Microfabricated high temperature sensing platform dedicated to scanning thermal microscopy (SThM)

The monitoring of heat flux is becoming more and more critical for many materials and structures approaching nanometric dimensions. Scanning Thermal Microscopy (SThM) is one of the tools available for thermal measurement at the nanoscale and requires calibration. Here we report on a micro-hotplate device made of a platinum heater suspended on thin silicon nitride (SiN) membranes integrating specific features for SThM calibration. These heated reference samples can include a localized resistive temperature sensors (RTD) or standalone platinum membranes (typically 10 x 10 mu m(2)) on which the temperature can be measured precisely. This functional area is dedicated to (1) estimate the thermal resistance between the SThM tip and hot surface contact; and to (2) evaluate the perturbation induced by the probe on the heat dissipation when the contact measurement is performed. The thermal design of these low-power calibration chips, their fabrication, including sensitive RTDs patterned using e-beam technology, as well as their electro-thermal and electro-mechanical characterizations are presented. Robust operation of the chips up to 500 degrees C has been demonstrated with their membrane mechanically stable up to 250 degrees C and a low-power consumption of 16 mW at this operating temperature. The temperature mapping of the active areas was performed using two physical principles: local SThM temperature measurement using a thermocouple-based micro-probe and optical imaging using Near-Infrared (NIR) microscopy. Measurements coupling on one hand SThM probe and the integrated RTD and, on the other hand, SThM probe with optical imaging, validated the functionality of the calibration chips. The latter open new perspectives in the calibration of SThM probes. (C) 2018 Elsevier B.V. All rights reserved.