Handbook of Silicon Based MEMS Materials and Technologies

Chapter Thirty Five. Bonding of CMOS Processed Wafers

Wafer bonding at the end of the wafer processing is a common method in MEMS fabrication, where a kind of wafer level assembly is performed by mounting protective caps over the mechanically sensitive MEMS structures. This seals the functional cavities, to stabilize chips or to apply other functional elements such as optical windows (Figure 35.1). Very often at least one of the wafers to be bonded has been processed by CMOS^[1] technology, either fully as an ASIC wafer, partially as a discrete MEMS sensor wafer, or additionally as an integrated MEMS sensor wafer. This chapter describes the special bonding processes and conditions required for bonding these types of highly sophisticated, processed ...