Monolithic electronic nose system fabricated by post CMOS micromachining

A monolithic electronic nose system, which has 12 independent channels, was fabricated by post CMOS micromachining process. Read-out integrated circuits were fabricated with the standard CMOS processes with design rule of 0.8 mum. And, the MEMS parts of the electronic nose were fabricated by hybrid etching, composed of bulk micromachining with TMAH (tetramethy lammonium hydroxide) and deep dry etching, on the backside of the wafer after the CMOS processes. Resistance matching circuit, instrumentation amplifier, multiplexer, and transducer circuits with bridge structure were included in the read-out circuitry. And, heat control circuits were also implanted in the monolithic circuit to maintain the temperature of the MEMS sensing parts as constant. Carbon black-polymer composites and Au nano-particles were used as sensor materials. The MEMS parts of the electronic nose were designed to have well-shaped structures. These structures are considered to be suitable for drop coating procedure

I. Introduction

Recently, the demand for monolithic sensor system has been increased due to the requirement of miniaturization of system and improvements of sensing performances[1], [2]. These integrated sensor systems are expected to be the major sensor systems in the ubiquitous era of the future.