Method for processing wide-bandgap semiconductor substrate and apparatus therefor
There are provided a processing method for a wide-bandgap semiconductor substrate and an apparatus therefor that use no abrasives or no abrasive grains, or no solution having a large environmental burden at all, can process a single crystal, which is SiC, GaN, AlGaN, or AlN, at a variety of processing speed, can obtain a surface of higher quality than the quality of a surface finished by CMP, and also have an excellent compatibility with a clean room. A catalytic substance having a function of promoting the direct hydrolysis of a work piece ( 5 ) or promoting the hydrolysis of an oxide film on the surface of the work piece is used as a processing reference plane ( 3 ). In the presence of water ( 1 ), the work piece is brought into contact with or extremely close to the processing reference plane at a predetermined pressure.
1. A processing method for a wide-bandgap semiconductor substrate in which a single crystal, which is SiC, GaN, AlGaN, or AN, is a work piece, and a surface of the work piece is planarized or processed into an arbitrary curved surface using no abrasive grain or no abrasive, the method comprising:
using a catalytic substance having a function of promoting direct hydrolysis of the work piece or promoting hydrolysis of an oxide film on the surface of the work piece as a processing reference plane;
in presence of water, disposing the work piece and the processing reference plane so that the work piece is brought into contact with or close to a distance where a catalytic reaction of a catalytic substance occurs to the processing reference plane at a predetermined pressure;
setting a potential of the processing reference plane in a range of ±1 V relative to an oxygen production potential to form a state in which oxygen is adsorbed to a catalyst surface;
relatively moving the work piece and processing reference plane to each other;
by a catalyst function of the processing reference plane, advancing a process of direct hydrolysis of the surface of the work piece or a process of oxidation of the surface of the work piece and hydrolysis of the oxide film in priority from a projection on the surface close to the processing reference plane; and
removing a decomposition product.
2. The processing method for a wide-bandgap semiconductor substrate according to claim 1 , wherein
for the processing reference plane, a surface of the catalytic substance is used, in which a metallic element is contained and a d orbital of an electron of the metallic element is at about Fermi level.
3. The processing method for a wide-bandgap semiconductor substrate according to claim 2 , wherein
the metallic element is a transition metallic element.
4. The processing method for a wide-bandgap semiconductor substrate according to claim 1 , wherein
the water is a mixture in which at least one kind of a pH regulator, a buffer solution, or a complex solution that assists dissolution of the decomposition product is mixed in pure water or ultrapure water.