AT520420A1 - Capacitive path measuring device for measuring a path information of a probe body - Google Patents

Abstract

Capacitive displacement measuring device (50) for measuring displacement information of a probe body (7), in particular for a scanning probe microscope (1), wherein the displacement measuring device (50) has two capacitor bodies (54, 56) which are at least partially electrically conductive, rigid and mutually immutable in their relative position, an electrically conductive and at least partially deformable capacitor body (58) deformably disposed between the rigid capacitor bodies (54, 56) and arranged to be deformed upon movement of the probe body (7), detecting means (60) for detecting electrical signals at least one of the capacitor bodies (54, 56, 58), and a determination device (62) for determining an information indicative of the path information of the probe body (7) based on the detected electrical signals.

Description

Capacitive Weamessvorrichtuna for measuring a Weainformation a probe body

The invention relates to a capacitive displacement measuring device and a method for measuring a displacement information of a probe body and a scanning probe microscope.

An Atomic Force Microscope (AFM) is mainly used for the lateral and vertical high-resolution investigation of surfaces (in particular topographical investigations of surfaces). In this case, a measuring probe (for example, a bending beam, which is also referred to as cantilever) with a nanoscopic needle (also referred to as a probe tip or probe tip) over the surface (ie rasterized or scanned) and the deflection of the cantilever, based on the Interaction of the cantilever with the surface, detected. Depending on the surface condition of the sample, the deflection of the cantilever is recorded depending on the position or tracking of the probe. The deflection of the cantilever or the tip can be measured capacitively (in particular piezoelectrically) or by means of optical sensors. This method allows a structural analysis of the surface of the sample up to atomic resolution. The distance of the cantilever to the surface of the sample to be examined can be set very accurately. Thus, various measurement methods, such as the contact mode (contact mode), non-contact mode (non contact mode), tactile AFM mode (tapping mode), etc. can be realized. US 5,406,832 A describes the structure of an AFM. For the control of a measuring device, in particular a scanning probe microscope, with a probe body, the knowledge of the exact position of the probe body is useful. Measuring accordingly

Path information is conventionally possible only with moderate resolution or great effort.

It is an object of the present invention to be able to determine path information of a probe body, in particular on a scanning probe microscope, with a compact design as well as simple and precise.

This object is solved by the objects with the features according to the independent claims. Further embodiments are shown in the dependent claims.

According to an embodiment of the present invention, a capacitive displacement measuring device (ie, in particular, a displacement measuring device in which a displacement measurement is based on a characteristic change of capacitance values of a capacitor arrangement depending on a position of a movable probe body to be measured) is for measuring a displacement information of a probe body (in particular information) Position or a distance covered by a movement of the probe body), in particular for a scanning probe microscope (or for another measuring device) created, the Wegmessvorrichtung two at least partially electrically conductive, rigid and mutually immutable in their relative position (for example, rigidly mounted, in rigid and immovable, especially in a movement of the

Probe body rigid and immovable) capacitor body, a (in particular completely) electrically conductive and at least partially deformable (in particular elastically deformable, ie reversibly from its original form can be brought) capacitor body (in particular electrically conductive electrode material of the deformable capacitor body can be deformed when moving the probe body), the deformable (and optionally at least partially displaceable) between the rigid capacitor bodies and is arranged to be deformed upon movement of the probe body, a detection device for detecting electrical signals to at least one of the capacitor body (in particular on the at least partially deformable capacitor body), and a detection means for Determining an indicative of the path information of the probe body indicative based on the detected electrical signals.

According to another embodiment of the present invention, there is provided a scanning probe microscope for detecting surface information regarding a specimen by scanning one surface of the specimen, the scanning probe microscope comprising a movable probe body having a probe tip for scanning the surface of the probe body and a capacitive displacement measuring device having the above described Having features for measuring a path information of the probe body.

According to a further exemplary embodiment, a method for capacitive measuring of a path information of a probe body, in particular of a scanning probe microscope is provided, wherein the method an electrically conductive and at least partially deformable capacitor body is deformed during movement of the probe body, wherein the at least partially deformable capacitor body deformable between two at least partially electrically conductive, rigid and arranged in their relative position to each invariable capacitor bodies, electrical signals to at least one of the capacitor body (in particular on the at least partially deformable capacitor body) are detected, and indicative of the path information of the probe body information based on the detected electrical signals is determined.

In the context of the present application, the term "scanning probe microscope" is understood to mean, in particular, a microscope in which an image or other surface information of a specimen is not generated with an optical or electron-optical imaging (ie using lenses), but via the interaction of a measuring probe the

Specimen. The sample surface to be examined is scanned point by point in a raster process by means of this measuring probe. The measured values resulting for each individual point can then be combined to form a picture or evaluated in another way.

In the context of the present application, the term "probe body" is understood to mean, in particular, a body with the aid of which it is possible to gain access to a site to be analyzed, miniaturized and / or restricted or difficult to access In particular, such a probe body may serve as a probe in a measuring device operatively coupled to a capacitive displacement measuring device (for example, but not limited to, a scanning probe microscope.) A displacement event of the probe body results in deformation according to one embodiment - or displacement event in the path measuring device, which allows a conclusion on the displacement event of the probe body.

In the example of a scanning probe microscope, the probe body can serve for scanning a surface of a test specimen.

In the context of the present application, the term "capacitor body" is understood to mean, in particular, a completely or partially electrically conductive body (which can be plate-shaped or planar, at least in a non-powered state), and which together with a respective other capacitor body has a capacitor (in particular In particular, each of the rigid capacitor bodies together with the deformable capacitor body may form a capacitor or capacitance

Capacitor body may therefore serve (in particular with a single contiguous) electrically conductive structure both for forming a first capacitor or a first capacitance with a first one of the rigid capacitor bodies and may simultaneously for forming a second capacitor

Capacitor or a second capacitor with a second of the rigid capacitor body serve.

