Performance Enhancement of ISFETs in Standard CMOS Technology Using Antireflection Coating as Ion-Sensitive Layer and FLOTOX Tunnel Devices

Abstract

We present the characterization results of ion-sensitive field-effect transistors (ISFETs) fabricated in standard CMOS technology with implemented tunnel structures for bidirectional electron tunneling in terms of sensitivity, drift, signal resolution, and trapped charge compensation. The measured CMOS ISFETs exhibit a mean pH sensitivity, drift and signal resolution of $44.7 \,\mathrm{m}\mathrm{V}/{\mathrm{pH}}$, $1.8 \,\mathrm{m}\mathrm{V}/{\mathrm{h}}$, and $0.002 \,{\mathrm{pH}}$, respectively. To the best of the authors' knowledge, these are the best performance parameters achieved to date for ISFETs with an ion-sensitive Si₃N₄ layer fabricated in standard CMOS process without customized modifications. We achieved this performance enhancement by using antireflection coating as ion-sensitive layer available in standard CMOS technology. This enables the use of our proposed CMOS ISFETs as biosensors in applications with high sensor demands, such as molecular diagnostics and deoxyribonucleic acid (DNA) sequencing.