Power Cycle Testing, Behaviour of Clip-Sintered Bare Dies

Sintering is a state-of-the-art die-attach method for high-reliability power modules, and double-sided sintering can further enhance device lifetime by replacing aluminum wire bonds with robust copper interconnections. We investigate the feasibility of thick Cu clip sintering as a top-side connection for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiC}$</tex> power devices, aiming to reduce parasitic inductance and improve thermal performance. The device under test, comprising a double-sided sintered <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiC}$</tex> MOSFET and a thick copper clip, is evaluated using scanning acoustic microscopy (SAM) and power cycling tests (PCT). SAM reveals variations in sintering quality, highlighting the need for process optimization. PCT results show a wide spread in cycles to failure, with early failures at only 2500 cycles while other devices survive more than 80000 cycles. Additionally, gate leakage currents in failed devices suggest potential gate oxide degradation due to thermomechanical stresses. Despite challenges, the study demonstrates the potential of Cu clip sintering for high-reliability <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiC}$</tex> power modules, emphasizing the need for further refinement in processing techniques.