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We present a novel thermopile-based infrared (IR) sensor array fabricated on a single CMOS dielectric membrane, comprising of poly-silicon p+ and n+ elements. Processing of the chip is simplified by fabricating the entire array on a single membrane and by using standard CMOS Al metal layers for thermopile cold junction heatsinking. On a chip area of 1.76 mm × 1.76 mm, with a membrane size of 1.2 mm × 1.2 mm, we fabricated IR sensor arrays with 8 × 8 to 100 × 100 pixels. The 8 × 8 pixel device has <2% thermal crosstalk, a responsivity of 36 V/W and enhanced optical absorption in the 8–14 µm waveband, making it particularly suitable for people presence sensing.

We present a new experimental technique to characterise the crosstalk of a thermopile-based thermal imager, based on bi-directional electrical heating of thermopile elements. The new technique provides a significantly simpler and more reliable method to determine the crosstalk, compared to a more complex experimental setup with a laser source. The technique is used to characterise a novel single-chip array, fabricated on a single dielectric membrane. We propose a theoretical model to simulate the crosstalk, which shows good agreement with the experimental results. Our results allow a better understanding of the thermal effects in these devices, which are at the center of a rising market of industrial and consumer applications.

We propose a numerical model for efficient design and optimization of a novel infrared (IR) detector array, fabricated on a single micro-electro-mechanical system (MEMS) membrane based on silicon on insulator (SOI) technology. The model is based on a finite element method (FEM) and is used to investigate the effect of heat transfer, at pixel scale, on the thermopile array's responsivity and crosstalk performance. We show that optimal operational conditions can be achieved by modifying a combination of design elements, including the pixel size, the interpixel metal heatsinking tracks, as well as the insertion of air gaps between pixels. We find that the combined effect of copper heatsinking tracks and that of air gaps can reduce pixel crosstalk by 65% while increasing the responsivity by 6.4%. The model improves our understanding of the thermal effects in these devices, and can serve as a design tool for a growing number of low-cost industrial and consumer applications.

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