Recrystallised Si nanofingers and nanowires for low cost biosensor applications

Kai, Sun, Hakim, M.M.A. and Ashburn, P. (2010) Recrystallised Si nanofingers and nanowires for low cost biosensor applications. International Symposium on Atom-scale Si Hybrid Nanotechnologies, Southampton, United Kingdom. 01 - 02 Mar 2010.

Abstract

Recently, Si nanowires and micron-wide nanoribbons are gaining much attention for biosensing because they offer real-time, label-free, high sensitivity sensing. Currently Si nanowires are fabricated using CMOS technology, SOI substrates and e-beam lithography, which give high costs. In this paper we investigate a lower cost alternative using TFT technology and study the lateral crystallization of Si nanoribbons for application in Si biosensors. A comparison is made of the crystallization of a-Si on SiO₂ and on air for use in top-gate and surround-gate sensors. The crystallization is assessed using Normarski microscopy, planar and cross-sectional SEM and defect etching. The results show better lateral crystallization for Si-on-Air than Si-on-Oxide. For a 10h anneal at 550°C, the crystallization extended 24µm for Si-on-Air and 11µm for Si-on-SiO₂, whilst a 20h anneal at 525°C gives 7.7µm and 4.9µm respectively. Plan-view SEM images also show slightly lower NiSi₂ precipitates in Si-on-Air than Si-on-Oxide. Cross-section SEM images show randomly nucleated grains at the bottom of the crystallized layer, with a density of 1.3/µm and 3.2/µm for Si-on-Air and Si-on-Oxide, indicating the suppression of random grain nucleation in Si-on-Air samples. These results promise better electrical performance from crystallized Si-on-Air sensors than Si-on-Oxide sensors.

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