Verification of ruggedness and failure in LDMOS under UIS

This paper presents the mechanism of unclamped inductive switching (UIS) failure on laterally diffused metaloxide-semiconductor (LDMOS). TCAD Simulations for more than hundred finger devices and analytical solution reveal the criteria for device stability during UIS test. It focuses on the problems that affect the stability and ruggedness of the device and the ways to improve them. This paper takes into account that the device stability depends on the negative value of partial differentiation of diffusion current density with respect to temperature. It is well known fact that variation in drain dose affects the diffusion current in turn varying the stability of the device. Power device ruggedness has been characterized based on the value of lambda (λ) that is proportional to the avalanche current. The improvement methods for the device using design variation are also discussed.