Estimating Current Distributions in Power Semiconductor Dies Under Aging Conditions: Bond Wire Liftoff and Aluminum Reconstruction

Bond wire liftoff and metallization reconstruction are two of the most frequent failures observed during power semiconductor module operation. Aging of the top-level power dies, which occurs due to power cycling, results in the redistribution of the current in the metallization layer and the elementary cells of the power dies (MOSFET-Metal Oxide Semiconductor Field Effect Transistor, or IGBT-Insulated Gate Bipolar Transistor), leading to a risk of critical failure when either the local current density or the local temperature reaches a critical value. This paper reports on the experimental estimation of the distribution of dc flowing in the power dies and investigates the effect of the local degradation of aluminum sheet resistance and bond wire liftoff on the current distribution. The local distribution of the current flowing in the metallization layer and in the power dies was estimated by mapping the electric potential of the source metallization. The obtained results facilitate the identification of failure risks that result from the aging process (which occurs due to current redistribution) of top-level power dies and provide an understanding of the physical origins of failures.