According to an exemplary embodiment of the invention, a displacement measuring system is provided for measuring displacement information of a probe body, in which a movement of the probe body is converted into a deformation of a deformable capacitor body arranged between two rigid capacitor bodies. Illustratively, the electrically conductive central capacitor body deformed as a result of the probe body movement (for example, deflected upwards or downwards) forms with each of the two rigid capacitor bodies a respective capacitor whose capacitance value is changed characteristically by the probe body movement. The change in the capacitance of these capacitors by a deflection is in opposite directions, since at a certain deflection vividly the distance between the two capacitor forming a capacitor body grows and the distance between the two condenser body forming a different capacitor decreases. This characteristic change in the capacitance of the two capacitors formed can be detected by a detection device in the form of electrical signals and converted by the detection device into path information. As a result, a very precise determination of path information of a probe body by means of a capacitive displacement measurement is made possible with a very simple structure.

In the following, additional exemplary embodiments of the path measuring device, the scanning probe microscope and the method will be described.

In particular, the capacitor body may each be formed as a plate. Illustratively, each of the rigid capacitor body forms a capacitor plate and the deformable capacitor body forms a respective second capacitor plate, which forms a respective capacitor with a respective capacitor plate of a respective one of the rigid capacitor body.

According to one embodiment, the rigid capacitor body and the at least partially deformable capacitor body may be arranged in a power-free state parallel to each other. In particular, the respective electrodes of the three capacitor bodies can be arranged parallel to one another in a force-free state. Thus acts on the part of the probe body no force on the deformable capacitor body, the three capacitor bodies are in particular formed as three mutually parallel planar plates. Preferably, the mutually facing pairs of capacitor bodies in the force-free state have the same distance from each other. Thus, two substantially identical capacitors can be generated whose output signals can cancel each other in the power-free state.

In one embodiment, at least one of the rigid capacitor bodies may include an electrically insulating substrate (eg, a ceramic substrate) and an electrode deposited thereon. Such a dielectric substrate may, for example, have a thickness in a range between 500 μm and 2 mm, in particular between 700 μm and 1.5 mm. An electrode can then be evaporated on, for example. The electrode may be formed of gold, for example. A thickness of such an electrode can be, for example, in a range between 100 nm and 1 pm, in particular between 300 nm and 500 nm.

According to one exemplary embodiment, the at least partially deformable capacitor body may have an electrode which is at least partially undeformed during operation and a region which adjoins and is bent during operation, in particular webs bent during operation. In this context, the term "in operation" is understood to mean an action of forces on the at least partially deformable capacitor body, as understood by those skilled in the art during the use of a Wegmessvorrichtung invention, especially in an application in the context of a scanning probe microscope, on the at least partially deformable The at least partially deformable capacitor body may have a substantially rigidly remaining electrode during operation and a bendable region, in particular bendable webs The electrode which is rigid during operation can act on the at least partially deformable capacitor even when a force of the probe body is exerted It is essentially free of deformation and can instead be displaced as a whole. The bendable and deformed in operation webs, however, can be bent or deformed under the action of a force of the probe body and therefore may have a membrane-like characteristic. The combination of the rigid in operation electrode with the bendable and the operation deformed webs can be effected by a force of the probe body, a substantially translational displacement of the electrode between the two substantially parallel rigid capacitor bodies, while the webs under the influence of such a force a plane parallel to the planes of the rigid capacitor body can be bent out. For example, two or four webs may be provided on opposite sides of the operationally rigid electrode. Due to the membrane-like behavior of such a deformable capacitor body in the edge region with simultaneous substantially translational displacement of the rigid in operation electrode in the central region, a particularly high sensitivity of the distance measuring device can be achieved.

One skilled in the art will understand that a substantially non-deforming property of the electrode during operation does not preclude minimal microdeformations in individual electrode regions. However, an electrode which is not deformed during operation will at most be subjected to extremely small deformations, which are much smaller than the deformations in the region bent during operation.

According to one embodiment, a surface of the electrode may be at least three times, in particular at least five times, a surface of a respective one of the webs. In this way, the deformable capacitor body as a whole can behave substantially as a translationally displaceable electrode and consequently operate with very high sensitivity, while at the same time the deformability due to the small webs can be maintained.

According to one embodiment, the at least partially deformable capacitor body may be formed completely (see FIG. 4B) or partially (see FIG. 5) as an elastic membrane. Such an elastic membrane shows a very strong reaction to a force due to a displacement of the probe body and therefore causes a high accuracy of measurement.

According to one embodiment, the diaphragm may be configured such that, upon deformation due to movement of the probe body, a first region of the membrane is less stressed than a second region of the membrane and the first region of the membrane is substantially parallel to the rigid capacitor bodies when the probe body moves remains. In other words, the elastically deformable membrane can thus be designed in such a way that upon deformation as a result of a movement of the probe body, individual regions of the membrane are subjected to little stress and remain largely parallel to the electrodes on the rigid capacitor or electrode bodies.

According to one embodiment, the diaphragm may be configured such that upon deformation as a result of movement of the probe body, a diaphragm region remains substantially parallel to the rigid capacitor bodies when compared with another diaphragm region of higher rigidity. In other words, the elastically deformable membrane may be shaped such that, upon deformation due to movement of the probe body, individual regions of the membrane may be due to increased rigidity in the membrane

Remain substantially parallel to the electrodes on the rigid capacitor or electrode bodies.

According to one embodiment, the at least partially deformable capacitor body may be formed in one piece and / or einstoffig. For example, the deformable capacitor body may be formed as a thin steel plate (for example, with a thickness of a few tenths of a millimeter) that can be machined by laser treatment so that the bendable webs are machined out from the rest of the plate.

In this way, the deformable capacitor body can be machined from one piece and the webs can remain integrally connected to the rigid electrode. This allows a cost-effective production. If the bendable webs are made much narrower than the electrode, webs and electrode can be machined out of a plate of common constant thickness, and at the same time a high degree of bendability can be imparted to the webs and a high degree of rigidity to the electrode.

According to one embodiment, the at least partially deformable capacitor body can be designed to be deflected in a central portion substantially free of deformation (in particular maximum) and deformed in an edge region when moving the probe body. A maximum deflection of the rigid electrode in the center in combination with the edge-side high deformation leads to a particularly high sensitivity of the path measuring device.

According to one embodiment, the at least partially deformable capacitor body may comprise or consist of steel. A steel plate allows a sufficiently high rigidity in a central area and at the same time enables a pronounced bending ability with a small width in the web area. Therefore, such a steel plate is an inexpensive and at the same time highly sensitive embodiment for the deformable capacitor body.

