JP2740281B2 - Method for producing crystalline silicon - Google Patents

Description

The present invention relates to a method for producing crystalline silicon represented by polycrystal or single crystal.

(B) Conventional technology Plasma CVD, a low-temperature film forming technology on the substrate surface, is a method of realizing the low-temperature film forming request and the large area request of the crystal film.
Non-single-crystal films such as amorphous films and polycrystalline films are obtained by a method, thermal CVD method, vacuum deposition method, or sputtering method, and the amorphous films are converted to polycrystalline films or single-crystal films. Or a method of converting a polycrystalline film into a single crystalline film. For example, in the prior art disclosed in Japanese Patent Application Laid-Open No. 63-17076, for example, an amorphous film is formed on a substrate surface in advance by a plasma CVD method at a low temperature, followed by annealing by laser beam irradiation. There is a method of obtaining a crystal film.

(C) Problems to be Solved by the Invention However, since the intensity distribution of the laser beam used for annealing generally exhibits a Gaussian distribution having a peak at the center, uniform annealing should be performed between the center and the periphery of the laser beam. However, since the crystal grain size of the polycrystalline film is determined by the annealing time and temperature, there is a problem in reproducibility.

(D) Means for Solving the Problems The present invention has been made in view of such problems, and after depositing an amorphous silicon film on a substrate surface, an energy beam is applied to the amorphous silicon film to reduce the size of the amorphous silicon film. At the same time, the micro-area is melted and recrystallized by focusing on the area, and at the same time, an inert ion beam is irradiated to obtain a crystal nucleus whose orientation is controlled, and crystalline silicon is grown based on the nucleus. .

(E) Function According to the present invention, since the crystal nucleus whose orientation is controlled by the inert ion beam is used as the nucleus for crystal growth, the quality of grown silicon is high and crystalline silicon with few defects can be obtained.

(F) Example In the first step of the present invention, as shown in FIG.
A lower amorphous silicon film 2 is formed on the surface of a substrate 1 made of an insulating material such as ceramic by a plasma CVD method or the like.
Is grown to a thickness of about 0.1 to 1 μm.

In the second step, a high power laser 3 such as an excimer laser is focused on the surface of the lower amorphous silicon film 2 to melt and recrystallize the film 2 to form crystal nuclei 4 and, at the same time, form the lower amorphous silicon film 2. The orientation of the crystal nuclei 4 is controlled by irradiating an inert ion beam 5 of Ar, He, H or the like from the side of the film 2. The high power laser 3 used here is focused by a lens system to a laser beam diameter of 1 μm or less, and the energy density on the surface of the lower amorphous silicon film 2 is 0.1 to 10 J.
/ cm ² . The inert ion beam 5 has an acceleration energy of several to several thousand eV, an ion current of 10 μA to several A,
Irradiation in the axial direction of a desired Si crystal nucleus is suitable. Under such conditions, ultraviolet light laser 2 for about 0.01 to 0.1 minutes,
And by irradiating the inert ion beam 5,
A silicon crystal nucleus 4 having a diameter of about several μm is obtained.
The temperature of the substrate 1 at this time is desirably 600 ° C. or less, which does not deform even if the substrate 1 is glass.

In the third step, a plasma including the crystal nuclei 4 is formed on the surface of the lower amorphous silicon film 2 having the crystal nuclei 4 partially.
The surface amorphous silicon film 6 having a thickness of about 0.1 to 10 μm is to be grown by a CVD method, a thermal CVD method, a vacuum evaporation method, a sputtering method, or the like (FIG. 3).

In the final step of the present invention, as shown in FIG. 4, the surface amorphous silicon film 6 on the surface of the substrate 1 is irradiated with a high-power laser beam 7 such as an Ar laser or an excimer laser to perform laser annealing on the amorphous silicon film 6. There. Specifically, for example, when using an Ar laser,
An output of 10 W / cm ² is used, and scanning is performed at a speed of several cm / sec. By performing this laser annealing process,
Single crystallization of the surface amorphous silicon film 6 proceeds with the crystal nucleus 4 as a recrystallization nucleus, and a single crystal region 8 having a diameter of about 0.01 to 1 mm is obtained.

The electron field effect mobility of the TFT formed in the single crystal region 8 thus obtained is 150 to 300 cm ² / V · s, and that of the conventional product obtained by using the plasma CVD method is 40 to 50 cm. ^{In view of 2} / V · s, the improvement in characteristics according to the present invention will be remarkable.

In the above embodiment, the surface amorphous silicon film 6 was grown on the surface of the amorphous silicon film 2 partially having the crystal nuclei 4, and the film 6 was crystallized using the crystal nuclei 4 as recrystallization nuclei. However, by continuing the growth process of the crystal nucleus 4 for a long time, specifically, about 0.1 to 1 hour, the single crystallization of the lower amorphous silicon film 2 is promoted by using the crystal nucleus 4 itself as a nucleus, and the diameter is about 10 to 1 hour. 100μ
It is also possible to use the single crystal region 8 of m.

(G) Effect of the present invention As is apparent from the above description, the present invention, after depositing an amorphous silicon film on a substrate surface, focuses an energy beam on a minute region of the amorphous silicon film and focuses the energy on the minute region. At the same time as melting and recrystallizing, a crystal nucleus with controlled orientation is obtained by irradiating with an inert ion beam, and crystalline silicon is grown based on the nucleus. Can be As a result, since the electron mobility in the crystalline silicon obtained by the present invention is high, the characteristics of elements such as a diode and a transistor can be improved.

[Brief description of the drawings]

1 to 4 are sectional views showing an embodiment of the method of the present invention in the order of steps. DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Lower amorphous silicon film, 3 ... 7 High power laser, 4 ... Crystal nucleus, 5 ... Inactive ion beam, 6 ... Surface amorphous silicon film, 8 ... Single crystal region .

Claims (1)

(57) [Claims] When growing crystalline silicon on a substrate surface, after depositing an amorphous silicon film on the substrate surface, an energy beam is focused on a minute region of the amorphous silicon film to melt the minute region. A method for producing crystalline silicon, characterized by irradiating an inert ion beam at the same time as recrystallization to obtain a crystal nucleus with controlled orientation, and growing crystalline silicon based on the nucleus.