Electro-thermal Characteristics Of IGBT

Insulate Gate Bipolar Transistor (IGBT) is a Darlington structure which composed by MOSFET and bipolar power transistor. It has many advantages, such as MOSFET's high input impedance, low power gate drive, simple drive circuit, high switching speed, bipolar transistor's high current density capability, low saturation voltage, high current processing capability. And it is an idea power device to meet the developing trend of many high voltage, high current and high switch speed. It is necessary of modularization for IGBT. At present, electro-thermal behaviors of module are main factors for the development of IGBT. So the primary work of this paper is the research of electro-thermal characteristics of IGBT. The main results were given as follows:Firstly, the structure and working principle of IGBT was presented, and the solution scheme of latch up effect also was proposed in the working condition of the device. Then the design scheme of the process model was established. The electrical parameters were set for choosing a suitable doping concentration and thickness. Then threshold voltage, breakdown voltage, turn-off time and switching time were simulated using Tsuprem4 and Medici software. The results were consisted with related parameters.Secondly, the two-dimensional temperature distribution model of IGBT in thermal stability was developed by solving the heat diffusion equation. Then the calculation formula of thermal resistance was given based on this model. It is a precondition for the formula of chip temperature, which was proposed by solving the formula of the power dissipation. Additionally, a method for determining chip temperature was given using the set process parameters when the temperature could not be measured.Lastly, the critical conditions of IGBT in the condition of thermal stability were discussed based on the two-dimensional temperature distribution model and the electric model. Furthermore, the relationship between thermal stability factors and temperature, gate voltages, thermal resistance, p-well doping concentration also has been investigated. The predictions of the model are consistent with those of two-dimension numerical simulator MEDICI.