Quarter-Micron Alignment of Chiplets via Positive Self-Aligned Structures

A simple self-aligning methodology is demonstrated for the accurate placement of chiplets on a substrate die. This approach is enabled by the registration of reflowed polymer domes both on the substrate and on the chiplet. Using flip-chip bonding, quarter-micron alignment accuracy is proposed and demonstrated on both Si and glass substrates. The vertical separation between chiplet and die is tailorable depending on the application. This methodology provides a potential building block for co-packaged optics.