Room-temperature pressureless wafer sealing using ultrathin Au films activated by Ar plasma

Silicon wafers with cavities and Si cap wafers were bonded by Au-Au surface activated bonding using ultrathin Au films (thickness: 15 nm) to achieve wafer-scale sealing. Pressurelessbonding (wafer pairs were simply placed in contact) was performed at room temperature in ambient air after surface activation by Ar plasma treatment. Bonding strength was measured using a razor blade test. Bonding strong enough to be broken from Si wafers was obtained. Evaluation of sealing quality with a He leak tester showed that the leak rate was below the lower limit of the tester (<; 1.6×10^-10 Pa·m³/s).