Table of Contents
Journal of Nanoscience
Volume 2014, Article ID 961720, 7 pages
Research Article

Self-Passivation by Fluorine Plasma Treatment and Low-Temperature Annealing in SiGe Nanowires for Biochemical Sensors

1Department of Electrical Engineering and Institute of Electronics, National Chiao Tung University, No. 1001, University Road, Hsinchu 300, Taiwan
2Department of Electronics Engineering, Chung Hua University, No. 707, Sec. 2, WuFu Road, Hsinchu 300, Taiwan
3Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan
4Department of Electronic Engineering, Huafan University, New Taipei City 223, Taiwan
5Department of Electrical Engineering, Chung Hua University, No. 707, Sec. 2, WuFu Road, Hsinchu 300, Taiwan

Received 1 March 2014; Revised 14 May 2014; Accepted 15 May 2014; Published 11 June 2014

Academic Editor: Oleg I. Lupan

Copyright © 2014 Kow-Ming Chang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Nanowires are widely used as highly sensitive sensors for electrical detection of biological and chemical species. Modifying the band structure of strained-Si metal-oxide-semiconductor field-effect transistors by applying the in-plane tensile strain reportedly improves electron and hole mobility. The oxidation-induced Ge condensation increases the Ge fraction in a SiGe-on-insulator (SGOI) and substantially increases hole mobility. However, oxidation increases the number of surface states, resulting in hole mobility degradation. In this work, 3-aminopropyltrimethoxysilane (APTMS) was used as a biochemical reagent. The hydroxyl molecule on the oxide surface was replaced by the methoxy groups of the APTMS molecule. We proposed a surface plasma treatment to improve the electrical properties of SiGe nanowires. Fluorine plasma treatment can result in enhanced rates of thermal oxidation and speed up the formation of a self-passivation oxide layer. Like a capping oxide layer, the self-passivation oxide layer reduces the rate of follow-up oxidation. Preoxidation treatment also improved the sensitivity of SiGe nanowires because the Si-F binding was held at a more stable interface state compared to bare nanowire on the SiGe surface. Additionally, the sensitivity can be further improved by either the N2 plasma posttreatment or the low-temperature postannealing due to the suppression of outdiffusion of Ge and F atoms from the SiGe nanowire surface.