WRH professors Junko Morikawa and Sven Ingebrandt (School of Materials and Chemical Technology) published a paper in Sensors and Actuators A: Physical.

“Micro-Joule heater and temperature sensor array on a suspended silicon nitride membrane for measurement of in-plane thin film thermal diffusivity”

https://doi.org/10.1016/j.sna.2023.114635

Abstract:
In this work, a microfabricated chip device for measurement of in-plane thin film thermal diffusivity by temperature wave analysis (TWA) is presented. The device consists of a suspended silicon nitride (SiNx) membrane with a micro-patterned electric Joule heater in the center and several temperature sensors at different distances from the center. The SiNx membrane serves as a thermally isolated platform for the thin film of interest. The design of the measurement device and its fabrication process are presented. Temperature calibration of the RTDs and measurement of the steady-state temperature rise on the membrane were carried out. Finally, the thermal diffusivity of the bare chip and the bare chip coated with polymeric Parylene C thin films of different thicknesses was measured by a temperature wave method. The steady state temperature and temperature wave measurement were performed in high vacuum (p < 1 × 10⁻⁵ mbar). For the 150 nm thick low stress SiNx membrane, a thermal diffusivity of (1.77 ± 0.10)× 10⁻⁶ m² s⁻¹ was measured. The device is sensitive to differences in the thermal diffusivity resulting from changes in Parylene C layer thickness of a few hundred nanometers.