(Invited) Supercritical Drying: A Sustainable Solution to Pattern Collapse of High-Aspect-Ratio and Low-Mechanical-Strength Device Structures

Abstract

Collapse of nanostructures with high aspect ratio and/or low mechanical strength during drying step in wet process has become a critical issue in semiconductor industry. Even current workable drying practices are facing steeply rising challenges from rapid device scaling advancements. The objective of this work, following evaluation of multiple advanced drying technique, is to develop a sustainable non-stiction drying solution incorporating supercritical fluids. Leaning-free performance has been consistently demonstrated with our supercritical drying sequence on 2x NAND STI (trench aspect ratio ~20) and low-k trench structures, where pattern collapses were observed under conventional solvent-assisted drying or even with advanced self-assembled monolayer approach. Release of sporadic stiction and complete recovery from global pattern leaning were both achieved with our integrated supercritical drying process. Particle performance < 50 adders @0.09μm in average was attained with background particles subtracted. Metallic contamination analysis with TXRF showed all metal components interested were below detection limit.