Fabrication of a novel oxygen sensor with CMOS compatible processes

A novel miniature dissolved oxygen sensor as a transducer for medical and environmental measurements is fabricated with a CMOS compatible process. The sensor is designed as a three electrode system. It has a Pt recessed ultramicroelectrode array structure as working electrode, a Pt counter electrode and a Ag/AgCl reference electrode. The recessed ultramicroelectrode array is made with a lift-off method which follows a SiO₂ reactive ion etching process. Different recessed ultramicroelectrode arrays varying in diameter and spacing have been designed to study the diffusion characteristic in order to find the optimal values. The chip size is 1.5 × 4 mm², small enough to enable implantation.