JPH03109731A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To obtain a thin semiconductor substrate layer uniformly on an insulating film by adhering a semiconductor substrate formed with the substrate layer having low impurity concentration on the surface of a semiconductor substrate having high impurity concentration to another substrate through an insulating film. CONSTITUTION:An epitaxial layer 2 having low impurity concentration is formed on a semiconductor substrate 1 having high impurity concentration, an oxide film 3 is formed on the layer 2, the substrate 1 is adhered to another substrate 4 to be adhered through the film 3, the substrate 1 is polished to be reduced in thickness, the adhered substrate 1 is immersed with etchant to remove the substrate 1 having high impurity concentration by etching, the layer 2 is oxidized to form an oxide film 5 in which the thickness of the epitaxial layer is reduced. The thickness of the layer 2 can be controlled to be thinner by the formation of the film 5. Here, if the thickness of the layer 2 is thicker than a desired thickness, the steps of forming and removing the film 5 may be repeated. Thus, the semiconductor substrate having a reduced thickness without irregularity in the thickness can be realized on the insulting film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor substrate in which semiconductor substrates are bonded together to form a thin semiconductor substrate layer on an insulating film.

[Summary of the invention]

In the present invention, a semiconductor substrate with a low impurity concentration semiconductor layer formed on the surface of a semiconductor substrate with a high impurity concentration is bonded to another substrate via an insulating film, and polishing, selective etching based on the difference in impurity concentration, and sacrificial oxidation are performed. The present invention provides a practical method for manufacturing a semiconductor substrate having a uniform and thin semiconductor substrate layer of 11M or less on an insulating film.

[Conventional technology]

2. Description of the Related Art Conventionally, a bonded substrate is known as a method for forming a thin semiconductor substrate layer on an insulating layer.

FIG. 2 is a cross-sectional view of a conventional bonded semiconductor substrate in the order of manufacturing steps.

An oxide film 23 is formed on the semiconductor substrate 21 (FIG. 2(a))
) The semiconductor substrate 21 is bonded to another bonded substrate 24 via the oxide film 23 (Fig. 2, crest)).

The semiconductor substrate 21 is polished to make the semiconductor substrate 21 thinner, and a conventional bonded semiconductor substrate is completed.

Figure 2 (C)).

[Problem to be solved by the invention]

The thickness of the semiconductor substrate 21 on the insulating film is preferably 1 ffl or less, but it is difficult to uniformly polish the entire surface of the semiconductor substrate to 111 m or less, and the maximum thickness of the semiconductor substrate 21 is about 2 to 3 mm. Ta.

[Means to solve the problem]

In order to solve the above problems, the present invention forms a thin epitaxial layer with a low impurity concentration on the surface of a semiconductor substrate with a high impurity concentration, and then bonds this substrate to another bonded substrate via an insulating film. Then, by combining polishing, selective etching based on the difference in impurity concentration, and sacrificial oxidation, the semiconductor substrate with high impurity concentration is removed, leaving only the epitaxial substrate layer with low impurity concentration on the insulating film. A thin and uniform semiconductor substrate layer is formed on the film.

〔Example〕 The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a step-by-step sectional view showing a method for manufacturing a semiconductor substrate according to the present invention.

FIG. 1 1al is a cross-sectional view of a process in which epitaxial N (hereinafter referred to as a shrimp layer) 2 with a low impurity concentration is formed on a semiconductor substrate 1 with a high impurity concentration of 10'''cm-' or more.

1st issue) is a cross-sectional view of the step of forming an oxide film 3 on the surface of the shrimp layer 2.

Figure 1 (C) shows oxidation! l! 3 is a cross-sectional view of a process in which the semiconductor substrate 1 is bonded to another bonded substrate 4 via the bonded substrate 3. FIG.

Figure 1 1dl is a cross-sectional view of the process of polishing and thinning the bonded semiconductor substrate 1.
The speed of thinning is fast. However, the thickness unevenness is large, so the semiconductor substrate 1 with a high impurity concentration is left thin.

FIG. 1 1et shows, for example, selectively etching only a semiconductor substrate with a high impurity concentration of 10"cs+-" or more.
This is a cross-sectional view of a process in which the semiconductor substrate 1 with a high impurity concentration is etched away by immersing the bonded semiconductor substrate 1 in an etching solution containing a 1:3:8 mixture of hydronic acid, nitric acid, and acetic acid. The semiconductor substrate 1 with a high impurity concentration is etched away by an etching solution, but the shrimp layer 2 with a low impurity concentration
remains unetched. Therefore, the remaining semiconductor substrate on the insulating film is only the shrimp layer 2, and its thickness is the shrimp layer 2.
It is almost determined by the shrimp layer when grown. It is easy to control the thickness of the shrimp layer, and there is almost no unevenness in the thickness.

Therefore, the thickness unevenness of the semiconductor substrate 1 on the insulating ridge caused by polishing can be eliminated.

FIG. 1 (fl is a cross-sectional view of the step of forming an oxide film 5 that oxidizes the shrimp layer 2 to reduce the thickness of the shrimp layer.

By forming this oxide film 5, the thickness of the shrimp N2 is controlled to be thinner. It also has the effect of removing defects on the surface of the shrimp layer 2 caused by selective etching.

FIG. 1(g) is a cross-sectional view of the step in which the oxide film 5 is removed by etching to complete the semiconductor substrate of the present invention. Also,
It is clear that if the thickness of the shrimp layer 2 is thicker than the desired thickness in this step, the steps of forming and removing the oxide film 5 may be repeated.

By using the manufacturing method of the present invention, it is possible to reduce the thickness of the semiconductor substrate layer on the insulating film to 0.5n or less, and the semiconductor substrate used for high-speed MOS integrated circuits etc. achieves ideal insulating film separation and junction capacitance. can be manufactured.

〔Effect of the invention〕

As is clear from the above description, the present invention involves forming a layer with a low impurity concentration on a semiconductor substrate with a high impurity concentration, bonding the layer to a bonded substrate via an oxide film, polishing and selective etching according to the impurity concentration, By combining this method with sacrificial oxidation, it is possible to realize a semiconductor substrate that is thin and has no thickness unevenness on an insulating film.

[Brief explanation of drawings]

FIG. 1 is a step-by-step cross-sectional view showing a method for manufacturing a semiconductor substrate according to the present invention, and FIG. 2 is a step-by-step cross-sectional view showing a conventional semiconductor substrate manufacturing method. 1121... Semiconductor substrate 2... - Shrimp layer 3.23... Oxide film 4゜24... Bonded substrate - Oxide film or more

Claims (1)

[Claims] A step of forming a layer with a low impurity concentration on the surface of a semiconductor substrate with a high impurity concentration; a step of laminating a substrate on the layer with a low impurity concentration via an insulating film; a step of polishing and thinning a semiconductor substrate with a high impurity concentration, a step of etching away the semiconductor substrate with a high impurity concentration, a step of oxidizing the layer with a low impurity concentration to form an oxide film, and a step of removing the oxide film. A method for manufacturing a semiconductor substrate comprising: