Non-selective NDIR array for gas detection

A micro component for a non-selective NDIR (non dispersive infrared) gas detection system is presented in this work. This device consist of an IR detection module composed of two matching arrays, one of filters and one of thermopile detectors. These arrays (up to 4x4 elements) are built on a silicon substrate using CMOS compatible materials and processes. Bulk micro-machining is used to build the membrane where the thermopiles are placed. The elements of the filter array are fabricated alternating thin films of different refraction index acting like Fabry-Perot structures with different core thickness. The transmitted filter peaks are not tuned for the detection of any specific substance: they configure a non selective general purpose filter array (400-4000cm), making signal processing and pattern recognition techniques necessary. Both devices have been fabricated and characterized and have been successfully attached using flip-chip techniques. The measured characteristics of these devices have been used to build an optical simulation tool that allows the assessment of the whole NDIR system behavior in operating conditions.