The Effect of the Doping Concentration in the Anode Region on the Voltage Temperature Coefficient of the FRD Chips

Fast Recovery Diode chips are widely used in power systems, often employed in reverse parallel packages with Insulated Gate Bipolar Transistor chips. Due to the growing demand for increased power system equipment capacity, there has been a corresponding rise in the requirement for the amount of FRD chips in IGBT devices. Consequently, the issue of parallel current evenness of FRD chips has garnered greater attention. Traditional FRD chips exhibit a negative voltage temperature coefficient, which can result in “current-heat” negative feedback due to uneven current distribution when operated in parallel and may lead to chip failure under severe conditions. To address this problem, a method is presented in this paper to optimize the forward voltage temperature coefficient of FRD chips by analyzing carrier concentration distribution and mobility distribution within the drift region through establishing FRD chip simulation models. This method involves reducing the anode doping concentration as a means of regulating the voltage temperature coefficient of FRD chips. Based on this approach, the 3300V 1125A FRD chips are fabricated and tested. It demonstrates less than 15% deviation between measured results and simulated results for room temperature forward voltage, high temperature forward voltage and voltage temperature coefficient, thereby validating the effectiveness of the proposed method.