ELECTRICAL LIMITATIONS OF ADVANCED LOCOS ISOLATION FOR DEEP SUBMICROMETER CMOS

Limitations to advanced LOCOS isolation of the Poly Buffer type have been examined by fabricating CMOS devices with active area widths and spaces to 200 nm. The impact of narrow-channel effects, field oxide thinning, and drain-induced barrier lowering (DIBL) of the field oxide transistors on deep submicrometer CMOS has been quantified. For a retrograde well process the narrow-channel effect is minimal for active device widths to 0.4-mu-m. DIBL is shown to limit the active device spacing to about 0.8-mu-m. SUPREM-4 and PISCES-2B simulations are utilized to illustrate the mechanism for the loss of isolation.