ADFET-a simple inexpensive power device

A new high-voltage power device, termed the ADFET for alloyed drain power MOSFET, provides an economical alternative to conventional power MOSFETs (epi-FETs) for many applications. Possessing qualities mid-way between a non-punchthrough (NPT) IGBT and an epitaxial power MOSFET, 1200 V ADFETs have on-voltages about half that of 1200 V epi-FETs and fall times of /spl sim/90 nsec. In addition, ADFET costs are dramatically lower than epi-FETs, not just because lower on-voltages reduce die sizes, but also because the floatzone (FZ) starting material is much less expensive than thick epitaxial layers. This paper discusses fabrication of the ADFET, provides actual 1200 V TO-220 device data with direct comparison to non-punchthrough IGBT and epitaxial power MOSFET data, and reviews MEDICI modeling performed to elucidate mechanisms.