SBIR-STTR Award

In 2014, approximately ~120,000 plug-in electric vehicles (PEV’s) were sold in the US alone, representing a 23% increase from 2013 and a 128% increase from 2012 and nearly 1/3 of the PEV’s sold worldwide, making the US the largest market for PEV and HEV adoption. It is expected that by 2023, there will be ~3.2 million PEV’s on the road in the U.S. alone. The EV Everywhere initiative has set the goal to make electric vehicles as affordable as gasoline vehicles by 2022. To meet the goals of the EV Everywhere initiative, the primary efforts lie in reducing costs for the batteries, PM motor and electric drive train while simultaneously reducing weight. Increasing the drive train conversion efficiency has a significant impact as it extends battery life, vehicle range and allows for a reduction of heavy cooling components through the reduction of heat generating losses. Therefore much attention is placed on increasing the efficiency of the traction power inverter that drives the electric motor. It is well documented that inverter efficiency and power density can be increased while simultaneously reducing weight through the use of Silicon Carbide (SiC) wide bandgap semiconductors. For example, demonstrations of inverters utilizing SiC-JFETs and SiC-MOSFETs are emerging, where the efficiencies are reaching >99% with 10X increased power densities. However, today’s electric vehicle motor drive applications require high current (200-400A) power modules. SiC devices have been limited to lower current (<50A) due to the material defects, lower yields and higher costs associated with large area devices. For the electric vehicle traction inverters, it is of great interest to push up the SiC device current to 100-200A per device to make full use of the SiC system. Material defect densities have dropped dramatically in recent years as the commercial acceptance of the SiC Schottky diode have driven higher volume and more state-of-the-art semiconductor fabrication. To address topic 14b, USCi proposes in Phase I to fabricate 100A 650V SiC Cascode Switches on 6” diameter wafers. The large area high current cascodes will be packaged in a stack format resulting in a very high power density potential. In Phase II, the cascodes will be packaged to assess performance with advanced high density modules. When integrated, the SiC cascodes will increase the efficiency of electric motor power conversion from the battery to the drive train. In Phase II, the goal will be to qualify the high current cascodes on the system level for automotive applications. Key Words: Silicon Carbide, Cascodes, Electric Vehicle, Inverters, High Current

Advanced power electronics are needed to realize cost and weight reductions which will make electric vehicles as affordable as gasoline powered vehicles. In this program, SiC switches are being developed as they are the key component to enable the electronics needed to meet this need. In 2016, over 700,000 plug-in electric vehicles were sold, which includes a 30% and 100% increase from 2015 in the leading EV markets of US and China respectively. It is expected that by 2023, there will be ~3.2 million plug-in electric vehicles on the road in the U.S. alone. The EV Everywhere initiative has set the goal to make electric vehicles as affordable as gasoline vehicles by 2022. To meet the goals, the costs for batteries, motor and electric drive train must be reduced while simultaneously reducing weight. Increasing the drive train conversion efficiency has a significant impact as it extends battery life, increases vehicle range and allows for a reduction of heavy cooling components through the reduction of heat generating losses. Therefore, increasing the efficiency of the inverter that drives the electric motor is needed and it is well known that inverter efficiency and power density can be increased while simultaneously reducing weight through the use of silicon carbide (SiC) devices. Electric vehicle motor drive applications require high current power modules while cost effective SiC devices have been limited to lower currents (<50A) due to the material defects, lower yields and higher costs associated with large area devices. It is now possible to develop and manufacture higher current devices cost effectively as the material quality of SiC wafers has improved dramatically and the use of the foundry model is enabling the cost effective production of 150 mm wafers in automotive certified fab. 650V, 100A switches are being developed to meet the needs of existing automotive applications with a bus voltage in the 400V range. To address topic 14b, 650V, 100A SiC cascode switches fabricated in a 6”, automotive certified wafer foundry were demonstrated in Phase I. The Phase I wafer lot demonstrated that the high process yield can lead to low cost production. Devices were characterized and tested and initial samples assembled for engineering evaluations. Discussions with tier 1 automotive companies have also provided insight into application and packaging requirements to help guide Phase II development. In Phase II, multiple lots of cascodes will be fabricated to produce a large number of samples which will be passed through rigorous automotive reliability testing. These lots will demonstrate the process yield, provide samples for qualification testing, and samples for evaluation by our automotive industry partners. The cascodes will be built using high through put, low cost production processes. Full device qualification for automotive use will be performed. When integrated into inverters, the SiC cascodes will increase the efficiency of electric motor power conversion from the battery to the drive train enabling higher performance, lower weight, lower cost electric vehicles.