DEVICE FOR DETECTING COMPLETION OF PROCESSING

摘要

PROBLEM TO BE SOLVED: To detect the completion of a reaction in a plasma apparatus which is used for processing of semiconductor wafer. SOLUTION: A light is emitted from a light-projecting part 22 to a semiconductor wafer 6 and a reflected light thereon is received by a light-receiving part 23. An output of received light is inputted into a signal processing circuit 26. An input signal is differentiated by the signal processing circuit 26. After the start of processing, a width change in derivative value becomes larger gradually, and based on its unchanging after the completion of processing completion of etching or ashing of the surface of a semiconductor can be detected.