Study On The Failure Characteristics Of The IGBT Module

Insulate Gate Bipolar Transistor (IGBT) is a Darlington structure composed byMOSFET and bipolar power transistor, which has many advantages, such as high inputimpendence, fast speed, well thermal stability,simple drive circuit; and low saturationvoltage, high withstand voltage, high current density capability and so on. Therefore it isusually applied for the circuit of inductive loading with high voltage and heavy current.The IGBT when they were in the work would sustain enormous electronic effect andthermal stress. With the widely application of the IGBT device, the breakdown ofequipments caused by the failure of devices leading to the economic losses is incalculable.And therefore, the study of the failure characteristic for IGBT would have very importantapplication significance.This paper is based on the deep-understanding of fundamental theory、workingcharacteristic of IGBT device and basic theoretical knowledge of failure for IGBT,focusing on analyzing the factors of over-voltage failure of IGBT devices and failuremechanisms. Use the computer simulation software-Silvaco to build simulation models,and simulate the forward blocking and dynamic turn-off characterizes for IGBT models.By analyzing the forward breakdown, we could find that the carrier density effectivelyconcentrated around the PN junction which had the outbreak of avalanche breakdown inthe device, current density、lattice heating and joule heat go up w ith the rising offorward blocking; by analyzing the characterizes of dynamic turn-off, we have observedthat the effective concentration of current especially in the period of occurring thedynamic avalanche breakdown-filament current. From the perspective of heat andenergy I find that the essence reasons of over-voltage breakdown failure is thermalfailure induced by cumulated heat inducing the rising of junction-temperature throughthe view of energy, and would cause the burning cracks on the surface of the chip. Aftercomparing with the actual IGBT chip which had occurred the over-voltage failure, wefind that the theoretical analysis are consistent with practical results。And at last, judgingfrom the theories and simulation, I find several methods to reduce over-voltage failurefor the IGBT, such as appropriately increasing the values of gate resistance and improving the environment temperature for the using of IGBT and so on, basing on theupon methods, we could put forward several improvement measures in theory to resistthe over-voltage failure for IGBT, in order to improve the technology and properapplication.