| This thesis addresses the development of micromachined probes for scanning thermal microscopy and microcalorimetry applications for photoresist research. A bolometer and a thin film metal thermocouple (TC) embedded within a polyimide probe shank are used as sensing elements. The probe tip is created by molding the thin film metal into an anisotropically etched notch in the silicon substrate resulting in a tip diameter about 50 nm. Tip clearance from the substrate is obtained by flipping over the polyimide probe, and restraining it by a thin film gold thermocompression bond. The flip-over method for providing the tip clearance exploits the mechanical flexibility of polyimide, and avoids the dissolution of the substrate material from underneath the tip. This unique surface micromachined process requires 7 masking steps, and can be executed at temperature ≤350°C, which is compatible with post processing a CMOS circuit because it eliminates high temperature steps and wafer dissolution. The advantages of these probes over the commercially available wire probe include high spatial resolution, high temperature sensitivity, and low contact force.; The fabricated Ni/W and chromel/alumel TC probes have Seebeck coefficient of 22.5 μV/K, and 37.5 μV/K, respectively with thermally limited frequency response about 500 Hz, and spring constant of 0.082 N/m for a 250 x 50 x 3 μm probe. The bolometer probes are used to study exposed but undeveloped photoresist latent images in features of 70 nm, the glass transition temperatures of photoresists UV6 and Shipley 1813, and the acid diffusion in photoresists during post exposure bake. The results drawn from the photoresist applications show that the probes are able to detect the photoresist thickness change smaller than 1% with spatial resolution of sub-50 um. These probes are also flexible enough to map soft materials even without contact force feedback control with spatial resolution better than 500 nm. Scanning of dried HeLa cells is also demonstrated with high quality. By covering the front side of the device with a polyimide layer, the probe is also shown to be suitable for scanning in aqueous environments. |
