Spontaneous mechanical oscillation of a DC driven single crystal

There is a large interest to decrease the size of mechanical oscillators since this can lead to miniaturization of timing and frequency referencing devices, but also because of the potential of small mechanical oscillators as extremely sensitive sensors. Here we show that a single crystal silicon resonator structure spontaneously starts to oscillate when driven by a constant direct current (DC). The mechanical oscillation is sustained by an electrothermomechanical feedback effect in a nanobeam, which operates as a mechanical displacement amplifier. The displacement of the resonator mass is amplified, because it modulates the resistive heating power in the nanobeam via the piezoresistive effect, which results in a temperature variation that causes a thermal expansion feedback-force from the nanobeam on the resonator mass. This self-amplification effect can occur in almost any conducting material, but is particularly effective when the current density and mechanical stress are concentrated in beams of nano-scale dimensions

Nondestructive Submicron Dimensional Metrology Using the Scanning Electron Microscope

The evolution of integrated circuit dimensions into the submicron region for the Very Large Scale Integration (VLSI) and Very High Speed Integrated Circuits (VHSIC) programs necessitates inspection techniques with a resolution exceeding that of the optical microscope. Inspection using scanning electron microscopes (SEM), operated in the low accelerating voltage mode, is becoming common place in the on-line fabrication of these submicron devices due to the high spatial resolution and greater depth of field afforded by these instruments. Use of the SEM is necessitated by the desire of many processing facilities which presently work at a 10% process control level to implement process control of 5% or better. This means that the process precision goal is now (or soon will be) in the nanometer range. Even though optical microscopes can be useful for critical linewidth measurement and inspection to about 0.5μm, many fabrication lines presently are integrating low-voltage scanning electron microscopes into the production sequence at chip levels of 1.25-μm geometry and below. This enables the training of operators and the acquisition and development of expertise and experience with control charts for this type of instrumentation. Advanced scanning e-beam instruments are presently being developed to facilitate this work and to do automated inspection