Tier Transfer of Ultrathin Reconstituted- SiO₂ Chiplet Tiers

Wafer-scale packaging techniques pave the way for achieving high-density integration in advanced chiplet-based architectures. In this letter, a wafer-scale chiplet reconstitution technology is presented, where the key idea is to encapsulate a “sea of chiplets” in low-temperature silicon dioxide (SiO2) to form a reconstituted chiplet tier. For the demonstration of an ultrathin reconstituted-SiO2 chiplet tier, 10–20- $\mu $ m-thick passive chiplets having a chiplet-to-chiplet gap of $50~\mu $ m are fabricated. These passive chiplets are then encapsulated in 18–20- $\mu $ m-thick silicon dioxide. However, to enable further postprocessing and fabrication of redistribution layers (RDLs) on the chiplet tiers, temporary bonding and debonding (TBDB) techniques are implemented. This letter explores different tier transfer (TBDB) techniques for the ultrathin SiO2 -chiplet tiers (<40- $\mu $ m-thick). Two temporary adhesives were evaluated for this purpose: Crystalbond and double-side thermal release tape. The experimental results revealed that the Crystalbond adhesive posed several challenges, while the double-side thermal release tape allowed for a more successful transfer of the ultrathin chiplet tier.