JPH0252419A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To crystallize a desired region by a method wherein ions are implanted selectively into an amorphous semiconductor film, a solid growth operation is executed in the amorphous semiconductor film and the amorphous semiconductor film is crystallized. CONSTITUTION:A polycrystalline Si film 14 is deposited on a quartz substrate 13 by using CVD; ions of Si<+> 15 are implanted into the polycrystalline Si film 14; this polycrystalline Si film is made amorphous. When an amorphous Si film 11 is formed, it is not required to implant the ions of Si<+> 15. Then, a mask 21 of a photoresist is formed in such a way that, in the amorphous Si film 11, regions 16 to be crystallized are covered and regions 17 not to be crystallized are exposed. In this state, ions of Co<+> 22 are implanted into the amorphous Si film 11; in addition, the mask 21 is removed; a solid growth operation is executed in the amorphous Si film 11 by using a low-temperature heat treatment. A nucleus 12 is not generated in the regions 17 into which the ions of Co<+> 22 have been implanted. Accordingly, crystallization proceeds only in the regions 16; the regions 16 become islands in a crystallized region; it is possible to form the crystallized region in a desired region.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor substrate having a semiconductor film on an insulating substrate.

[Requirement of the invention]

The present invention provides a method for manufacturing a semiconductor substrate as described above.
Selective ion implantation of carbon, oxygen, or a substance containing these into an amorphous semiconductor film on an insulator substrate, and solid phase growth is performed on this amorphous semiconductor film to crystallize the amorphous semiconductor film. By doing so, it is possible to manufacture a semiconductor substrate in which only desired regions are crystallized (semiconductor substrates with large crystal grain sizes).

[Prior Art] Semiconductor substrates having a semiconductor film on an insulating substrate are used for forming thin film transistors, etc., and for example, there is one in which a polycrystalline Si film is deposited on a quartz substrate by CVD.

However, simply depositing a polycrystalline Si film by CVD does not result in a very large crystal grain size. Therefore, the carrier mobility is not very high, and a high-performance thin film transistor cannot be obtained.

Therefore, by ion-implanting St'' into a polycrystalline Si film deposited by CVD to temporarily form an amorphous Si film, solid phase growth is performed using this amorphous Si film, and polycrystalline Si with a large crystal grain size is grown. A method of forming a film is being considered (for example, Japanese Patent Application Laid-open No. 61-1
27118).

[Problem to be solved by the invention]

However, in solid phase growth, crystallization nuclei 12 are generated at random positions in the amorphous Si pattern, as shown in FIG.

Therefore, in the conventional example described above, it is not possible to manufacture a semiconductor substrate in which only desired regions are crystallized.

In addition, solid phase growth stops when the crystal grains grown from the nuclei 12 come into contact with each other, but the nuclei 12 are generated at random positions, so even in the conventional example described above, semiconductor substrates with sufficiently large crystal grain sizes can be manufactured. Can not do it.

[Means for Solving the Problems] A method for manufacturing a semiconductor substrate according to the present invention includes an insulator substrate 13
a step of forming an amorphous semiconductor film 11 on the amorphous semiconductor film 11; and a step of forming an amorphous semiconductor film 11 on the amorphous semiconductor film 11;
and a step of performing solid phase growth on the amorphous semiconductor film 11 into which the ions have been implanted to crystallize the amorphous semiconductor 11% 11, respectively. There is.

[Function] In the method for manufacturing a semiconductor substrate according to the present invention, in the selectively ion-implanted region of the amorphous semiconductor film 11,
The incidence of crystallization nuclei 12 is extremely low.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3.

In this embodiment, as shown in FIG. 1A, a polycrystalline Si film 14 is deposited on a quartz substrate 13 by CVD.
This polycrystalline Si film 14 is formed by ion-implanting Si" 15 into
becomes amorphous.

However, if an amorphous Si film is formed on the quartz substrate 13 from the beginning, ion implantation of Si'' 15 is not necessary.

Next, as shown in FIG. 1B, in the amorphous Si film 11 made from the polycrystalline Si film 14, only the region 16 to be crystallized is covered, and the region 17 to be suppressed from crystallization is covered. A photoresist mask 21 is formed to expose the area.

In this state, CO''22 is ion-implanted into the amorphous Si film 11 with a dose repellency of 5 x 10''cm-2 or more, and then the mask 21 is removed and the amorphous silicon is removed by low-temperature heat treatment. Solid phase growth is performed on the quality Si film 11.

Then, a region 16 where CO''22 is not ion-implanted
Then, by heat treatment for about 0.5 hours, crystallization nuclei 12 are generated and crystallization begins. On the other hand, in the region 17 into which CO''22 is ion-implanted, the nucleus 12 is not generated unless heat treatment is performed for about 146 hours.

Therefore, as shown in FIG. 2, if region 16 is surrounded by region 17 and the solid phase growth time is controlled, crystallization will proceed only in region 16, and region 16 will become an island of crystallized regions. In other words, a crystallized region can be formed in a desired region.

Furthermore, if a plurality of regions 16 are formed in the region 17 while being separated from each other, a plurality of islands of crystallized regions are formed, and the regions between the islands that remain amorphous can be used as element isolation regions. Can be done.

Furthermore, as shown in FIG. 3A, if an extremely narrow region of the amorphous Si film 11 is defined as a region 16 and the remaining wide region is defined as a region 17, before the nucleus 12 is generated in the region 17, the region The crystallization started at 16 can be extended to region 17.

Therefore, as is clear from FIG. 3B, the grain size of the crystal grains 23 grown from the region 16 is very large, and the amorphous Si film 1
There is also a possibility that 1 can be made into a single crystal.

Therefore, carrier mobility is high in the polycrystalline Si film 24 having the crystal grains 23, and high performance thin film transistors and the like can be formed in this polycrystalline Si film 24.

In order to suppress crystallization of the amorphous Si film 11, CO''22 was ion-implanted in this embodiment, but ions of C or O as a single atom can also be used, and other ions including C or 0 can also be used. Molecular ions can also be used.

〔Effect of the invention〕

In the method for manufacturing a semiconductor substrate according to the present invention, the rate of occurrence of crystallization nuclei in the selectively implanted regions of the amorphous semiconductor film is extremely low, so that the semiconductor substrate is crystallized only in the desired regions. can be manufactured.

In addition, it is possible to manufacture semiconductor substrates with large crystal grain sizes by performing ion implantation from areas where ion implantation is not performed and where the rate of nucleus generation is high to areas where the rate of nucleus generation is low. can.

FIG. 3 is a plan view showing the situation, and FIG. 3 is a side sectional view sequentially showing the case where a semiconductor substrate with a large crystal grain size is manufactured in one embodiment.

FIG. 4 is a plan view corresponding to FIG. 2, showing the generation of crystallization nuclei in a conventional example of the present invention.

In addition, in the symbols used in the drawings, L L---1・---1---Amorphous Si film 11-
1・−1−−−−−Nucle 13−−−−−・−−−−−−−1 Quartz substrate 22−1−
----------CO'' 23----------One crystal grain 24--
---It is a polycrystalline Si film.

Claims (1)

[Claims] A step of forming an amorphous semiconductor film on an insulating substrate, a step of selectively ion-implanting carbon, oxygen, or a substance containing these into the amorphous semiconductor film, and the ion implantation. A method for manufacturing a semiconductor substrate, comprising the steps of performing solid phase growth on the amorphous semiconductor film that has been subjected to the above steps to crystallize the amorphous semiconductor film.