Slanted Oxide-Bypassed Superjunction Power MOSFETs

The superjunction power MOSFET devices, such as p-n column superjunction (named SJ) devices and oxide bypassed (OB) devices, are highly recognized for their higher blocking capability and lower on-state resistance. However, the performance of SJ devices is greatly handicapped due to difficulties in the formation of perfect charge-balanced SJ p-n columns by the current process technology, especially when the SJ drift region width is smaller than 1 mu. OB devices shift the emphasis from the difficulty in achieving a precise doping match to the easily achievable control in the oxide thickness. However, it is hard to obtain a breakdown voltage comparable to the SJ devices due to the non-uniform electric field in the OB drift region. In this paper, a novel structure for power MOSFETs, called the slanted OB structure (SOB) is proposed. The SOB device can outperform other superjunction devices in the low to medium voltage range, such as devices below 120 V with the drift region width smaller or equal to 1 mu. Combining the advantages of simple fabrication process, high breakdown voltage and low specific on state resistance, the SOB device promises to be an alternative to other superjunction devices for the low to medium voltage applications