Experimental validation of the ‘FLoating Islands’ concept: 95 V breakdown voltage vertical FLIDiode

The present 14V automotive electrical system will soon become 42V. For these future automotive applications, development of 80V power MOSFETs exhibiting low on-resistance is desired. The 'FLoating Island' MOSFET (FLIMOSFET) is one of the new candidates to break the conventional silicon limit, which is the 'specific on-resistance/breakdown voltage' trade-off limit of power MOSFETs. In the paper, the 'FLoating Island' concept has been implemented on silicon for the first time: vertical FLoating Island diodes (FLIDiodes) and MOSFETs (FLIMOSFETs) have been fabricated, using a two step epitaxy process. Experimental results confirm the predictive simulations: the FLIDiode exhibits an important breakdown voltage (above 85V) with an N - epitaxial layer doping concentration (1.1 × 10 16 cm -3 ) usually dedicated to 50V devices. The FLIMOSFET exhibits a lower breakdown voltage (73V) but also an improved specific on-resistance compared to conventional VDMOSFET (33% reduction of the specific on-resistance for the same breakdown voltage). These measurements validate the 'FLoating Island' concept and the efficiency of the original edge cell that is used in the FLIMOS technology.