According to one exemplary embodiment, the determination device can be designed to determine the information indicative of the path information of the probe body by differentiating the electrical signals detected by the two capacitors. Since with a certain movement of the probe body, the capacitance of one capacitor increases and that of the other capacitor decreases accordingly, a difference between the two, these capacitors associated electrical signals causes a particularly high accuracy in the determined path information.

According to one embodiment, the determining means may be arranged for determining the information indicative of the path information of the probe body by synchronous demodulation. The principle of synchronous demodulation, which is described in detail with reference to FIG. 8 and FIG. 9, permits high-precision detection of the path information.

According to an exemplary embodiment, the detection device may be configured to detect the electrical signals in response to the application of an electrical excitation signal between a respective one of the rigid capacitor bodies and the at least partially deformable capacitor body. The electrical excitation signal may, for example, be a respective electrical voltage, in particular generated by means of a common signal source (for example a voltage source). In particular, alternating voltage signals can be applied between the two mutually facing each capacitor plates, and it can be detected a corresponding reaction signal. If the same voltage source is used to excite both capacitors, voltage fluctuations and the like lead to a much smaller extent to Meßwertverfälschungen.

According to one embodiment, the distance measuring device may comprise a coupling body, in particular a spherical coupling body, which is in operative connection with the at least partially deformable capacitor body and in operative connection with the probe body, so that upon movement of the probe body of the probe body shifts the coupling body and the

Coupling body deforms and / or displaces the at least partially deformable capacitor body. Such a coupling body may be arranged to transmit preferably centrally a force applied from the probe body to the deformable capacitor body. It is particularly preferred to accomplish this power transmission by means of a ball, since then a particularly effective suppression of parasitic force injections can be achieved. Alternatively, however, it is also possible, for example, to use a cylinder as a coupling body which, for example, acts on the deformable capacitor body or even can be attached thereto. Advantageously, the coupling body made of an electrically insulating material (for example, glass) are made so that no influence of the coupling body on the decisive for the detection of electrical capacitances of the capacitive

Distance measuring device occur.

According to one embodiment, the path measuring device may comprise a respective spacer between a respective one of the rigid capacitor bodies and the at least partially deformable capacitor body. Such a spacer can set and maintain a well-defined distance between opposing capacitor bodies. For example, such a spacer can be made of a steel plate, a copper sheet or a ceramic foil.

According to one embodiment, a distance between the rigid capacitor bodies may be at most 700 pm, in particular at most 500 pm. A thickness of the at least partially deformable capacitor body may be, for example, at most 500 pm, in particular at most 200 pm. The path measuring device can therefore be designed as a very compact, approximately plate-shaped or layered arrangement in the vertical direction, which nevertheless can provide path information concerning the probe body with very high precision.

According to one exemplary embodiment, the path measuring device can be designed to apply an excitation signal to at least a part of the capacitor bodies (in particular to the rigid capacitor bodies) on a first side of the capacitor bodies and to transmit the electrical signals of at least one part of the capacitor bodies (in particular of the at least partially deformable capacitor body). on a second side opposite the first side. If the positions of cables or electrical lines, by means of which excitation signals are applied to capacitor bodies or response signals are detected by a capacitor body, are spatially separated from one another, the influence of parasitic capacitances generated by such cables or electrical lines on the measuring capacitances be strongly suppressed between the capacitor bodies. The path information can then be determined with particularly high accuracy.

According to an exemplary embodiment, the scanning probe microscope can have a measuring probe which is designed to scan the surface of the sample body in a scanning manner. In this way, the measuring tip or probe can scan the surface of the sample body and thereby provide information about the surface condition of the sample body.

According to an exemplary embodiment, the scanning probe microscope can have a displacement device, which is set up to move the probe body and is rigidly coupled to the probe body and the displacement measuring device. In particular, such a displacement device can be designed as a piezo actuator. In the case of a piezoactuator, the latter can undergo an associated deflection by applying an electrical signal to the piezoactuator. This deflection leads to displacement of the probe body and due to a force coupling between the probe body and Wegmessvorrichtung to a corresponding deformation and / or displacement of the deformable or displaceable capacitor body between the rigid capacitor bodies. The displacement or deformation of the deformable

Capacitor body then forms a fingerprint for the corresponding or correlated displacement of the probe body and thus allows for capacitive detection of the deformation of the deformable capacitor body a conclusion on the displacement of the probe body.

According to an exemplary embodiment of the invention, the path measuring device for measuring path information of the probe body may be arranged in a vertical direction and / or perpendicular to a scanning plane. In other words, by means of the path measuring device, a position or displacement of the probe body in a direction corresponding to a normal direction to the sample to be measured can be measured. The scanning plane may be the horizontal plane along which the probe and the sample are moved relative to each other during operation.

According to one exemplary embodiment of the invention, the scanning probe microscope can be designed as an atomic force microscope. The Atomic Force Microscope, also called Atomic Force Microscope or Atomic Force Microscope (AFM), is a special scanning probe microscope. It serves as a tool in surface chemistry and surface characterization and is used for mechanical scanning of surfaces and the measurement of atomic forces on the nanometer scale.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the following figures.

FIG. 1 shows a scanning probe microscope with a capacitive displacement measuring device according to an exemplary embodiment of the invention.

FIG. 2 shows a circuit diagram of a capacitive displacement measuring device for measuring displacement information of a probe body for a scanning probe microscope according to an exemplary embodiment of the invention.

FIG. 3 shows a cross-sectional view of a capacitive displacement measuring device for measuring displacement information of a probe body for a scanning probe microscope according to an exemplary embodiment of the invention.

FIG. 4A shows a condenser body of a position measuring device, which is displaced in parallel and rigid in relation to two rigid capacitor bodies.

FIG. 4B shows a deformable capacitor body, which is deflected like a bulb relative to two rigid capacitor bodies, of a displacement measuring device according to an exemplary embodiment of the invention.

FIG. 5 shows a plan view of a movable capacitor body of a path measuring device according to an exemplary embodiment of the invention.

FIG. 6 shows a movable condenser body of a position-measuring device, which is displaced partly parallel to two rigid condenser bodies and partially deflected like a bell, in accordance with an exemplary embodiment of the invention.

FIG. 7 shows a three-dimensional sectional view of a path measuring device according to an exemplary embodiment of the invention.

