On the Fracture Toughness of Polysilicon MEMS Structures

2000 ◽  
Vol 657 ◽  
Author(s):  
H. Kahn ◽  
R. Ballarini ◽  
A.H. Heuer
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Microelectromechanical Systems ◽  
Materials Science ◽  
Grain Structure ◽  
Processing Conditions ◽  
Mems Devices ◽  
Electrostatic Actuators ◽  
Wide Range ◽  
Sensitive Property

ABSTRACTThe mechanical properties of micromachined polysilicon are of great interest to designers of microelectromechanical systems (MEMS) devices. Numerous investigations have been carried out to determine the strength of MEMS-fabricated polysilicon structures, and the experimental results vary widely, depending on the experimental techniques, specimen geometries, and processing conditions. In order to determine whether these variations are inherent to all mechanical properties of MEMS materials, the fracture toughness, Kcrit, of micromachined polysilicon has been investigated, using a wide range of material microstructures (microstructure is used here in the Materials Science sense to mean the grain structure visible in a microscope, and not in the MEMS sense to mean small structures). Since fracture toughness is a fundamental materials property, whether or not it varies with microstructure and processing is an interesting question. We have confirmed that Kcrit is not a microstructure-sensitive property, using surface-micromachined specimens with sharp pre-cracks which are integrated with electrostatic actuators. The measured Kcrit is 1.0±0.1 MPa √m for a wide range of miscrostructures.

Grain Refinement and Deformation Behavior of Ultrafine Grained Pd and Pd-Ag Alloys Produced by HPT

2008 ◽  
Vol 584-586 ◽  
pp. 182-187
Author(s):  
Lilia Kurmanaeva ◽  
Yulia Ivanisenko ◽  
J. Markmann ◽  
Ruslan Valiev ◽  
Hans Jorg Fecht
Keyword(s):  
Mechanical Properties ◽  
Deformation Behavior ◽  
Materials Science ◽  
High Pressure Torsion ◽  
Uniform Elongation ◽  
Grain Structure ◽  
Coarse Grained ◽  
Ultrafine Grain ◽  
Ultrafine Grained ◽  
Ultrafine Grain Structure

Investigations of mechanical properties of nanocrystalline (nc) materials are still in interest of materials science, because they offer wide application as structural materials thanks to their outstanding mechanical properties. NC materials demonstrate superior hardness and strength as compared with their coarse grained counterparts, but very often they possess a limited ductility or show low uniform elongation due to poor strain hardening ability. Here, we present the results of investigation of the microstructure and mechanical properties of nc Pd and Pd-x%Ag (x=20, 60) alloys. The initially coarse grained Pd-x% Ag samples were processed by high pressure torsion, which resulted in formation of homogenous ultrafine grain structure. The increase of Ag contents led to the decrease of the resulted grain size and change in deformation behavior, because of decreasing of stacking fault energy (SFE). The samples with larger Ag contents demonstrated the higher values of hardness, yield stress and ultimate stress. Remarkably the uniform elongation had also increased with increase of strength.

Wafer-Level Strength and Fracture Toughness Testing of Surface-Micromachined MEMS Devices

1999 ◽  
Vol 605 ◽  
Author(s):  
H. Kahn ◽  
N. Tayebi ◽  
R. Ballarini ◽  
R.L. Mullen ◽  
A.H. Heuer
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Microelectromechanical Systems ◽  
Reliability Prediction ◽  
Bend Strength ◽  
Mems Devices ◽  
Wafer Level ◽  
Toughness Testing ◽  
Loading Devices

AbstractDetermination of the mechanical properties of MEMS (microelectromechanical systems) materials is necessary for accurate device design and reliability prediction. This is most unambiguously performed using MEMS-fabricated test specimens and MEMS loading devices. We describe here a wafer-level technique for measuring the bend strength, fracture toughness, and tensile strength of MEMS materials. The bend strengths of surface-micromachined polysilicon, amorphous silicon, and polycrystalline 3C SiC are 5.1±1.0, 10.1±2.0, and 9.0±1.0 GPa, respectively. The fracture toughness of undoped and P-doped polysilicon is 1.2±0.2 MPa√m, and the tensile strength of polycrystalline 3C SiC is 3.2±1.2 GPa. These results include the first report of the mechanical strength of micromachined polycrystalline 3C SiC.

