| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of etching an insulation film, in which the end point of the etching operation of a semiconductor wafer can be detected stably, even if the open area ratio of the semiconductor wafer is low. SOLUTION: In the method of etching the insulation film, including a silicon oxide film or a low-k film composed of a low-permittivity material, the end point of its etching operation is determined so as to finish the etching operation. The determination processing operation of the end point of the etching operation comprises a step, in which the noise of an input signal waveform is reduced by a first digital filter 18, a step in which the (primary or secondary) differential coefficient of the signal waveform is found by differentiation processing using a computing circuit 19, a step in which the noise component of a time-series differential coefficient waveform found by the step is reduced by a second digital filter 20, so as to find a smoothing differential coefficient value and a step in which the smoothing differential coefficient value is compared with a preset value by a discrimination means 22, so as to determine the end point of the etching.
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