FIG. 8 shows an evaluation circuit with a detection device and a detection device of a displacement measuring device according to an exemplary embodiment of the invention.

Figure 9 shows a schematic diagram of an electronic circuit including evaluation logic of a Wegmessvorrichtung according to an exemplary embodiment of the invention.

FIG. 10 shows a displacement device for displacing a probe body and a displacement measuring device for measuring a displacement of a displacement of the probe body by means of the displacement device according to an exemplary embodiment of the invention.

Figure 11 shows a movable capacitor body with a rigid electrode and bendable webs of a Wegmessvorrichtung according to an exemplary embodiment of the invention in an operating condition in which the webs are not bent, but are coplanar with the rigid electrode.

FIG. 12 shows the movable capacitor body according to FIG. 11 in another operating state, in which the webs are bent and bent out of the plane of the rigid electrode.

The same or similar components in different figures are provided with the same reference numerals.

Before describing exemplary embodiments of the invention with reference to the figures, a few general aspects of the invention and the underlying technologies will be explained:

In one exemplary embodiment of the invention, a capacitive displacement measuring device (50) is provided for measuring displacement information of a probe body (7), in particular for a scanning probe microscope (1), wherein the displacement measuring device (50) comprises two electrodes (66) which are at least partially electrically conductive , rigid and relatively fixed condenser body (54, 56), an elastically deformable diaphragm (see reference numeral 72 or condenser body 58) disposed between the rigid condenser bodies (54, 56), which functions as a variable electrode and which is arranged Movement of the probe body (7) to be deformed, a detecting means (60) for detecting electrical signals to at least one of the capacitor body (54, 56, 58), and a detecting means (62) for determining an indicative of the path information of the probe body (7) Information based on the detected electrical signals eist.

According to an exemplary embodiment of the invention, a capacitive z-direction sensor is provided for measuring path information of a probe body including a (preferably digital) sensor data evaluation. In particular, an embodiment of the invention provides a contacting, capacitive displacement measurement system (i.e., sensor data evaluation) that can be configured, in particular, for a displacement range in the range of less than 10 pm and a resolution of less than 1 nm. The sensor itself is characterized in embodiments mainly by a compact design and low production costs.

In a preferred embodiment, the capacitive displacement measuring system has a differential capacitor arrangement. As a result, a particularly high sensitivity can be achieved.

In another embodiment of the invention, a Scanning Probe Microscope (SPM) and in particular an Atomic Force Microscope (AFM) with a

Displacement device is provided, with which a probe receptacle together with probe body (for example a cantilever with measuring tip) in the z-direction (i.e., in the vertical direction relative to a laboratory system) can be moved in very fine steps or over very short distances. This displacement device can be formed, for example, as a piezo stage or as a piezo actuator.

In such an embodiment, a displacement of the

Probe body (and thereby caused deformation or

Displacement of a deformable capacitor body of a capacitive displacement measuring device) over a change in length of a piezo actuator, as soon as a voltage is applied to this, are effected. This shift in the z-direction can be measured capacitively via the displacement of the deformable capacitor body.

Conventionally, such a displacement in the z direction can be determined from a deflection known for the particular piezoactuator used or determined by calibration, which occurs when a defined voltage is applied. However, aging or drifting of the piezoelectric actuator or environmental influences such as temperature changes can lead to incorrect measurements. Conventional capacitive distance sensors are used, but they are often inaccurate or prone to changes in temperature or humidity. Although more complex conventional sensors have a higher accuracy, a better resolution and a reduced sensitivity to environmental influences. However, their space requirement is high, so that they are not suitable for installation in many measuring devices, in particular in an SPM / AFM.

In contrast to such conventional approaches, according to an exemplary embodiment of the invention, a distance or path measuring device is provided for determining a vertical displacement of a probe body, in particular in an SPM / AFM, which on the one hand has a high accuracy and a high resolution and on the other hand is compact enough to be installed in a measuring device (such as an SPM / AFM).

A capacitive sensor of a displacement measuring device according to an exemplary embodiment of the invention comprises three superimposed capacitor bodies (which in particular have a total of exactly three electrodes, i.e. preferably exactly one electrode per capacitor body), the middle of which may be formed as a movable or deformable membrane. Such a deformable membrane may be deformed in response to a displacement of the probe body completely or preferably only in sections (see for example the embodiment of Figure 5), which deformation can be used as a basis for the distance measurement. In exemplary embodiments, dimensions in the z-direction (i.e., in particular, a thickness of the membrane between opposing electrodes) are very small and may be, for example, only a few tens of pm, in other embodiments, for example, only a few hundred pm.

FIG. 1 shows a Scanning Probe Microscope (SPM) or Scanning Probe Microscope 1 according to an exemplary embodiment of the invention

Invention designed as Atomic Force Microscope (AFM).

In scanning probe microscope 1, a cantilever deflection, i. a change in position or a change in shape of a measuring probe 11 (which is also referred to as cantilever), detected by means of an optical sensor. The measuring probe 11 is made of a measuring tip 5 and a bearing this

Probe body 7 is formed. The probe body 7 is mounted on a mounting device 4. An electromagnetic radiation source 2 (for example a laser source) transmits an electromagnetic primary beam 13 (in particular a light beam) to the measuring probe 11 via a focusing device 12 (which may be an arrangement of one or more optical lenses). The electromagnetic reflected from the measuring probe 11 Secondary beam 3 propagates to a photo- and position-sensitive detector 10 (in particular, the electromagnetic secondary beam 3 can be deflected by means of a deflecting mirror 14 or another optical deflecting element onto the position-sensitive detector 10). If the measuring probe 11 is brought into motion via a displacement device 80 (for example a piezoactuator, which can effect a change in position in the vertical z-direction according to FIG. 1) and / or if the measuring probe 11 changes its shape, a change in the laser light at position-sensitive detector 10 are detected. Depending on the interaction of the measuring tip 5 (also referred to as cantilever tip) of the measuring probe 11 with a sample body 6 to be examined or to be characterized on a sample holder 52, the deflection of the measuring probe 11 will vary and an associated region on the detector 10 will be hit by the electromagnetic secondary beam 3. The detector signal can then be processed in an evaluation unit 8. The resulting high-resolution image of the surface of the sample body 6 can then be displayed by means of a display device 9. A surface of the sample body 6 may be scanned with the measuring tip 5 (i.e., a sensitive tip of the measuring probe 11). A sample table is movable in the horizontal plane (i.e., in an orthogonal to the z-axis x-direction and y-direction) in the horizontal plane according to Figure 1 by means of actuators. The scanning probe microscope 1 thus serves to determine surface information with regard to the sample body 6 by means of scanning scanning of a surface of the sample body 6 by means of the measuring probe 11.

