Post-CMOS Processing and 3-D Integration Based on Dry-Film Lithography

This paper presents a chip-level post-complementary metal oxide semiconductor (CMOS) processing technique for 3-D integration and through-silicon-via (TSV) fabrication. The proposed technique is based on dry-film lithography, which is a low-cost and simple alternative to spin-coated resist. Unlike conventional photolithography methods, the technique allows resist patterning on very high topography, and therefore chip-level photolithography can be done without using any wafer reconstitution approach. Moreover, this paper proposes a via sidewall passivation method which eliminates dielectric etching at the bottom of the via and simplifies the whole integration process. In this paper, two 50- μm-thick chips were post-processed, aligned, bonded, and connected by Cu TSVs, which have parylene sidewall passivation. Daisy-chain resistance measurements show 0.5- Ω resistance on average for 60- μm-diameter TSVs, with a yield of more than 99% for 1280 TSVs from five different chip stacks. Subsequently, the techniques were applied to CMOS microprocessor stacking as a test vehicle. Die-level post-CMOS processing for 40- μm-diameter via etching, redistribution layer patterning, and chip-to-chip bonding were successfully demonstrated with the real chips.