Development of High-Temperature, High-Power, High-Efficiency, High- Voltage Converters Using Silicon Carbide (SiC) Delivery Order 0003: SiC High Voltage Converters, N-Type Ohmic Contract Development for SiC Power Devices

摘要

The durability and reliability of metal-semiconductor contacts are two of the main factors limiting the operational high-temperature limits of SiC electronic devices. To date, nickel (Ni) has been the most widely used metal for ohmic contacts to n-type SiC. The way to make smooth Ni-silicide/SiC interfaces and silicide top surfaces is important for producing uniformly low contact resistances to achieve device operation at high-current levels without hot spot formation and contact degradation. For as-deposited single Ni thin layers, agglomeration of Ni-silicide after annealing can happen depending on the conditions of deposition and thermal annealing processes. This is mainly due to the residual stress on the Ni films after deposition on SiC with a significantly lower coefficient of thermal expansion. Typically, an additional stress reduction layer, such as titanium, is deposition on top of the Ni thin contact film to prevent silicide agglomeration. The objective of this Delivery Order Task was to study and develop a process to produce robust, smooth ohmic contact, with low contact resistivity, to n-type SiC for high power, high temperature, and harsh radiation environments.