Patent ID: 7611993

Claim:
A plasma processing method for processing a sample by applying a high-frequency bias power for each period (T) which is divided into a first sub-period (T 1 ), a second sub-period (T 2 ), and a third sub-period (T 3 ) along a time axis; wherein the first sub-period (T 1 ) is used as a sub-period for which feedback control of a CD gain is executed; the second sub-period (T 2 ) used a sub-period for which feedback control of a select ratio is executed; and the third sub-period (T 3 ) is used as a sub-period for which feedback control of the CD gain and feedback control of the select ratio are executed; wherein the applied power is set at a large value in the first sub-period; wherein a duty ratio T 1 /T is controlled in accordance with the CD gain; and wherein the processing method comprises the steps of: controlling for each period (T), the first sub-period (T 1 ) so as to be applied with a largest amplitude power of the sub-periods (T 1 -T 3 ), the second sub-period (T 2 ) so as to be applied with a smallest amplitude power of the sub-periods (T 1 -T 3 ), and the third sub-period (T 3 ) so as to be applied with an intermediate amplitude power which is intermediate the largest and smallest amplitude power; processing a plurality of samples with a predetermined processing condition; measuring the CD gain, the select ratio and an etching speed of each of the samples; and executing a feedback control for each processing unit of the samples in accordance with a change of processing state of each of the samples so that the duty ratio T 1 /T is controlled in accordance with the measured CD gain, and an average applied power over each period (T) is constant.