Adhesion and Friction Studies of Silicon and Hydrophobic and Low Friction Films and Investigation of Scale Effects

2004 ◽  
Vol 126 (3) ◽  
pp. 583-590 ◽  
Author(s):  
Bharat Bhushan ◽  
Huiwen Liu ◽  
Stephen M. Hsu
Keyword(s):  
Microelectromechanical Systems ◽  
Scale Effects ◽  
Single Crystal Silicon ◽  
Operating Conditions ◽  
Nanoelectromechanical Systems ◽  
Low Friction ◽  
Self Assembled Monolayer ◽  
Crystal Silicon ◽  
Solid Films ◽  
Friction Measurements

Tribological properties are crucial to the reliability of microelectromechanical systems/nanoelectromechanical systems (MEMS/NEMS). In this study, adhesion and friction measurements are made at micro and nanoscales on single-crystal silicon (commonly used in MEMS/NEMS) and hydrophobic and low friction films. These include diamondlike carbon (DLC), chemically bonded perfluoropolyether (PFPE), and self-assembled monolayer (SAM) films. Since MEMS/NEMS devices are expected to be used in various environments, measurements are made at a range of velocities, humidities, and temperatures. The relevant adhesion and friction mechanisms are discussed. It is found that solid films of DLC, PFPE, and SAM can reduce the adhesion and friction of silicon. These films can be used as anti-adhesion films for MEMS/NEMS components under different environments and operating conditions. Finally, the adhesion and friction data clearly show scale dependence. The scale effects on adhesion and friction are also discussed in the paper.

Thermal Conductivity of Single-Crystal Silicon Microbridges Measured by Electrical Resistance Thermometry and Time-Domain Thermoreflectance

2012 ◽  
Author(s):  
Timothy S. English ◽  
Leslie M. Phinney ◽  
Patrick E. Hopkins ◽  
Justin R. Serrano
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Time Domain ◽  
Electrical Resistance ◽  
Microelectromechanical Systems ◽  
Single Crystal Silicon ◽  
Operating Conditions ◽  
Equation Modeling ◽  
Crystal Silicon ◽  
Resistance Thermometry

Accurate thermal conductivity values are essential to the modeling, design, and thermal management of microelectromechanical systems (MEMS) and devices. However, the experimental technique best suited to measure thermal conductivity, as well as thermal conductivity itself, varies with the device materials, fabrication conditions, geometry, and operating conditions. In this study, the thermal conductivity of boron doped single-crystal silicon-on-insulator (SOI) microbridges is measured over the temperature range from 77 to 350 K. The microbridges are 4.6 mm long, 125 μm tall, and two widths, 50 or 85 μm. Measurements on the 85 μm wide microbridges are made using both steady-state electrical resistance thermometry and optical time-domain thermoreflectance. A thermal conductivity of ∼ 77 W/mK is measured for both microbridge widths at room temperature, where both experimental techniques agree. However, a discrepancy at lower temperatures is attributed to differences in the interaction volumes and in turn, material properties, probed by each technique. This finding is qualitatively explained through Boltzmann transport equation modeling under the relaxation time approximation.

Mean Free Path Effects on the Experimentally Measured Thermal Conductivity of Single-Crystal Silicon Microbridges

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Timothy S. English ◽  
Leslie M. Phinney ◽  
Patrick E. Hopkins ◽  
Justin R. Serrano
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Microelectromechanical Systems ◽  
Single Crystal Silicon ◽  
Operating Conditions ◽  
Silicon On Insulator ◽  
Beam Diameter ◽  
Boltzmann Transport ◽  
Crystal Silicon ◽  
Thermal Conductivities

Accurate thermal conductivity values are essential for the successful modeling, design, and thermal management of microelectromechanical systems (MEMS) and devices. However, the experimental technique best suited to measure the thermal conductivity of these systems, as well as the thermal conductivity itself, varies with the device materials, fabrication processes, geometry, and operating conditions. In this study, the thermal conductivities of boron doped single-crystal silicon microbridges fabricated using silicon-on-insulator (SOI) wafers are measured over the temperature range from 80 to 350 K. The microbridges are 4.6 mm long, 125 μm tall, and either 50 or 85 μm wide. Measurements on the 85 μm wide microbridges are made using both steady-state electrical resistance thermometry (SSERT) and optical time-domain thermoreflectance (TDTR). A thermal conductivity of 77 Wm−1 K−1 is measured for both microbridge widths at room temperature, where the results of both experimental techniques agree. However, increasing discrepancies between the thermal conductivities measured by each technique are found with decreasing temperatures below 300 K. The reduction in thermal conductivity measured by TDTR is primarily attributed to a ballistic thermal resistance contributed by phonons with mean free paths larger than the TDTR pump beam diameter. Boltzmann transport equation (BTE) modeling under the relaxation time approximation (RTA) is used to investigate the discrepancies and emphasizes the role of different interaction volumes in explaining the underprediction of TDTR measurements.

