Acceleration Factors in Acceleration Life Test of Thermal Oxides on 4H-SiC Wafers
Acceleration factors in acceleration life test of thermal oxides grown on 4H-SiC(0001) wafers and influences of dislocations on oxide reliability have been investigated using time-dependent dielectric breakdown measurements. The thermal oxides are formed by dry oxidation at 1200°C followed by annealing in nitrogen atmosphere. Then, post oxidation annealing in wet ambient at 950°C or hydrogen atmosphere at 800°C were carried out for some of the oxides. Aluminum or poly-Si films with thickness of 300 nm were formed as gate electrodes. The temperature dependence of time-to-breakdown (tBD) indicates that activation energy (Ea) values for the Al-gate and Poly-Si-gate thermal oxides are 0.59 eV - 0.79 eV and 0.34 eV - 0.72 eV, respectively. Analyzing the electric field dependence of tBD, it was indicated that the values of electric acceleration parameters (β) are 2.7 cm/MV - 7.0 cm/MV and 5.8 cm/MV - 7.1 cm/MV for the Al-gate and poly-Si-gate thermal oxides, respectively. In addition, the charge-to-breakdown decreases with increase in the density of basal plane dislocation.
N. Wright, C.M. Johnson, K. Vassilevski, I. Nikitina and A. Horsfall
J. Senzaki et al., "Acceleration Factors in Acceleration Life Test of Thermal Oxides on 4H-SiC Wafers", Materials Science Forum, Vols. 556-557, pp. 635-638, 2007