Method for producing semiconductor base members

Details Method for producing semiconductor base members Method for producing semiconductor base members

1999-07-21

2001-01-30

Bowers, Charles (Department: 2812)

Semiconductor device manufacturing: process

Bonding of plural semiconductor substrates

Subsequent separation into plural bodies

C438S479000, C438S964000

Reexamination Certificate

active

06180497

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing a semiconductor base member having a nonporous layer formed on a porous layer and a method of using this semiconductor base member to produce a semiconductor member such as an SOI wafer.
2. Related Background Art
In order to manufacture a light emitting element or an SOI wafer, it is necessary to prepare a semiconductor base member having a porous layer and a nonporous layer formed thereon.
An example of preparation of the semiconductor base member will be described with reference to
FIGS. 9A
to
9
F.
As shown in
FIG. 9A
, a silicon base material
1
such as a CZ silicon wafer having a polished surface is prepared and at least its surface is made porous by anodization or the like.
After the inner wall surfaces of pores in a porous layer
2
are oxidized, the silicon base material is cleaned with a dilute hydrofluoric acid to remove an oxide film from the surface of the porous layer
2
.
As shown in
FIG. 9B
, the porous layer
2
is subjected to a heat treatment in a hydrogen-containing atmosphere, and a silicon-containing gas is then introduced to epitaxially grow a nonporous layer
3
.
As shown in
FIG. 9C
, the surface of the nonporous layer
3
is oxidized to form an insulating film
4
.
As shown in
FIG. 9D
, a first member comprising a silicon base material
1
having the porous layer
2
, the nonporous layer
3
, and the insulating layer
4
is bonded to a second member
5
separately prepared to form a multilayer structure having the nonporous layer
3
inside.
As shown in
FIG. 9E
, the silicon base material
1
is removed. The method for removing the silicon base material
1
includes a method of eliminating the silicon base material
1
itself by grinding, polishing, or etching from the back surface and a method of cracking the inside of the porous layer
2
and/or its interface to separate and remove the silicon base material
1
.
As shown in
FIG. 9F
, the porous layer
2
remaining on the surface of the second member
5
is removed to obtain an SOI wafer having the nonporous layer
3
formed on the second member
5
via the insulating layer
4
.
The above method is disclosed in Japanese Patent Application Laid-Open No. 5-21338 (Japanese Patent No. 2608351), U.S. Pat. No. 5,371,037, U.S. Pat. No. 5,856,229, Japanese Patent Application Laid-Open No. 9-102594, and Appl. Phys. Lett. 64, 1994, p. 2108, and the like.
However, there is a demand for further improvement of the quality of the nonporous layer formed on the porous layer, in particular, surface smoothness and crystal defects.
For example, in the above method for producing an SOI wafer, when the surfaces to be bonded are not smooth, a void, that is, a non-bonded area which is observed by ultrasonic waves or infrared transmitted light is easily generated in bonding.
In addition, in producing a device such as an MOS transistor using the nonporous layer, metal impurities may be conventionally segregated into crystal-defect sites. When metal impurities are segregated into crystal-defect sites, the device characteristics is easily degraded.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for producing a semiconductor base member which can improve the surface quality of a thin nonporous film formed on a porous layer to reduce the crystal defect density.
Another object of the present invention is to provide a method for producing a semiconductor base member which can make the pore size distribution of the porous layer uniform to efficiently seal the pores in the surface of the porous layer and at the same time improve the surface smoothness and which can reduce the crystal defect density in the nonporous film formed on the porous layer.
This invention is characterized in that a surface comprising atom steps and atom terraces is formed on a silicon base material and then made porous, followed by the formation of a nonporous film.


REFERENCES:
patent: 5371037 (1994-12-01), Yonehara
patent: 5856229 (1999-01-01), Sakaguchi et al.
patent: 5869387 (1999-02-01), Sato et al.
patent: 6100166 (2000-08-01), Sakaguchi et al.
patent: 5-021338 (1993-01-01), None
patent: 9-102594 (1997-04-01), None
Nobuhiko Sato et al.; Epitaxial Growth on Porous Si for a New Bond and Etchback Silicon-on-Insulator; J. Electrochem. Soc., vol. 142, No. 9, Sep. 1995, The Electrochemical Society, Inc.
Applied Physics Letters; G.S. Higashi et al.; Comparison of Si(111) Surfaces Prepared Using Aqueous Solutions of NH4F Versus HF; vol. 58, No. 15, Apr. 15, 1991, pp. 1656-1658.
S. Verhaverbeke; “The Effect of H2Annealing on the SI Surface, and its Use in the Study of Roughening During Wet Chemical Cleaning”; 1994, vol. 94-10, pp. 1170-1181, Proceedings of the Seventh International Symposium on Silicon Materials Science and Technology, Semiconductor Silicon/1994, The Electrochemical Society, Inc. (Pennington, NJ 1994).
Journal of the Electrochemical Society; R. Herino et al.; “Porosity and Pore Size Distributions of Porous Silicon Layers”; Aug. 1987, vol. 134, No. 8A, pp. 1994-2000.
Applied Physics Letters; T. Yonehara et al.; “Epitaxial Layer Transfer by Bond and Etch Back of Porous Si”; vol. 64, No. 16, Apr. 18, 1994, pp. 2108-2110.
Extended Abstracts (The 42ndSpring Meeting, 1995); The Japan Society of Applied Physics and Related Societies; Mar. 28, 1995; No. 2, p.602, 19p-ZB-8.
Extended Abstracts (The 55thAutumn Meeting, 1994); The Japan Society of Applied Physics; Sep. 19, 1994; No. 2, p. 762, 29a-PA-11.

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