Heterogeneous Integration of Compound Infrared Focal Plane Arrays (FPAs) and Silicon Read-Out Integrated Circuits (ROICs) Using Laser-Assisted Bonding at a 15µm-Pitch

초록

This paper presents a fine-pitch heterogeneous bonding process for compound infrared focal plane arrays (FPAs) and silicon read-out integrated circuits (ROICs) using Laser-Assisted Bonding with Compression (LABC). The integration of compound semiconductor FPAs with CMOS-based ROICs is a key enabling technology for high-resolution infrared imaging systems; however, continued scaling of pixel pitch has a significant impact on alignment accuracy and bonding process control.Indium solder bumps were employed as interconnects owing to their low melting temperature, high ductility and favorable thermo-mechanical compliance for infrared detector applications. The LABC process combines localized laser heating with simultaneous compressive loading, enabling transient thermal activation at the bonding interface while limiting thermal exposure of the overall chip assembly. Using the LABC process, fine-pitch bonding was achieved at an interconnection pitch of 15μm.Optical inspection confirmed uniform chip attachment after bonding, while electrical measurements exhibited stable current-voltage characteristics across representative pixel-level interconnects. Cross-sectional analysis further revealed well-formed interconnects without observable voids or interfacial defects. This study demonstrates that LABC can be applied to fine pitch heterogenous integration of compound infrared FPAs and silicon ROICs at a 15μm pitch, providing a practical bonding approach under reduced thermal exposure.

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