Development of RC-IGBT with a New Structure That Contributes to Both Reduced Size of Power Control Unit and Low Loss in Hybrid Electric Vehicles

In order to improve the fuel efficiency of Hybrid Electric Vehicles (HEVs), it is necessary to reduce the size and power loss of the HEV Power Control Units (PCUs). The loss of power devices (IGBTs and FWDs) used in a PCU accounts for approximately 20% of electric power loss of an HEV. Therefore, it is important to reduce the power loss while size reduction of the power devices. In order to achieve the newly developed PCU target for compact-size vehicles, the development targets for the power device were to achieve low power loss equivalent to its previous generation while size reduction by 25%. The size reduction was achieved by developing a new RC-IGBT (Reverse Conducting IGBT) with an IGBT and a FWD integration. As for the power loss aggravation, which was a major issue due to this integration, we optimized some important parameters like the IGBT and FWD surface layout and backside FWD pattern. As a result, it was possible to avoid the snapback characteristic (IGBT loss aggravation). In addition the substrate thickness was reduced by 24% compared to its previous generation. In order to address the deterioration of breakdown voltage due to a thinner substrate, the buffer layer structure was optimized to achieve the loss target while ensuring both high breakdown voltage performance and reliability. Parts reduction of the power module equipped with this new RC-IGBT greatly contributed to achieving downsizing and low power loss of the newly developed PCU, and helping the improvement of fuel efficiency for new compact-size HEVs.