| Power electronics technology can be used to process and convert electrical energy and improve the efficiency of power consumption at the same time.It is of great significance to make high-efficiency and low-power power semiconductor devices for saving energy and protecting the environment.The continuous updating of the power semiconductor devices will drive the development of power electronics technology.The new SJ-ACCUFET（Super Junction-Accumulation Field Effect Transistor）with integrated Schottky junction is studied in this paper,which is a novel type of power device based on VDMOS.The base region of the ACCUFET device is N-type doped,which is different from the traditional NMOS structure.The accumulation layer of electrons generated by the gate bias is used for conduction.Thanks to the higher mobility of electrons in the accumulation layer,the ACCUFET device has lower specific on-resistance.At the same time,the P-type body region of the source region in the conventional VDMOS forms a parasitic BJT,which may cause device failure when the device undergoes avalanche breakdown.Therefore,the ACCUFET device proposed in this paper removes the P-type body region while using Schottky.The barrier diode assists in depleting the N-type base region to ensure the breakdown characteristics of the device,and the addition of the Schottky structure also improves the reverse recovery characteristics and switching characteristics of the device.By adding a super junction structure,the device achieves a low specific on-resistance with a specified withstand voltage.The main contents of this work include:1.Firstly,the structure,working principle and development history of common ACCUFET devices are introduced.Then the theory of the super-junction and the improvement of the characteristics of the specific on-resistance in the drift region through super-junction theory are also described.The structure and characteristics of VDMOS devices and the approximate calculation of the threshold voltage and the resistance are provided.And the forward,reverse and switching characteristics of the Schottky barrier diode are analyzed.Then the avalanche tolerance and UIS theory are also mentioned.2.The ACCUFET device integrated with a Schottky diode is simulated with Medici software in comparison with the conventional VDMOS device.Under the same breakdown voltage and the same VDS with a value of 1V,when VGS=5V and 10V,the specific on-resistance of ACCUFET device decreases by 44%and 42.7%,respectively.The current density of the proposed device is higher than the conventional one under the same gate voltage.And the peak current is reduced by 82%during the reverse recovery process,and the softness factor S is 7.33 times than the conventional device.Then the influence of characteristics of the Schottky electrode in the device is discussed.3.A novel super-junction ACCUFET device with integrated Schottky diode is simulated with Medici software in comparison with a conventional super-junction VDMOS device.With the same breakdown voltage and the same VDS with a value of 1V,when VGS=5V,10V and 15V,the specific on-resistance of the ACCUFET decreases by8.07%,4.28%and 3.27%,respectively.And in the reverse recovery characteristics,the peak current and reverse recovery time are decreased by 25.2%and 15.4ns,and the softness factor S is increased by 0.05,respectively.Furthermore,the simulation result also show that the avalanche tolerance of the proposed device is more stable compared with the conventional one. |