Furthermore, FIG. 1 schematically illustrates a capacitive displacement measuring device 50 described in more detail below for measuring displacement information of the probe body 7, which forms part of the scanning probe microscope 1. FIGS. 2 through 12 illustrate embodiments of components of the path measuring device 50 in accordance with exemplary embodiments of the invention.

FIG. 2 shows a circuit diagram of such a capacitive displacement measuring device 50 for measuring displacement information of the probe body 7 of the scanning probe microscope 1 according to an exemplary embodiment of the invention. FIG. 3 shows a cross-sectional view of a concrete structural realization of the capacitive displacement measuring device 50 according to FIG. 2 according to an exemplary embodiment of the invention.

The path measuring device 50 has two partially electrically conductive and partially electrically insulating, rigid (in the illustrated embodiment, rigidly mounted and inherently rigid) and in their relative position to each other unchangeable capacitor body 54, 56. These are both rigidly mounted on the path measuring device 50 and rigid in itself, i. do not change their position and shape upon movement of the probe body 7. In addition, a capacitor body 58 which is deformable during a movement of the probe body 7 is arranged to be deformable or movable between the rigid capacitor bodies 54, 56. The deformable capacitor body 58 consists in the illustrated embodiment entirely of an electrically conductive material (but may alternatively be made partly of an electrically conductive and partially of an electrically insulating material). The deformable capacitor body 58 is adapted to be deformed upon movement of the probe body 7, whereby the movement of the probe body 7 can be detected capacitively. As shown in Figure 2 and Figure 3, the rigid capacitor body 54, 56 and the deformable capacitor body 58 are arranged in a power-free state parallel to each other. If, however, the probe body 7 moves, then the capacitor body 58 is deformed in a corresponding manner and deflected out of the equilibrium position according to FIG. 2 and FIG.

As a detail 25 in FIG. 3 shows, the rigid capacitor body 54 has an electrically insulating substrate (for example, a ceramic substrate) 64 and an electrode 66 deposited thereon, which may be formed, for example, as a deposited gold electrode. The thickness of the substrate 64 may be, for example, in a range between 500 μm and 3 mm, for example 1 mm. The thickness of the electrode 66 may, for example, be in a range between 100 nm and 1 pm, in particular have a thickness between 300 nm and 500 nm.

As a detail 27 in FIG. 3 shows, the deformable capacitor body 58 is made of a one-piece (and preferably single-material) plate of electrically conductive material, for example a sheet steel. A coupling body 76 described in more detail below rests on a recess 23 of the plate, which is formed here as a through hole. This ensures a good transfer of force from the coupling body 76 on the plate. A distance D between the two rigid capacitor bodies 54, 56 is for example 600 pm. A thickness d of the deformable capacitor body 58 is, for example, 400 pm.

As a detail 29 in FIG. 3 shows, the rigid capacitor body 56 has an electrically insulating substrate (for example, a ceramic substrate) 64 and an electrode 66 deposited thereon, which may be formed, for example, as a deposited gold electrode. The thickness of the substrate 64 may be, for example, in a range between 500 μm and 3 mm, for example 1 mm. The thickness of the electrode 66 may, for example, be in a range between 100 nm and 1 pm, in particular have a thickness between 300 nm and 500 nm.

As already described, the path measuring device 50 has the coupling body 76, which in the illustrated embodiment is formed from an electrically insulating material such as glass and in the form of a sphere. The coupling body 76 is on the one hand in operative connection with the deformable capacitor body 58, on the recess 23 of the coupling body 76 rests. On the other hand, the coupling body 76 is also in operative connection with the probe body 7, not shown in FIG. 3, so that upon movement of the probe body 7, the coupling body 76 and the coupling body 76 displace or deform the deformable capacitor body 58 (see, for example, FIG. 10). , The configuration of the coupling body 76 as a ball has the advantage that parasitic coupling phenomena between the probe body 7 and the deformable capacitor body 58 are thereby particularly effectively suppressed. Alternatively, the coupling body 76 but also have other shapes, for example, be designed as a cylinder which may rest loosely on the capacitor body 58 or rigidly secured thereto.

In an alternative embodiment, the coupling body 76 relative to a laboratory system or the scanning probe microscope 1 as a whole be formed fixed, static or static, for example, be mounted on a stationary frame of the scanning probe microscope 1. In such a configuration, the capacitor bodies 54, 56, 58 can move when the displacement device 80 moves the probe body 7.

FIG. 3 further shows that a respective rigid spacer 78, 79 can be interposed between a respective one of the rigid capacitor bodies 54, 56 formed with external electrodes on the one hand and the deformable capacitor body 58 in the form of a center electrode, each having a defined spacing between adjacent capacitor electrodes in the force-free state established. The spacers 78, 79 may, for example, a steel plate, a copper sheet, a

Ceramic film or the like can be produced. A person skilled in the art will understand that - at least in one configuration of the spacers 78, 79 of an electrically conductive material - the electrodes 66 of the capacitor bodies 54, 56 preferably do not laterally extend to the spacers 78, 79 to undesirable electrical effects (for example a short circuit).

An excitation signal in the form of a respective electrical voltage, which can be generated by means of a common electrical excitation source 75, can be applied to the rigid capacitor bodies 54, 56. A detection means 60 shown schematically in FIG. 2 serves to detect electrical signals (in response to the application of the electrical voltages) to the deformable capacitor body 58. The electrical signals are generated in response to the application of the excitation signal and depend on the position of the probe body 7 because, depending on this position, the capacitor body 58 is deformed more or less severely. This deformation alters the capacitive properties of the path measuring device 50 and therefore also influences the detected electrical signals. A determination device 62, likewise shown schematically in FIG. 2, is configured to determine indicative information for the path information of the probe body 7 based on the detected electrical signals, these electrical signals being supplied to the detection device 62 by the detection device 60.

