Double-Level Temporary Protective Packaging of TSV-Based Micro-Mirror Array for Optical-Window-Free Vertical Integration

Aimed at vertical integration of released through-silicon-via-based (TSV-based) micro-mirror array (MMA), this paper demonstrates its temporary protective packaging. A double-level temporary packaging method is proposed, composed of wafer-level cap and die-level cap. Wafer-level cap is used to guarantee that MMA is sealed for under-bumping-metallization (UBM) fabrication, while die-level cap is removable, which allows for optical-window-free direct light reflection after the process of dicing, bumping and flip-chip. An ultraviolet-curing strippable adhesive with resistance to water, chemical solvent and high temperature is employed to bond die-level cap with MMA. The adhesive is injected to pre-fabricated trenches on MMA by a programmable dispenser. Experimental results reveal that this temporary protective packaging scheme can keep MMA free of damage, liquid, and dust in vertical integration.