A Cost Effective Via Last TSV Technology Using Molten Solder Filling for Automobile Application

We propose combined solder-TSVs and microbumpsfor cost reduction of 3-D integration. Conventional via-last TSV technology requires microbump formation. We eliminate the microbump process for low cost 3-D process. In our process, TSVs and microbumps are formed simultaneously with solder. We demonstrate this process by fabricating daisy chain chips with 20-μm-pitch TSVs. The TSVs are 7-μm diameter, 20-μm deep, and a total number of 39,000 per chip. Its electrical characteristics are 1.05 ± 0.64 Ω/TSV (3σ, n=20).