Patent ID: 7615131

Claim:
A plasma etching chamber for etching only the periphery of a wafer by mounting the wafer on a stage such that the periphery of the wafer is positioned between ring-shaped top and bottom electrodes, blowing a nitrogen gas to the center of the wafer through the center of a top-sided stem while making a non-discharged region, and blowing a reaction gas to the periphery of the stem to make a gas discharge, the plasma etching chamber comprising: a cathode mounted within the stage to apply radio frequency to the wafer; a ring-shaped bottom anode placed at the outer circumference of the stage while being positioned lower than the periphery of the wafer; a stem installed over the stage such that the stem moves up and down; insulator having an annular groove formed in a side wall of an outer side periphery of the concave portion being formed at the center of the bottom surface of the stem while facing the top surface of the stage, the insulator having an annular groove formed in a side wall of an outer side periphery of the insulator, the groove extending parallel to the wafer and making a point of inflection in the flow of the reaction gas along the outer side periphery of the insulator; and a ring-shaped top anode placed at the outer circumference of the insulator while interposing a reaction gas outlet such that a plasma is generated between the periphery of the wafer and the ring-shaped top and bottom anodes.