Evaluation of Hybrid Bonding Interface Quality by Contact Resistivity Measurement

With the rise of hybrid bonding as a solution for fine pitch 3-D integration, new methods are required to evaluate the bonding quality at a wafer level. Contact resistance is widely used for process control but measurements can be corrupted by the 3-D stack complexity and the misalignment of wafers. In order to measure the specific contact resistivity of dual-damascene interconnects and evaluate the Cu/Cu bonding interface, 3-D cross Kelvin resistors (3-D CKRs) have been specially designed. Electrical characterizations and complementary simulations demonstrate that test structures are functional if the specific contact resistivity is higher than 10^-8 Ω·cm². Despite bonding defects evidenced by morphological characterization, the specific contact resistivity remained below the measurement limit. The good reconstruction of Cu/Cu interface does not allow contact resistance measurement.