Papers by Keyword: MOS Reliability

Abstract: Low-temperature post-oxidation annealing (POA) process of high-reliability thermal oxides grown on 4H-SiC using new apparatus that generates atomic hydrogen radicals by high-temperature catalyzer has been investigated. Atomic hydrogen radicals were generated by thermal decomposition of H2 gas at the catalyzer surface heated at high temperature of 1800°C, and then exposed to the sample at 500°C in reactor pressure of 20 Pa. The mode and maximum values of field-to-breakdown are 11.0 and 11.2 MV/cm, respectively, for the atomic hydrogen radical exposed sample. In addition, the charge-to-breakdown at 63% cumulative failure of the thermal oxides for atomic hydrogen radical exposed sample was 0.51 C/cm2, which was higher than that annealed at 800°C in hydrogen atmosphere (0.39 C/cm2). Consequently, the atomic hydrogen radical exposure at 500°C has remarkably improved the reliability of thermal oxides on 4H-SiC wafer, and is the same effect with high-temperature hydrogen POA at 800°C.

Abstract: Gate oxide reliability measurements of 4H-SiC DMOSFETs were performed using the Time Dependent Dielectric Breakdown (TDDB) technique at 175°C. The oxide lifetime is then plotted as a function of the electric field. The results show the projected oxide lifetime to be > 100 years at an operating field of ~3 MV/cm. Device reliability of 2.0 kV DMOSFETs was studied by stressing the gate with a constant gate voltage of +15 V at a temperature of 175°C, and monitoring the forward I-V characteristics and threshold voltage for device stability. Our very first measurements show very little variation between the pre-stress and post-stress conditions up to 1000 hrs of operation at 175°C. In addition, forward on-current stressing of the MOSFETs show the devices to be stable up to 1000 hrs of operation.

Abstract: The effects of dislocations in n-type 4H-SiC(0001) epitaxial wafers on the reliability of thermal oxides have been investigated. Charge-to-breakdown (QBD) values of thermal oxides decrease with increase in the dislocations under a gate-oxide area. Nomarski microscope observations show that dielectric breakdown of thermal oxides occurs at the position of dislocation in epitaxial layer. It is reavealed that basal plane dislocation is the most common cause of the dielectric breakdown.