A silicon micromachined scanning thermal profiler with integrated elements for sensing and actuation

The thermal profiler is a scanning probe microscope with a miniature thermocouple (TC) at its tip which provides topographic and thermographic information by sensing heat conducted across a small air gap. The silicon micromachined thermal profilers (SMTP's) described in this paper are structurally comprised of a probe that can be longitudinally actuated by an integrated electrostatically driven suspension. A polysilicon-gold TC is located near the probe tip, which overhangs a glass substrate; a resistive heater is integrated with the base. An IC-compatible, 8-mask fabrication process has been developed and SMTP's with various types of frames and probes have been designed, fabricated, and thermally characterized. The maximum thermoelectric signal available from a 7-TC thermopile probe has been measured at 824 mV/W of input power to the heater, whereas from a simpler design it was 48 mV/W. Simple dithered and nondithered scans are presented to demonstrate the basic functionality of fabricated devices. The noise due to our test setup has been measured at approximate to 20 mK. For a 1 mu m x 0.5 mu m tip and a 0.1 mu m long air gap the spatial resolution and the device NETD have been theoretically estimated as approximate to 3.33 nm and approximate to 0.1 mK/root Hz, respectively.