Improvement of Threshold Voltage With ZrO2/HfO2 Gate Dielectric and CF4 Plasma Treatment on AlGaN/GaN HEMT

We propose a method for CF4 plasma treatment of the ZrO2/HfO2 gate dielectric to increase the threshold voltage of AlGaN/GaN HEMT with a low output current loss of 19.0% compared to the deep-gate-recessed device of 54%, which threshold voltage is about 2V. The ZrO2/HfO2 gate dielectric is chosen to confining the fluorine and improve the device stability. The effect of ZrO2/HfO2 gate dielectric annealing temperature on CF4 plasma treatment is investigated. At an appropriate annealing temperature of 400 degrees C, the threshold voltage can shift positive and maintain a low gate leakage current at a high gate voltage. The introduction of fluorine has less effect on the on-resistance and breakdown voltage. The results of high-resolution STEM EDS line scans and TOS-SIMS suggest significant limitations of fluorine. The interface state of device is extracted by capacitance-voltage (C-V) test and I-V pulse mode measurement. The device annealed at 400 degrees C has fewer shallow and deep traps than the device annealed at 500 degrees C, resulting in a lower gate leakage current and good reliability.