AVS1997 Session NS-WeA: Nanomechanical Sensors
Wednesday, October 22, 1997 2:00 PM in Room K
Wednesday Afternoon
Time Period WeA Sessions | Abstract Timeline | Topic NS Sessions | Time Periods | Topics | AVS1997 Schedule
| Start | Invited? | Item |
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| 2:00 PM |
NS-WeA-1 Temperature Controlled INCISIVE Tips on Piezoresistive Atomic-Force-Microscope Cantilevers
R.P. Ried, H.J. Mamin, B.D. Terris, D. Rugar (IBM Almaden Research Center) We have fabricated and tested 19 µm-long, 0.34 µm-thick piezoresistive atomic force microscope (AFM) cantilevers with separate, integrated resistors for localized heating of the tip1. The tip heater has a 4 µs thermal time constant. These four-legged cantilevers with combined imaging and thermal-mechanical surface modification capabilities have been developed for applications in scanning-probe data storage. The devices have been used to thermal-mechanically write a pseudorandom data pattern at 50 kb/s on a spinning polycarbonate sample and subsequently read the data. Indentations are formed when the tip is briefly heated above the glass transition temperature of the polycarbonate2. The cantilevers are fabricated from a silicon-on-insulator (SOI) wafer using a frontside-only release process. IN-plane CrystallographIcally-defined-SIlicon, VariablE aspect-ratio (INCISIVE) tips3 are used to reduce cantilever mass in order to reduce the thermal time constant and increase cantilever resonant frequency. In operation, the cantilevers are inclined at roughly 45° with respect to the sample surface in order to accomodate the in-plane tips. Quality AFM imaging with INCISIVE tips has been demonstrated. Ten µm-long cantilevers without heaters have an estimated spring constant of 2 N/m and measured resonant frequencies of 6.4 MHz, mechanical response times less than 90 ns, sensitivities of (ΔR/R)/Å = 1.1 x 10-5, and 2 x 10-3 Å/√Hz resolution. The fabricated cantilevers have sufficient displacement resolution to detect their own mechanical-thermal noise in vacuum, and for some some designs, even in air.
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| 2:20 PM |
NS-WeA-2 Nano-Mechanical Structures in Single Crystal Silicon
D.W. Carr, H.G. Craighead (Cornell University) We have fabricated a variety of free standing single crystal silicon mechanical structures with minimum feature sizes below 30 nm. Using high resolution electron beam lithography and a combination of reactive ion etching and chemical etching, we have fabricated a wide range of geometries in silicon-on-insulator systems. These are integrated with electrodes for driving the structure motion. Utilizing devices with dimensions in this new size regime will allow us to study important physical quantities related to the energy dissipation and mechanical response of single crystal silicon. We are applying this technology towards making devices that may be useful in optical applications. We have fabricated a micron sized Fabry-Perot interferometer formed by suspending a 50 nm thick silicon paddle 400 nm above the underlying surface. This paddle can be moved in a direction perpendicular to the substrate by applying a voltage between the paddle and the surface beneath it. Such a technology can be applied towards making a high speed IR modulator for fiberoptic applications. Such devices operating in a resonant mode may also be useful as high-sensitivity chemical sensors. While these ultra-small nano-electro-mechanical systems provide advantages in terms of frequency response and sensitivity of detection, they also present new challenges in the fabrication area, including critical dimension control and stiction. The fabrication issues and properties of these ultra-small systems will be discussed. |
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| 2:40 PM |
NS-WeA-3 Using Nanoscale Science with Micromechanics as Ultimate Limit Sensors
J. Gimzewski (IBM Research Division, Switzerland) The development of atomic force microscopy was accompanied by fairly wide spread use of Silicon and Silicon Nitride based force sensors. Various schemes were developed to read out cantilever motion enabling extreme sensitivity and resolution. There has been a growing interest in detecting other signal domains using this technology. In particular, we have investigated a variety of chemically related phenomena whereby changes in mass, surface stress or thermal properties are converted into changes in mechanical properties of cantilevers either coated with reactants, catalysts, etc. or where tiny samples are mounted instead of conventional tips. The sensitive of these new methods (atto-nano) is often beyond the detection limits of macroscopic methods. The mechanical transduction scheme also allows sensitivity and response time to be optimised by mechanical design of the form of the cantilever sensor and its component layers using finite element analysis. We shall discuss exploratory experiments such as following the kinetics of molecular self assembly up to a monolayer, specific molecular recognition and also nanogravimetric thermal analysis and calorimetry. Recent extensions to arrays of micromechanical sensors and the specific advantages of such arrays will be introduced. One goal of the research is to produce large arrays of sensors which are seamlessly integrated into CMOS microelectronics. Both non-specific and specific (Bio-) analysis is feasible in vacuum air and liquids. An outlook and progress status will conclude the talk. |
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| 3:20 PM |
NS-WeA-5 Design, Fabrication and Testing of a Wafer-Scale Manufactured Tunneling Infrared Sensor.
J. Grade, C.H. Liu, A. Barzilai (Stanford University); L.M. Miller (Jet Propulsion Laboratory); H. Jerman (Quinta Corporation); T.W. Kenny (Stanford University) This paper reports on the first successful fabrication of tunneling infrared sensors on the wafer-scale. The sensors use a tunneling displacement transducer to measure thermal expansion of a small reservoir of gas trapped in a micromachined sensor structure. In previous work, we have demonstrated state-of-the-art performance for this uncooled infrared sensor. In this work, we have adapted the design and fabrication of the sensors to allow wafer-scale techniques, such as wafer bonding, to be used. The resulting process yields more than 300 sensors from a single set of 4" wafers. We will describe the fabrication process and present measurements of the resulting performance characteristics.1
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