Hermeticity and Reliability of Al-Al Thermocompression Wafer Bonding

Hermeticity and reliability of laminates bonded by Al-Al thermocompression bonding applying different bonding parameters have been investigated. Laminates of diameter 150 mm were realized by bonding a wafer containing membrane structures to wafers with patterned bonding frames. The laminates were bonded applying a bond force of 36 or 60 kN at temperatures ranging from 300 to 400 °C for 15, 30 or 60 minutes. The hermetic properties were estimated by optical measurement of membrane deflection after bonding. Reliability was tested by exposing the laminates to a steady-state life test, a thermal shock test, and a moisture resistance test. Laminates bonded applying a bond force of 60 kN at temperatures of 350 °C or higher resulted in hermetic and reliable bonds. All the dies on the laminates survived steady-state life test and thermal shock test. Leakage was observed in some dies after exposure to moisture resistance test. Measurements of membrane deflection estimated a maximum leak rate below 10-11 mbar×l×s-1 for all tested bonding parameters.