<title>Supercritical fluid processing: a new dry technique for photoresist developing</title>

Abstract

Supercritical fluid (SCF) technology is investigated as a dry technique for photoresist developing. Because of their unique combination of gaseous and liquid-like properties, these fluids offer comparative or improved efficiencies over liquid developers and, particularly carbon dioxide, would have tremendous beneficial impact on the environment and on worker safety. Additionally, SCF technology offers the potential for processing advanced resist systems which are currently under investigation as well as those that may have been abandoned due to problems associated with conventional developers. An investigation of various negative and positive photoresist systems is ongoing. Initially, supercritical carbon dioxide (SC CO<SUB>2</SUB>) as a developer for polysilane resists was explored because the exposure products, polysiloxanes, are generally soluble in this fluid. These initial studies demonstrated the viability of the SCF technique with both single layer and bilayer systems. Subsequently, the investigation focused on using SC CO<SUB>2</SUB> to produce negative images with polymers that would typically be considered positive resists. Polymers such as styrenes and methacrylates were chemically modified by fluorination and/or copolymerization to render them soluble in SC CO<SUB>2</SUB>. Siloxane copolymers and siloxane-modified methacrylates were examined as well. The preliminary findings reported here indicate the feasibility of using SC CO<SUB>2</SUB> for photoresist developing.