Reverse Recovery Evaluation of Conventional and Super Junction MOSFET Body Diodes

摘要

MOSFETs with good body diode characteristics and ruggedness are needed in many high voltage switching applications. Super junction(SJ) charge balance concept devices [1,2] are gaining popularity as they have much lower Rdson compared to regular MOSFETs. However, one draw back of SJ devices has been the poor body diode reverse recovery characteristics. Early generation SJ devices had high reverse recovery current and failed during some reverse recovery events. Even though the body diode characteristics have improved over time, they are still not as rugged as conventional MOSFET body diodes. We show that competition SJ device body diodes fail during moderate di/dt conditions. Fairchild has used two dimensional numerical simulations in mixed mode circuit and device conditions to analyze what is happening inside the device during the reverse recovery transient. This has helped us understand the reasons behind the failure and have designed a rugged SuperFETTM SJ device. Reverse recovery measurements show that competitors SJ MOSFET body diodes fail at a di/dt of just 100A/μs where as SuperFETTM devices are virtually indestructible, surviving ＞1000A/μs.Fairchild has also introduced rugged SuperFETTM devices with fast recovery body diodes which have low Trr and Qrr.