Pull-In Behavior of Electrostatically Actuated Multistable Microstructures

2007 ◽  
Author(s):  
Slava Krylov ◽  
Shimon Seretensky ◽  
David Schreiber
Keyword(s):  
Electrostatic Force ◽  
Ritz Method ◽  
Actuation Voltage ◽  
Single Crystal Silicon ◽  
Multiple Equilibrium ◽  
Stable States ◽  
Crystal Silicon ◽  
Straight Beam ◽  
Equilibrium Configurations ◽  
Multiple Stable States

We present an analysis of the electromechanical behavior and stability of a capacitive-based Micro Electro Mechanical Systems (MEMS) device with non-monotonous stiffness-deflection dependence. As an example, we consider a flexible initially curved double clamped micro beam actuated by a distributed electrostatic force. Since the system exhibits both mechanical snap-through buckling and electrostatic pull-in instability, the equilibrium curve has two bifurcation points implying the existence of multiple equilibrium configurations. The multistability phenomenon described in the present work is a result of interaction between mechanical and electrostatic nonlinearities of the system and differs from the electrostatic pull-in based bistability and mechanical bistability associated with the snap-through buckling. The governing equations of the geometrically nonlinear curved Euler-Bernoulli beam are formulated in the framework of the shallow arch approximation. Actuating force is calculated using second order perturbation solution of the Laplace equation for an electric potential. A coupled electro mechanical model is built by the Rayleigh-Ritz method with linear undamped eigenmodes of a straight beam as base functions. After verification of the model results, we analyze the influence of initial geometry of the beam on the location (in terms of actuation voltage and deflections) of the critical points on the bifurcation diagram. It was found that for snap-through to take place, the initial elevation of the beam should be larger than a certain value whereas the existence of electrical pull-in instability is unconditional. In addition, the stable relative deflection of a curved beam is larger than of initially straight beam. Based on the model results, we present an example of a multistable actuator design. Devices of various configurations were fabricated of single crystal silicon using deep reactive ion etching and the existence of multiple stable states and multiple instability points was demonstrated experimentally.

Multistable Textured Shell Structures

2008 ◽  
Vol 54 ◽  
pp. 168-173 ◽  
Author(s):  
A.D. Norman ◽  
M.R. Golabchi ◽  
K.A. Seffen ◽  
Simon D. Guest
Keyword(s):  
Stable Equilibrium ◽  
Shell Structures ◽  
Stable Configuration ◽  
Reconfigurable Systems ◽  
Textured Surface ◽  
Stable States ◽  
Corrugated Shell ◽  
Equilibrium Configurations ◽  
Multiple Stable States ◽  
Structural Scale

Multistable structures are a promising basis for reconfigurable systems. A multistable structure will remain in one of its stable configurations until actuation forces it to move to another stable configuration. This paper will describe a promising method of forming structures with useful multiple stable states by using prestressed textured shell surfaces. Textured shell structures have features at a scale intermediate between the global structural scale, and the material scale, and can have some remarkable structural properties. This paper will describe two simple examples: a globally flat, but corrugated shell, and a globally curved, doubly corrugated shell. Both structures show additional stable equilibrium configurations that would not be possible without the textured surface.

Binary Excitation of a High-Q Bulk Acoustic Microresonator by Actuation Polarity Inversion

2008 ◽  
Author(s):  
Joshua E.-Y. Lee ◽  
Ashwin A. Seshia
Keyword(s):  
Actuation Voltage ◽  
Single Crystal Silicon ◽  
Quality Factors ◽  
Crystal Silicon ◽  
Polarity Inversion ◽  
High Q ◽  
Resonant Modes ◽  
Bulk Mode ◽  
Silicon Bulk ◽  
Modes Of Vibration

We present a technique for independently exciting two resonant modes of vibration in a single-crystal silicon bulk mode microresonator using the same electrode configuration through control of the polarity of the DC actuation voltage. Applications of this technique may include built-in temperature compensation by the simultaneous selective excitation of two closely spaced modes that may have different temperature coefficients of resonant frequency. The technique is simple and requires minimum circuit overhead for implementation. The technique is implemented on square plate resonators with quality factors as high as 3.06 × 106.

