Micro arc monitoring by detecting charge build-up on glass surface of viewing port due to plasma dispersion in plasma processing equipment

We report a new method of monitoring micro arc discharge in plasma processing equipment in which we detect the change in wall potential at the inner surface of the glass of the viewing port. The change in the wall potential is detected through a transparent indium-tin-oxide (ITO) film electrode adhered to the outside surface of the glass of the viewing port. It is demonstrated that by means of this method, we can detect micro arc discharge both in direct-current (DC) and radio-frequency (RF) plasma processing equipment. The results indicate that the method is useful for monitoring the occurrence of micro arc discharge presenting a very easy-to-use tool. The results also suggest that the method is useful for monitoring the state of RF plasma.