New design rule for high voltage field ring structure

High voltage Non-Punch-Through (NPT) IGBTs are used in inverters to drive electric vehicles, such as express trains and electric cars. In order to achieve an appropriate high breakdown voltage in a 3300 V IGBT used to operate express trains, edge termination of the 3300 V breakdown voltage must be realized because of reliability issues in high power devices. A 3300 V edge termination using the multiple floating field limiting ring method depends on many variable parameters, such as the ring width, ring depth, ring space, and ring doping concentration, to achieve the appropriate breakdown voltage. It is difficult to attain a high breakdown voltage up to 3300 V in silicon using a field ring structure because of the variable parameters and the limit of the critical electric field in silicon using the minimum area. The area of the edge termination region is an unnecessary area that leads to a loss of specific on-resistance. Therefore, in this paper, an unbalanced design method for a 3300 V IGBT field ring is proposed to comply with a 3300 V breakdown voltage in a minimum edge termination area, thereby reducing the specific on-resistance to 90.25%.