Carbon dioxide-based supercritical fluids as IC manufacturing solvents

The production of integrated circuits (ICs) involves a number of discrete steps which utilize hazardous or regulated solvents and generate large waste streams. ES&H considerations associated with these chemicals have prompted a search for alternative, more environmentally benign solvent systems. Here, the authors describe how an emerging technology for conventional solvent replacement is the use of supercritical fluids based on carbon dioxide (CO₂). Research work, conducted at Los Alamos in conjunction with the Hewlett-Packard Company, has lead to the development of a CO₂-based supercritical fluid treatment system for the stripping of hard-baked photoresists. This treatment system, known as supercritical CO₂ resist remover, or SCORR, uses a two-component solvent composed of a nonhazardous, nonregulated compound, dissolved in supercritical CO₂. The solvent/treatment system has been successfully tested on metallized Si wafers coated with negative and positive photoresist, the latter both before and after ion-implantation