Evolution of structured adhesive wafer to wafer bonding enabled by laser direct patterning of polymer resins

The paper reviews structuring methods of adhesive layers which can be subsequently used for thermo-compression type wafer to wafer bonding processes. With respect to limitations of the state-of-the-art adhesive structuring approaches laser direct patterning of polymer resins is introduced. The process features a 248 nm excimer laser stepper with mask based pattern projection and high speed XY-moving stage. Non-cured polymer precursors such as Cyclotene™ resins can be well structured with this direct ablation method. As additional feature of the new structuring method patterning of polymer compound layers is introduced and discussed. This approach enables structuring of polymer layer stacks having different cure conditions enabling adjusted material flow and squeeze capabilities in subsequent wafer bonding processes. The experimental setups as well as the results of structuring and bonding trials with different polymer layers are discussed in this work.