EP2409165A1 - Microscope à force atomique à balayage - Google Patents

Microscope à force atomique à balayage

Info

Publication number
EP2409165A1
EP2409165A1 EP09775848A EP09775848A EP2409165A1 EP 2409165 A1 EP2409165 A1 EP 2409165A1 EP 09775848 A EP09775848 A EP 09775848A EP 09775848 A EP09775848 A EP 09775848A EP 2409165 A1 EP2409165 A1 EP 2409165A1
Authority
EP
European Patent Office
Prior art keywords
cantilever
sensor tip
longitudinal axis
force microscope
central longitudinal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP09775848A
Other languages
German (de)
English (en)
Inventor
Henning Heuer
André STRIEGLER
Jörg Opitz
Malgorzata KOPYCINSKA-MÜLLER
Sascha Naumann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Technische Universitaet Dresden
Original Assignee
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Technische Universitaet Dresden
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV, Technische Universitaet Dresden filed Critical Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Publication of EP2409165A1 publication Critical patent/EP2409165A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
    • G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
    • G01Q60/24—AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
    • G01Q60/38—Probes, their manufacture, or their related instrumentation, e.g. holders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
    • G01Q70/00—General aspects of SPM probes, their manufacture or their related instrumentation, insofar as they are not specially adapted to a single SPM technique covered by group G01Q60/00
    • G01Q70/08—Probe characteristics
    • G01Q70/10—Shape or taper

