Study On New Structure And Mechanism Of High Voltage And Low Loss IGBT Devices

The power semiconductor device IGBT（Insulated Gate Bipolar Transistor）,which is known as the core of power electronic devices and systems,has many advantages such as small on-state loss,large breakdown voltage（BV）,low driving power,high input impedance,low power loss and so on.Especially LIGBT（Lateral IGBT）device is used in intelligent power integrated circuits because of its easy integration.The bipolar device LIGBT has a very low on-state voltage drop(V_on)due to the strong conductivity modulation effect in the drift,but at the same time it also burdens the turn-off,resulting a longer current tailing time and larger turn-off loss(E_off),so there is a contradiction relationship between E_off and V_on of the LIGBT device.In order to speed up the turn-off of the LIGBT and thus reduce E_off,a short anode structure is introduced,but it also brings a new problem which is called voltage snapback effect.In order to deal with the above problem,this article will provide two new LIGBT devices.1.A novel 600V snapback-free high-speed silicon-on-insulator lateral insulated gate bipolar transistor is proposed and investigated by simulation.The proposed device features an embedded NPN structure at the anode side,and double trenches together with an N-type Carrier Storage（N-CS）layer at the cathode side,named DT-NPN LIGBT.At the forward conduction stage,the NPN structure acts as an electron barrier and hinders the electron from flowing through the N+anode directly to eliminate the snapback effect in the on-state within a smaller cell pitch.During the turn-off stage,the shallow P-well is fully depleted by the high anode voltage and the electron could sweep rapidly,and then E_off decreases.The double cathode trenches and N-CS layer hinder the hole from being extracted by the cathode quickly.Then they enhance carrier storing effect and lead to a reduced V_on.Hence,the DT-NPN LIGBT obtains a superior tradeoff between the V_on and E_off.The DT-NPN LIGBT exhibits an improved blocking capability and weak dependence of BV on the P+anode doping concentration,since the NPN structure suppresses triggering the PNP transistor.Additionally,the latch-up immunity is improved by the hole bypass of the double cathode trenches.The proposed LIGBT reduces the E_off by 55%at the same V_on,and improves the BV by 7.3%compared to the conventional LIGBT.The implantations for N-CS and N-buffer layer are implemented at the same time to achieve better performance without more cost.2.A shorted-anode LIGBT device with segmented P-type buried layers is proposed.The proposed device features the segmented P-type buried layers below the anode.At the forward conduction state,the segmented P-type buried layers extend the path of the electron flowing to the N+anode region and thus increase the anode distributed resistance,eliminating the snapback effect effectively.During the turn-off process,the N-type doped gap between segmented P buried layers provides a low-resistance path to rapidly release electrons stored in the drift region,and finally this proposed device effectively alleviates the contradiction relationship between E_off and V_on.In the forward blocking state,the proposed device exhibits a blocking mechanism like power LDMOS and a higher BV value,because the electron current flows through the N type doping gap between segmented P buried layers to the N+anode,and the voltage drop cannot turn the P+\N-buffer junction on suppressing the hole injection.In addition,an improved device is proposed which furthers a P-type buried layer at the cathode side to improve the latch-up and short-circuit immunity.Simulation results show that the E_offff value of the proposed LIGBT is lower 13.2%than that of CON LIGBT at the same V_on.Meanwhile,the proposed LIGBT realizes 37%reduction in the V_on at the same E_offff compared with SSA LIGBT.