Charge storage in metallic nanodots embedded into a dielectric layer has received much attention because of their potential advantages in storage capacity in comparison to semiconducting quantum dots (QD).  Uniform formation of metallic nanodots with an areal density over ~10¹¹cm^-2 without degrading gate oxide reliability caused seriously by metal diffusion is one of major technological challenges.  We have developed a new fabrication method of nanometer-scale metal dots on thermally-grown SiO₂ with a fairly uniform size distribution and a high areal density, in which ultrathin films of Ni, Pt and Pd are exposed to remote H₂ plasma at room temperature [1]. 

In this work, we extended our research to form metal silicide dots showing good thermal stability compared with elemental metal dots.

Si-QDs with a dot density of ~2x10¹¹cm^-2 were first self-assembled on ultrathin SiO₂ by controlling the early stages of LPCVD using SiH₄.  Subsequently, Ni or Pt evaporation on Si-QDs was performed and followed by remote H₂ plasma treatment without additional heating.

AFM measurements at each process step confirm uniform formation of Si-QDs on SiO₂ before metal evaporation, conformal coverage with a very thin metal layer just after evaporation and an increase in the dot height without no change in the dot density after the H₂ plasma treatment.  By using an electrically-baised AFM tip, we have also verified that electrical separation among nanodots on SiO₂ is restored by the H₂ plasma treatment.  The silicidation of Si-QDs was confirmed from changes in core lines and valence band spectra and photoemission cut-off energy as detected by high-resolution XPS.  In addition, the temporal decay in the surface potential after charge injection to the dots shows that retention characteristics of silicide dots is superior to Si-QDs with almost the same size as expected in a deeper potential well for electrons in silicide dots than pure Si-QDs.

[1] K. Makihara et al., JJAP, 47 (2008) 3099.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/16245 must be provided.