The Characteristics Of Power Mosfet’s Termination Breakdown Voltage

Power Semiconductor devices play an important role for the development of Power Electronics Technology. Due to its high input impedance, low drive power, high switching speed, perfect frequency characeristics as well as good thermal stability etc, the study of the performances and structures has been conducted rapidly and many achievements have been made since its first birth. Trench power MOSFET (UMOSFET) is developed on the basis of LDMOS and VDMOS, and because of its high current, low on-resistance, fast switching speed and other aspects of the advantages, it has become a mainstream of high-frequency low-voltage application.Nowadays, much more study focus on a design of smaller size of cell and termination, since a smaller cell size means greater channel density and lower on-resistance, or you can get a smaller chip area with the same on-resistance and thereby costs could be reduced, however,a much shoter termination length indicates an increasing cell number in case of a fixed chip size. A contradiction between high breakdown voltage and low on-resistance exists, because we can not achieve both of them in the same time, which has become the main direction of today’s power MOSFET development.The main contents of this paper is to optimize the design of voltage power devices:firstly the mechanism of breakdown for device itself; then termination design of the device as well as its optimizations including a complex application of filed ring and field plate, which is a traditional one, and a modle realized by a varied lateral dophing. details are showed as follows:1. The parameters of vertical power MOSFET, of which breakdown voltage is a critical one. By theory and simulation, a study between interaction of vertical power device design and its breakdown performance has been made.2. In order to achieve a convergence of the electric field at the end of the chip termination, usually a complex application of field plate and the field ring will ba used, in our study some key parameters of field plate and field ring have been discussed in order to achieve a high voltage under a smaller chip area.3. In order to achieve a higher breakdown voltage within a shorter termination length, the paper also discusses a realization of vertical lateral dophing technique, through theory and simulation, the paper also discuss its key parameter as well as its real breakdown ability.