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Optimal design of the MEMS thermopile element for an IR imager array  

 Fedirko V.A.
 Khafizov R.Z.
 Fetisov E.A.
Date of publication

 Uncooled infra-red (IR) imagers have been actively developed lately based on MEMS technology compatible with silicon CMOS batch technology. In this paper the problem of the optimal engineering of a thermopile thermal element for IR sensor array is considered. The results of theoretical analysis and computer simulation are presented.
Theoretical relations are obtained which optimise the sensor structure to achive the preassigned characteristics of the imager array: image format, frame time and temperature resolution. The quantitative requirements to the structure and material parameters are formulated to realize the specified characteristics. The larger the image format, and the higher the frame frequency, and the smaller temperature resolution the higher are demads to the materials parameters and the structure geometry.
Estimations are made for a sensor element with polysilicon micro-thermopile for some typical structure parameters. By diminution of the thickness and width of the thermocouple buses and by optimising the interplay between the Seebeck coefficient and resistivity of polysilicon an IR imager array of, say, 128x128 elements with a pitch 50-60 microns with noise equivalent temperature difference NETD about some milli-Kelvin can be realized.
Optimised element for a 6464 IR sensor array with a pitch 125 microns on a chip ~99mm is presented and modelled with SYNOPSYS TCAD packet. Its characteristics, obtained by the numerical simulation coincide with theoretical prediction.
The work was carried out with the financial support by the Ministry of Education and Science of the Russian Federation, Subsidy agreement RFMEFI57814X0009. Results of the project No 15-07-06082 of the Russian Foundation for Basic Research were used in the work.
 IR imagers, thermopile, thermocouple, Seebeck effect, thermopower, IR sensor array, optimization, MEMS-technology.
Library reference
 Fedirko V.A., Khafizov R.Z., Fetisov E.A. Optimal design of the MEMS thermopile element for an IR imager array // Problems of Perspective Micro- and Nanoelectronic Systems Development - 2016. Proceedings / edited by A. Stempkovsky, Moscow, IPPM RAS, 2016. Part 4. P. 59-64.
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