Recessed Oxidation Process to Reduce Boron Concentration Around Perimeter of Active Device Regions
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-10
Thick seki-recessed silicon dioxide 10 used to isolate MOSFETs and n+ diffusions has a p+ layer 9 implanted thereunder to obtain high thick oxide threshold voltage. This boron implantation is done at the beginning of the fabrication process and consequently is driven in by subsequent heat cycles. That portion of the boron which spreads laterally significantly increases the p-type doping concentration around the perimeter of the active device regions containing MOSFETs and n+ diffused inter-connections, as illustrated in the Fig. 1 cross-section.