As shown in Figure 2, the plate-like plate-like (see plates A, B) capacitor bodies 54, 58 spaced apart together form a first capacitor having a capacitance Ci. Similarly, the spaced apart plate-like (see plates B, C) form

Capacitor 56, 58 together a second capacitor with a capacitance C2. Does the respective mutual distance between the capacitor bodies 54, 58 and 56, 58 changes due to a movement or

Deformation of the capacitor body 58 in response to a position change of the probe body 7 to be detected changes this in a more characteristic manner

Detect the electrical signals detected by the detection device 60, from which the determination device 62 can reconstruct the position information relating to the probe body 7.

In a clear and simplified form, the determination device 62 serves to determine the information indicative of the path information of the probe body 7 by subtraction of the detected electrical signals. A movement of the probe body 7 leads to an increase in the distance between the respective capacitor bodies 54, 58 or 56, 58 and at the same time leads to a reduction of the distance between the respective other two capacitor bodies 56, 58 or 54, 58. The voltage applied to the two capacitors Ci , C2 generated electrical signals change in a movement of the probe body 7 in opposite directions or in opposite directions, so that the accuracy of the measured path information can be increased by differentiating the two electrical signals. As will be explained in more detail with reference to FIG. 8 and FIG. 9, the determination means 62 for determining the information indicative of the path information of the probe body 7 is arranged by synchronous demodulation.

Preferably, the detection device 60 detects the electrical signals in response to the application of a respective electrical voltage, which is preferably generated by means of a common electrical excitation source 75. This prevents voltage fluctuations or two incompletely identical voltage sources from causing artefacts on the system that could affect the sensitivity.

The sensor in the form of the capacitive displacement measuring device 50 is formed from three superimposed electrodes (see reference numerals 66, 58, 66 in FIG. 3) with a very small distance from one another, wherein only the central electrode in the form of the deformable capacitor body 58 is designed to be movable. By this arrangement, two capacitors, namely the capacitor Ci between plates A and B (corresponding to capacitor bodies 54, 58) and the

Capacitor C2 between plates B and C (corresponding to capacitor bodies 56, 58). If the movable plate B is brought closer to the plate A, the capacitance of the capacitor Ci increases while the value of the capacitance of the capacitor C2 decreases, and vice versa. The difference C1-C2 is indirectly a measure of the displacement of the plate B.

On the one hand, this differential design doubles the sensitivity of the sensor in the case of a fixed capacitor area and, on the other hand, reduces the susceptibility to errors under fluctuating ambient conditions (humidity, temperature, etc.) because these changes equally affect both capacitors C 1, C 2. In addition, the achievable by the described arrangement high stability and pronounced symmetry of the electrical excitation signals leads to particularly stable measurements. This can be achieved in particular in that the excitation signals of the capacitors C 1 and C 2 are derived from a common signal source (see reference numeral 74 and DAC 31 in FIG. 8) and their amplitude is changed by a further two-channel DAC (see reference numeral 33 in FIG. 8) can be. Since the channels of the two-channel DACs 33 are thermally coupled very well, a temperature change leads to an in-phase increase or decrease of the excitation amplitudes and thus to a temperature compensation.

Thus, as shown in FIG. 3, the path measuring device 50 can essentially be made up of five layers stacked on top of one another (see reference numbers 54, 78, 58, 79, 56) and thus extremely compact and simple. The uppermost layer and the lowermost layer form the rigid and inherently rigid capacitor bodies 54, 56, which in the illustrated embodiment are formed as thin ceramic substrates 64 onto which the electrodes 66 of gold are evaporated. The rigid capacitor bodies 54, 56 form the (at least relative to each other) immovable outer electrodes. The middle layer is realized in the form of the deformable capacitor body 58 and formed in the embodiment shown as a thin steel foil. Capacitor body 58 acts as a movable center electrode. As

Spacers 78, 79 formed remaining two intermediate layers in the unloaded state ensure the correct distance between the three electrodes. To form the spacers 78, 79, in turn, steel foils can be used because they can be manufactured with very small thicknesses (a few 10 pm) and very high precision.

FIG. 4A shows a capacitor body 99 of a displacement measuring device 89 that is parallelly displaced relative to two rigid capacitor bodies 95, 97. FIG. 4B, on the other hand, shows a movable capacitor body 58 of a displacement measuring device 50 deflected in a bulbous manner relative to two rigid capacitor bodies 54, 56 in accordance with an exemplary embodiment of the invention. According to this embodiment, the deformable capacitor body 58 thus has an elastic membrane 72.

Instead of carrying out the center electrode as a rigid plate, as shown in FIG. 4A, and displacing it in parallel via a complicated mechanism, the capacitor body 58 acting as center electrode is designed and deformed as a diaphragm 72 according to the described exemplary embodiment of the invention. Such a structure can be realized both extremely compact and with little effort. Finally, it can be formed predominantly on the basis of sheet metal parts and flat ceramic substrates (see FIG. 3). In addition, in such a structure, the moving mass remains small, which has a positive effect on the dynamic behavior on the mechanical side (for example mechanical natural frequency).

In the following, with reference also to FIG. 5, a capacitive displacement measuring device 50 according to a preferred exemplary embodiment of the invention will be described, which has an even higher measuring accuracy than an exemplary embodiment with a continuously deformable elastic diaphragm 72.

In a pure parallel displacement of the center electrode, as shown in Figure 4A, the displacement to be measured leads to a uniform change in the distance between the electrodes.

In the case of a pure and continuous membrane approach, the displacement only works completely at the force introduction point. The further one approaches the bearing point of the diaphragm 72, the less the distance between outer electrode and center electrode changes (see FIG. 4B). This leads on the one hand to a reduced change in capacity with respect to the shift and, on the other hand, to a non-linear relationship between displacement and capacity difference. Thus, while the use of a continuously deformable membrane 72 as center electrode has the advantage of being particularly easy to produce, the exemplary embodiment of the invention described below with reference to FIGS. 5 and 6 has the advantage of a particularly high sensitivity of measurement.

FIG. 5 shows a plan view of a movable capacitor body 58 of a path measuring device 50 according to an exemplary embodiment of the invention.

