Low Temperature Cu/SiO2 Hybrid Bonding with Metal Passivation

Cu/SiO2 hybrid bonding process with short duration (1 minute) has been successfully performed at low temperature (120 °C) under the atmosphere with metal passivation material. Electrical performance (over 15K daisy chain and 10−8 Ω-cm2 specific contact resistance), mechanical strength (>15kgf), and reliability have been conducted to verify its excellent bonding quality. This method of hybrid bonding therefore provides a wide range of applications and a new solution for 3D integration.

Introduction

For growing demands of 3D stacked chips with high density and communication speed, such as CMOS image sensor (CIS) and high bandwidth memory (HBM), hybrid bonding (Fig. 1a) with lower communication loss and shorter connection length is a preferred technology, comparing to copper pillar with solder joint [1] (Fig. 1 b). However, for reliable Cu-Cu contacts, conventional hybrid bonding requires additional surface pretreatment steps and high annealing temperature (350–400 °C) [2]–[4]. In this work, a low temperature CU/SiO₂ direct hybrid bonding process has been demonstrated by using the metal passivation layer, which provides more product realization options with 3D integration. Bonding schematic and real chip demonstration are shown in Fig. 2.