초임계 이산화탄소를 이용한 고종횡비 패턴웨이퍼의 효율적인 건조법

Abstract

An effective drying technique was developed using supercritical carbon dioxide (scCO2) to prevent pattern collapse that may arise during semiconductor fabrication by cleaning process. Efforts were undertaken to mitigate the limitaion of conventional wet drying solvent (like IPA) by scCO2. The possibility of the substitution of IPA by scCO2 were evaluated. It was observed that the solubility of IPA was 30 wt% at 40 ℃ and 140 bar, though without stirring it took long time to dissolve. However, it was observed that IPA could be quickly mixed with scCO2 within 30 second by controlling flow of scCO2. The residual amount of IPA was quantified by VOC (Volatile Organic Compounds) method. The effect of flow time, temperature, and pressure on the removal of IPA was also examined. Based on the above results, the stiction phenomenon can be detected by using a high aspect ratio MEMS cantilever beam. The aspect ratio increased if flow time was longer. A cantilever beam having aspect ratio of 65 can be fabricated within 12 minute. The drying efficiency of MeOH and EtOH were compared with IPA, but the performance was not encouraging. Applying repetitive pulse processing system with scCO2 drying technique was found to be superior. Finally, micro-sized poly-Si cantilevers with high aspect ratios 75 were fabricated successfully without any stiction using this scCO2 protocol. It is highly expected that this improved method would find versatile applications in the next generation MEMS.