Advances in semiconductor device designs are placing demanding requirements on the semiconductor tool sets used to fabricate devices in the cleanroom. The stripping of photoresists, particularly those used as implantation masks, represents a nagging problem for which very few new tools have evolved. This is so in spite of demands for cleaner, particulate and damage free tools from the semiconductor fabrication community.

Gas-phase ozone stripping represents one of the few new, potential solutions to this semiconductor industry-wide problem. We have used a single wafer ozone ashing system, an apparatus especially developed to remove photoresist from silicon wafers, to evaluate the potential of ozone stripping technology. With a direct sampling mass spectrometer, the composition of the asher's gaseous effluent stream was monitored in real-time during operation of the ozone asher. A series of surface sensitive techniques including optical microscopy, AFM, and TXRF, were applied in order to obtain detailed information on the topography and composition of the wafer surface following ashing.

A basic understanding of the gas-phase and surface chemistry involved in ozone ashing provides a data base from which both environmentally sound disposal issues and post ashing wet cleans can be designed.