Research On Physical Model And Novel Structures Of High Speed LIGBT Devices

Lateral Insulated Gate Bipolar Transistor（LIGBT）has a series of advantages such as low drive power consumption,high current density and reduced conduction voltage due to its conductance modulation effect.However,there are some disadvantages such as large tail current and slow turn-off speed at turn-off stage.The shorted anode（SA）LIGBT introduces an anode short-circuit structure on the anode side,which effectively solves the problem of large turn-off loss.However,the snapback phenomenon will occur at forward conduction stage.In order to solve the above problems,this thesis first introduces the working mechanism and characteristics of LIGBT,then the physical mechanism of snapback is discussed and studied,and the following three novel devices are proposed.1.A SA LIGBT integrating LDMOS（Laterally Diffused Metal Oxide Semiconductor）and LIGBT is proposed.The device mainly has the following characteristics:an independent LDMOS region and LIGBT region are integrated in the new device.The unipolar mode and bipolar node are separated into two different regions to achieve.Therefore,the snapback phenomenon that occurs when the two modes transform is avoided.At turn-off stage,the N+anode of the LDMOS region can extract some excess carriers in the drift region,which relieves the tailing current phenomenon at turn off stage.The simulation results show that at the same V_onof 1.2 V,the E_offof the MRC LIGBT reduced by 58%and 10%compared with those of conventional LIGBT and VPN LIGBT,respectively.At the same E_offof 1.3 m J/cm²,the V_onof MRC LIGBT is 9%lower than that of the conventional LIGBT.2.A LIGBT with multiple passageway and current plugs is proposed.The main features of the device are:three separated and parallel p-type current plugs（MCP）are introduced below the P+anode.At forward conduction stage,three current plugs deplete the electron channels in unipolar mode,which increases the anode distribution resistance.Thus,the snapback phenomenon is efficiently suppressed.At turn-off stage,the electrons in the drift region can be quickly extracted by the N+anode through three electron channels,which can ensure that the device has good turn-off characteristics.The simulation results show that at the same V_on,the E_offof the new device is reduced by 45%,22%and 14%compared with those of VPN LIGBT,SSA LIGBT and NCA LIGBT,respectively;at the same the V_on,the new device is decreased by 41%,18%and 12%compared with those of VPN LIGBT,SSA LIGBT and NCA LIGBT,respectively.Therefore,the new device achieves a good tradeoff between on-stage voltage drop and turn-off loss.3.A LIGBT with a controlled barrier layer and polysilicon resistance is proposed.The main features are:the p-type floating layer and polysilicon layer are introduced on the anode side,and the dielectric isolation layer under the polysilicon layer divided the drift region into two parts.When conducting,the electron current can only flow to the N+anode through the P-type floating layer and polysilicon layer.By adjusting the doping concentration of the P-type floating layer and the polysilicon layer,the height of the electron barrier and the resistance value of the electron path can be changed,respectively.Thus,the snapback phenomenon can be eliminated,and the tradeoff between the forward conduction and turn-off loss can be optimized.The simulation results show that the E_offof the new device is 73%lower than that of the conventional LIGBT under the premise of keeping a certain V_on;at the same E_off,the V_onof the new device is 24%lower than that of the conventional LIGBT.