Method of manufacturing GaN-based film

Abstract

A method of manufacturing a GaN-based film includes the steps of preparing a composite substrate, the composite substrate including a support substrate in which a coefficient of thermal expansion in its main surface is more than 0.8 time and less than 1.0 time as high as a coefficient of thermal expansion of GaN crystal in a direction of a axis and a single crystal film arranged on a main surface side of the support substrate, the single crystal film having threefold symmetry with respect to an axis perpendicular to a main surface of the single crystal film, and forming a GaN-based film on the main surface of the single crystal film in the composite substrate, the single crystal film in the composite substrate being an SiC film. Thus, a method of manufacturing a GaN-based film capable of manufacturing a GaN-based film having a large main surface area and less warpage without crack being produced in a substrate is provided.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method of manufacturing a GaN-based film capable of obtaining a GaN-based film having a large main surface area and less warpage.[0003]2. Description of the Background Art[0004]A GaN-based film is suitably used as a substrate and a semiconductor layer in a semiconductor device such as a light emitting device and an electronic device. A GaN substrate is best as a substrate for manufacturing such a GaN-based film, from a point of view of match or substantial match in lattice constant and coefficient of thermal expansion between the substrate and the GaN-based film. A GaN substrate, however, is very expensive, and it is difficult to obtain such a GaN substrate having a large diameter that a diameter of a main surface exceeds 2 inches.[0005]Therefore, a sapphire substrate is generally used as a substrate for forming a GaN-based film. A sapphire substrate and a GaN crystal are significantly...

AI Technical Summary

Benefits of technology

[0010]The composite support substrate disclosed in Japanese National Patent Publication No. 2007-523472 (corresponding to WO2005 / 076345) above has a coefficient of thermal expansion substantially the same as that of the GaN crystal and hence warpage of the GaN layer grown thereon can be less. Such a composite support substrate, however, has a complicated structure, and design and formation of the structure is difficult. Therefore, cost for design and manufacturing becomes very high and cost for manufacturing a GaN film becomes very high.

[0011]An object of the present invention is to solve the problems above and to provide a method of manufacturing a GaN-based film capable of manufacturing a GaN-based film having a large main surface area and less warpage without crack being produced in a substrate.

[0014]According to the present invention, a method of manufacturing a GaN-based film capable of manufacturing a GaN-based film having a large main surface area and less warpage without crack being produced in a substrate can be provided.

Problems solved by technology

Therefore, it becomes difficult to obtain a GaN film less in warpage as the main surface has a greater diameter.

In addition, when GaN crystal grown on a sapphire substrate much higher in coefficient of thermal expansion than GaN crystal is cooled, the sapphire substrate is subjected to large tensile stress and crack is likely.

Such a composite support substrate, however, has a complicated structure, and design and formation of the structure is difficult.

Therefore, cost for design and manufacturing becomes very high and cost for manufacturing a GaN film becomes very high.