The Characteristics Research Of Power Umosfet Devices And New Structures Design

Power semiconductor devices are the basis for the development of power electronics technology. Power MOSFETs have achieved rapid progress since the first born, due to its high input impedance, low drive power, high switching speed, excellent frequency characteristics and good thermal stability characteristics. Trench power MOSFET (UMOSFET) is a semiconductor device which is developed based on LDMOS and VDMOS, because of its high breakdown voltage, high current, low on-resistance and fast switching speed, it is becoming the main stream of high frequency and low voltage power MOSFET.The development trend of low-voltage power MOSFET is to shrink the size of the device, because the smaller size means that a greater channel density and lower on-resistance, or in the same on-resistance can get a smaller chip area, thereby reducing costs. The main contradiction of power MOSFET design is increasing the breakdown voltage BV and decreasing the on-resistance Rds(on), it has also become the main direction of the power MOSFET technology development.The main ideas of this paper is by the study power MOSFET performance parameters and design process. First, study the optimum design of on-resistance for low-voltage MOSFETs, this part mainly focuses on the lateral device parameters; then study the improved MOSFET device characteristics, including the body profile optimization and epitaxial optimization MOSFET devices, this part focuses on the vertical device parameters. The detailed contents are described as following:(1) On-resistance is an important parameter of power UMOSFET, this paper study the differences of optimized on-resistance for low-voltage (<100V) UMOSFET under different breakdown voltage. Through theory and simulation methods study the relationships between key parameters of UMOSFET and on-resistance optimization design.(2) The on-resistance of power UMOSFET is mainly composed of epitaxial resistance and channel resistance, we can reduce channel resistance by means of shortening channel length, thereby reducing on-resistance. However, the channel length of traditional UMOSFET is restricted by punch-through breakdown effect. This paper has obtained short channel length by optimizing body doping profile, reducing the on-resistance and improving the breakdown voltage.(3) The epitaxial resistance is the main on-resistance component of UMOSFET. By optimizing the epitaxial structures which can be used in high-voltage UMOSFET, VDMOSFET, and edge termination, which can increase BV while reduce on-resistance, and improve the reverse transfer capacitance characteristics.