Tensile Test of Bulk- and Surface-Micromachined 0.1-νm Thick Silicon Film using Electrostatic Force Grip System

2001 ◽  
Vol 687 ◽  
Author(s):  
Toshiyuki Tsuchiya ◽  
Jiro Sakata ◽  
M. Shikida ◽  
K. Sato
Keyword(s):  
Thin Film ◽  
Force Measurement ◽  
Electrostatic Force ◽  
Silicon Film ◽  
Single Crystal Silicon ◽  
Surface Micromachining ◽  
Crystal Silicon ◽  
Release Process ◽  
Tensile Tester ◽  
Small Force

AbstractSingle-crystal silicon films of sub-micrometer thicknesses were tensile tested using a thin film tensile tester with an electrostatic force grip. The tester has been newly designed for this thin film. It uses a servo-controlled balance for small-force measurement with a resolution of less than 100 νN. The specimens were fabricated using bulk- and surface-micromachining starting with a SIMOX wafer, and an epi-SOI wafer. The bulk micromachined specimens were released from a wafer by anisotropic etching from the backside of the wafer. The specimen size was 0 to 500 νm long, 20 or 50 νm wide and 0.14 νm thick. The thinner specimens were fabricated by surface micromachining and dry release process using XeF2 and vapor HF etching to avoid stiction of the specimens. The size was 0 to 600 νm long, 1 to 20 νm wide and 0.05 νm thick. These wafers were (100) oriented and the loading axis of the specimen was <110>. The tensile strength of the bulk micromachined specimens ranged from 1.4 to 4.8 GPa for twelve samples and that of the surface micromachined specimens ranged from 1.0 to 6.8 GPa for seven samples.

Toward MEMS Displacement Sensor Based on Resonant Frequency Monitoring of Slightly Curved Beams

2015 ◽  
Author(s):  
Naftaly Krakover ◽  
Bojan R. Ilic ◽  
Slava Krylov
Keyword(s):  
Electrostatic Force ◽  
Single Crystal Silicon ◽  
Displacement Sensor ◽  
Design Parameters ◽  
Curved Beams ◽  
Crystal Silicon ◽  
Suggested Approach ◽  
Electrostatically Actuated ◽  
Frequency Monitoring ◽  
Post Buckling

In this work we report on operational principle, design and characterization of a generic electrostatically actuated micro displacement/acceleration sensor based on frequency monitoring of an initially curved double-clamped microbeam actuated by a close gap electrode. The displacement of the electrode attached to a proof mass results in varying electrostatic force and changing effective stiffness and frequency of the beam. The sensitivity is improved by choosing the working configurations in the vicinity of the critical snap-through buckling points of the beam. Reduced order model of the device was built by means of Gelerkin decomposition and was used for the feasibility study, evaluation of the design parameters and comparison with the experimental data. Devices of several configurations, which included initially straight as well as curved beams were fabricated from single crystal silicon and operated in open air environment. The responses were registered optically by laser Doppler vibrometry (LDV). Consistently with the model prediction, significant reduction in the frequency in the vicinity of the critical point followed by an increase of the frequency in the post-buckling configurations was observed in the experiments. Our theoretical and experimental results collectively demonstrate the feasibility of the suggested approach.

HREM observation of dislocations near room temperature fractures in silicon

1988 ◽  
Vol 46 ◽  
pp. 892-893
Author(s):  
M. H. Rhee ◽  
W. A. Coghlan
Keyword(s):  
Cross Section ◽  
Room Temperature ◽  
Single Crystal Silicon ◽  
Dislocation Nucleation ◽  
Back Side ◽  
Ion Milling ◽  
Crystal Silicon ◽  
Flat Surfaces ◽  
Induced Fractures ◽  
Vicker’S Microhardness

Silicon is believed to be an almost perfectly brittle material with cleavage occurring on {111} planes. In such a material at room temperature cleavage is expected to occur prior to any dislocation nucleation. This behavior suggests that cleavage fracture may be used to produce usable flat surfaces. Attempts to show this have failed. Such fractures produced in semiconductor silicon tend to occur on planes of variable orientation resulting in surfaces with a poor surface finish. In order to learn more about the mechanisms involved in fracture of silicon we began a HREM study of hardness indent induced fractures in thin samples of oxidized silicon.Samples of single crystal silicon were oxidized in air for 100 hours at 1000°C. Two pieces of this material were glued together and 500 μm thick cross-section samples were cut from the combined piece. The cross-section samples were indented using a Vicker's microhardness tester to produce cracks. The cracks in the samples were preserved by thinning from the back side using a combination of mechanical grinding and ion milling.

