Wafer-Level Dynamic On-Resistance Testing and Characterization of GaN HEMTs

On-resistance ($\mathrm{R}_{\mathrm{DSon}}$) is a critical parameter in the performance and reliability of Gallium Nitride (GaN) devices. This paper introduces a novel on-wafer test system designed to rapidly and accurately measure the dynamic $\mathrm{R}_{\mathrm{DSon}}$ of GaN enhancement-mode High Electron Mobility Transistors (HEMTs) during hard switching operations. The system allows for the characterization of multiple device designs directly on the same wafer. The test method employs continuous hard-switching stress, in accordance with and exceeding JEDEC committee guidelines [1]. The system’s specialized probe card and optimized test pads ensure precise measurement while taking great care to minimize parasitic capacitance and inductance. We present both long-term and short-term test data, examining reliability across wafers at different frequencies, gate drive voltages, and unit cell designs. We provide results from two different probe cards, one with lower parasitic capacitance, demonstrating significant differences in dynamic Roson behavior at higher frequencies. Furthermore, we compare the $\mathrm{R}_{\mathrm{DSon}}$ trends between on-wafer test die and packaged die, both with same cell design under identical test conditions.