In-situ temperature-dependent sheet resistance study of Cu films in oxygen ambient for heterogeneous integrations

Abstract

Controlling and preventing Cu oxidation is crucial for improving the performance and reliability of Cu-Cu bonding. Ni-B films were selectively deposited on Cu films to block the Cu oxidation. The resistivity changes of the Cu films in N2 and O2 ambient were measured by using a four-point probe in the in-situ temperature-dependent resistance measurements at the temperature from room temperature to 400°C. The resistivity changes of the 100nm-thick Cu films without Ni-B increased rapidly at a higher temperature (284°C) in the O2 ambiance. The change of resistivity-increase of 100nm-thick Cu with ~50 nm-thick Ni-B (top) film was lower than the Cu films without Ni-B films due to the blocking diffusion of O2 atoms by the Ni-B films. The resistivity-change and oxidation barrier properties were studied using SEM, FIB, TEM, EDX, and SIMS tools. The proposed article will be helpful for the upcoming advancement in Cu-Cu bonding using selected-area deposition.