Patent ID: 8207066

Claim:
A dry etching method for plasma etching a sample wafer, the sample wafer having a silicon substrate and a mask pattern on the silicon substrate, the mask pattern having at least a single layer and including an isolated portion and a dense portion, the method comprising: a first etching step in which an etching rate of the dense portion of the mask pattern is greater than an etching rate of the isolated portion the etching rate of the isolated portion of the mask pattern; and a second etching step in which the etching rate of the isolated portion of the mask pattern is greater than the etching rate of the dense portion of the mask pattern, wherein the first etching step uses a mixed gas composed of a CF-based gas and nitrogen gas; and wherein an etching time ratio of the first etching step and the second etching step is controlled so that an absolute value of the difference of an etching depth of the isolated portion and the dense portion of the mask pattern is set to a predetermined value.