Investigation of the thinning mechanisms of Cu/Ti heterostructure in the through glass via wafer

KZ Xu and YQ Zhou and WB Hui and YX Chen and ZN Yu and JG Xie and CJ Wang and FL Zhu, SURFACES AND INTERFACES, 73, 107573 (2025).

DOI: 10.1016/j.surfin.2025.107573

Through glass via (TGV) interconnect structures are vital components in 3D high-density packaging, and the Cu/ Ti heterostructure is one of the typical interfacial structures in TGV wafer. Atomistic simulations are used to study surface and interfacial evolution mechanisms of Cu/Ti heterostructure during nanoscale thinning. The results reveal that plastic deformation in Cu is dominated by 1/6 < 112> Shockley dislocations and stacking faults, while Ti is governed by 1/3 < 1 - 210> dislocations and localized HCP-to-FCC phase transitions. The initial semi-coherent interface is damaged after thinning, especially at larger thinning depths. There is a significant stress concentration at the abrasive-workpiece contact region and the interface. Due to the limited plasticity, the Ti layer still has relatively high residual stresses after thinning. A reduction in thinning forces near the interface is attributed to the formation of soft stacking faults and amorphous atoms. The increase in tangential force with increasing thinning depth is more noticeable than the increase in normal force. Shear strain and temperature analysis demonstrate that plastic deformation and thermal accumulation intensify as the thinning depth increases. The Cu/Ti interface exhibits a barrier effect to heat transfer owing to its lattice mismatch. This study provides atomic-level insights into thinning-induced structural responses of Cu/Ti heterostructure, offering theoretical support for optimizing the thinning of TGV wafer.

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