The partially deformable capacitor body 58 shown in FIG. 5 has an electrode 68 that is not deformed during operation (ie, forces that normally occur on the capacitor body 58 as a result of a displacement of a probe body 7), and an adjoining and operating device (ie, forces, as they normally occur on the capacitor body 58 due to a displacement of a probe body 7) bent portion realized by webs 70 bent in operation. Advantageously, according to FIG. 5, the capacitor body 58 is designed as a condenser body 58 which is only partially deformable and which in a central region has an electrode 68 which is rigid during operation and thus substantially non-deformable and oblong and in operation (here four circumferential or two pairwise opposite) edge regions has deformed or bendable webs 70. A

The area of the operationally rigid electrode 68 is a multiple of a surface area of a respective one of the deformed webs 70. The exactly partially deformable capacitor body 58 is formed in one piece and monolithic, more specifically, from a single plate (for example, steel) as shown in FIG Homogeneous thickness worked out. For example, such a steel flake or other metal flake may be machined by, for example, a laser to form elongate through holes 87 in the flake, thereby delimiting the elongated bendable webs 70 but remaining integrally bonded to the operationally rigid electrode 68 in the central region. As a result of this processing, it is possible for the capacitor body 58, which during operation of the probe body 7 in the central section (ie, in the region of the rigid electrode 68) to be deflected in its maximum substantially deformation-free manner, and only in an edge region (ie deformed in the region of the bendable or in operation deformed webs 70). The plate is mounted on both sides of a respective support or mounting body 85. On the two opposing major surfaces of a respective support or mounting body 85 then spacers (see reference numeral 78, 79 in Figure 3) can be arranged.

A length E of the plate forming the capacitor body 58 according to FIG. 5 may, for example, be in a range between 5 mm and 15 mm, for example 8 mm. For example, a width L of the wafer may be in a range between 2 mm and 8 mm, for example 4 mm. A length b of a respective web 70 may, for example, be in the range between 0.5 mm and 3 mm, in particular between 1 mm and 2 mm. A width I of a respective web 70 may be, for example, a few tenths of a millimeter, for example between 0.2 mm and 0.8 mm. An aspect ratio of a respective ridge 70, i. a ratio b / l may be, for example, at least 2, in particular at least 3, more particularly between 3 and 10.

Illustratively, the exemplary embodiment described combines the advantages of FIG. 4A and FIG. 4B with a significantly reduced mechanical outlay compared to FIG. 4A. The embodiment according to FIG. 5 on the one hand has the advantage that the electrode 68, which is rigid during operation, is displaced substantially translationally and strongly when a force is applied by the coupling body 76, which leads to a very high sensitivity. At the same time, the elastic bending capability or deformation of the webs 70 during operation leads to a significant deformation of the webs 70 even with small forces acting on the coupling body 76 and consequently to a significant deflection of the electrode 68, and consequently to a large deflection Sensor signal comes. The condenser body 58 of a membrane-like design according to FIG. 5 is thus configured in such a way that upon deformation as a result of a movement of the probe body 7, a first region of the membrane 72, which is inner or central according to FIG. 5, is subjected to less stress than a second outer, according to FIG. Area of the membrane. During a movement of the probe body 7, the first region of the membrane will remain substantially parallel to the rigid capacitor bodies 54, 56 not shown in FIG. 5 and arranged in planes above or below the plane of the paper according to FIG. In other words, the membrane-like capacitor body 58 according to FIG. 5 is designed so that, when deformed as a result of movement of the probe body 7, the first region of the membrane remains substantially parallel to the rigid capacitor bodies 54, 56 with a higher rigidity compared to the second region of the membrane.

In order to achieve the described advantages of the exemplary embodiment according to FIG. 5, the two tasks which according to FIG. 4B fulfill the membrane 72 (namely mechanical guidance and forming an electrode surface) are separated. The webs 70 according to FIG. 5, like the membrane 72 according to FIG. 4B, are elastically deformed during operation and in this way act as guides for the electrode surface of the electrode 68 which is rigid during operation. Advantageously, however, the webs 70 are so small in terms of area that they only have one low contribution to

Capacity of the respective capacitor Ci, C2 supply. Alternatively, the respective mating surfaces could be completely removed from the lands 70 on the outer electrodes (i.e., the rigid capacitor bodies 54, 56). Advantageously, in this embodiment, the webs 70 hardly contribute to the capacity. The electrode surface of the rigid electrode 68 in operation is hardly connected to the suspension of the membrane section according to FIG. Consequently, their deflection is significantly reduced, which in turn increases the sensitivity. The stiffer the electrode surface of the rigid electrode 68 in operation with respect to the webs 70, the more level it remains and the higher the sensitivity.

FIG. 6 shows a movable capacitor body 58 of a path measuring device 50, which is displaced partly parallel to one another and partly deflected like a bell, in relation to two rigid capacitor bodies 54, 56 according to an exemplary embodiment of the invention. Illustratively, FIG. 6 shows that the webs 70 behave when subjected to a force such as diaphragm 72 according to FIG. 4B, whereas the rigid electrode 68 behaves when a force acts as shown in FIG. 4A.

FIG. 7 shows a three-dimensional representation of a path measuring device 50 according to an exemplary embodiment of the invention. In particular, FIG. 7 shows that the excitation signal is applied to the rigid ones

Capacitor 54, 56 on a first side (according to Figure 7 on the left side) of the capacitor body 54, 56, 58 are applied, for which supply cable 91 are used. In a corresponding manner, the electrical signals which are then detected by the detection device 60 and evaluated by the determination device 62, of the exactly partially deformable

Capacitor body 58 on one of the first side opposite second side (according to Figure 7 on the right side) removed by means of a removal cable 93. In this way, the supply cable 91 are spatially decoupled from the removal cable 93. This reduces a parasitic capacitance which the feed cables 91 and the take-off cable 93 can form together.

In particular, unwanted parasitic coupling of the feeder cables 91 and / or the removal cable 93 to the capacitor bodies 54, 56, 58 can be avoided or at least greatly suppressed in this way.

In order to keep an unwanted crosstalk of excitation signals and the sensor signal low or possibly even minimize, according to Figure 7 on one side of the sensor, the plates A and C with the excitation signal and on the other side the plate B with the input of a connected in Figure 8 transimpedance amplifier 35 shown. In order to achieve a very compact design, the cables can be soldered 91, 93 on the board front side by attaching a Kantenmetallisierung. The layer structure of the board can be designed as a rigid-flex combination, whereby an optimal adaptation to the given structures can take place.

