%D 2024
%O © 2024 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
%J Electrochimica Acta
%V 477
%A Lewis Keeble
%A Arthur Jaccottet
%A Daryl Ma
%A Jesus Rodriguez-Manzano
%A Pantelis Georgiou
%L discovery10185432
%T An electroplated Ag/AgCl quasi-reference electrode based on CMOS top-metal for electrochemical sensing
%I Elsevier BV
%K CMOS,
Reference electrode,
Electroplating,
Electrochemical,
Electroless
%X The integration and mass-production of reference electrodes for CMOS-based electrochemical sensing systems
pose a challenge for the accessibility and commercial-viability of such devices. In this paper, a method of
electroplating an Ag/AgCl quasi-reference electrode using CMOS top-metal as a base is presented for the first
time. The aluminium bond-pad of a CMOS microchip was zincated, an electroless nickel immersion gold layer
applied, and a thick silver layer electroplated and chemically chlorinated. The resulting reference electrode was
able to provide a stable potential with a drift rate of 0.3 mV/h for up to 18 h. This validates the approach of a
fully electroplated bond-pad reference electrode, which offers simplified post-processing and greater scalability
of production. Further work towards an entirely electroless process is envisaged