FABRICATION OF SUB-50-NM GATE LENGTH N-METAL-OXIDE-SEMICONDUCTOR FIELD-EFFECT TRANSISTORS AND THEIR ELECTRICAL CHARACTERISTICS

A method of fabricating 40-nm gate-length n-metal-oxide-semiconductor field effect transistors (MOSFETs) is described in detail. The fabrica tion of MOSFETs with gate lengths of this order poses two major proble ms: how to fabricate such small-geometry gate electrodes, and how to f abricate the ultrashallow source and drain junctions required. Two spe cial techniques are used to overcome these problems: a resist-thinning process using isotropic oxygen plasma ashing for the fabrication of t he gate electrodes, and a process of solid-phase diffusion from phosph orus-doped silicated-glass gate sidewalls for fabrication of the sourc e and drain junctions. The resulting 40-nm gate electrodes and ultrash allow 40-nm junctions have an adequate impurity concentration and have been shown to function successfully. It has been confirmed that these 40-nm gate-length n-MOSFETs have good electrical characteristics at r oom temperature, Certain details of small-geometry MOSFET electrical c haracteristics are studied using these devices. (C) 1995 American Vacu um Society.