Research On Novel Structure Of High Voltage,High Performance LIGBT Device

LIGBT?Lateral Insulated Gate Bipolar Transistor?is a typical representative of new power semiconductor devices and has the advantages of low on-state voltage drop(V_on),high input impedance,high current capability,high breakdown voltage?BV?,good thermal stability and easy integration.In rencently years,SOI?Silicon on Insulator?technology develops rapidly,compared with bulk silicon,SOI has higher device integration,better isolation and anti-radiation capabilities,which makes SOI LIGBT widely used in smart power intergrated circuits,such as vehicle electronics and switching power supply.Although LIGBT has low V_on due to the conductivity modulation effect in the drift region,it suffers high turnoff loss(E_off)since large number of the excess carriers retaining in the drift region should be removed during turnoff process,which limits the appalication of LIGBT.Therefore,researches on the turnoff mechanism and novel LIGBT structure to improve the tradeoff between V_on and E_off are always most importance issueses in academic and engineering field.In this paper,E_off V_on tradeoff is focused and the approach for low E_off of lateral IGBT?LIGBT?is researched.Relationship between the extraction of excess carrier during turnoff and depletion region capacitance,and relationship between carrier distribution during on-state and hole barrier are studied.The turnoff model of LIGBT with p-buried layer and two types of novel LIGBT structure are proposed based on SOI.The proposed novel LIGBT can realize much lower E_off.What's more,super junction structure is introduced to LIGBT and novel LIGBT devices with super junction?SJ?are proposed and manufactured.The main contents and innovations are as follows:1.The turnoff model of the LIGBT with p-buried layer is established and the relative new LIGBT structures are proposed.The proposed turnoff model contains E_off model and dV/dt model.The E_off model is universal and reveals three approaches for low E_off: reducing the total integral current charges,reducing the average anode voltage in the first phase and increasing the charge factor k.Based on the expansion mode of the depletion region of the device,the model of d V/dt is established,which reveals the lager capacitance effect during voltage raise phase of turnoff process.The turnoff model can also be applied to the SJ IGBT.Three new structures of SOI LIGBT with p-buried layer concept are as following:?1?SOI LIGBT with p-buried layer?PB SOI LIGBT?.PB SOI LIGBT features a p-buried layer in the n-drift region.Due to the p-buried layer,large capacitance effect exists during turnoff process and large number of carrier is swept out under low anode voltage.The three approaches for low E_off are demonstrated in the PB SOI LIGBT.The turnoff characteristic of the PB SOI LIGBT is researched by modeling and simulation.The influences of the key parameters on turnoff loss are analyzed.Compared with conventional structure,E_off of PB SOI LIGBT can be reduced by 85 % when V_on is 1.2 V.?Related research was published in IEEE Transactions on Electron Devices,2015,62?11?: 3774-3780??2?Dual-gate SOI LIGBT with p-buried layer?DG-PB SOI LIGBT?.The DG-PB SOI LIGBT induces an extra trench gate to form dual-gate structure.The induced trench gate plays the role of enhanced electron injection,which helps reduce the E_off.E_off of DG-PB SOI LIGBT is reduced by 40 % compared with the PB SOI LIGBT.?Related research was published in IEEE ICSICT,2016??3?SOI LIGBT with U-shape SJ structure and trench drift?USJT SOI LIGBT?.USJT SOI LIGBT features an oxide trench in the drift region to withstand the lateral BV and a surrounded p-drift to form U-shape SJ structure.The device not only has low E_off,but also can shield the influence of back-gate voltage on BV.The paper first analyzes the carriers movement mode during device switching is analyzed.Besides,the influences of device parameters and back-gate on E_off and BV are studied.2.The novel LIGBT structures based on the concept of enhanced trench gate are proposed.The novel device structures are SOI LIGBT with enhanced trench gate?ETG SOI LIGBT?and dual-gate SOI LIGBT with enhanced trench gate and carrier stored layer?DETG-CS SOI LIGBT?.Different from conventional trench gate LIGBT,ETG SOI LIGBT just inserts the trench gate between pwell and n-drift.In the on-state,the trench gate acts as a carrier barrier and carrier stored effects is realized.During turnoff,the trench gate can assist the depletion of n-drift and speed up the removal of carriers.Compared with the conventional trench gate SOI LIGBT,E_off of DETG SOI LIGBT is 59 % lower when V_on is 1.1 V.DETG-CS SOI LIGBT introduces double trench gate and carrier stored layer structures,which help increase the carrier concentration below pwell of the ETG SOI LGIBT,thus further improving the E_off V_on tradeoff.?Related researches were published in Superlattices and Microstructures,2016,89: 179-187 and Chinese Physics B,2016,25?12?: 127304?3.Novel SJ LIGBT is designed and manufactured.The SJ structure is introduced to LIGBT.The surface SJ bulk LIGBT?SSJ LIGBT?and the partial SJ LIGBT based on thin SOI layer?PSJ SOI LIGBT?are proposed.The device design,intergrated process,layout design,experimental results of the two devices are presented in this paper.SSJ LIGBT features longitudinal stacking SJ structure in the drift region by implant P-type and N-type impurities successively.The manufactured SSJ LIGBT shows BV of 693 V and on-specific resistance?Ron,sp?of 6.45 ?·mm2.Besides,the large capacitance effect exists in the measured turnoff waveform,which proves the large capacitance effect of PB SOI LIGBT.PSJ SOI LIGBT introduces the design,which the thickness of drift silicon is different at cathode side and anode side.The design combines advantages of the high critical electric field of thin silicon and low resistance of SJ structure,realizing high BV and low Ron,sp of the device.The manufactured PSJ SOI LIGBT realizes BV of 825 V and the Ron,sp is 60 % lower than that of the conventional structure.