US Patent 9922802 Power supply system, plasma etching apparatus, and plasma etching method

A power supply system 90 includes high frequency power supplies 92 and 93 that supply a high frequency power for plasma generation; a DC power supply 91 that supplies a DC voltage to be applied to an electrode; and control unit 94 that controls the high frequency power supplies 92 and 93 and the DC power supply 91 including a first DC power supply unit 101 that supplies a first negative DC voltage V1, a second DC power supply unit 102 that supplies a second negative DC voltage V2 having a higher absolute value than the first negative DC voltage V1, and a selecting circuit 103 that selectively connects the first DC power supply unit 101 and the second DC power supply unit 102 to the electrode; and a discharging circuit 104 connected with a node 109 between the first DC power supply unit 101 and the selecting circuit 103.