Analysis of Silicon-On-Insulator Structures Formed By Oxygen Ion Implantation

1985 ◽  
Vol 43 ◽  
pp. 300-301
Author(s):  
N. Lewis ◽  
E. L. Hall ◽  
A. Mogro-Campero ◽  
R. P. Love
Keyword(s):  
Ion Implantation ◽  
Single Crystal ◽  
Single Crystal Silicon ◽  
Silicon Layer ◽  
Device Fabrication ◽  
Silicon On Insulator ◽  
High Dose ◽  
Crystal Silicon ◽  
Oxygen Ion ◽  
Oxygen Ion Implantation

The formation of buried oxide structures in single crystal silicon by high-dose oxygen ion implantation has received considerable attention recently for applications in advanced electronic device fabrication. This process is performed in a vacuum, and under the proper implantation conditions results in a silicon-on-insulator (SOI) structure with a top single crystal silicon layer on an amorphous silicon dioxide layer. The top Si layer has the same orientation as the silicon substrate. The quality of the outermost portion of the Si top layer is important in device fabrication since it either can be used directly to build devices, or epitaxial Si may be grown on this layer. Therefore, careful characterization of the results of the ion implantation process is essential.

Strain measurement by means of bend contour microscopy

1989 ◽  
Vol 47 ◽  
pp. 210-211
Author(s):  
Philip D. Hren
Keyword(s):  
Strain Measurement ◽  
Large Angle ◽  
Single Crystal Silicon ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Silicon Membrane ◽  
Crystal Silicon ◽  
Contour Pattern ◽  
Convergent Beam ◽  
Low Symmetry

The pattern of bend contours which appear in the TEM image of a bent or curled sample indicates the shape into which the specimen is bent. Several authors have characterized the shape of their bent foils by this method, most recently I. Bolotov, as well as G. Möllenstedt and O. Rang in the early 1950’s. However, the samples they considered were viewed at orientations away from a zone axis, or at zone axes of low symmetry, so that dynamical interactions between the bend contours did not occur. Their calculations were thus based on purely geometric arguments. In this paper bend contours are used to measure deflections of a single-crystal silicon membrane at the (111) zone axis, where there are strong dynamical effects. Features in the bend contour pattern are identified and associated with a particular angle of bending of the membrane by reference to large-angle convergent-beam electron diffraction (LACBED) patterns.

TEM characterization of Au/Polysilicon interactions

1990 ◽  
Vol 48 (4) ◽  
pp. 650-651
Author(s):  
N. David Theodore ◽  
Leslie H. Allen ◽  
C. Barry Carter ◽  
James W. Mayer
Keyword(s):  
Solid Phase ◽  
Single Crystal Silicon ◽  
Chemical Vapor ◽  
Electrical Contacts ◽  
Silicon Substrates ◽  
Crystal Silicon ◽  
Transmission Electron ◽  
Polysilicon Films ◽  
The Stability

Metal/polysilicon investigations contribute to an understanding of issues relevant to the stability of electrical contacts in semiconductor devices. These investigations also contribute to an understanding of Si lateral solid-phase epitactic growth. Metals such as Au, Al and Ag form eutectics with Si. reactions in these metal/polysilicon systems lead to the formation of large-grain silicon. Of these systems, the Al/polysilicon system has been most extensively studied. In this study, the behavior upon thermal annealing of Au/polysilicon bilayers is investigated using cross-section transmission electron microscopy (XTEM). The unique feature of this system is that silicon grain-growth occurs at particularly low temperatures ∽300°C).Gold/polysilicon bilayers were fabricated on thermally oxidized single-crystal silicon substrates. Lowpressure chemical vapor deposition (LPCVD) at 620°C was used to obtain 100 to 400 nm polysilicon films. The surface of the polysilicon was cleaned with a buffered hydrofluoric acid solution. Gold was then thermally evaporated onto the samples.

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