| 摘要 |
PURPOSE:To prevent defective etching, and to control a device easily by a method wherein the elapsed time after the application of high-frequency power is calculated, bias voltage in the vicinity of a cathode generated by plasma by discharge is compared with a set value, an interlock is applied on short power and an error output is emitted. CONSTITUTION:A controller 5 emits a signal by the start of discharge in an etching chamber 1 and a photo-coupler 11 is turned ON, and a timer relay 12 is operated and a constantly-opened contact 12' is closed. Plasma is generated in the chamber 1 up to that time, a bias relay 14 is turned ON and a constantly- closed contact 14' is opened when a bias voltage is brought to a set value or more, a relay 15 is turned OFF and is not interlocked, bias voltage is displayed 14. When bias voltage is made lower than the set value,the relay 14 is turned OFF and the contact 14' is closed, and the relay 15 is turned ON and a contact 15' is opened and the relay 15 is interlocked. Likewise, the relay 15 is turned ON and interlocked as the contact 14' for the bias relay 14 is left as it is closed when the bias voltage does not exceed the set value yet when the timer relay 12 is turned ON, the supply of power is interrupted, and an error output is emitted.
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