Assembly and Testing of Surface Micromachined, Piezoresistive Polysilicon Pressure Sensors

1999 ◽  
Author(s):  
Todd F. Miller ◽  
David J. Monk ◽  
Gary O’Brien ◽  
William P. Eaton ◽  
James H. Smith
Keyword(s):  
Pressure Sensor ◽  
Microelectromechanical Systems ◽  
Pressure Sensors ◽  
Single Crystal Silicon ◽  
Surface Micromachining ◽  
Process Technology ◽  
Crystal Silicon ◽  
Noise Characteristics ◽  
Testing Techniques ◽  
Piezoresistive Pressure Sensors

Abstract Surface micromachining is becoming increasingly popular for microelectromechanical systems (MEMS) and a new application for this process technology is pressure sensors. Uncompensated surface micromachined piezoresistive pressure sensors were fabricated by Sandia National Labs (SNL). Motorola packaged and tested the sensors over pressure, temperature and in a typical circuit application for noise characteristics. A brief overview of surface micromachining related to pressure sensors is described in the report along with the packaging and testing techniques used. The electrical data found is presented in a comparative manner between the surface micromachined SNL piezoresistive polysilicon pressure sensor and a bulk micromachined Motorola piezoresistive single crystal silicon pressure sensor.

scholarly journals The Effects of Cold Arm Width and Metal Deposition on the Performance of a U-Beam Electrothermal MEMS Microgripper for Biomedical Applications

Micromachines ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 167 ◽  
Author(s):  
Marija Cauchi ◽  
Ivan Grech ◽  
Bertram Mallia ◽  
Pierluigi Mollicone ◽  
Nicholas Sammut
Keyword(s):  
Microelectromechanical Systems ◽  
Coefficient Of Thermal Expansion ◽  
Numerical Models ◽  
Lateral Displacement ◽  
Single Crystal Silicon ◽  
Silicon On Insulator ◽  
Adhesion Promoter ◽  
Crystal Silicon ◽  
Element Analysis ◽  
Human Red Blood Cells

Microelectromechanical systems (MEMS) have established themselves within various fields dominated by high-precision micromanipulation, with the most distinguished sectors being the microassembly, micromanufacturing and biomedical ones. This paper presents a horizontal electrothermally actuated ‘hot and cold arm’ microgripper design to be used for the deformability study of human red blood cells (RBCs). In this study, the width and layer composition of the cold arm are varied to investigate the effects of dimensional and material variation of the cold arm on the resulting temperature distribution, and ultimately on the achieved lateral displacement at the microgripper arm tips. The cold arm widths investigated are 14 μ m, 30 μ m, 55 μ m, 70 μ m and 100 μ m. A gold layer with a thin chromium adhesion promoter layer is deposited on the top surface of each of these cold arms to study its effect on the performance of the microgripper. The resultant ten microgripper design variants are fabricated using a commercially available MEMS fabrication technology known as a silicon-on-insulator multi-user MEMS process (SOIMUMPs)™. This process results in an overhanging 25 μ m thick single crystal silicon microgripper structure having a low aspect ratio (width:thickness) value compared to surface micromachined structures where structural thicknesses are of the order of 2 μ m. Finite element analysis was used to numerically model the microgripper structures and coupled electrothermomechanical simulations were implemented in CoventorWare ® . The numerical simulations took into account the temperature dependency of the coefficient of thermal expansion, the thermal conductivity and the electrical conductivity properties in order to achieve more reliable results. The fabricated microgrippers were actuated under atmospheric pressure and the experimental results achieved through optical microscopy studies conformed with those predicted by the numerical models. The gap opening and the temperature rise at the cell gripping zone were also compared for the different microgripper structures in this work, with the aim of identifying an optimal microgripper design for the deformability characterisation of RBCs.

Multiple Wafer Bonding for MEMS Applications

2001 ◽  
Vol 681 ◽  
Author(s):  
M. Reiche ◽  
M. Haueis ◽  
J. Dual ◽  
C. Cavalloni ◽  
R. Buser
Keyword(s):  
Wafer Bonding ◽  
Microelectromechanical Systems ◽  
Single Crystal Silicon ◽  
Force Sensor ◽  
Semiconductor Wafer ◽  
Crystal Silicon ◽  
Static Loads ◽  
3 Dimensional ◽  
Wafer Direct Bonding ◽  
Better Than

ABSTRACTMost of the microelectromechanical systems (MEMS) require a 3-dimensional architecture which can efficiently be realized by multiple semiconductor wafer direct bonding. The present paper demonstrates the method on a force sensor for high resolution measurements of static loads. To minimize temperature stress an all-in silicon solution was developed in contrast to micromachined resonant force sensors published already in the literature.The presented force sensor integrates load coupling, the excitation and detection of the vibration of the microresonator in one and the same single crystal silicon package. First measurements proved a sensitivity of 26 Hz/N and a resolution better than 3 mN.

