Engineered Solder-Directed Self-Assembly Across Length Scales

Abstract

ABSTRACTWe report on recent progress in the directed self-assembly of discrete inorganic semiconductor device components. Different from prior research, the goal is to enable the integration of increasingly small dies while supporting unique-angle orientation and contact pad registration. The process is based on the reduction of surface free energy between liquid solder coated areas on the substrate and metal-coated binding sites on the semiconductor dies. Recent advances include flip-chip assembly with unique angular orientation accomplished using “two-element” docking sites that contain pedestals that act as chaperones for the solder directed assembly to take place. The scale reduction to 20 μm sized components involves the use of a liquid-liquid interface to concentrate component delivery and speed up the self-assembly process to prevent oxidative dissolution of the solder sites prior to completion.