Three-Mask Polysilicon Thin-Film Transistor Biosensor

Journal article

Authors / Editors

Ditshego, Nonofo

Research Areas

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Publication Details

Author list: Sun K, Zeimpekis I, Lombardini M, Ditshego NMJ, Pearce SJ, Kiang KS, Thomas O, de Planque MRR, Chong HMH, Morgan H, Ashburn P

Publisher: Institute of Electrical and Electronics Engineers (IEEE)

Place: PISCATAWAY

Publication year: 2014

Journal: IEEE Transactions on Electron Devices (0018-9383)

Journal acronym: IEEE T ELECTRON DEV

Volume number: 61

Issue number: 6

Start page: 2170

End page: 2176

Number of pages: 7

ISSN: 0018-9383

Languages: English-Great Britain (EN-GB)

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Abstract

Biosensors are commonly produced using a silicon-on-insulator (SOI) CMOS process and advanced lithography to define nanowires. In this paper, a simpler and cheaper junctionless three-mask process is investigated, which uses thin-film technology to avoid the use of SOI wafers, in situ doping to avoid the need for ion implantation and direct contact to a low-doped polysilicon film to eliminate the requirement for heavily doped source/drain contacts. Furthermore, TiN is used to contact the biosensor source/drain because it is a hard resilient material that allows the biosensor chip to be directly connected to a printed circuit board without wire bonding. pH sensing experiments, combined with device modeling, are used to investigate the effects of contact and series resistance on the biosensor performance, as this is a key issue when contacting directly to low-doped silicon. It is shown that in situ phosphorus doping concentrations in the range 4 x 10(17)-3 x 10(19) cm(-3) can be achieved using 0.1% PH3 flows between 4 and 20 sccm. Furthermore, TiN makes an ohmic contact to the polysilicon even at the bottom end of this doping range. Operation as a biosensor is demonstrated by the detection of C-reactive protein, an inflammatory biomarker for respiratory disease.

Keywords

biosensor, pH sensor, plasma chemical vapor deposition, semiconductor device fabrication, thin-film transistors (TFTs)

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