Interfacial Fluid Pressure and Its Effects on SiO2 Chemical Mechanical Polishing

2000 ◽  
Vol 613 ◽  
Author(s):  
C. Zhou ◽  
L. Shan ◽  
J. R. Hight ◽  
S.H. Ng ◽  
A. J. Paszkowski ◽  
...  
Keyword(s):  
Material Removal ◽  
Removal Rate ◽  
Fluid Pressure ◽  
Single Crystal Silicon ◽  
Ambient Fluid ◽  
Crystal Silicon ◽  
Order Of Magnitude ◽  
Interfacial Fluid ◽  
Friction Measurements ◽  
P Type

ABSTRACTIn this paper, the experimental results of interfacial fluid pressure and friction measurements during polishing are presented, as well as their dependence on some major process variables. Under simulated conditions, a sub-ambient fluid pressure was observed, and its magnitude was of the same order of magnitude as the applied polishing load. Since this fluid pressure is non-uniformly distributed, the contact stress, obtained by combining the effects of both applied load and the fluid pressure, is not uniform across the wafer and will result in non-uniform material removal. The mechanism of the presence of the fluid pressure was investigated, and an analytical model was developed to predict the magnitude and distribution of this fluid pressure. The effects of the sub-ambient fluid pressure on material removal rate and profile were tested with thermally grown silicon dioxide on 100mm diameter, P-type (100), single crystal silicon wafers. The polishing experiments show the effect of sub-ambient fluid pressure on polishing rate and profile.

Micromechanical and tribological characterization of doped single-crystal silicon and polysilicon films for microelectromechanical systems devices

1997 ◽  
Vol 12 (1) ◽  
pp. 54-63 ◽  
Author(s):  
Bharat Bhushan ◽  
Xiaodong Li
Keyword(s):  
Single Crystal ◽  
Microelectromechanical Systems ◽  
Single Crystal Silicon ◽  
Crystal Silicon ◽  
Polysilicon Film ◽  
Type Silicon ◽  
Boron Doped ◽  
Polysilicon Films ◽  
Tribological Characterization

Microelectromechanical systems (MEMS) devices are made of doped single-crystal silicon, LPCVD polysilicon films, and other ceramic films. Very little is understood about tribology and mechanical characterization of these materials on micro- to nanoscales. Micromechanical and tribological characterization of p-type (lightly boron-doped) single-crystal silicon (referred to as “undoped”), p+-type (boron doped) single-crystal silicon, polysilicon bulk, and n+-type (phosphorous doped) LPCVD polysilicon films have been carried out. Hardness, elastic modulus, and scratch resistance of these materials were measured by nanoindentation and microscratching using a nanoindenter. Friction and wear properties were measured using an accelerated ball-on-flat tribometer. It is found that the undoped silicon and polysilicon bulk as well as n+-type polysilicon film exhibit higher hardness and elastic modulus than the p+-type silicon. The polysilicon bulk and n+-type polysilicon film exhibit the lowest friction and highest resistance to scratch and wear followed by the undoped silicon and with the poorest behavior of the p+-type silicon. During scratching, the p+-type silicon deforms like a ductile metal.

Microfrictional Properties of Titanium Carbide

2003 ◽  
Vol 782 ◽  
Author(s):  
Syed Imad-Uddin Ahmed ◽  
Giuseppe Bregliozzi ◽  
Henry Haefke
Keyword(s):  
Thin Films ◽  
Relative Humidity ◽  
Titanium Carbide ◽  
Microelectromechanical Systems ◽  
Tribological Behavior ◽  
Surface Characteristics ◽  
Operating Conditions ◽  
Film Material ◽  
Self Assembled Monolayer ◽  
Silicon Based

ABSTRACTThe tribological issues associated with silicon-based microelectromechanical systems (MEMS) are well known. A popular solution to improve the tribological behavior is to apply different kinds of thin films. One film material, shown to have favorable properties in specialty applications, and which may also be suited for MEMS, is titanium carbide (TiC).This paper examines the microfrictional properties of titanium carbide surfaces with two surface roughnesses sliding against polished 2 mm diameter TiC counterbodies. A comparison of the microfrictional behavior is made with various other surfaces sliding against the same material. Results indicate that the microfriction of smooth TiC sliding against a smooth TiC surface is low and similar to silicon or TiC sliding against a hydrophobic self-assembled monolayer. However, friction increases when the polished TiC ball slides against a rough TiC surface. Experiments at various relative humidities show that friction increases with increase in the relative humidity for two smooth TiC surfaces sliding against one another, but is reduced at higher relative humidity if the surface of one of the sliding partners is considerably rough.This microfrictional study shows that TiC is well suited for microtribological applications. However, for optimal performance, the surface characteristics need to be tailored to the operating conditions.

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