A Dual-Mode Anemometer Fabricated in 65-nm CMOS BEOL Without Postprocessing

A thermal anemometer was industrially fabricated without any pre-, co- or post-processing for the first time. The total sensor footprint is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.245 \,\mathrm{m}\mathrm{m}^{2}\,$</tex-math></inline-formula> using TSMC's <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$65$</tex-math></inline-formula>–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathrm{n}\mathrm{m}$</tex-math></inline-formula> CMOS process. The dual-mode anemometer measures wind speeds up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.2 \,\mathrm{m}\mathrm{/}\mathrm{s}$</tex-math></inline-formula> with a precision of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$3.1 \,\%$</tex-math></inline-formula> (or <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.037 \,\mathrm{m}\mathrm{/}\mathrm{s}$</tex-math></inline-formula>) calorimetrically. Alternatively, using the second hot-element mode the sensor measures in the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0 \,\mathrm{m}\mathrm{/}\mathrm{s}\,{\mathrm{to}}\, 7.5 \,\mathrm{m}\mathrm{/}\mathrm{s}$</tex-math></inline-formula> with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.1 \,\mathrm{m}\mathrm{/}\mathrm{s}$</tex-math></inline-formula> accuracy and an average <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.34 \,\%$</tex-math></inline-formula> precision. This is the first industrially fabricated thermopile-based CMOS anemometer, paving the way for a compact foundry SoC with inbuilt underlying computing for low-cost air speed monitoring.