Definitions

  • the invention relates to an atomic force microscope according to the preamble of claim 1, which can be used for investigations on surfaces of samples.
  • Atomic Force Microscopes which are used in the scanning probe microscopy
  • various investigations can be performed on samples.
  • SPM Scanning Probe Microscopy
  • a sample (sample) in at least one axial direction take place. and / or y-direction.
  • the vertically aligned axis is then the z-axis.
  • a sensor tip is aligned with a cantilever so that its tip is at an angle of approximately 90 ° with respect to the central longitudinal axis in the direction (i.d.R.
  • Axis on the surface of a sample to be detected be aligned and in the form of a pyramid, which tapers conically in the direction of the surface to be detected, formed and arranged in the plane of the central longitudinal axis of the cantilever.
  • sensor tips made of the same material from which the spring bar is formed, such as monocrystalline silicon, are used.
  • Sensor bar cantilevers may additionally be provided with suitable actuators, e.g. Piezoactuators in
  • Oscillation are added, this should preferably be done at a resonant frequency.
  • the object of the invention is to provide an atomic force microscope with which surface regions of samples can be detected which are oriented at a steeply inclined angle with respect to the central longitudinal axis of a cantilever of the atomic force microscope.
  • Essential elements known from the prior art may be present on an atomic force microscope according to the invention. These are, for example, the control and evaluation electronics, elements for the execution of movements and the measuring technique.
  • an optical measurement of movements of the cantilever in which a reflected from the cantilever laser beam is directed to an optical detector.
  • Preference is given to spatially resolved detecting optical detectors, such as a four-quadrant photodiode.
  • the cantilever may be vibrated with at least one piezo actuator when detection is to be performed in a dynamic mode.
  • a modified arrangement and / or design of at least one sensor tip present on a cantilever is realized with an atomic force microscope in order to be able to detect the steeply inclined surface areas of samples. These surface areas may be oriented at an angle of 90 ° ⁇ 20 ° with respect to a generally horizontally oriented plane (xy plane).
  • the sensitive region of a sensor tip is arranged at a distance to and in addition to the central longitudinal axis of the cantilever. This can also be achieved with sensor tips whose base point is arranged at a distance next to the central longitudinal axis of the cantilever.
  • a combination of sensitive area and foot point arranged next to the central longitudinal axis can also be realized.
  • a sensor tip can be angled or curved at an angle ⁇ 90 ° with respect to the central longitudinal axis of the cantilever.
  • the sensitive area of a sensor tip is that part of the sensor tip which points in the direction of the surface to be detected. As with known sensor tips it has the smallest cross-section, since here too a conical taper of the sensor tip is realized in the direction of the surface to be detected.
  • a plurality of sensor tips can also be present on a spring bar.
  • two sensor tips may be present on two opposite sides of the cantilever with respect to its central longitudinal axis.
  • Two or three sensor tips can be aligned at angular intervals of 90 ° to each other.
  • At least one second sensor tip can be present on the spring bar, the sensitive area of which is arranged at a distance and next to the central longitudinal axis of the cantilever.
  • the sensitive area points in a lateral direction next to the spring bar.
  • Sensor tips can also be dimensioned and designed so that the sensitive area projects beyond an outer edge of the cantilever in the unfixed area of the cantilever. This should be the case if an obliquely inclined surface area is to be detected whose length in this axial direction is greater than the distance between the sensitive area Area of the sensor tip and the spring bar is.
  • the at least one sensor tip may be aligned or angled with respect to the central longitudinal axis of the cantilever at an obliquely inclined angle.
  • An orientation of the sensitive area of a sensor tip is preferably at an angle of almost 90 ° with respect to the orientation of the surface area of the respective sample to be detected.
  • the sensor tip (s) should be able to approach a surface to be detected. This can be achieved by a vertical deflection of the cantilever. With the detection of the mechanical restoring forces of the cantilever, a detection of the topography of the surface area of the sample can be achieved.
  • the sensor tip should therefore be able to absorb forces acting in the vertical direction without being damaged. It should have sufficient rigidity so that it deforms only negligibly during detection itself.
  • the frequency with which the spring bar with sensor tip (s) are vibrated can lead to a deformation of the cantilever, which can bend or twist. This should be done in a targeted manner in order to take into account the deformation of the cantilever during the evaluation. However, the sensor tip should not deform or twist.
  • Sensor tips which can be used in the invention can be angled as an obliquely inclined or tilted pyramid, the tip of which forms the sensitive area, as a one-sidedly bent cone Cone or as a fibrous structure which is bent or inclined in one direction, be formed.
  • the production can be carried out in such a way that they are produced analogously to conventional standard sensor tips in silicon technology, taking into account the new orientation of the sensitive region.
  • a fibrous structure can be at least one carbon nanotube.
  • One or more of such tubes can be formed by a suitable method, which can be done by a pre-formed in the spring bar opening.
  • An aperture (for example bore) can be formed in a correspondingly inclined angle by the spring bar, with which the orientation of such a sensor tip can be specified.
  • Extra manufactured sensor tips made of a wide variety of materials, including metals, can also be attached to a spring bar. This can preferably be done cohesively.
  • the preparation can also be done by silicon etching with subsequent material removal.
  • a spring bar made of silicon can be etched with an approach for a sensor tip so that a connected to its smallest cross-section with the spring bar truncated pyramid has been formed on the spring bar on which subsequently a targeted shaping material removal takes place.
  • the material removal can be carried out, for example, with an ion beam, which is preferably focused.
  • the spring bar can assume a cross-sectional shape rotated through 180 °. men.
  • Sensor tips can also be arranged on a spring bar asymmetrically to its central longitudinal axis.
  • the base point of the sensor tip are connected to the sensor tip and cantilever with each other or merge into each other, be arranged on one side next to the central longitudinal axis.
  • a second oppositely inclined sensor tip may also be present on a spring bar.
  • a balancing mass can also be favorable in the case of an asymmetrical mass distribution in relation to the central longitudinal axis of the cantilever.
  • two lateral opposite wall regions of a depression can be detected by means of a spring bar and the two sensor tips, without requiring replacement or re-clamping of the sample or the cantilever.
  • Figure I A - D four examples of usable on a cantilever sensor tips in a sectional view
  • FIG. 2 three further examples of sensor tips in a sectional view
  • FIG. 3 in stages, the procedure for approaching and detecting
  • FIG. 4 shows a detection in contact mode
