Optimization of surface preparation for direct silicon-silicon bonding

The primary objective of this paper is to present an optimum surface preparation technique for subsequent silicon wafer bonding with direct bonding process. Several key factors that govern the quality of the wafer surfaces, such as the degree of hydrophobicity, HF etching time, composition of HF etching solution and DI water rinse, are examined. Moreover, to optimize the surface preparation, an argon ion sputtering scheme is also successfully introduced after the HF etching to further minimize the oxide growth on the silicon wafer surface. Analyses using XPS are presented to show surface composition changes in conjunction with the argon ion sputtering and the subsequent air exposure before wafer contacting