Temporary bonder used in vacuum environment to avoid air bubbles

Abstract

In recent years, thin wafer applications are expanded in Through Silicon Via (TSV), flexible electronics, MEMS, power device etc. Especially high density TSV applications drive the need for ultra-thin wafers. As wafer thickness decreases, thin wafer handling technology have to be required. Thin wafer is less stable, more vulnerable to stress and, so it has to be protected mechanically. Temporary bonding of the thin wafer and the carrier allows further semiconductor manufacturing process without the risk of wafer breakage. The carrier wafer material is silicon or glass that gives mechanical stability on thin wafer and protects the fragile thin wafer. One of several conditions of temporary bonder must not ingenerate air bubble in temporary bonding process. Because some semiconductor processes proceed in vacuum environment, there must not be air bubble. Some conditions need to bond without air bubble. First, the uniformity of the adhesive is important since air bubble trapped within the adhesive will result in blistering. Second, the coating thickness of adhesive must be uniform. Third, the bonding process should be achieved in vacuum environment. This study is related to the third condition and temporary bonder used in vacuum environment. Compared with air environment, the most difficult problem is the wafer handling in bonder used in vacuum environment. When the size of device wafer is equal to the size of carrier wafer, the wafer handler must pick the wafer behind. Vacuum picker is used most usually to wafer handling but it is impossible in vacuum environment. In this study, we developed mechanical picker to solve this problem and studied about pressure uniformity that became an issue in thermo compression bonding usually.