A scanning thermal microscopy system with a temperature dithering, servo-controlled interface circuit

This paper describes a thermal imaging system which includes a customized micromachined thermal probe and circuit interface for a scanning microscopy instrument. The probe shank is made from polyimide for mechanical compliance and high thermal isolation, and has a thin-film metal tip of ≈50 nm in diameter. The circuit provides closed-loop control of the tip temperature and also permits it to be dithered, facilitating scanning microcalorimetry applications. This paper explains system design and optimization including both electrical and thermal analyses. Sample scans of patterned photoresist demonstrate noise-limited resolution of 29 pW/K in thermal conductance. Applications of the thermal imager extend from ULSI lithography research to biological diagnostics.