D2W and W2W Hybrid Bonding System with Below 2.5 Micron Pitch for 3D Chiplet AI Applications

Hybrid bonding is an emerging ultra-fine pitch interconnect joining technology for multi-chip/multi-stack high performance chiplet systems. With sub $-\mu \mathrm{m}$ contact sizes, it is projected to achieve ~106/mm2 interconnection densities, as needed for these systems. Aspects of system density, performance, functionality, reliability all feed into the co-optimized system architecture, thermal budget, design, process, and materials. In this paper, we discuss the latest developments in bonding surface topography and cleanliness vs. protection and handling, for dielectric and metal density related bonding. We examine the metal-metal solid-state fusion performance by grain structure distributions, along with other design, thermal, and process issues and solutions for $<$ 2.5 $\mu \mathrm{m}$ pitch $(1.6\times 10^{5}/\text{mm}^{2})$ die-to-die (D2D), die-to-wafer (D2W), and wafer-to-wafer (W2W) hybrid bonded systems.