Low Temperature Hybrid Bonding for Die to Wafer Stacking Applications

The direct bond interconnect (DBI®) technology is a platform technology that offers a hermetically sealed hybrid bond with solid metal-metal (Cu-Cu is the most common) interconnect at a relatively low thermal budget. The Xperi wafer to wafer hybrid bonding technology has been in high volume production since 2015. The Xperi die to wafer hybrid bonding technology, DBI® Ultra, is now ready for industry adoption and ramp to manufacturing. The bond takes place at room temperature in an ambient environment in a class 1000 cleanroom; therefore, offers bond throughput comparable to mass reflow flip chip assembly. A low temperature batch anneal after bonding results in a solid Cu-Cu connection surrounded by dielectric for improved thermal performance. The value of the hybrid bonded Cu-Cu technology may be realized at various interconnect pitches for different applications. For die to wafer and die to die application with through silicon vias (TSVs), significant performance and cost advantages can be achieved at sub-40um pitch through elimination of both the solder and underfill materials from the package. Additionally, the technology may be scaled to sub-micron interconnects to enable widespread disaggregation and chiplet architecture innovation. Xperi's development efforts target the sub-40um pitch die-to-wafer stacking, which can be enabled with the existing Si supply chain. Previously, we have reported assembly results with daisy chain die in single layer and in die-to-wafer stacking with or without TSVs. In this paper, we report on a 5-die stack hybrid bonded module with TSV and the latest fabrication, assembly process, electrical testing and reliability performance. The reliability tests include autoclave, high temperature storage and temperature cycling with pre-conditioning at MSL3 per JEDEC specification.

I. Introduction

Direct Bond Interconnect (DBI®), a low temperature hybrid bonding technology [1]–[3], was first demonstrated by Ziptronix in a die-to-wafer (D2W) bonding format. However, for the first high volume manufacturing product was wafer-to-wafer (W2W) application. In 2015, Sony adopted the technology for CMOS image sensors [4]. Since then, development work has focused on high volume manufacturing of die-to-wafer hybrid bonding technology to enable enhanced performance in electronic products.