An SOI thermal-diffusivity-based temperature sensor with ±0.6 °C (3σ) untrimmed inaccuracy from −70 °C to 225 °C

This work presents the first thermal-diffusivity-based temperature sensor realized in SOI technology; it has an untrimmed inaccuracy of ±0.6 °C (3σ) from −70 °C up to 225 °C and uses up to 7× less power than prior art. The sensor uses the phase shift of an Electrothermal Filter (ETF) as a proxy for the thermal diffusivity of silicon, D, which has a well-defined 1/T1.8 temperature dependence. The ETF's output is then digitized by a phase-domain sigma-delta modulator. Measured data from several process lots show that that the sensor's inaccuracy is mainly limited by lithographic spread, and not by wafer-to-wafer or batch-to-batch variations.