Integrated movable micromechanical structures for sensors and actuators

Abstract

Abstract-Movable pin joints, gears, springs, cranks, and slider structures with dimensions measured in micrometers have been fabricated using silicon microfabrication technology. These micromechanical structures, which have important transducer applications, are batch-fabricated in an IC-compatible process. The movable mechanical elements are built on layers that are later removed so that they are freed for translation and rotation. A new undercut-and-refill technique that makes use of the high surface mobility of silicon atoms undergoing chemical vapor deposition is used to refill undercut regions in order to form restraining Ranges. Typical element sizes and masses are measured in millionths of a meter and billionths of a gram. The process provides the tiny structures in an assembled form, avoiding the nearly impossible challenge of handling such small elements individually.

Study of surface morphology and optical characterization of crystalline and multi-crystalline silicon surface textured in highly diluted alkaline solutions

“…The etch rate at 80 o C in the 1% KOH solution used here is estimated to approximately 0.15 µm/min which agrees with previous results (Alvi et al, 2008) and which, by fitting the experimental results could be expressed by the Arrhenius expression R = 7 x 10 7 exp (-0.6/kT) µm/min (1) Where the 0.6 eV activation energy lies within the 0.53-0.6 eV range previously reported for KOH etching mixtures ( Seidel et al, 1990;Fan et al, 1988;Zhou et al, 2008), and is far from the 1.2 eV Si deposition activation energy which consolidates the hillock formation by etching, rather than by deposition. These values and results, however, should be taken very cautiously, since much smaller pyramid and much dense pyramid distribution are obtained in wafers, which have received a saw damage removal in 30% KOH solution prior to texturing in 1% KOH at 80 o C as depicted in Figure 5, which shows that in this case the pyramids seem to maintain their small size in the 2-3 µm range, but are densely nucleated and cover all the surface area.…”

Characterization of Dynamic Friction in MEMS-Based Microball Bearings

“…Several different bearing and support structures were demonstrated for use in micromachines based on two categories: contact-type and noncontact-type. Previous contact-type bearings, like center-pin bearing with sliding bushings as support in the early polysilicon surface-micromachined micromotors [7], [8] suffered drastically from friction and wear. The friction and wear problems were less in wobble [9] and conical [10] micromotors, however, with a downfall in rotation speed.…”

A 100 GHz coplanar strip circuit tuned with a sliding planar backshort

“…A different device, such as a monolithically fabricated diode or SIS tunnel junction, could be used as the detector and a second tuning stub could be incorporated to provide further improvement in the response. Future versions of the sliding short could be fabricated on the transmission line itself, captivated by a micromechanical guiding structure with an integral means of electromechanical drive [3].…”

“…A sliding metal pattern, used to form a movable RF short circuit on a planar transmission line by spatially modulating the impedance, is introduced. This sliding, planar backshort can be readily fabricated by a variety of techniques, including micromachining techniques [3], which are particularly useful for short millimeter wavelength and submillimeter wavelength applications where characteristic dimensions are very small. …”