Microcalorimetry applications of a surface micromachined bolometer-type thermal probe

This article describes a surface micromachined scanning thermal probe that uses polyimide as the structural material and an embedded thin film metal resistor as the sensing element. The typical dimensions of a fabricated probe are 350 μm in length, 50 μm in width, and 3–10 μm in thickness. The resistor and the scanning tip are formed by sputter-deposited films of nickel and tungsten, which provide temperature coefficient of resistance of 2963 ppm/K. The probe is used to map surface and subsurface spatial variations in the thermal conductivity of a test sample. It is also used as a spatially localized microcalorimeter to measure the glass transition temperature of photoresists: the values obtained for Shipley 1813 and UV6 are 118±1 °C and 137±1 °C, respectively. These are in close agreement with results obtained by other methods that utilize larger samples.