SELF-LIMITING OXIDATION FOR FABRICATING SUB-5 NM SILICON NANOWIRES

The ability to control structural dimensions below 5 nm is essential f or a systematic study of the optical and electrical properties of Si n anostructures. A combination of electron beam lithography, NF3. reacti ve ion etching, and dry thermal oxidation has been successfully implem ented to yield 2-nm-wide Si nanowires with aspect ratio of more than 1 00 to 1. With a sideview transmission electron microseopy technique, t he oxidation progression of Si nanowires was characterized over a rang e of temperature from 800 to 1200-degrees-C. A previously reported sel f-limiting oxidation phenomenon was found to occur only for oxidation temperatures below 950-degrees-C. A preliminary model suggests that in crease in the activation energy of oxidant diffusivity in a highly str essed oxide may be the main mechanism for slowing down the oxidation r ate in the self-limiting regime.