MOSFET temperature sensors for on-chip thermal testing

•A MOSFET can be used as a sensor to measure on-chip thermal variations caused by the power dissipated by other embedded circuits.•In the context of on-chip thermal testing, temperature sensors based on MOSFET have advantages versus those based on BJT.•The main advantages are in terms of compatibility to process, layout area and sensitivity to thermal variations.•Theoretical models, simulations, and experimental data resulting from a 0.35 μm CMOS technology prove the previous ideas.

This paper analyses theoretically and experimentally the temperature dependence of metal–oxide–semiconductor field-effect transistors (MOSFET) with the aim of using them as a temperature sensor in on-chip thermal testing applications. The proposed analysis provides rules for the selection of the dimensions and the bias current of the MOSFET in order to have a high sensitivity to on-chip thermal variations generated by the circuit under test (CUT). These theoretical predictions are then contrasted with simulations and experimental data resulting from MOSFETs fabricated in a commercial 0.35 μm CMOS technology. Simulations and experimental results with MOSFETs are also compared with those obtained using a parasitic bipolar junction transistor (BJT). Such a comparison shows that MOSFET-based temperature sensors offer, in the context of on-chip thermal testing, the following advantages: fully compatible with the fabrication process, less area required around the CUT, and more sensitive to on-chip thermal variations caused by the CUT.