On the Use of Carbon Dioxide in Microelectronics Processing

The low viscosity, low surface energy and highly controllable density and solubility properties of carbon dioxide near its critical point provide some excellent opportunities for its use in several processes in the fabrication of integrated circuits. This paper discusses the potential use of CO2 in photolithography. In particular, we are interested in the use of CO2 with surfactants and cosolvents for the removal of water from semiconductor wafers that have been developed in aqueous solvents. This approach would help eliminate the problem of image collapse. Other applications presented include the use of CO2 instead of high temperature heating to remove residual solvents prior to exposure, spin coating of photoresists and direct development using CO2. The use of CO2 in these applications raises some fundamental issues on the thermodynamics of interactions of high-pressure fluids with polymeric thin films that can affect both polymer dilatation and mass absorption.