Method of producing semiconductor wafer

Abstract

A semiconductor wafer is produced at a step of forming a lattice relaxation or a partly lattice-relaxed strain relaxation SiGe layer on an insulating layer in a SOI wafer comprising an insulating layer and a SOI layer, wherein at least an upper layer side portion of the SiGe layer is formed on the SOI layer at a gradient of Ge concentration gradually decreasing toward the surface and then subjected to a heat treatment in an oxidizing atmosphere.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein:

FIG. 1 is a flow chart illustrating steps of producing a semiconductor wafer by a production method according to the invention;

FIG. 2 is a view of an embodiment of SiGe layer before heat treatment (Example 1) in which (a) is a section view of the SiGe layer before heat treatment and (b) shows a Ge concentration corresponding to a thickness of the SiGe layer of (a);

FIG. 3 is a view of another embodiment of SiGe layer before heat treatment (Example 2) in which (a) is a section view of the SiGe layer before heat treatment and (b) shows a Ge concentration corresponding to a thickness of the SiGe layer of (a);

FIG. 4 is a view of the other embodiment of SiGe layer before heat treatment (Example 3) in which (a) is a section view of the SiGe layer before heat treatment and (b) shows a Ge concentration corresponding to a thickness of the SiGe layer of (a);

FIG. 5 is a view of a still further embodiment of SiGe layer before heat treatment (Example 4) in which (a) is a section view of the SiGe layer before heat treatment and (b) shows a Ge concentration corresponding to a thickness of the SiGe layer of (a);

FIG. 6 is a view of an embodiment of SiGe layer before heat treatment (Comparative Example) in which (a) is a section view of the SiGe layer before heat treatment and (b) shows a Ge concentration corresponding to a thickness of the SiGe layer of (a); and

FIG. 7 is a graph showing an evaluation result of a defect density.

Claims

1. A method of producing a semiconductor wafer comprising a step of forming a lattice relaxation or a partly lattice-relaxed strain relaxation SiGe layer on an insulating layer in a SOI wafer comprising an insulating layer and a SOI layer, wherein at least an upper layer side portion of the SiGe layer is formed on the SOI layer at a gradient of Ge concentration gradually decreasing toward the surface and then subjected to a heat treatment in an oxidizing atmosphere at the step of forming the strain-relaxed SiGe layer.

2. A method of producing a semiconductor wafer according to claim 1, wherein the heat treatment is carried out at a temperature of not lower than 1100° C.

3. A method of producing a semiconductor wafer according to claim 1 or 2, wherein a whole of the SiGe layer before the heat treatment is formed on the SOI layer at the gradient of Ge concentration gradually decreasing toward the surface thereof.

4. A method of producing a semiconductor wafer according to claim 1 or 2, wherein a portion of the SiGe layer facing the wafer before the heat treatment is formed on the SOI layer at a constant Ge concentration and then the upper layer side portion of the SiGe layer is formed at the gradient of Ge concentration gradually decreasing toward the surface thereof.

5. A method of producing a semiconductor wafer according to claim 1 or 2, wherein a portion of the SiGe layer facing the wafer before the heat treatment is formed on the SOI layer at a gradient of Ge concentration gradually increasing toward the surface thereof and then the upper layer side portion of the SiGe layer is formed at the gradient of Ge concentration gradually decreasing toward the surface thereof.

6. A method of producing a semiconductor wafer according to claim 1 or 2, wherein the SiGe layer before the heat treatment is formed as a laminate by laminating a plurality of one or more SiGe layers before the heat treatment selected from the SiGe layers before the heat treatment.

7. A method of producing a semiconductor wafer according to any one of claims 1-2, wherein a Si layer is further formed on the SiGe layer before the heat treatment prior to the heat treatment.

8. A method of producing a semiconductor wafer according to any one of claims 1-2, wherein the SiGe layer before the heat treatment has a maximum value of Ge concentration of not more than 30 mass %.

9. A method of producing a semiconductor wafer according to any one of claims 1-2, wherein the SiGe layer before the heat treatment has a gradient of Ge concentration of not more than 2 mass %/nm.