A NOVEL DUAL-LAYER BONDING PLATFORM AS A TECHNICAL ENABLER FOR WAFER LEVEL PACKAGING APPLICATION

摘要

Driven by the mobile market's need for greater flexibility, higher performance, and smaller form factor, wafer-level packaging (WLP) has now been adopted for large-scale production. In a relatively short period of time, various WLP technologies have seen tremendous innovation and evolution, such as package-on-package (PoP), fan-out integration, and through-silicon via (TSV) technologies. Temporary bonding and debonding has been widely studied and developed over the past 10+ years as a key technology enabler for handling thinned substrates (<100 μm) that can no longer self-support and enhancing handling in post-processing applications. A simple and efficient bonding/debonding technology that allows easy material handling and withstands high-temperature processing is demanded, particularly with regard to reduction of cost-of-ownership and throughput improvement. In this paper, a newly developed dual-layer temporary bonding system and associated enabling materials are reported. Unlike other temporary bonding materials that are mainly based on thermoplastics, the new system includes two layers: 1) a thermoplastic layer with high glass transition temperature (T_g) and 2) a curable layer that can be either UV- or thermally cured depending on the application. After applying these materials to the substrates, the substrates can be bonded at low bonding temperatures (≤100°C) or even at room temperature, with reduced bonding time (≤120 s). The curable layer is then cured, resulting in significant reduction in its mobility on the substrates at elevated temperatures. Coupled with the high-T_g thermoplastic as the underlayer in the bilayer system, this platform provides an extremely high degree of mechanical support to device wafers so that they can survive high-temperature and high-vacuum processes. After processing, the bonded wafer pairs can be selectively debonded by simple mechanical peeling at the material interface. As an alternative debonding method, the bonded wafer pair can also be laser-released at 308 nm or 355 nm.