LIBRARIES An Evaluation of Three Dimensional Integration Technology

The first part of the research is an overview of existing three-dimensional (3-D) integration technologies such as wafer bonding, selective epitaxy, multi-chip modules, and micromaching (MEMS) methods. Each technological option was evaluated based on several variables, which include both processing constraints, applications, and viability. Indirect wafer bonding, specifically using copper metal as the bonding adhesive, was chosen because it offers advantageous schemes such as heat dissipation conduits, inter-wafer vias, and interconnect ground planes. The technology development consists of copper wafer bonding at 4000C, satisfying the processing tem-perature requirements for aluminum back-end technology. Silicon wafers, coated with 300 nm of evapo-rated copper, were successfully bonded at 4500C for 30 min with a post-bonding anneal in N2 for 30 min. Post-bonding anneal was required for successful bonding, but annealing temperature did not influence the bond strength from 400 0C to 6200C. The inclusion of tantalum diffusion barrier layer for Cu did not affec