Potential of 4H-SiC CMOS for High Temperature Applications Using Advanced Lateral p-MOSFETs

Abstract

In this work, the impact of the n-well doping concentration on the channel mobility and threshold voltage of p-MOSFETs and their applications in CMOS-devices is evaluated. For this purpose lateral p-channel MOSFETs with different channel lengths (L = 800 μm, 10 μm, 5 μm, and 3 μm) and doping concentrations (ND = 1015 cm-3 and 8·1015 cm-3) were fabricated and the respective field-effect mobility was extracted from the transfer-characteristics. Comparable to n-MOSFETs the mobility of p-MOSFETs was found to be the highest for the lowest doping concentration in the channel and the absolute value of the threshold voltage increases with increasing doping concentration [4]. To investigate its suitability for CMOS applications, inverters with different doping concentrations for n-MOSFET (NA = 1015 cm-3 and 1017 cm-3) und p-MOSFET (ND = 1015 cm-3 and 8·1015 cm-3) were built. For logic levels of 0 V and 10 V, the voltage transfer characteristic with the highest input ranges was obtained for a low p-MOSFET and a high n-MOSFET doping concentration. The lowest propagation delay time could be achieved with a low p-MOSFET and a low n-MOSFET doping concentration. At room temperature as well as at high temperatures T = 573 K the drain current of p-MOSFETs with channel lengths below 3 μm is hampered by the series resistance of the source and drain region which limits the performance of CMOS devices.