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

这个小型企业技术转移(STTR)第一阶段项目解决了碳化硅(SIC)功率MOSFET技术的主要障碍之一。由于碳化硅优异的材料性能，碳化硅功率MOSFET在提高功率转换器的效率和降低成本方面具有巨大的潜力。遗憾的是，由于高的沟道电阻和阈值电压的不稳定，它们并没有发挥出它们的潜力。这些限制主要是由于碳化硅和二氧化硅之间的界面质量差造成的。最先进的栅氧化物形成工艺实现了适度的沟道迁移率，并表现出阈值电压的不稳定性。这项研究的目标是开发一种替代栅氧化物处理技术，该技术将在消除不稳定性的同时实现显著更高的沟道迁移率。最初的研究将集中在测试结构上，以研究潜在的技术，并了解导致机动性差和不稳定的机制。一旦最有希望的技术被确定和优化，它将被用于制造碳化硅功率MOSFET。凭借更高的沟道迁移率和稳定的阈值电压，这一新工艺有望实现碳化硅功率MOSFET技术，与当今的电力系统相比，这将带来更便宜、更紧凑、效率更高的功率转换器。该项目对功率转换器的广泛影响/商业潜力是相当深远的，功率转换器是许多系统的关键组件，如光伏逆变器、电力逆变器、电机驱动器等。现有的转换器使用具有高开关损耗的硅IGBT。与硅IGBT相比，碳化硅MOSFET具有更低的开关损耗，但目前可用的碳化硅MOSFET过于昂贵，其可靠性尚未得到验证。该项目可以实现可靠、经济的碳化硅功率MOSFET。低损耗的碳化硅MOSFET使功率转换器具有更高的效率。由于开关损耗较低，SIC MOSFET还将实现更高频率的功率转换，从而实现更紧凑的功率转换器，从而减少其他无源元件所需的材料。较低的损失还会导致系统中产生的热量减少和冷却成本的降低。总体而言，这将降低电源转换器的成本。更低的损耗和更便宜、紧凑的电力转换器将特别有利于可再生能源发电和电动汽车，从而直接减少温室气体排放，并为社会带来相关好处。

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.