Synthesis of Cobalt-Based Nanocrystal Layer in Silicon Dioxide for Nonvolatile Memory Applications

Cobalt silicide (CoSi) nanocrystal (NC) layer distributed within narrow spatial region is synthesized by thermal annealing of a sandwich structure comprised of a thin cobalt (Co) film sandwiched between two silicon-rich oxide (SiO _x ) layers. It is shown that the size of the CoSi NCs can be controlled by varying the Co film thickness, an increase in the size with increasing thickness. Capacitance–voltage (C–V) measurements on a test metal/oxide/semiconductor (MOS) structure with floating gate based on CoSi NCs of 3.8 nm in diameter and 1.4×10¹² cm² in density are shown to have C–V characteristics suitable for nonvolatile memory applications, including a C–V memory window of about 9.5 V for sweep voltages between −15 V and +8, a retention time >10⁸ s, and an endurance >10⁶ program/erase cycles.