Research On Control And Integration Technology Of Novel Power Devices

As the core of power electronics technology,power semiconductor devices play a vital role in power control and conversion.Under the unremitting efforts of researchers and engineers,various types of power semiconductor devices are designed to meet different application fields.Compared with vertical discrete devices,lateral power devices have obvious advantage in process compatibility with low-voltage circuits.The Smart Power Integrate Circuit?SPIC?consisting of a lateral power device and a low voltage circuit has great advantages in the medium and low voltage range,which significantly improves the integration degree and stability of the power electronics system.Since lateral power devices require to sustain voltage and conduct large currents,they tend to occupy most of the chip area.Compared with LDMOS?Lateral Double-diffusion Metal-Oxide-Simeconductor?,LIGBT?Lateral Insulated Gate Bipolar Transistor?has higher current capability,higher power density and occupies a smaller chip area.But as the bipolar power device,the longer current tail limits its application in the high frequency field.In addition,when the load is an inductor,the LIGBT needs to be equipped with a freewheeling diode to conduct the reverse current.The lateral freewheeling diode needs the same drift region length as the LIGBT to sustain voltage,which also costs part of the chip area and introduces the parasitic effects.Under the guidance of Professor Chen Xingbi,I have carried out a series of researches aiming at the problems existing in the lateral power devices,and obtained some achievements in the control and integration of power devices.The main content is divided into the following aspects:1.A novel level-shifter integrated on the edge termination region of the high voltage device is proposed.An integrated structure consisting of LDMOS and p-i-n diode is used to level the low-side signal up to the high-side region.There is no high-voltage interconnection across the low-voltage region of the proposed integrated structure,thus the interconnection-induced breakdown is avoided.Meanwhile,the level-shifter can be integrated at the isolated terminal region,which saves the chip area.The simulation results verified the blocking capability and the level-shifting function of the integrated structure.2.A novel ultra-low turn-off loss SOI-LIGBT is proposed.A high-voltage p-i-n diode is integrated on the field oxide which is located upon the surface of the drift region.When the LIGBT is turning off,the gate signal of the device can be transmitted to the anode-side by the high-voltage p-i-n diode to short the emitter junction?P-anode/N-buffer?.Thus,the injection of the holes from P-anode region into the N-drift region is prevented,and the turn-off speed of the proposed LIGBT is significantly improved.It is verified by simulation that compared with the conventional LIGBT at the same breakdown voltage level,the turn-off loss of the novel LIGBT is only 43.1%of the normal device at V_on=1.38 V.3.Two kinds of snapback-free reverse conducting SOI-LIGBTs are proposed.The first is an improvement over the previously proposed structure.An n-MOSFET is embedded in the anode side of the LIGBT to short the emitter junction?P-anode/N-buffer?during the turn-off transient,thus allowing the LIGBT to be turned off rapidly without excessive tail current and conduct the reverse conducting current.In the forward-conducting state,the n-MOSFET is turned off,then the RC-LIGBT operates like a conventional one and the snap-back is avoided.The gate electrode of n-MOSFET can be controlled synchronously by the gate signal of the LIGBT,and therefore,the RC-LIGBT still maintains a three-terminal configuration.The turn-off loss and reverse recovery charge of the RC-LIGBT is reduced by 58.3%and 38.9%,respectively,compared with the conventional LIGBT and the freewheeling diode.The second kind of RC-LIGBT is based on an anti-parallel Schottky diode connecting the emitter junction?P-anode/N-buffer?of the LIGBT.And the snapback effect of the conventional anode-short RC-LIGBT during the forward conduction is eliminated without increasing the on-state voltage drop.The simulation results show that the second kind of RC-LIGBT has a higher breakdown voltage which is not affected by the P-anode doping concentration.In addition,the proposed device reduces the reverse recovery charge by 15.2%and increases the soft factor by more than one time.4.A process for realizing the structure of high-voltage diode integrated on the surface of voltage-sustained region is developed.Three kinds of structures including“Terminal with integrated p-i-n diode on field oxide,Accumulated LDMOS with p-type field ring,and Low-voltage power supply integrated in the cell region of high-voltage device”are verificated and tested by experiments.The current capability of the LDMOS with accumulation layer is significantly improved compared to the conventional one.