The Experts below are selected from a list of 78 Experts worldwide ranked by ideXlab platform
Bharat Bhushan - One of the best experts on this subject based on the ideXlab platform.
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micromechanical and tribological characterization of doped single crystal silicon and Polysilicon Films for microelectromechanical systems devices
Journal of Materials Research, 1997Co-Authors: Bharat BhushanAbstract: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.
Thomas W Kenny - One of the best experts on this subject based on the ideXlab platform.
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hermeticity and diffusion investigation in Polysilicon Film encapsulation for microelectromechanical systems
Journal of Applied Physics, 2009Co-Authors: Bongsang Kim, R N Candler, R Melamud, M A Hopcroft, S Yoneoka, Hyung Kyu Lee, M Agarwal, Saurabh A Chandorkar, Gary Yama, Thomas W KennyAbstract:The hermeticity and diffusion behavior of “epi-seal” encapsulation [R. N. Candler et al., J. Microelectromech. Syst. 15, 1446 (2006); B. Kim et al., Proceedings of the ASME 2007 InterPACK Conference (InterPACK’07), 33234 (2007)], an epitaxially deposited Polysilicon Film encapsulation for microelectromechanical systems (MEMSs), were investigated. MEMS resonators with pressure sensitive quality factor were fabricated inside episeal cavities. By measuring the quality factor and inferring cavity pressure, leakage through the encapsulation was studied as a continuation of previous hermeticity investigations [B. Kim et al., Proceedings of the 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE, pp. 413–416 (2004)]. During long-term monitoring performed at 100 °C in a normal atmosphere, the encapsulated cavity pressure increased at a rate of 5–10 mTorr/yr, whereas no measurable pressure change could be detected in our previous room temperature measurement performed with identically designed and encapsulated resonators. To identify the cause of this pressure increase, the diffusive gas species and diffusion pathways in the epi-seal encapsulation were investigated experimentally. Various gas species in the atmosphere were tested in a 400 °C accelerated environment. These tests identified hydrogen and helium as highly diffusive gas species and showed argon and nitrogen to be much less diffusive under these conditions. Also, a series of devices with modifications of encapsulation geometry was tested in a hydrogen environment at 400 °C. Silicon dioxide, used for sacrificial and passivation layers, was identified as the primary diffusion pathway through the epi-seal encapsulation. These experimental results and diffusion pathway models were compared with the diffusion activation energy of various gas species in semiconductor materials, enabling design and process optimization for improved hermeticity of wafer-scale thin-Film encapsulation for MEMS devices.
K Najafi - One of the best experts on this subject based on the ideXlab platform.
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An all-silicon single-wafer micro-g accelerometer with a combined surface and bulk micromachining process
Journal of Microelectromechanical Systems, 2000Co-Authors: Navid Yazdi, K NajafiAbstract:This paper reports an all-silicon fully symmetrical z-axis micro-g accelerometer that is fabricated on a single-silicon wafer using a combined surface and bulk fabrication process. The microaccelerometer has high device sensitivity, low noise, and low/controllable damping that are the key factors for attaining /spl mu/g and sub-/spl mu/g resolution in capacitive accelerometers. The microfabrication process produces a large proof mass by using the whole wafer thickness and a large sense capacitance by utilizing a thin sacrificial layer. The sense/feedback electrodes are formed by a deposited 2-3 /spl mu/m Polysilicon Film with embedded 25-35 /spl mu/m-thick vertical stiffeners. These electrodes, while thin, are made very stiff by the thick embedded stiffeners so that force rebalancing of the proof mass becomes possible. The Polysilicon electrodes are patterned to create damping holes. The microaccelerometers are batch-fabricated, packaged, and tested successfully. A device with a 2-mm/spl times/1-mm proof mass and a full bridge support has a measured sensitivity of 2 pF/g. The measured sensitivity of a 1-mm/spl times/1-mm accelerometer with a cantilever support is 19.4 pF/g. The calculated noise floor of these devices at atmosphere are 0.23 /spl mu/g//spl radic/Hz and 0.16 /spl mu/g//spl radic/Hz, respectively.
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An all-silicon single-wafer fabrication technology for precision microaccelerometers
Proceedings of International Solid State Sensors and Actuators Conference (Transducers '97), 1997Co-Authors: Navid Yazdi, K NajafiAbstract:This paper reports a novel all-silicon single-wafer fabrication technology for high precision capacitive accelerometers. This technology combines both surface and bulk micromachining to attain a large proofmass, controllable/small damping, and a small airgap for large capacitance variation. The microfabrication process provides large proofmass by using the whole wafer thickness, and a large sense capacitance by utilizing a thin sacrificial layer. The sense/feedback electrodes are formed by a deposited 2 /spl mu/m Polysilicon Film with embedded 20-30 /spl mu/m thick vertical stiffeners. These electrodes, while thin, are made very stiff by the thick embedded stiffeners so that force rebalancing of the proofmass becomes possible. The Polysilicon electrodes are patterned to create damping holes. Several prototype microaccelerometers are fabricated successfully. Sensitivity of the devices with 2 mm/spl times/1 mm proofmass and full-bridge support are measured to be 2pF/g.
Laurent Pichon - One of the best experts on this subject based on the ideXlab platform.
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Silicon nanowires based resistors as gas sensors
Sensors and Actuators B: Chemical, 2011Co-Authors: Fouad Demami, Régis Rogel, Anne-claire Salaün, Laurent PichonAbstract:Silicon nanowires (SiNWs) are synthesized following two methods: i) the VLS (Vapor-Liquid-Solid) growth technique (bottom up approach), and ii) the sidewall spacer fabrication (top down approach) commonly used in microelectronic industry. The VLS growth technique uses gold nanoparticles to activate the vapor deposition of the precursor gas and to initiate 100 nm diameter SiNWs network growth. In the case of the sidewall spacer method, a Polysilicon layer is deposited by LPCVD (Low Pressure Chemical Vapor Deposition) technique on SiO2 wall patterned by conventional UV lithography technique. Polysilicon Film is then plasma etched. Accurate control of the etching rate leads to the formation of spacers with a 100 nm curvature radius that can be used as Polysilicon NWs. Each kind of nanowires is integrated into resistors fabrication. Electrical measurements show the potential use of these SiNWs based resistors as gas sensors for ammonia (NH3) and smoke detection.
H Ahmed - One of the best experts on this subject based on the ideXlab platform.
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electrical and structural properties of solid phase crystallized polycrystalline silicon and their correlation to single electron effects
Journal of Applied Physics, 2001Co-Authors: Y T Tan, Z A K Durrani, H AhmedAbstract:Single-electron transistors have been fabricated in solid phase crystallized polycrystalline silicon Films deposited on SiO2 layers grown on silicon substrates. The single-electron transistors consist of lateral side-gated nanowires. A Coulomb staircase is observed at 4.2 K, which is fully modulated by the side-gate voltage. Two-period conductance oscillations are observed in nanowires fabricated on 10-nm-thick buried oxide layers, while single-period oscillations are observed in nanowires fabricated on 40-nm-thick buried oxide layers. The two-period oscillations are attributed to the formation of a charge layer in the silicon substrate. The single-electron effects are also studied as a function of the nanowire dimensions and annealing or oxidation treatments. The effects are correlated to the structure of the Polysilicon Film, characterized using transmission electron microscopy, Raman spectroscopy, and electron spin resonance analysis. These measurements demonstrate the significance of single-electron c...