Analytical design methodology of a novel drift-layer for super-junction power MOSFET: CoolMOS (TM)

Here a simple methodology for design of the drift layer using Super-Junction Theory is developed. Analytically designed drift layer is used to simulate the CoolMOS and it is verified for the design parameters and terminal characteristics. Simulation result shows that this methodology does give a first order design method. The On resistance and Break down voltage conflict at high voltage drift layer is also discussed along with possible solution. The limitations of the SJ-Theory for implementation in CoolMOS, are also discussed

Analysis of breakdown voltage and on resistance of super junction power MOSFET CoolMOSTM using theory of novel voltage sustaining layer

Conventional VDMOS (vertically double diffused metal oxide semiconductor) Technology for power devices was constrained by the Silicon Limit. This is now improved to have a linear relation between on resistance (Ron) and breakdown voltage (BV) instead of the quadratic relation. Theory of novel voltage sustaining layers (SJ-theory) recently published analytically models the super junction drift layers (SJ-drift layer). The authors have designed SJ-layers based on this theory and used to construct the SJ-MOSFET: CoolMOS structure. The claim of the theory that the doping level in the drift layer can now be increased by at least me order of magnitude without lowering BV is analyzed in detail. With the new silicon limit, one now can increase BV of a power device, just by increasing thickness of the SJ-drift layer. R on and BV relationship as the thickness of the device varies is analyzed with the help of simulation. The limitations and constraints of applying SJ-theory for the CoolMOS structure are discussed. The SJ- theory does not model the behavior of Ron and BV for a fixed geometry as doping level changes. The authors observed that for a fixed geometry the rate of reduction of the BV depends on the cell pitch. This rate is large for the higher cell pitch. The effect of charge imbalance created due the channel region in CoolMOS is also investigated.© IEE

Analysis and design of superjunction power MOSFET: CoolMOS™ for improved on resistance and breakdown voltage using theory of novel voltage sustaining layer

In this paper, we have observed that the drift layer of conventional power device can be modified to SJ-drift layer for improvement in the breakdown voltage (BV). Doping level of SJ-drift layer increased by one order of magnitude gives at least 5 times improvement in on resistance Ron, without reducing the BV. Further increase in the BV is possible by increasing the thickness of the SJ-drift layer where we observed the proportional increase in Ron. Theory of novel voltage sustaining layer (SJ-theory) recently published is used for the first time to analyze and design CoolMOS structure. We observed that for a fixed cell-pitch, increasing the height of drift layer proportionately increases the BV. The rate of increasing BV is higher for smaller cell-pitch. The Ron also increases proportionally. For a fixed geometry increasing doping level by one order of magnitude reduces the BV and the rate of reduction of this BV is dependent on the cell-pitch.© IEE