Low Cost Metal Mini-Cap Process for Suspended MEMS Device Packaging

A new wafer capping process is investigated in this study. The objective of this study is to come out a simple and low cost wafer capping process to make the capped MEMS device wafers “transparent” to traditional IC assembly processes. The carrier wafers with metal mini-caps are bonded on the MEMS device wafers through solder bonding, and the mini-caps are then transferred and left on the MEMS device wafer through a selective etching of the carrier wafers. The metal mini-cap capped device wafers are virtually of the same thickness as original ones; in addition, the transferred metal mini-caps provide a mechanical protection to the MEMS devices during the consequent assembly processes such as wafer dicing, die bonding, molding, etc. With an additional design of 2nd level interconnection on the mini-cap carrier wafer, the transferred MEMS device wafers can be singulated and become a wafer level package with compliant leads.