  • FIG. 5 shows a detection in an intermittent mode.
  • FIG 1 four examples of a cantilever sensor tip unit are shown in sectional views. It is clear from the cross-sectional representations that the sensitive regions 2 'of the sensor tips 2 are arranged offset to one side with respect to the central longitudinal axis of the cantilever 1.
  • the central longitudinal axis of the spring bar 1 is illustrated with the vertically aligned line, in the illustrated cross section of the cantilever 1.
  • Example A shows a pyramid tilted diagonally to the side.
  • examples A, C and D the sensor pointed angled and curved in Example B.
  • Example B may be formed with a fibrous structure which, as explained in the general part of the description, may be formed with at least one carbon nanotube.
  • Example C A starting from the prior art modified sensor tip 2 is shown with Example C.
  • the sensor tip 2 made of silicon, as well as the cantilever 1 is formed. Only the part of the sensor tip 2 facing the sensitive surface 2 'in the direction of the detecting surface is angled accordingly.
  • the sensor tip 2 of Example D was brought into the form shown by material removal with a focused ion beam (FIB technology).
  • FIB technology focused ion beam
  • a semi-finished silicon product of the spring bar 1 was produced with a truncated cone formed thereon, which is indicated by the dashed line.
  • the finished contour of the sensor tip 2 is illustrated by a solid line after the material removal.
  • sensor tips 2 can also be aligned at an angle of 90 ° on the spring bar 1, so that the sensitive area 2 'should then be pointed out of the plane of the drawing.
  • FIG. 2 shows three further examples of spring beam sensor tip units B1 to B3. Again, cross-sectional views were chosen.
  • the cantilever 1 protrudes on one side beyond the edge, but is mounted symmetrically with respect to the central longitudinal axis of the cantilever 1 at this.
  • the examples B2 and B3 show correspondingly asymmetrical arrangements of sensor tips 2 on cantilever 1, in which the bases of the sensor tips 2 are arranged offset to the central longitudinal axis of the cantilever 1 at a distance from the longitudinal axis. They differ by the inclination angle and the dimensioning of the sensor tips 2 and also by the orientation of the cantilever 1, in which once the narrower side is arranged vertically below at B2 and once vertically above at B3.
  • sensor tip 2 with spring bar 1 is moved horizontally in the x-axis direction to a surface area of sample 3 which is vertically aligned here (see step 3) until the sensitive area 2 'of sensor tip 2 touches this surface area or has been recognized by the atomic force microscope , With simultaneous movement in the z-axis direction - step 4, the determination can be made on the vertically aligned surface area of the sample 3 in modes known in atomic force microscopes.
  • a detectable torsional force acts upon impact of the sensitive area 2 'of the sensor tip 2 on the surface of the surface area to be detected on the spring bar 1.
  • a region of the surface region of the sample 3 to be detected can thus consist of several detected lines. It is approximately in the y-z plane, which corresponds to a vertical surface / plane. The surface can be scanned in this way.
  • the spring constant or spring characteristic of the cantilever 1 influences the measuring accuracy and the contact force between the sensor tip 2 and the surface of the sample 3.
  • the stiffness in the vertical bending direction (z-axis) should be higher than that in the lateral direction. A possibly occurring vertical deflection of the cantilever 1 can be detected during the measurement and compensated in a suitable form during the evaluation.
  • a spatially resolved measuring optical system should preferably be used.
  • shear detector such as a four-quadrant photodiode can be used.
  • FIG. 1 The implementation of a modified contact mode is to be illustrated with FIG. During the detection, the sensor tip 2 is kept in permanent contact with the surface to be detected.
  • a constant contact force between the contacting parts of the sensor tip 2 and the sample 3 is set by a constant held deflection of the cantilever 1. If a change in the height occurs during the movement of the sensor tip 2 over the surface area, a change in the contact force occurs, which can be compensated by a change in the position of the clamping of the cantilever 1. From this height tracking, a quantitative statement can be made regarding the surface topography of a surface to be detected in the case of several measurement runs to be performed.
  • the torsion of the cantilever 1 should be kept constant about its central longitudinal axis.
  • the contact forces acting between the sensor tip 2 and the surface of the sample 3 can be calculated from the respective torsion angles with the spring stiffness of the cantilever 1 about its central longitudinal axis.
  • a constant torsion can be observed during detection by changing the position of the clamping of the cantilever 1 in the horizontal x-axis direction, in which it is tracked.
  • the course of the surface contour can thus be detected by determining the change in position of the clamping of the cantilever 1.
  • the non-fixed part of the cantilever 1 is excited to torsional vibrations, as shown in Figure 5.
  • the excitation of the torsional vibrations about the central longitudinal axis can be achieved with a pair of piezoactuators, which oscillate in opposite phase and are arranged laterally.
  • a constant excitation frequency should be selected which corresponds to an n-th order torsional resonance frequency of the freely oscillating cantilever 1, but is at least close to this frequency.
  • a possibly existing influence of an asymmetrical mass distribution can be compensated for by a balancing mass to be attached correspondingly to the spring bar 1 or to be formed there.
  • the torsional vibrations can be taken into account by changing the position of the clamping of the cantilever 1 in the x or y axis direction. There is a tracking according to the surface topography in the detected surface area. By evaluating the correspondingly changing positions of the clamping of the cantilever 1, the respective topography curve can be determined. This is shown by the dotted line in FIG.
  • an error image can be generated via the changing amplitude of the torsional vibrations, and with the detected phase shift, further information about the respective sample can be obtained.
  • Et al elastic properties of the sample can be determined.
  • a horizontal movement of the sensor tip 2 in the y-axis direction can also be achieved by exciting bending vibrations. This movement allows the detection of steeply inclined surfaces, which are aligned approximately to the longitudinal axis of the cantilever 1, by tracking the oscillation amplitude.
  • the cross-sectional geometry of the cantilever 1 should take into account whether torsional or bending vibrations are used.
  • piezo actuators When positioning the clamping of the spring beam 1 in space (x, y and z axis direction), probably in contact mode, as well as in dynamic mode piezo actuators are used, which have an effect on the mechanical forces acting between sensor tip 2 and sample 3 (x-axis direction) as well as during a scanning movement (y- and z-axis direction) achieve high accuracy.
  • conventionally trained atomic force microscopes which are supplemented only with the invention, can meet these requirements. If mobility in a conventional atomic force microscope is not sufficiently great, in particular in the z-axis direction, a sample stage which can be positioned very accurately can be used.
  • a positioning unit can take into account the required travel, the travel speed and the required positioning accuracy.

