Low cost nanowire biosensor fabrication using thin film amorphous silicon crystallisation technologies

Abstract

Recently, Si nanowires are receiving much attention for biosensing because they offer the prospect of real-time, label-free, high sensitivity sensing. The most popular approach to silicon nanowire fabrication uses electron-beam lithography to define silicon nanowires on SOI wafers. While this approach has the advantage of CMOS-compatibility, it has the disadvantage of high cost, because both the lithography and the SOI wafers are expensive. In this paper we demonstrate a low cost, CMOS-compatible fabrication process for silicon nanowire biosensors, which is based on thin film transistor technology. The key steps in the fabrication process are the deposition of an amorphous Si layer over a sharp step in an insulating film and an anisotropic Si etch to create a silicon nanowire on the side of the step. The anisotropic etch was performed on an ICP etcher using the Bosch process, which gives well-defined, rectangular amorphous silicon nanowires with a geometry of 80 x 120 nm, measured by cross-sectional SEM. Metal induced lateral crystallization is then used to crystallize the amorphous silicon at a temperature around 500°C to create polycrystalline silicon nanowires. The approach used for nanowire functionalisation produces a maleimide activated surface that is amenable to the immobilization of biomolecules with a free thiol