FACE-TO-FACE WAFER ALIGNMENT AND BONDING

摘要

Precision aligned wafer bonding is a key enabling technology for 3D Interconnects, wafer level packages (WLP) and advanced MEMS devices. Unlike MEMS, which frequently involve double side processing, IC and CMOS manufacturing utilize only single side processing steps. Therefore wafer-to-wafer alignment must use alignment targets situated in the bond interface i.e. face to face. The ability to align and bond such wafers with one micron precision is becoming a critical issue for a variety of applications. This paper will report on the principal steps of the face to face alignment method, and on the latest results reporting one micron or better alignment accuracy that are routinely obtained with a specially developed alignment system that uses this method. The principal equipment designs for wafer-to-wafer alignment and bonding, as well as their modularity for full integration into high volume production lines will be discussed.