Nickel-tin transient liquid phase (TLP) wafer bonding for MEMS vacuum packaging

This paper reports vacuum data for nickel-tin transient liquid phase (TLP) wafer bonding. Two wafers, one with a titanium getter and another with Pirani vacuum sensors, were bonded for 1.5 hours at 300 degrees C. Initial pressures were as low as 200 mTorr and have remained stable for half a month. After several days, some of the packages were heated to 400 degrees C for 10 minutes to test the thermal integrity of the TLP bond. The bond remained intact; the pressure inside each of the cavities dropped by further activating the getter and has remained steady at the new lower pressure for several weeks.