Breakthrough of Sublimation Drying by Liquid Phase Deposition

Abstract

Damage-free drying becomes increasingly difficult with the scaling of semiconductor devices. In this work, we studied a new sublimation drying technology for 3nm node and beyond. In order to investigate the collapse factor by conventional sublimation drying, we observed the pattern with cryo-SEM and revealed that the collapse occurred when the liquid film on the substrate solidified. Based on this result, we considered that it was important to deposit a solidified film uniformly from the substrate side to suppress collapse. Two key process parameters were evaluated to achieve the uniform formation of the solidified film. One is interfacial free energy and the other is film thickness of solution just before solidification. By optimizing two key parameters, it was successfully demonstrated to suppress pattern collapse of challenging devices. In this paper, we report on a new drying method: sublimation drying by LPD (Liquid-phase deposition).