| 摘要 |
<p>The present invention makes it possible, with regard to a power modulation method in which high-frequency power used for plasma generation is modulated to a pulse form, to ignite the plasma in a reliable manner and commence the plasma process under a predetermined process condition in a stable and reliable manner. In this duty ratio control method, the duty ratio of a high-frequency wave (RF1) that is to be power-modulated is at an initial value (90%), at which plasma can be ignited in a reliable manner under a discretionary power modulation condition in relation to practical use, at the time (t0) at which the process is commenced. When the process is commenced, the duty ratio of the high-frequency wave (RF1) is gradually lowered from the initial value of 90% at a uniform negative gradient or in a ramp waveform, and lowered to the inherent setting value (Ds) used for the etching process at the time (t2) at which a predetermined time (Td) (Td > Ta) has elapsed. After the time (t2), the duty ratio is fixed or held at the setting value (Ds) until the process is complete (time (t4)).</p> |
