The Investigation Of Characterisitics And Novel Structure Of Reverse-Conducting IGBT

Insulated Gate Bipolar Transistor(IGBT)is a kind of power semiconductor device which is widely used in all kinds of power electronic equipments;its performance has been approaching the theoretical limit of silicon-based devices in recent years.Si C based power semiconductor devices have been developed rapidly and have been widely used in photovoltaic inverters,new energy vehicle on-board chargers,and new energy vehicle motor drive inverters,it shows a good development prospect.However,Si C devices are still face with such prominent problems as low technology maturity and high cost.Derivative devices represented by RC-IGBT have received extensive attention from academia and industry in recent years.It is expected to replace IGBT in many applications,further improve the power density of devices and reduce the cost.In this paper,the development status and existing technical problems of RC-IGBT devices are systematically studied.A novel RC-IGBT device structure with a back gate is presented in this paper,it can solve the problem of output characteristic snap-back within a single MOS cell scale,and the reverse recovery performance of the diode can be effectively improved.Then,in view of the large difference between RC-IGBT and traditional IGBT in the operating mode,the negative gate capacitance characteristics of RC-IGBT devices were simulated and experimentally studied,and its unique negative gate capacitance characteristics were revealed.In the last part of the paper,a 750V high-current RC-IGBT chip is designed and taped out based on the trench gate field stop technology platform.The packaging and performance tests of the750V module show that the performance and reliability of the device basically meet the design expectations and preliminarily meet the application requirements.Specifically,the main work and research results of this paper include the following aspects:By sorting out and synthesizing the research status,the main problems of RC-IGBT device development are summarized.These problems include:snap-back characteristic of IGBT forward output characteristic,optimization of turn-off and diode reverse recovery characteristic,optimization of carrier concentration distribution in drift region,uniformity of carrier density and electric field distribution in transverse direction,the temperature characteristics of the device,the complexity of the process and the 3D device simulation problems,at the same time,the characteristics of the latest generation RC-IGBT devices are briefly introduced.A novel device structure,ATG-TB-RC-IGBT,is proposed.Its main characteristics include two aspects.Firstly,the back of the device adopts an open-trench gate structure,through which the back gate can effectively sense the external bias voltage to realize the self-control of the back gate.At the same time,it can effectively inhibit the snap-back phenomenon of the forward output characteristic within the scale of one cell,and obtain a uniform internal current density distribution in static and dynamic states.Secondly,the trench shielding structure and carrier storage layer structure are used to replace the heavy doping and deep P+anode structure in the traditional RC-IGBT structure,so that the shallow and light doped anode region can be used.Under the condition of no carrier life control measures,the voltage drop close to the nowadays independent fast recovery diode and better reverse recovery performance can be obtained.In this paper,the negative capacitance effect of RC-IGBT devices in different working modes is deeply studied.The simulation and experimental results reveal that for RC-IGBT devices with snap-back characteristics,when the turn-on load current I_C of the device is greater than the snap-back critical current,even though the device firstly goes through unipolar MOSFET conduction mode and then turns into bipolar IGBT conduction mode,the device will still show the negative capacitance effect as strong as conventional IGBT devices.Simulation analysis reveals that the physical mechanism is the built-in electric field,it will extract flow of electrons,but reject hole carrier,make its gathered around the gate oxide layer,which finally induced the negative capacitance in RC-IGBT devices.In this study,a 750V high-current RC-IGBT device sample was fabricated by single lithography and laser annealing on an 8-inch process line based on the trench field stop platform of the OEM.Then the RC-IGBT device was packaged and tested in the automotive half bridge module,the static and dynamic parameters of the device and the dynamic characteristics such as turn-on,turn-off and diode reverse recovery under different conditions were extracted.Finally,the reliability of the device is tested,and the results show that the device basically meets the design expectation and meets the application requirements.