3D TCAD Mixed-Mode Simulation of Current Filaments in IGBT Multicell Array under Short-Circuit Condition
Background
A power IGBT (Insulated Gate Bipolar Transistor) is conventionally made up of a repetitive array of homogenous IGBT cells. Such a homogenous configuration renders a uniform current flow across the active surface area of the IGBT chip when the IGBT is turned on. Under a short-circuit condition, however, the IGBT being turned on is exposed to a very high collector-to-emitter voltage. In this condition, the IGBT conducts a very high collector current, leading to correspondingly high power dissipation in the form of heat flowing uniformly across the chip. If the heating of the chip exceeds a critical level during a short-circuit operation, the device may fail or even get destroyed by local overheating in conjunction with the establishment of current filaments in a localized area, or the hot spots, within the device.
Modeling and Simulation
In cell mode of Victory Process an IGBT array consisting of 8 cells, as shown in Figure 1, is generated by joining 8 copies of the IGBT single cell together. This IGBT multicell array is uniform along its width of 40 µm. Each IGBT single cell is 20 µm long and features a 1.3 kV trench-gate design with a fieldstop layer (n-buffer) that consumes 16 µm out of the n-drift region thickness of 134 ¨µm. For the sake of convenience, the doping profiles of the cell structure are modeled with analytic functions.