Measurement of Force and Displacement for the Tribological Analysis of MEMS

2005 ◽  
Author(s):  
Joshua S. Wiehn ◽  
Michael T. Dugger ◽  
Thomas E. Buchheit
Keyword(s):  
Friction And Wear ◽  
Microelectromechanical Systems ◽  
Mems Devices ◽  
Force Output ◽  
Electrostatic Actuators ◽  
Friction Forces ◽  
Tangential Forces ◽  
Tribological Analysis ◽  
Output Characteristics ◽  
Force Calibration

The tribological interfaces in microelectromechanical systems (MEMS) pose a significant hurdle in the advancement of MEMS. In order to gain a better understanding of these tribological interfaces, meaningful friction and wear measurements of MEMS devices must be made at loads and speeds relevant to MEMS operation. Devices containing isolated tribological contacts from which quantitative friction forces can be extracted have been developed. Since independent in-plane measurement of forces are not available for structures that are on the order of microns thick, the normal and tangential forces between structures are typically estimated based on the calculation of the force output of electrostatic actuators, and the force required to bend compliant suspensions. We will discuss the uncertainties associated with the measurement of applied and friction forces in MEMS tribometers, and metrology needs for improved tribological analysis of dynamic microsystems. We will also present a method of independent force calibration in these devices, and compare measured output characteristics with those predicted from mechanics and electrostatics.

On-Chip Testing of Mechanical Properties of MEMS Devices

MRS Bulletin ◽  
2001 ◽  
Vol 26 (4) ◽  
pp. 300-301 ◽  
Author(s):  
H. Kahn ◽  
A.H. Heuer ◽  
R. Ballarini
Keyword(s):  
Mechanical Properties ◽  
Physical Environment ◽  
Microelectromechanical Systems ◽  
Mems Devices ◽  
Electrical Signals ◽  
Chip Testing ◽  
On Chip

The field of microelectromechanical systems (MEMS) involves the interaction of the physical environment with electrical signals through the use of microbatchfabricated devices. MEMS is a growing technology, and commercial MEMS products are becoming commonplace.

Hall-Petch and Multiple Linear Regression Equations for the Prediction of Mechanical Properties in Gamma-Based Titanium Aluminides

1996 ◽  
Vol 460 ◽  
Author(s):  
W. O. Soboyejo ◽  
A. B. O. Soboyejo ◽  
Y. Ni ◽  
C. Mercer
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Linear Regression ◽  
Multiple Linear Regression ◽  
Titanium Aluminides ◽  
Regression Equations ◽  
Combined Effects ◽  
Wide Range ◽  
Elongation To Failure ◽  
Prediction Of Mechanical Properties

In a recent paper, Mercer and Soboyejo [1] demonstrated the Hall-Petch dependence of basic room- and elevated-temperature (815°C) mechanical properties (0.2% offset strength), ultimate tensile strength, plastic elongation to failure and fracture toughness) on the average equiaxed/lamellar grain size. Simple Hall-Petch behavior was shown to occur in a wide range of extruded duplex α2-γ alloys (Ti-48A1, Ti-48Al-1.4Mn Ti-48Al-2Mn and Ti-48Al-1.5Cr). As in steels and other materials [2–5], simple Hall-Petch equations with were derived for the above properties [1]. However, the Hall-Petch equations did not include the effect of other variables that can affect to the basic mechanical properties of gamma alloys. Multiple linear regression equations for the prediction of the combined effects of several (alloying, microstructure and temperature) variables on basic mechanical properties temperature are presented in this paper.

scholarly journals Direct-Write Dewetting of High Melting Temperature Metals on Flexible Substrates

2019 ◽  
Vol 9 (15) ◽  
pp. 3165
Author(s):  
Anthony J. Ferrer ◽  
Anna Halajko ◽  
Glenn G. Amatucci
Keyword(s):  
Thin Films ◽  
Melting Temperature ◽  
Near Infrared ◽  
Microelectromechanical Systems ◽  
Modern Technology ◽  
Direct Write ◽  
High Melting ◽  
Mems Devices ◽  
High Melting Temperature ◽  
Wide Range

Microelectromechanical systems (MEMS) are pervasive in modern technology due to their reliability, small foot print, and versatility of function. While many of the manufacturing techniques for MEMS devices stem from integrated circuit (IC) manufacturing, the wide range of designs necessitates more varied processing techniques. Here, new details of a scanning laser based direct-write dewetting technique are presented as an expansion of previous demonstrations. For the first time, the ability to pattern a high melting temperature and high reflectance metallic thin films of Ni and Ag, respectively, on polymer substrates is reported. Novel methods for reducing the power necessary for processing highly reflective films are demonstrated by depositing very thin films of high near-infrared absorbance.

