Measuring and testing – Surface and cutting edge testing – Roughness
Patent
1996-11-15
1998-08-04
Williams, Hezron E.
Measuring and testing
Surface and cutting edge testing
Roughness
73579, G01N 2902
Patent
active
057896666
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a resonant sensor with a vibrating body for the determination of at least two physical values. It is especially suitable for use in Scanning Kelvin Probe Force Microscopy.
STATE OF THE ART
A resonant sensor consists essentially of a vibrating body, a component which excites this vibrating body into resonant vibration and a component which measures the vibratory behavior of the vibrating body.
The vibrating body must be appropriate to the measuring task as regards its mechanical properties, in particular its elasticity constant, resonance frequency and quality factor.
Vibrating bodies usually exhibit infinitely many degrees of freedom and hence infinitely many natural vibrations or resonance modes with infinitely many associated resonance frequencies. The lowest resonance frequency is designated the first resonance frequency while its associated resonance mode is designated the fundamental vibration frequency or fundamental mode.
Various possible ways of exciting the vibrating body into vibration are described in "Micromechanics" by Anton Heuberger, Springer Publishing House, Berlin 1989, pages 355-418. In particular this excitation can be effected by the periodic application of thermal energy, by electromagnetic or electrostatic forces or by piezoelectric actuators.
Various applications of resonant sensors are described in "Resonant sensors and Applications" by P. Hauptmann, Sensors and Actuators A. 25 to 27 (1991), pages 371-377. Especially prominent among the advantages of resonant sensors are their high resolution, the availability of low-cost manufacturing processes and the generation of a frequency-analogue or quasi-digital output signal.
Air-damping effects in the use of quartz resonators as tactile and non-tactile sensors are described by M. Weinmann et al. in "Measuring profile and position by means of vibrating quartz resonators used as tactile and non-tactile sensors", Sensors and Actuators A37-38 (1993), pages 715-722. The associated air-flow and viscosity relationships must be taken into account when using resonant sensors.
The use of resonant force sensors in scanning force microscopy (SFM) is described by M. Nonnemacher at al. in "Scanning Force Microscopy with Micromachine Silicon Sensors", Journal of Vacuum Science and Technology B9(2), 1991, pages 1358-1362. Here long-range force interactions between the vibrating body and the surface of the object under examination are measured and the surface topography of the object thus established. For this application vibrating bodies with an elasticity constant of approximately 10 to 100 N/m and a resonance frequency of approximately 200 to 1000 kHz haste proved particularly suitable. In order to increase the lateral resolution of the force sensor the vibrating body used as the sensing probe is configured as a transverse beam with a fine tip.
In European Patent Application EP-A2-0 472 342, "Micro-displacement type information detection probe device and microscope and information processing device by use thereof", Date of Application Aug. 13th, 1991 an information-recognising measurement probe of the displacement type is described where a transverse beam of a first stage is displaced by means of piezo-electrical actuators and a transverse beam of a second stage carries the measurement probe. By the configuration of the transverse beams of the first and second stage, greater displacement of the measurement probe is made possible in comparison with the state of the art, thus making it possible to follow topographical features and variations in the .mu.m region of a recording medium or of a substrate.
In M. Nonnemacher et al. "Kelvin Probe Force Microscopy", Applied Physics Letters, 58 (1991) Pages 2921-2923, a resonant sensor is introduced, which is used for the determination of two physical values. By means of electro-static excitation of the vibrating body at its resonance frequency and the use of a closed measurement loop, the contact potential difference or the exit work-function difference between the v
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Bayer Thomas
Greschner Johann
Schmid Gerhard
Wolf Volker
International Business Machines - Corporation
Miller Rose M.
Strunck Stephen S.
Williams Hezron E.
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