Process for the production of thin semiconductor material films

Abstract

Process for the preparation of thin monocrystalline or polycrystalline semiconductor material films, characterized in that it comprises subjecting a semiconductor material wafer having a planar face to the three following stages: a first stage of implantation by bombardment (2) of the face (4) of the said wafer (1) by means of ions creating in the volume of said wafer a layer (3) of gaseous microbubbles defining in the volume of said wafer a lower region (6) constituting the mass of the substrate and an upper region (5) constituting the thin film, a second stage of intimately contacting the planar face (4) of said wafer with a stiffener (7) constituted by at least one rigid material layer, a third stage of heat treating the assembly of said wafer (1) and said stiffener (7) at a temperature above that at which the ion bombardment (2) was carried out and sufficient to create by a crystalline rearrangement effect in said wafer (1) and a pressure effect in the said microbubbles, a separation between the thin film (5) and the mass of the substrate (6).

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a process for the production of thin semiconductor material films, preferably applicable to the production of monocrystalline films.[0002]It is known that for producing monocrystalline semiconductor films there are various methods and processes, which are often complex and expensive to carry out, because although it is relatively easy to produce polycrystalline or amorphous material films, it is much more difficult to produce monocrystalline films.[0003]Among the methods used for producing monocrystalline films are those used for producing socalled “silicon on insulator” substrates, where the aim is to produce a monocrystalline silicon film resting on a substrate electrically insulated from the film.[0004]By crystal growth heteroepitaxy methods make it possible to grow an e.g. thin film silicon crystal on a monocrystalline substrate of another type, whose lattice parameter is close to that of silicon, e.g. a sapphire ...

AI Technical Summary

Benefits of technology

[0012]The present invention relates to a process for producing thin semiconductor material films making it possible to overcome the aforementioned disadvantages without requiring an initial substrate of a different nature from that of the chosen semiconductor, without requiring very high implantation doses, or an etch-stop, but which still makes it possible to obtain a film having a uniform, controlled thickness.

[0018]According to a variant of the process according to the invention, it can be advantageous to carry out ion implantation in a semiconductor material through one or more layers of materials, said “encapsulating” layers being chosen in such a way that the ions traverse the same and penetrate the semiconductor. For example, the encapsulating layers can be used as means for reducing the penetration of ions in the semiconductor for producing finer membranes or as a means for protecting the semiconductor from possible contamination, or as a means for controlling the physiochemical state of the semiconductor surface. When the substrate constituting the wafer is made from silicon, it can be advantageous to choose an encapsulating layer constituted by thermal silicon oxide with a thickness e.g. between 25 and 500 nm. These encapsulating layers can be retained or removed following the implantation state.

Problems solved by technology

It is known that for producing monocrystalline semiconductor films there are various methods and processes, which are often complex and expensive to carry out, because although it is relatively easy to produce polycrystalline or amorphous material films, it is much more difficult to produce monocrystalline films.

The various methods for producing thin monocrystalline films suffer from the disadvantages associated with the production procedures.

Heteroepitaxy methods are limited by the nature of the substrate, because the lattice parameter of the substrate is not precisely the same as that of the semiconductor, the film having numerous crystal defects.

In addition, these substrates are expensive and fragile and only exist with limited dimensions.

The SIMOX method requires a very high dose ion implantation requiring a very heavy and complex implantation machine.

The output of such machines is limited and it would be difficult to significantly increase it.

Thinning methods are not competitive from the uniformity and quality standpoints except when using the etch-stop principle.

Unfortunately, the creation of said etch-stop makes the process complex and in certain cases can limit the use of the film.

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