Failure Mode and Mechanism Analysis for Cu Wire Bond on Cu/Low-k Chip by Wire Pull Test and Finite-Element Analysis

In this paper, failure mode and mechanism analysis on Cu wire bond and bond pad reliability for Cu/low-k chip are investigated through wire pull test and finite-element analysis (FEA). The wire pull test has been carried out for the bonded Cu wires with changing pull position to reveal different failure modes. Failed load is monitored and failure mode is analyzed for different wire pull test conditions. It is observed that the pull position influences failed pull force and failure mode. Failure modes include broken wire neck and wire wedge, ball lift, and pad peel and the failed force decreases with a changing pull location from the ball bond toward the wedge bond. FEA simulation is performed to help further understand failure mechanism and establish failure criteria. Finally, failure mechanism and criteria are presented for different failure modes and materials. In addition, the influence of wire loop height is also studied.