GAS ETCHING SYSTEM INCLUDING END POINT DETECTION

摘要

A gas etching system includes a plasma etching chamber (1), a pressure sensor (9) adapted to sense the pressure within the chamber (1) and a constant displacement vacuum pump (2) adapted to extract gases from the chamber (1). The etchant gases entering the chamber (1) have their flow regulated by a feedback loop which includes the pressure sensor (9). Changes in the chemical composition within the chamber (1) which occur in time proximity to the end point of etching affect the chamber pressure and are detected as variations in the gas flow rates. These variations are depicted visually on a strip chart recorder (12). The system detects the end point of etching with high sensitivity.