New edge-defined vertical-etch approaches for submicrometer MOSFET fabrication

This paper describes a new, convenient "undercut and backfill" technique for forming edge-defined submicrometer elements based only on standard optical lithography and vertical (anisotropic) dry etching. MOSFETs having physical channel lengths from 0.3 \micro m to \simeq 1.0 micro m can be fabricated using this approach, This method is compared with an alternative vertical etch, edge-defined technique which is capable of fabricating physical gate lengths oF 0.1-0.4 \micro m. In particular, MOSFETs having L \simeq 0.1 \micro m, believed to be the smallest reported to date, have been made. A vertical etching technique which forms a passivating sidewall oxide is also described. Modifications of this technique to fabricate self-aligned shallow/deep n+/n++ junctions having reduced series resistance and short-channel effects (in particular punchthrough) are illustrated.