4H SiC Lateral Single Zone RESURF Diodes

Abstract

Abstract : Silicon Carbide is an attractive material for development of high voltage and high frequency devices. The critical electric field of Silicon Carbide is more than 10 times higher than that of Silicon and hence a larger breakdown voltage can be supported in a smaller drift length as compared to Si devices. From Si studies it is known that the breakdown voltage is low for very high and very low doses and high for intermediate doses and that it increases linearly with the RESURF length till it reaches a maximum value limited by breakdown at the epi-substrate junction. This work deals with simulations on 4H SiC RESURF diode. From our simulations, the maximum breakdown voltage that we obtained was 2240V at a dose of 1x10 to the 13th power per cm square which is around 94% of the ideal parallel plane breakdown voltage. Electric field in the oxide at such high voltages can become quite high and can lead to premature breakdown of the device. To solve this problem, we used nitride as the dielectric. The optimum dose in this case, was found to be 7 x 10 the 12th power per cm square which gave the maximum breakdown voltage of 2100 V. The electric field in nitride does not exceed 3.5 x 10 to the sixth power V/cm which is much less than the nitride rupture field of 1 x 10 to the 7th power V/cm. For both oxide and nitride cases, we obtained a good range (7x10 to the 12th power/ sq cm - 2 x 10 to the 13th power/sq cm) of dose where the breakdown voltage is quite high (2000V and above), which is not seen in Si RESURF devices.