ROLE OF WAFER BOW AND ETCH PATTERNS IN DIRECT WAFER BONDING

摘要

Direct wafer bonding is an important technology in the manufacture of silicon-on-insulator (SOI) substrates and micro-electromechanical systems (MEMS). The increasing use of direct wafer bonding in demanding applications requires that the effect of flatness variations and etch patterns on the bonding process be understood fully. A general bonding criterion, based on a comparison between the work of adhesion and the strain energy that is required to accommodate flatness variations has been developed. The criterion was employed to assess the effect of wafer bow and global etch patterns on direct bonding. Experiments in which wafers were intentionally deformed using a residually stressed film and patterned with shallow etch patterns were performed. The experiments show, as the model suggests, higher curvature and thicker wafers result in smaller bonded areas. The model and experimental results are compared and discussed in detail.