Crosstalk Analysis of a CMOS Single Membrane Thermopile Detector Array

Abstract

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.

Modeling of CMOS Single Membrane Thermopile Detector Arrays

“…1(a) shows the top view (optical image) of the real chip, while Fig. 1(b) shows the top view of its 3D model, where the heater pixel (circled by the red square) is electrically biased (heated) to extract its thermorelectric voltage output V h [18]. Its R can be computed by the ratio of V h to that of the applied power.…”

“…V T 2 between the signal generated by an optically irradiated pixel (V T 1 ), to that generated by an adjacent non-irradiated pixel (V T 2 ) [2], [18]. C is typically caused by the unwanted heat diffusion from the irradiated pixel to its neighbours [2], [19], and it can limit the FPA's spatial resolution (a measure of the smallest object that a sensor can distinguish [20]).…”

“…Processing of the chip was also simplified by the use of a single membrane and standard CMOS tungsten layers for thermopile cold junction heatsinking [10], [11]. Subsequently, we presented a novel technique based on a bi-directional electrical heating of the thermopile elements, to measure its C, making it significantly simpler that traditional methods [18]. In our previous work, we introduced a model for thermoelectric signal generation (and relevant temperature distribution) which was validated through extensive experimental results, with errors of less than 5% [18].…”

“…Subsequently, we presented a novel technique based on a bi-directional electrical heating of the thermopile elements, to measure its C, making it significantly simpler that traditional methods [18]. In our previous work, we introduced a model for thermoelectric signal generation (and relevant temperature distribution) which was validated through extensive experimental results, with errors of less than 5% [18]. In the following, we consider the effect of the heatsinking tracks on R and C, and in particular the introduction of air gaps between pixels.…”

A Review of Thermal Spectral Imaging Methods for Monitoring High-temperature Molten Material Streams

“…Furthermore, FPAs exhibit unwanted transfer of signals, that is leakage of photons and electrons between pixels. Such pixel-topixel crosstalk can affect the spatial resolution of the detector and thus complicate the reconstruction of the desired image [38]. Another major contributor to this problem is sizeof-source effect (SSE), which arises due to imperfections within the optical system leading to reflections and scattering inside the instrument [39].…”