Gallium Nitride Substrate, and Gallium-Nitride-Substrate Testing and Manufacturing Methods

Abstract

Fracture-resistant gallium nitride substrate, and methods of testing for and manufacturing such substrates are made available. A gallium nitride substrate (10) is provided with a front side (12) polished to a mirrorlike finish, a back side (14) on the substrate side that is the opposite of the front side (12). A damaged layer (16) whose thickness d is 30 μm or less is formed on the back side (14). Given that the strength of the front side (12) is I1 and the strength of the back side (14) is I2, then the ratio I2/I1 is 0.46 or more.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a section diagram schematically representing a gallium nitride substrate involving the present invention;

FIG. 2 is a diagram schematically illustrating one example of a strength measurement device for measuring the strength of the front side and of the back side of a gallium nitride substrate;

FIG. 3 is process-step section diagrams schematically illustrating a gallium-nitride-substrate manufacturing method involving the present invention; and

FIG. 4 is a flow chart outlining a gallium-nitride-substrate testing method involving the present invention.

Claims

1. A gallium nitride substrate provided with a first surface polished to a mirrorlike finish, and a second surface on the substrate side that is the opposite of the first-surface side, with a damaged layer of 30 μm thickness or less being formed on the second surface; wherein, letting the strength of the first surface be I1 and that of the second surface be I2, the ratio I2/I1 is 0.46 or more.

2. A gallium nitride substrate provided with a first surface polished to a mirrorlike finish, and a second surface on the side that is the opposite of the first-surface side, with a damaged layer of 10 μm thickness or less being formed on the second surface; wherein, letting the strength of the first surface be I1 and that of the second surface be I2, the ratio I2/I1 is 0.69 or more.

3. A gallium-nitride-substrate testing method comprising: a step of measuring the strength of a first surface of a gallium nitride substrate, and the strength of a second surface on the substrate side that is the opposite of the first-surface side;a step of measuring the thickness of a damaged layer formed on the second surface; anda step of determining that the substrate is a conforming product if the thickness of the damaged layer is 30 μm or less, and if, letting the strength of the first surface be I1 and that of the second surface be I2, the ratio I2/I1 is 0.46 or more.

4. A gallium-nitride-substrate manufacturing method comprising: a step of polishing a first surface of the gallium nitride substrate to a mirrorlike finish;a step of processing a second surface on the side that is the opposite of the first-surface side, to form a damaged layer on the second surface; anda step of etching the damaged layer so that the thickness of the damaged layer will be 30 μm or less, and so that, letting the strength of the first surface be I1 and the strength of the second surface be I2 the ratio I2/I1 will be 0.46 or more.