An Investigation on Particle Embedding Capability of Wafer Level Spin-on Polymer Underfill Enabling Low Temperature Bonding of Hybrid Bonding Sysem

A hybrid bonding system is developed with epoxy-based spin-on polymer underfill. This study enables (i) a low temperature (≤200 °C) hybrid bonding technique, (ii) high particle embedding (≥3 µm height), (iii) scaling the micro-bump pitch down to 5 µm (for Cu-Sn/organic system), and (iv) a high removal rate for CMP is achieved. The polymer underfill material showed excellent bond strength in low-temperature bonding conditions (50 °C), and the strength is not affected by the plasma treatment and the high-temperature storage (HTS) test. This study focused on the particle embedding capability and revealed that the underfill curing is a key factor.