A comparison of chilled DI water/ozone and CO2-based supercritical fluids as replacements for photoresist-stripping solvents

Part of the Hewlett Packard Components Group´s Product Stewardship program is the ongoing effort to investigate ways to eliminate or reduce as much as possible the use of chemical substances in manufacturing processes. Currently used techniques to remove hard-baked photoresists from semiconductor wafers require the use of inorganic chemicals or organic strippers and associated organic solvents. Environmental, health and safety, and cost considerations prompted the search for alternative, more environmentally-benign, and cost-effective solutions. Two promising, emerging technologies were selected for evaluation: the chilled DI water/ozone technique and supercritical fluids based on carbon dioxide (CO₂). Evaluation of chilled DI water/ozone shows this process to be effective for positive photoresist removal, but may not be compatible with all metallization systems. Testing of a closed-loop CO₂-based supercritical fluid process, known as supercritical CO₂ resist remover, or SCORR, at Los Alamos, on behalf of Hewlett-Packard, shows that this treatment process is effective in removing photoresists, and is fully compatible with commonly used metallization systems. In this paper, we present details of the testing programs conducted with both the chilled DI H₂O/ozone and SCORR treatment processes