Wafer-Level Vacuum Packaging by Thermocompression Bonding Using Silver after Fly-Cut Planarization

A novel wafer-level vacuum thermocompression bonding using electroplated Ag bonding frames which were planarized by diamond fly cutting was described. At relatively low temperature and press pressure, high shear strength and vacuum sealing were achieved. The diffusion of Ag into a Si substrate was suppressed by the implementation of a TiN barrier layer. Leak rate was measured by zero balance method was at approximately 3.6×10-14 Pa·m3/s. Therefore, the proposed process was useful for both wafer-level heterogeneous integration, such as the integration of MEMS and LSI circuits, and hermetic packaging for various microsystems.