STTR Phase I: High-Reliability SiC power MOSFETs for Energy Efficient Power Electronics Infrastructure

This Small Business Technology Transfer (STTR) Phase I project addresses one of the key roadblocks for Silicon Carbide (SiC) power MOSFET technology. SiC power MOSFETs have huge potential of increasing efficiency and reducing cost of power converters due to superior material properties of SiC. Unfortunately, they have not fulfilled their potential due to high channel resistance and instability of threshold voltage. These limitations are primarily due to poor quality of the interface between SiC and silicon dioxide. State-of-the-art gate oxide formation processes achieve moderate channel mobility and demonstrate instability of threshold voltage. The objective of this research is to develop an alternate gate oxide processing technique that will achieve significantly higher channel mobility while eliminating the instabilities. Initial studies will focus on test structures to study potential techniques and to gain understanding into the mechanism that cause poor mobility and instability. Once the most promising technique is identified and optimized, it will be used to fabricate SiC power MOSFETs. With higher channel mobility and stable threshold voltage, this new process is expected to enable SiC power MOSFET technology that will result in cheaper and more compact power converters with higher efficiency compared to today's power systems. The broader impact/commercial potential of this project is quite far reaching for power converters which are a critical component in many systems like the photovoltaic inverter, electric inverter, motor drives, etc. Existing converters use silicon IGBTs which have high switching losses. SiC MOSFETs have significantly lower switching losses compared to silicon IGBTs but currently available SiC MOSFETs are too expensive and their reliability has not been proven yet. This project can realize reliable and affordable SiC power MOSFETs. Lower losses of SiC MOSFET result in power converters with higher efficiency. Due to lower switching losses, SiC MOSFETs will also enable higher frequency power conversion which results in more compact power converters that need less material for other passive components. Lower losses also result into less heat generation and reduction in cooling costs in a system. Overall, this will reduce the cost of power converters. Lower losses and cheaper, compact power converters will particularly benefit renewable energy generation and electric vehicles resulting in direct reduction of greenhouse gas emission and associated benefits to the society.