror surface wafer, a silicon single crystal thin film having a mirror surface was obtained.

[0013]

As described above, according to the method of the present invention, it is possible to obtain a high quality on a foreign substance substrate (including a case where the substrate is silicon, the surface layer of which is a substance other than silicon). The crystalline silicon thin film can be produced in a large area. Therefore, it can be applied to various semiconductor devices and can contribute to cost reduction.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a step of depositing silicon on a fiber by a CVD method.

FIG. 2: Melt recrystallization of silicon on fiber,
It is a conceptual diagram of the process of obtaining a crystalline silicon thin film. (A) is a plan view and (b) is a side view.

[Explanation of symbols]

 1 Heat Resistant Fiber 2 CVD Reaction Chamber 3 Precipitated Silicon 4 Fiber Winding Drum 6 Silicon Coated Fiber 7 Linear Heater 8 Heat Resistant Substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Suichiro Aiga 2-6-1 Otemachi, Chiyoda-ku, Tokyo Shin-Etsu Chemical Co., Ltd. (72) Inventor Hide Arai 2-chome, Otemachi, Chiyoda-ku, Tokyo No. 6-1 Shin-Etsu Chemical Co., Ltd. Head Office (72) Inventor Jun Ozaki 2-6-1 Otemachi, Chiyoda-ku, Tokyo Shin-Etsu Chemical Co., Ltd. Head Office

Claims (8)

[Claims] 1. A heat-resistant fiber is coated with silicon around the heat-resistant fiber, and the heat-resistant fiber is arranged on a heat-resistant substrate. Then, a part of the coated silicon is heated and melted, and recrystallization is performed while gradually moving the melted region. A silicon crystal thin film, which is formed on a substrate by oxidization. 2. A crystalline silicon thin film, wherein the surface of the crystalline silicon thin film according to claim 1 is etched and / or polished. 3. A crystalline silicon thin film, wherein the heat resistant fiber according to claim 1 is a glass fiber. 4. A crystalline silicon thin film, wherein the glass fiber according to claim 3 is a quartz glass fiber. 5. A heat-resistant fiber is coated with silicon around it, and the heat-resistant fiber is arranged on a heat-resistant substrate. Then, a part of the coated silicon is melted by heating and recrystallized while gradually moving the melting region. A method for producing a silicon crystal thin film on a substrate by oxidization. 6. A method for producing a crystalline silicon thin film, which comprises etching and / or polishing the surface of the crystalline silicon thin film obtained by the method according to claim 5. 7. A method for producing a crystalline silicon thin film, wherein the heat resistant fiber according to claim 5 is a glass fiber. 8. A method for producing a crystalline silicon thin film, wherein the glass fiber according to claim 7 is a quartz glass fiber.