Development of an UHV surface activated bonding machine for MEMS packaging

An ultra high vacuum (UHV) surface activated bonding (SAB) machine has been developed for micro electro mechanical systems (MEMS) packaging at low temperature. The bonder accommodates of wafer up to 8 inches diameter. The principle features of the bonder are the automatic parallel adjustment for 8-inch wafers to a margin of error within ±1 μm and the X, Y, and θ axis alignments accuracy is ±0.5 μm. Various combinations of 3-8 inches patterned and bare silicon, Al silicate glass and Quartz wafers have been successfully bonded by the SAB process using a low energy argon ion beam at low temperature. Fine leak test of sealed silicon cavities shows a leak rate of 1.0×10^-9 Pa/m³s, which is lower than that of the American military standard encapsulation for the MEMS devices in harsh environments. Void free interfaces with bonding strength comparable to bulk materials are found.