JPH07183477A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To form an SOI substrate with a ultrathin film layer readily with good reproducibility by joining a silicon substrate forming a main surface through an insulation film and a supporting substrate and by removing an oxide film after polishing the main surface. CONSTITUTION:A silicon substrate 1 forming a main surface and a silicon substrate 2 which becomes a supporter are joined through an insulation film 3, and thermal treatment is performed at 900 deg.C or higher for at least one hour to realize firm junction between the insulation film 3 and the silicon substrates 1, 2. A surface of the silicon substrate 1 is polished and ground to form a few mum-thick silicon layer 4. The silicon layer 4 is made to remain about 0.1mum thick by thermal oxidation as required. An oxide film is etched and removed by hydrofluoric oxide water solution, etc., and an SOI substrate with a ultrathin film layer 5 is acquired. Thereby, a uniform ultrathin film SOT substrate of extremely good reproducibility of thickness and little crystal defect can be readily acquired.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to semiconductor substrates, especially SOI.
The present invention relates to a method for manufacturing a substrate.

[0002]

2. Description of the Related Art Various methods for manufacturing an SOI substrate have been proposed. For example, the direct bonding method (wafer direct bonding), the SIMOX method and the like are well known.
The former can obtain good crystallinity, but it is difficult to form a thin film, and the latter has a defect such as poor crystallinity although it is easy to form a thin film. Suggestions have been made to improve these.
That is, FIG. 2 shows the method disclosed in Japanese Patent Application Laid-Open No. 2-252265. The N-type thin film layer 12 is formed on the P-type silicon substrate 11 by epitaxial growth and bonded to the support substrate 2 via the insulating film 3. P-type silicon substrate 1
One surface of No. 1 is ground and polished to a thickness of about several μm. Next, the P-type silicon substrate 11 is made porous by the anodization method, converted into a SiO2 layer by thermal oxidation, and removed by etching.
An N-type thin film layer 12 of about 1 μm is obtained.

A structure formed by using an oxide film as a polishing stopper is shown in FIG. 3 of Japanese Patent Laid-Open No. 1-133628.

[0004]

SUMMARY OF THE INVENTION These conventional thin films S
In the method of forming the OI substrate, in the embodiment of FIG. 2, the variation of the thin film layer due to epitaxial growth becomes large, and the crystal defects on the surface of the N-type thin film after etching removal increase, and in the embodiment of FIG. There was a problem that the surface flatness was deteriorated due to excess.

[0005]

According to the method of manufacturing a semiconductor substrate of the present invention, a process of grinding and polishing one main surface of a substrate bonded via an insulating film until a thickness of several μm remains, and a process of several μm. The method includes a thermal oxidation step of forming an oxide film until a silicon layer having a thickness of about 0.1 μm is left, and a step of etching away the oxide film.

[0006]

The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a method for manufacturing an SOI substrate according to an embodiment of the present invention. As shown in FIG. 1A, a silicon substrate 1 forming a main surface and a silicon substrate 2 serving as a support body.
Are bonded via the insulating film 3 and heat treatment is performed at 900 ° C. or higher for 1 hour or longer to strengthen the bond between the insulating film 3 and the silicon substrates 1 and 2. Here, the insulating film 3 before bonding is formed on one or both of the silicon substrates 1 and 2.
Next, as shown in FIG. 1B, one surface of the silicon substrate 1 is ground and polished to form a silicon layer 4 having a thickness of several μm. In the conventional technique, if the remaining thickness is several μm, polishing can be performed with high precision.

Next, as shown in FIG. 1 (c), by thermal oxidation,
The silicon layer 4 is left to have a required thickness of about 0.1 μm. There is little variation in the formation of an oxide film by thermal oxidation of several μm, and it can be performed more accurately than in the conventional film thickness control by epitaxial growth. Here, if the thickness of the silicon layer 4 before oxidation is measured to determine the oxidation conditions, generality and accuracy are improved. The measurement of the thickness of the silicon layer is nondestructive, easy and accurate, and a method of measuring the thickness is generally known, which does not increase the cost and complicate the process and is very useful.

Then, as shown in FIG. 1D, the oxide film can be removed by etching with an aqueous solution of hydrogen fluoride oxide to obtain an SOI substrate having an ultrathin film layer 5. According to this manufacturing method, it is possible to form an N-type or P-type ultrathin film layer.

[0010]

As described above, according to the present invention, one surface of the SOI substrate is polished to several μm and only the oxidation process is performed.
Forming a silicon thin film layer, removing oxide film, 0.1μm
It is possible to form a very thin film layer. According to the above manufacturing method,
Uniform and extremely good thickness reproducibility. An ultra-thin film SOI substrate with few crystal defects can be easily obtained.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a method for manufacturing an SOI substrate according to an embodiment of the present invention.

FIG. 2 is a process drawing showing a conventional method for manufacturing an SOI substrate.

FIG. 3 is a sectional view of an example according to another conventional manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Supporting silicon substrate 3 Insulating film 4 Silicon layer 5 Ultra thin silicon layer 6 Oxide film 11 P type silicon substrate 12 N type thin film layer 13 P type silicon layer 21 Ultra thin silicon layer 22 Stopper oxide film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/316 S 7352-4M 21/762

Claims (1)

[Claims] 1. A step of joining a first silicon substrate and a second silicon substrate via an insulating film, a step of polishing one main surface of the first silicon substrate, and the formed composite substrate And a step of removing the oxide film, the method of manufacturing a semiconductor substrate.