Method for fabricating semiconductor device

A method for fabricating a semiconductor device comprising:

• forming a first Ta layer on an AlGaN layer, the first Ta layer having a thickness of 4 nm to 8 nm and the AlGaN layer having an Al composition ratio of 0.2 or greater and having an RMS roughness less than 0.3 nm;
• and
• annealing the first Ta layer to make an ohmic contact with the AlGaN layer;
• forming an Al layer on the first Ta layer before the annealing;
• and
• forming a second Ta layer on the Al layer before the annealing.

A method for fabricating a semiconductor device comprising:

• forming a recess to an AlGaN layer by etching, the AlGaN layer having an Al composition ratio of 0.2 or greater, the recess having a bottom having an RMS roughness less than 0.3 nm;
• forming a first Ta layer having a thickness of 4 nm to 8 nm on the bottom of the recess;
• annealing the first Ta layer to make an ohmic contact in the AlGaN layer;
• forming an Al layer on the first Ta layer before the annealing;
• and
• forming a second Ta layer on the Al layer before the annealing.

A method for fabricating a semiconductor device comprising:

• forming a recess to an AlGaN layer by etching, the AlGaN layer having an Al composition ratio of 0.2 or greater, the recess having a bottom having an RMS roughness less than 0.3 nm;
• forming a first Ta layer having a thickness of 4 nm to 8 nm on the bottom of the recess;
• and
• annealing the first Ta layer to make an ohmic contact in the AlGaN layer,
• wherein the etching is performed by plasma etching using an etching gas that is one of a mixed gas of boron chloride gas and chlorine gas, a mixed gas of boron chloride gas, silicon chloride gas and chloride gas, and a mixed gas of silicon chloride gas and chlorine gas,
• the plasma etching is an inductive coupled plasma etching under a condition of RF power of 20 W to 300 W is applied at a pressure of 0.2 Pa to 4 Pa.

A method for fabricating a semiconductor device comprising:

• forming a first Ta layer on an AlGaN layer, the first Ta layer having a thickness of 4 nm to 8 nm and the AlGaN layer having an Al composition ratio 0.2 or greater and having an RMS roughness less than 0.3 nm;
• annealing the first Ta layer to make an ohmic contact with the AlGaN layer,
• forming an Al layer on the first Ta layer before the annealing;
• and
• forming a second Ta layer on the Al layer before the annealing,
• wherein the annealing is performed at a temperature of 500° C. to 600° C.