Process development and material characterization of Cu-Cu thermo-compression bonding (TCB) for high-conductivity electrical interconnects.

Abstract In this work, we focus on metal-metal Thermo-Compression Bonding (TCB) for realizing assembly of dielets to a silicon interconnect fabric (IF). The popular metal choices include bare Cu, Cu plated with Au and Au. Our approach simplifies the metallurgies used in classic chip-to-package assemblies by avoiding the use of solder and the concomitant issues of intermetallic formation such as electrical resistance and brittleness. In this paper, we address TCB parameter optimization and material characteristics of these metal-metal TCB joints. The roles of two physical mechanisms on Cu-Cu interface voiding i.e. surface roughness prior to TCB, oxide presence at bonding interface are evaluated in detail.