Self‐aligning silicon interposer tiles and silicon bridges for large nanophotonics enabled systems

Abstract

A two-and-a-half-dimensional (2.5D) platform for enabling silicon nano-photonics and dense electrical interconnections between interposers in a tile-like configuration is presented. Three 20 × 20 mm silicon interposer tiles are assembled directly on an FR4 printed wiring board (PWB), and two 6 × 20 mm silicon bridges are assembled on top of the interposer tiles. Accurate alignment of interposer tiles to bridges, an important metric in enabling highly efficient optical coupling, is provided using positive self-alignment structures (PSASs). It is demonstrated that by using PSAS on two silicon substrates, sub-micron alignment between substrates is possible; in the cascaded configuration involving FR4, <5 μm alignment accuracy is obtained. In addition, electrical interconnection via a bridge using mechanically flexible interconnects (MFIs) is demonstrated, which made non-bonding interconnections from one interposer tile to another via a silicon bridge, allowing silicon bridges as well as the interposer tiles to be replaced. Total silicon interposer area available is 960 mm2.