VOID-FREE SILICON-WAFER-BOND STRENGTHENING IN THE 200-400 DEGREES-C RANGE

Silicon-wafer-bond strengthening in the 200-400-degrees-C range can be successfully applied for wafers having temperature-sensitive device s tructures. The bond quality and specific surface energy of the bond ha ve been studied experimentally with respect to the surface hydrophiliz ation state. The kinetic bond model of Stengl et al. is applied to low -temperature bond strengthening and agreement between calculated and m easured data points is established. Wafer bonding by means of static p ressure is shown to be effective in the enhancement of the bond streng th by overcoming most of the local waviness during room-temperature wa fer bonding. Specific surface energies of 1.9 and 2.3 J/m2 can be reac hed using surface plasma-activated wafers in bond strengthening at 200 and 400-degrees-C, respectively. A problem in low-temperature wafer-b ond strengthening is the voids that are generated in the 200-700-degre es-C range. Our results support the opinion that they are caused by in terface water released in the bond reaction. Void-free bond strengthen ing is possible by the insertion of a shallow groove structure into th e silicon or the oxidized silicon surface of one of the wafers.