Structure And Terminal Design Of Alternating Isolated Oxide RC-IGBT

The development of the power semiconductor field is focused on high-power discrete devices,the typical structure of which is a bipolar power transistor and a thyristor.Insulated gate bipolar transistors(IGBTs)have been invented in response to the slow switching speed and large switching losses of these devices.RC-IGBT(Reverse Conducting Insulated-Gate Bipolar Transistor IGBT)is a new device structure derived from the development of IGBT.The structure is to use a part of the IGBT as a diode,and the two share the same substrate,thereby reducing The device size is also called a reverse conducting IGBT because the new device has the ability to forward and reverse the currentAlthough the RC-IGBT reduces the size of the device from the structure and reduces the cost,it brings about an inevitable voltage folding problem in the conduction process,which is called Snapback phenomenon in the industry.The existence of this problem affects the parallel conduction of the device,so that the device can not be turned on at the same time when it is turned on,which affects the device shunt,and thus there is a safety hazard in the circuit.In this paper,after studying the device structure and mechanism of RC-IGBT,an AO-RC-IGBT with alternating isolation structure of oxide trench is designed,which adopts the same trench as the front gate process.The etching technique forms an alternate oxidation cell structure on the back side of the device.The introduction of the oxidation cell structure increases the short-circuit resistance between the N+Collector and the P+Collector on the back of the RC-IGBT,so that the device can be normally guided during the conduction process.through.In order not to increase the process difficulty,the width of the oxidation groove and the width of the gate are completely identical.The effect of the aspect ratio of the oxidation cell on the Snapback phenomenon and the effect of the N+Collector and P+Collector doping lengths on the device characteristics between the oxidation cells were investigated.The results show that there is no Snapback problem in the design of the new structure,and compared with the traditional structure,the cell size is reduced by 2/3,and the device recovery loss is reduced by 30%.On this basis,the parameters of the new structure are optimized.Its electrical characteristics are superior to traditional structures.After completing the cell structure design of AO-RC-IGBT,a trench type termination structure is given for the withstand voltage problem of the power device.The trench structure manufacturing process and the front gate structure are simultaneously performed,Simple manufacturing process,reduced chip area,and uniform electric field at the edge of the chip compared with the conventional one.The trench type terminal has obvious improvement on the blocking voltage.When the terminal area is the same,the blocking voltage is compared with the field limiting ring and the field plate combined structure.It is nearly 400V higher.