Abstract

L'invention concerne un microscope à force atomique à balayage qui peut être utilisé pour différentes analyses sur les surfaces d'échantillons. Le but de l'invention est de mettre à disposition un microscope à force atomique à balayage avec lequel des zones de surface d'échantillons peuvent être détectées, lesquelles sont orientées par rapport à l'axe longitudinal central d'un levier élastique du microscope à force atomique à balayage à un angle fortement incliné. Dans un microscope à force atomique à balayage selon l'invention, au moins une pointe de sonde est disposée sur un levier élastique et sa zone sensible est disposée à une distance du levier élastique. Selon l'invention, le levier élastique retenu sur un côté frontal, pouvant être amené à osciller par au moins un actionneur et muni de la pointe de sonde et l'échantillon peuvent être déplacés l'un par rapport à l'autre le long d'au moins un axe. La zone sensible d'une pointe de sonde et/ou la base d'une pointe de sonde sont disposées à une distance sur le levier élastique et à côté de l'axe longitudinal centrale du levier élastique. La pointe de sonde peut seule ou en plus être coudée ou courbée à un angle < 90° par rapport à l'axe longitudinal central du levier élastique.
EP09775848A 2009-03-16 2009-03-16 Microscope à force atomique à balayage Withdrawn EP2409165A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/DE2009/000382 WO2010105584A1 (fr) 2009-03-16 2009-03-16 Microscope à force atomique à balayage

Publications (1)

Publication Number Publication Date
EP2409165A1 true EP2409165A1 (fr) 2012-01-25

Family

ID=41349308

Family Applications (1)

Application Number Title Priority Date Filing Date
EP09775848A Withdrawn EP2409165A1 (fr) 2009-03-16 2009-03-16 Microscope à force atomique à balayage

Country Status (2)

Country Link
EP (1) EP2409165A1 (fr)
WO (1) WO2010105584A1 (fr)

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5519212A (en) 1992-08-07 1996-05-21 Digital Instruments, Incorporated Tapping atomic force microscope with phase or frequency detection
JP4656761B2 (ja) * 2001-05-31 2011-03-23 オリンパス株式会社 Ｓｐｍカンチレバー
US7168301B2 (en) * 2002-07-02 2007-01-30 Veeco Instruments Inc. Method and apparatus of driving torsional resonance mode of a probe-based instrument
US7089787B2 (en) * 2004-07-08 2006-08-15 Board Of Trustees Of The Leland Stanford Junior University Torsional harmonic cantilevers for detection of high frequency force components in atomic force microscopy
US7735147B2 (en) * 2005-10-13 2010-06-08 The Regents Of The University Of California Probe system comprising an electric-field-aligned probe tip and method for fabricating the same

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2010105584A1 *

Also Published As

Publication number Publication date
WO2010105584A1 (fr) 2010-09-23

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