The Investigation Of Power Mosfet Cell About600V

The power MOSFET has high input impedance, low drive power, fast switching speed, good frequency characteristics and thermal stability advantages, more widely used. Widely used in the market put forward higher requirements on the MOSFET product. The direction of the development of the power MOSFET still continue to improve device performance parameters (high-voltage, low on-resistance, low capacitance). Demand for energy saving is the need to reduce the power loss of the device. Power losses include switching losses and conduction losses. The lower gate-drain capacitance Cgd of the device, the switching loss is low, but also in the high frequency applications. Reduce conduction losses to lower on-resistance. Conduction the contradiction of resistance and the breakdown voltage, so that the application of the high-pressure area, holding the case of breakdown voltage, reducing Conduction resistance, a key to the development of MOSFET technology.This paper mainly cell design research of high-pressure devices. First, Optimization the design of high voltage600V power VDMOS devices. And then improve the device structure and optimize the gate-drain capacitance.Finally, research semi-super junction structure devices. By the regulation of the process flow, simulating a low-resistance, high Breakdown voltage semi-super junction structure device model.The detailed contents are described as follows:(1) Abrupt junction breakdown theory to calculate the vertical structure parameters, Simulation select the most suitable epitaxial thickness65μm, Optimized gate width WG, meeting pressure requirements, select the least specific on-resistance width WG=5μm.(2) In order to meet the demand of high frequency and to reduce the power loss. Use two methods to optimize the VDMOS structural gate-drain capacitance Cgd. Depositing a thick oxide layer under the gate electrode, the increase in the distance of the overlapping area of the gate and drain, the gate-drain capacitance Cgd can be reduced, By this method Cgd can be reduced to39.15%, the breakdown voltage is maintained slightly increases the specific on-resistance of7.4%. Depositing a thick polysilicon layer below the gate and98.03%of the gate-to-drain capacitance Cgd can be reduced by optimizing, gate-drain capacitance Cgd equivalent traditional VDMOS structure fiftieth, And to maintain the Specific On-resistance is essentially the same but also enhance the breakdown voltage value of6.18%, ease the contradiction between the resistance and pressure resistance.(3) Super junction devices can break the contradictions of Specific On-resistance and breakdown voltage. In order to reduce the process complexity, the paper through multiple epitaxial Boron ion implant, diffusion to create a semi-super junction device models. Adjustment width of ion implantation mask, the concentration of ion implantation and increase the epitaxial concentration, the final optimization the good performance of the semi-super junction device. The gate-drain capacitance Cgd is reduced by87.8%compared with VDMOS structure, Specific On-resistance is reduced by20.6%, and Breakdown voltage increased16.7%, Semi-super junction devices have excellent performance.