Microsensors based on resonant structures are attractive because of their wide dynamic range, high sensitivity, and frequency shift output. In this paper we discuss theoretical and experimental charateristics of a two-terminal, or one-port, resonant microstructure. An equivalent circuit model that is useful for design and analysis of these devices is presented. This model is verified by experimental measurements, with a worst case error between between model and experimental parameters of 30%. We also describe a process for integrating polysilicon resonant microstructures with onchip NMOS circuitry. A novel feature of this process is the use of rapid thermal annealing (RTA) for strain-relief of the ion-implanted phosphorus-doped polysilicon. The RTA-strain-relieved polysilicon has a Young's modulus of 0.9~1012 dynes/cm2 and residual strain of 0.002% as measured by resonant frequency techniques. This low value of strain indicates that RTA is a useful strain-relief technique.

Microsensors based on active polysilicon resonant microstructures are attractive because of their wide dynamic range, high sensitivity and frequency shift output. In this paper, we discuss processing issues for integrating electrostaticallydriven and-sensed polysilicon microstructures with on-chip nMOS devices. Surface-micromachining using sacrificial spacer layers is used to obtain released microstructures. A novel feature is the use of rapid thermal annealing (RTA) for strain relief of the ion-implanted, phosphorousdoped polysilicon. Resonance frequencies of cantilever beams indicate a lower-bound Young's modulus of about 90 GPa and an upper-bound compressive residual strain of only 0.002%, indicating that RTA is potentially useful for strain relief.

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The atomic force microscope (AFM) has become a practical tool for mapping surface features with a resolution better than 10 nm. As such, in recent years the demand from industry for the AFM has increased significantly. For the AFM to be a practical instrument, however, its operation must be user friendly and its performance must be consistent. The essential element of an AFM is a microprobe which uses a cantilever mounted with a sharp stylus as a force sensor. For reproducible measurements, it is crucial that the physical dimensions of the cantilever and its stylus be consistent. Typical dimensions of the cantilever are 100–200 μm in length, 20–50 μm in width, and 0.5–1.2 μm in thickness. Typical stylus dimensions include a height of at least 3 μm and a radius of tip curvature of less than 100 nm. Silicon micromachining techniques were applied to fabricate microprobes with built-in alternating-current excitation of the polysilicon cantilevers in our previous work. This article presents a compatible process for the formation of a fine grained polysilicon stylus on the cantilever and an optical port for fiber-optic interferometry readout. The process demonstrates the feasibility of integrating both electronic drive and sensing circuitry onto the microprobe for future use in multichannel AFM systems.