Patent ID: 8343306

Claim:
A plasma processing apparatus provided with a housing chamber adapted to house a substrate; a mounting stage disposed within said housing chamber and mounted with said substrate; an annular member disposed in said mounting stage so as to surround the periphery of said mounted substrate; and a power supply unit adapted to supply high-frequency power to said mounting stage; and configured to perform a plasma processing on said substrate using plasma produced within said housing chamber, said plasma processing apparatus comprising: an observation unit adapted to optically observe the plasma sheath distorted over the annular member; a voltage applying unit adapted to apply a negative DC voltage to said annular member; and a control unit adapted to cause said voltage applying unit to apply said negative DC voltage to said annular member so as to remove distortion of sheath over the substrate and annular member, the control unit adapted further to lower the value of high-frequency power to be supplied to said mounting stage which is a member other than said annular member on the basis of observed sheath thickness after application of negative DC voltage to the annular part, wherein said voltage applying unit includes a screw member connecting said annular member and said mounting stage and applies said negative DC voltage to said annular member through said mounting stage and said screw member.