Multiplexed thermal-diffusivity-based temperature sensors
Öykü Tansel (TU Delft - Electrical Engineering, Mathematics and Computer Science)
KAA Makinwa – Mentor (TU Delft - Microelectronics)
Dante Muratore – Graduation committee member (TU Delft - Bio-Electronics)
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Abstract
Due to the precise lithography and highly pure silicon used in IC technology, thermal-diffusivity (TD) temperature sensors can achieve high accuracy without the need for trimming. TD sensors employ electrothermal filters (ETFs) to measure the thermal diffusivity of silicon, i.e. the rate at which heat diffuses through silicon, which is a well-defined function of temperature. This thesis presents two approaches to improve the accuracy and resolution of TD sensors. The first approach investigates the effect of variations in ETF geometry on sensor resolution and proposes a multiplexing scheme to utilize a single readout circuit for reading out multiple ETFs. The second approach aims to investigate the effect of improvements in CMOS technology on sensor accuracy by scaling two ETFs to the 65nm process from the 180nm process. A first-order phase-domain delta-sigma modulator is designed for the readout of the ETFs in the 65nm process, and the previously designed multiplexing scheme is used for cost and time-efficient tape-out. Based on the estimated lithographic error of the 65nm process, the two ETFs are expected to achieve untrimmed inaccuracies of 0.18℃(3𝜎) and 0.36℃(3𝜎), respectively.