A Novel Method for Mems Wafer-Level Packaging: Selective and Rapid Induction Heating for Copper-Tin Slid Bonding

Innovative packaging techniques are essential for the development of new microsystems. To integrate different materials into one package, the thermal stress on the devices has to be minimized. This paper presents a method for selective and energy-efficient induction heating of Cu-Sn layers to support and enhance the bonding process at wafer-level. Technological challenges include the inductor design for homogeneous heating, the use of high-frequency electromagnetic fields up to frequencies of f = 2.0 MHz, and the integration of the induction equipment into an industrial wafer bonder. Infrared thermography imaging was used to characterize the selective heat generation with very fast heating rates of ΔT > 150 K/s. Consequently, the wafer bonding process could be performed in t
_bond
= 120.0 s by applying a low pressure of p = 2.2 MPa.