C2W Hybrid Bonding Interconnect Technology for Higher Density and Better Thermal Dissipation of High Bandwidth Memory

Abstract

Cu/Oxide Hybrid Bonding Interconnect (HBI) technology has been used in the mass production of CMOS Image Sensors and advanced packages for fine pitch heterogeneous interconnection. Furthermore, HBI can be implemented for high density products demanding good heat dissipation due to HBI's structure lacking micro bumps and polymer underfill. Thus, HBI is widely studied in the field of semiconductor assembly. Recently, we have demonstrated HBI technology in chip-to-wafer (C2W) multi stack High Bandwidth Memory (HBM) real devices and obtained promising results. We developed wafer supporting system materials to maintain Cu pad clean and focused on optimizing plasma activation conditions for high bond strength and minimizing change in Cu recess level for stable Cu/Cu joints even in low temperature annealing. Even a single void induced by various particles can cause electrical failures and reliability problems. In C2W, particles can be introduced by various processes and environments prior to bonding, unlike in wafer on wafer (WOW). Hence, an all-in-one stacking equipment with a pre-treatment function was developed to prevent such particles. Through several core technological improvements, we were able to obtain better cumulative yields than anticipated from HBM 8Hi real devices. Although further researches on C2W HBI technology are needed, we have obtained highly reliable HBM through HBI. HBI implemented HBM showed good electrical functions similar to that of conventional HBM, but had a thermal resistance at less than 20% of that of conventional HBM. In addition, we confirmed that HBI can be a powerful solution for 16hi HBM since the stack height can be reduced by more than 15% of conventional HBM. Since HBI has many advantages, we expect it to be widely used in 3D/2.5D packages in the near future.