Laser ablation patterning for low cost 3D die packaging

High cost has been the barrier in the wide spread application of high density 3D die packaging. Current industry technologies add $75 to $300 per die to provide packaged die in a 3D memory cube format. A novel patterning approach employing excimer laser ablation reduces the die reroute process and cube fabrication process steps by over two thirds. This reduces the estimated added cost to well under $25 per die. Two process developments were necessary to achieve this step function reduction in cost; a vapor deposited polyimide process and a thin film metal ablation process, both processes are accomplished on bare die. The vapor deposition polymerization process allows the formation of solventless films through vacuum co-evaporation of a dianhydride and diamine. The excimer laser ablation process is widely used to ablate vias in polyimide at a very high rate. Its use as a method of patterning thin film metal is atypical. Its use in patterning die on the face and edge in a single process set-up is unique. Results on using both processes to build inexpensive 3D memory products will be presented