Design And Analysis Of Novel LIGBT With Fast-switching And Low Loss

Due to the advantages of small size,high reliability and green energy saving,the Insulated Gate Bipolar Transistor(IGBT),as an important Power Semiconductor Device(PSD),is widely used in new energy,electric locomotives and smart grids.With its excellent conduction performance and integration characteristics,lateral IGBT(LIGBT)is expected to become an important part of intelligent power integrated circuits in the future,so as to reduce the overall power consumption of circuit modules and provide more efficient product performance."Fast" in fast-switching and low-loss LIGBT means fast turn-off speed."Low-loss" means low turn-on and turn-off losses.When the LIGBT is turned on,the conductivity modulation effect produced by excess carriers in the drift region brings low on-resistance and low forward voltage drop.When the LIGBT is turned off,the long recombination process produced by a large number of excess carriers also brings long turn-off time and high turn-off loss.It shows that there is a contradictory relationship between turn-on loss and turn-off loss.As one of the main problems in the design of the LIGBT,this paper improves the trade-off relationship between the forward voltage drop and the turn-off time or loss,which finally achieves fast-switching and low-loss device performance of devive.This paper starts from two ideas to optimize the compromise between forward voltage drop and turn-off speed of the device: One is improving forward conduction performance,and that is adjusting the charge storage effect of excess carriers in the drift region of device conduction process.By studying the electric field modulation technology,the electric field and carriers distribution of the device are improved,and the resulting performance optimization includes directly improved breakdown voltage capability and indirectly optimized forward and turn-off characteristics,and then establishes electric field and potential distribution model,so as to design and analyze three novel LIGBT with electric field modulation for fast-switching and low-loss,including the novel PBAD LIGBT(P-Buried layer and Assisted Depletion N-region,PBAD),the novel SSBO LIGBT(Single Step Buried Oxide,SSBO)and the novel BPSOI LIGBT(Buried Partial Silicon-On-Insulator,BPSOI).Second is improving turn-off performance,and that is enhancing controlling ability of the rapid extraction of excess carriers at the moment of breakdown.Through the research on the shorted-anode technology,the advantages of the shorted-anode structure to accelerate electron extraction are clarified,and the inhibition of the current tailing phenomenon during the turn-off process is beneficial to the improvement of the turn-off speed,and then the shorted-anode model of turn-on and turn-off are established,so as to design and analyze three kinds of shorted-anode novel LIGBT for fast-switching and low-loss,including novel TBSA LIGBT(Trench Barriers and Shorted-Anode,TBSA),novel ASTC LIGBT(Anode Schottky Trench Contact,ASTC)and novel EGSA LIGBT(Electron-controlled Gate and Schottky Anode,EGSA).The main innovations and work contents of this paper are as follows:The electric field modulation technology can improve breakdown voltage by optimizing the horizontal and vertical electric field distribution of the device,thereby indirectly shortening the length of the device under the same voltage level.The established electric field and potential distribution model demonstrate the basic principle of electric field optimization.The analysis results show that small-sized LIGBT can accelerate the depletion process of the drift region by reducing the number of excess carriers,so as to reduce the turn-off time,and at the same time low forward voltage drop is maintained under the effect of low resistivity by conductivity modulation.The influence on RESURF principle is realized by flexibly applying three main substrate types,including the bulk silicon substrate with non-buried layer,the bulk silicon substrate with buried layer,and the SOI substrate.Therefore,three novel fast-switching and low-loss LIGBTs based on electric field modulation mechanism are proposed and analyzed.The three novel LIGBTs have improved the breakdown voltage ability,which can achieve the purpose of shortening the effective length of the drift region under the same voltage level,and finally obtain faster turn-off speed and lower forward voltage drop.Three novel LIGBT structures based on electric field modulation technology include:(1)The novel PBAD LIGBT with P-type buried layer and assisted depletion N-type region.The bulk silicon substrate with different buried layers realizes the lateral and longitudinal electric fields with additional high electric field peaks and uniform distribution at the same time.(2)The novel SSBO LIGBT with single stepped buried oxide layer,the electric field peak will be generated at the stepped interface caused by the change of buried oxide layer thickness,so the lateral electric field of the device is optimized.(3)The novel BPSOI LIGBT with P-type buried layer and partial SOI buried layer,the electric field peak will be generated at the interface between P-type buried layer,P-type substrate and partial SOI buried layer,and the lateral electric field of the device will be further optimized.The shorted-anode technology reduces the concentration of non-equilibrium carriers at anode region by providing an additional electron carrier extraction path,and relieves the recombination pressure of electron-hole pairs at the moment of turn-off,so that it has a faster turn-off speed and can reduce the turn-off loss.For the shorted-anode structure,the conduction model for potential modulated voltage snapback shows that the voltage snapback phenomenon caused by the sudden change of the on-resistance can be completely suppressed.The charge-controlled turn-off model shows the change of the forward anode current and bias voltage of the device with time,which clarifies the advantages of shorted-anode structure in terms of device turn-off performance.By using three design ideas including providing fixed or variable anode resistance and increasing the turn-on potential difference of parasitic anode region can completely eliminate the on-state negative resistance region phenomenon.Therefore,three novel LIGBTs with fast-switching and low-loss based on the shorted-anode method are proposed and analyzed,and all of them achieve significantly improved trade-off characteristics between forward voltage drop and turn-off loss.Three novel LIGBT structures based on shorted-anode technology include:(1)The novel TBSA LIGBT features fixed anode resistance,which generates a narrow and long electron current channel by using trench barriers to form a fixed anode resistance.(2)The novel ASTC LIGBT features variable anode resistance uses the lateral space charge region formed by Schottky trench contact to introduce variable anode resistance as changing anode bias voltage.(3)The novel EGSA LIGBT features fixed anode turn-on voltage,and the electrons control gate gains lower turn-on loss of the circuit module.Maintaining the electric field in the low doped P-type substrate region is conducive to reducing the size of the circuit module.The highly doped N-buffer accelerates the formation of the depletion region,and the Schottky anode accelerates the turn-off process.In this paper,the effects of electric field modulation and shorted-anode technology on the optimization of conventional LIGBT are studied in detail.In terms of device conduction process,the advantages of the two ideas lie in the increase of on-state current density and on-state snapback-free.While in terms of device turn-off process,the advantages of the two ideas lie in the reduction of depletion region area and the acceleration of excess electrons extraction.Finally,the proposed six novel LIGBTs for fast-switching and low-loss have significantly improved the contradictory relationship between forward voltage drop and turn-off time or loss,so that can better meet the application requirements of medium and high voltage intelligent power integration.