Effect of Moulding Temperature on Flexure, Impact Strength and Interlaminar Fracture Toughness of CF/PEI Composite

1996 ◽  
Vol 15 (11) ◽  
pp. 1117-1130 ◽  
Author(s):  
Meng Hou ◽  
Lin Ye ◽  
Yiu-Wing Mai
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Impact Strength ◽  
Woven Fabric ◽  
Mode I ◽  
Mode Ii ◽  
Void Content ◽  
Processing Conditions ◽  
Interlaminar Fracture ◽  
Fracture Growth

The effects of processing conditions on the mechanical properties of a CF/PEI woven fabric composite have been investigated. A compression moulding procedure using a hot press was applied to simulate the effects of various processing conditions. The mechanical properties of the CF/PEI composite were characterised by flexure, impact strength and interlaminar fracture tests in relation to the consolidation quality. Consolidation quality was studied through void content and density measurement. The results indicated that the consolidation quality of the composites was highly dependent on the processing temperature. The flexure properties. Mode I and Mode II fracture toughness for crack initiation and Mode II interlaminar fracture growth resistance correlated directly with consolidation quality. However, the Charpy impact strength and Mode I interlaminar fracture growth resistance both increased as the void content was increased because of a “multiple-crack” failure mechanism.

Novel Grain Refiner for Hypo- and Hyper-Eutectic Al-Si Alloys

2011 ◽  
Vol 690 ◽  
pp. 49-52 ◽  
Author(s):  
Magdalena Nowak ◽  
Nadendla Hari Babu
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Al Alloys ◽  
Grain Structure ◽  
Grain Refiner ◽  
Silicon Alloys ◽  
Fine Grain ◽  
Cooling Conditions ◽  
Wide Range ◽  
Master Alloys

A novel effective grain refiner for hypo and hyper-eutectic Aluminium-Silicon alloys has been developed. The composition of the grain refiner has been optimized to produce a fine grain structure and finer eutectic. Effectiveness of grain size under various cooling conditions has also been investigated to simulate various practical casting conditions. For comparative purposes, a wide range of Al alloys have been produced with the addition of commercially available Al-5Ti-B master alloys. The results show that the addition of novel grain refiner reduces the grain size significantly. As a result of fine grains, the porosity in the solidified alloys is remarkably lower. A notable improvement in mechanical properties has also been observed.

Mechanical properties of ion-implanted amorphous silicon

2004 ◽  
Vol 19 (1) ◽  
pp. 338-346 ◽  
Author(s):  
D.M. Follstaedt ◽  
J.A. Knapp ◽  
S.M. Myers
Keyword(s):  
Mechanical Properties ◽  
Phase Transition ◽  
Fracture Toughness ◽  
Finite Element ◽  
Elastic Modulus ◽  
Amorphous Silicon ◽  
Microelectromechanical Systems ◽  
Amorphous Structure ◽  
Alternative Material ◽  
Amorphous Si

We used nanoindentation coupled with finite element modeling to determine the mechanical properties of amorphous Si layers formed by self-ion implantation of crystalline Si at approximately 100 K. When the effects of the harder substrate on the response of the layers to indentation were accounted for, the amorphous phase was found to have a Young’s modulus of 136 ± 9 GPa and a hardness of 10.9 ± 0.9 GPa, which were 19% and 10% lower than the corresponding values for crystalline Si. The hardness agrees well with the pressure known to induce a phase transition in amorphous Si to the denser β–Sn-type structure of Si. This transition controls the yielding of amorphous Si under compressive stress during indentation, just as it does in crystalline Si. After annealing 1 h at 500 °C to relax the amorphous structure, the corresponding values increase slightly to 146 ± 9 GPa and 11.6 ± 1.0 GPa. Because hardness and elastic modulus are only moderately reduced with respect to crystalline Si, amorphous Si may be a useful alternative material for components in Si-based microelectromechanical systems if other improved properties are needed, such as increased fracture toughness.

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