Degradation in Electrothermal Characteristics and Failure Mechanism of SiC JBS With Different Die Attach Materials Under 300 ∘C Power Cycle Stress

In this article, new electrothermal characteristics degradation and failure mechanism of silicon carbide junction barrier Schottky (SiC JBS) devices with different die attach materials under 300 °C power cycle (PC) stress were investigated and found based on thermal structure function and failure analysis. The results showed that the electrothermal characteristics (thermal resistance,
$R_{\mathrm {th~j-d}}$
, and on-resistance,
$R_{\mathrm {ON}}$
) were consistent, which were different in that decreased first and then increased for nanosilver, but increased overall for alloy solders under 300 °C PC, both strongly related to the evolution of porosity, second-phase, interface cracks, and grain size in the die attach layer. However, the electrothermal characteristics were affected by die attach evolution to varying degrees due to different diffusion mechanisms, causing different failure phenomena (50, 1200, and 4000 failure cycles for high-lead, Au-Ge solder, and nanosilver, respectively). Meanwhile, the reverse leakage current (
$I_{\mathrm {R}}$
) and breakdown voltage (
$V_{\mathrm {R}}$
) variations mainly depended on chip interface states, including the Schottky barrier lowering effect (induced by AlW intermetallic compound (IMC) and large cracks generated at the Schottky contact metal layer/chip interface) and electrons and holes trapped at the SiO2/4H-SiC interface in the termination zone. Finally, this article discussed three failure mechanisms observed in devices employing three die attach materials under 300 °C PC.