Characterization of non-uniform Ni/4H-SiC Schottky diodes for improved responsivity in high-temperature sensing

Abstract

The development of high-temperature sensors (up to 450 °C), based on SiC Schottky diodes, which are able to work in harsh conditions, requires using high-barrier Schottky contacts, such as nickel silicide. It is well known that post metallization annealing, targeting silicide formation, leads to Schottky barrier height (SBH) non-uniformity on the contact surface. On the other hand, sensor performances are intimately tied to the value and stability of SBH. This paper discusses solutions for assessing temperature sensing performances of inhomogeneous SiC Schottky diodes, particularly targeting high-temperature, harsh industrial applications where conventional solutions are unreliable. Microphysical investigations and electrical measurements are carried out on Ni/4H-SiC Schottky diodes with varying levels of non-uniformity. Devices are characterized using SEM and EDX analyses, together with electrical parameter evaluation techniques. It is demonstrated that, despite highly inhomogeneous electrical behavior, SiC-Schottky diodes exhibit stable sensitivity (up to 2.33 mV/°C) with excellent linearity (R2 > 99.9%) over wide temperature (up to 450 °C) and bias ranges (at least 100 nA–10 µA).