Study Of Double-line Breakdown Phenomenon For Power Transistor With SIPOS Passivation Layer

Power transistor with SIPOS passivation layer uses multilayer surface passivation technology which are Semi-Insulating oxygen-doped Polycrystalline-Silicon and SiO₂ passivation layers. As a new passivation technology used on the Si Substrate, Semi-Insulating oxygen-doped Polycrystalline-Silicon(SIPOS) film can shield external electric field effectively and protect electrical stability of the device. SIPOS film also improves SiO₂ film's disadvantage which masks Na⁺ and other alkali metal ion badly, has interface effect between SiO₂—Si and can easily store avalanche hot carriers. So power transistor can get a higher breakdown voltage because of the use of SIPOS passivation layer.Some batches of power transistor with SIPOS passivation layer was found that the curve of breakdown voltage was abnormal phenomenon during testing phase which was"Double-line"breakdown voltage curve. The transistors with this abnormal phenomenon took 90% of the whole wafer and this abnormal phenomenon caused early failure which seriously affected product's yield.Aiming at"Double-line"breakdown voltage curve's phenomenon of power transistor with SIPOS passivation layer, this paper analyzed structure and preparation process of power transistor with SIPOS passivation layer ,as well as SIPOS film's characteristics and mechanism of passivation. Erode each layer of power transistor with SIPOS passivation layer and test its breakdown voltage in accordance with the structure of power transistor. Find the result of test without"Double-line"breakdown voltage curve's phenomenon after eroding SIPOS film. Get a result that oxygen content is about 45% in SIPOS layer exceeding the standard approximately 10% through elements spectrum analysis to SIPOS layer, and also discuss the relationship between QT-2 transistor characteristics testbench and"Double-line"breakdown voltage curve's phenomenon.The results show that seriously exceeding oxygen content in SIPOS layer can make SIPOS layer come out SiO₂'s characteristics, and cause interface effects at SIPOS-Si, which are primary causes of"Double-line"breakdown voltage curve's phenomenon. And there is a stable"Double-line"breakdown voltage curve in the QT-2's display when the empting time of interface traps is longer than the saturation time of interface traps and the scanning time of QT-2 is longer than both of them.