Patent ID: 8426317

Claim:
A plasma processing method for performing a plasma process on a substrate in a plasma processing apparatus which includes a mounting table for mounting thereon the substrate and a focus ring provided on the mounting table so as to surround the substrate, wherein the focus ring includes a dielectric ring provided so as to surround a substrate mounting portion of the mounting table and a conductive ring provided on the dielectric ring, the conductive ring is connected with a voltage sensor for detecting a floating voltage thereof and a DC power supply for applying a DC voltage thereto, the conductive ring includes an outer ring and an inner ring as one body, the outer ring being provided so as to surround a peripheral portion of the substrate and having a top surface higher than the substrate mounted on the substrate mounting portion, and the inner ring extending inwardly from the outer ring so as to be positioned under the peripheral portion of the substrate and having a top surface lower than the substrate, further wherein the plasma processing method comprises: obtaining an optimum application voltage value to be applied to the conductive ring based on a floating voltage of the conductive ring detected by the voltage sensor and storing the obtained optimum application voltage value in a storage; when a plasma process is performed, detecting a floating voltage of the conductive ring by the voltage sensor for each plasma process, obtaining a variation of the floating voltage, and adjusting the optimum application voltage value stored in the storage based on the variation in the floating voltage; and performing the plasma process on the substrate by applying a voltage corresponding to the adjusted optimum application voltage value to the conductive ring from the DC power supply.