Process control challenges in 3D packaging

Recent trends in heterogeneous integration and development in chiplet architectures are pushing the limits of 3D packaging. As 3D packaging evolves from microbumps to hybrid bonding at the die-to-die interface, the need for process control is becoming more imperative. This is driving the adoption of process control solutions that have been traditionally prevalent in the semiconductor front-end manufacturing fabs into high-end advanced packaging lines. Interconnect densities have now started to scale down to sub-micron levels. This requires processes to have extremely tight process control and tool precisions measured in nanometers, rather than microns. In this paper, we discuss various new process control solutions developed for advanced 3D packaging. Hybrid bonding requires several new processes that must be controlled with nanometer accuracy to achieve good yields. New inspection and metrology solutions are required to enable process control for these new processes. One of the key parameters in hybrid bonding is Cu dishing profile control. Cu dishing is achieved by the CMP process but requires sub-nm precision to measure the profile accurately. This can be achieved using Machi