SPIRAL JUNCTION TERMINATION

A new junction termination structure composed of a decreasing width sp iral diffused resistor connecting anode and cathode region Is presente d. Leakage current through the spiral resistor results in optimized vo ltage distribution between the spiral turns which effectively reduces high electric field at the anode junction curvature, By circuit mode d evice modeling approach, the influence of several design parameters of importance on the breakdown properties were investigated. A major con cern has shown to be the possibility of a premature reach-through betw een the spiral turns, resulting in increased leakage current and soft breakdown characteristics. A design with nonuniform spiral width and o ptimized spacing between the spiral turns is proposed, enabling almost ideal breakdown voltages,vith reduced spiral leakage current and elim inated reach-through between the spiral turns, Low susceptibility to o xide charges is confirmed by irradiation test, showing improvement of breakdown properties after irradiation, Further improvement in operati on is obtained by a floating spiral structure due to spiral resistance limiting the increase of the multiplication induced current through t he spiral. In comparison with common termination structures the spiral junction termination offers simple design and processing, close to id eal breakdown voltages and high reliability of operation.