FIG. 8 shows an evaluation circuit with an excitation source 75, a detection device 60 and a detection device 62 of a path measuring device 50 according to an exemplary embodiment of the invention.

A control device 37 controlling the signal generation and signal evaluation can be embodied, for example, as an electronic chip (for example an FPGA, Field Programmable Gate Array, or a DSP, digital signal processor). The control device 37 is given a clock by means of a clock source 39. This clock signal is supplied to a signal source 74 and a block 41, which may have a synchronous demodulator and filters.

The signal source 74 may, for example, generate a sinusoidal signal with a defined phase shift. In addition, an amplitude and phase module 43 forms part of the control device 37.

A signal generated by the signal source 74 is supplied to a digital to analogue converter (DAC) 31 and subsequently to an amplifier 45. An output signal of the amplifier 45 is supplied to two amplifiers 47, 49 which generate mutually inverse signals. Illustratively, the amplifiers 47, 49 can generate signals in phase opposition to one another (for example sinusoidal signals)

Signals with a phase shift of 180 ° to each other). These electrical signals are supplied to the two-channel DAC 33 to perform an adjustment of the amplitudes. Subsequently, a further amplification by means of amplifiers 51, 53 takes place in each of the two paths.

The electrical excitation source 75 is formed by the components with the reference numerals 39, 74, 31, 45, 47, 49, 33, 51 and 53, as shown schematically in FIG.

The output signals of the amplifiers 51, 53 are fed to the two capacitors indicated in FIG. 2 by Ci (formed between plates A and B) and C2 (formed between plates B and C) (the capacitor Ci according to FIG. 2 in FIG. 8 corresponds to the capacitor Cp (t) and corresponds to the capacitor C2 of Figure 2 in Figure 8 the capacitor Cn (t)). Ideally, through the capacitor Cp (t) and through the capacitor Cn (t) in the power-free state, identical currents with different signs, which cancel each other out at a junction, flow. If a displacement device 80 generates a force acting on the capacitor body 58 via a coupling body 76, the system of capacitor Cp (t) and capacitor Cn (t) is detuned, and a current characteristic of an associated displacement information can be taken from the capacitor body 58 , If the capacitors Cp (t) and Cn (t) are slightly out of tune with each other in the off-state, this may optionally be compensated by configuring the constituents DAC1, DAC2 of the two-channel DAC 33.

An electrical signal taken from the deformable capacitor body 58 by means of the removal cable 93 is then supplied to the transimpedance amplifier 35, which can be assigned to the detection device 60. Its output signal is amplified by one (or more) further amplifier 55 and fed to an analog-to-digital converter 57. Illustratively, the amplifier 55 can adapt the output signal to the analog-to-digital converter 57. Its output signal is transmitted to the block 41. Block 41 multiplies the output of analog-to-digital converter 57 by a control signal which generates signal source 74. One

Output from block 41 may be supplied to the amplitude and phase module 43 and from there to a sensor output unit 59. Alternatively, an output signal from block 41 may also be provided directly to the sensor output unit 59. At a calibration unit 61, a calculation of the sensor output signal to a path normal can be made, so that at an output sensor 63, an output signal (for example, in microns) may be provided, which corresponds to the path information or the vertical position of the probe body 7. Blocks 41, 43, 59, 61 and 63 may be assigned to the determination device 62.

Both the generation of the excitation signal and the evaluation of the sensor signal is digital in the control device 37. The digital signal generation in the control device 37 delivers a sinusoidal excitation signal to the DAC 31 and two further sinusoidal signals with exactly the same frequency (λ (t), λ90 ° (t)) and an arbitrary phase shift φ0 to a dual lock-in in the form of block 41, which may be formed essentially of two synchronous demodulators (mixers) and digital filter stages.

The sinusoidal excitation signal is converted by the DAC 31 into an electrical signal and phase-shifted by a corresponding amplifier circuit for the DAC2 by 180 °. DAC1 and DAC2, which may preferably be in the same IC package, adjust the amplitudes of the two excitation signals so that the sensor can be operated at its desired operating point.

One possible variation can be made as follows: DAC 31 is eliminated, DAC1 and DAC2 not only provide gain but directly generate the time-varying sinusoidal excitation signal. The thermal coupling and the use of a common voltage reference are advantageous.

By shifting the disk B relative to disks A, C, a modulated current signal through the transimpedance amplifier 35 (TIA) becomes

Converted voltage signal. One or more downstream

Amplifier circuits (see reference numeral 55) provide for a

High pass filtering and matching to an input voltage range of the ADC 57.

The digital raw data from the analog-to-digital converter 57 is synchronously demodulated in the dual lock-in module (see block 41) and low-pass filtered, whereby the signals ALp, i = uAdc * a, ALp, q = Uadc * Ä90 ° are obtained. The signals ALp, i and ALp, q (in-phase and quadrature-phase) can be further processed directly and / or by forming amplitude and phase. The amplitude is calculated from R = (ALp, i2 + ALp, q2) 1/2 and the phase from θ = atan2 (ALp, Q, ALp, i). Both the signals ALp, i and ALp, q and the amplitude R are a measure of the displacement of the disk B to the plates A and C. For calibration, these signals can be compared with a normal en (t). For example, normal en (t) can be measured with an interferometer, or a precise specification of en (t) by a nanopositioning device is carried out. For a particularly good performance, it is advantageous to use a common, thermally stable and long-term stable, jitter-poor clock source 39, from which all other clocks are derived. This ensures a proper function of the synchronous demodulation.

FIG. 9 shows a schematic diagram of an electronic circuit including evaluation logic of a path measuring device 50 according to an exemplary embodiment of the invention. The evaluation of the measurement takes place according to FIG. 9 and FIG. 8 according to the method of synchronous demodulation. The final product of the calculation according to FIG. 9 is the output (voltage) signal Alp (t). A path length can be calculated from this by means of a calibration, which is effected for example by means of an interferometer or via a precise specification by a nanopositioning device. FIG. 9 also shows a summation unit 65, a multiplication unit 67 and a low-pass filter 69.

A derivation of mathematical relationships of a differential capacitive displacement measuring device 50 according to an exemplary embodiment of the invention will be described below. The following assumptions are made for this: HTiA (jcü) -HVA (jcü) = G = const. DCoffset = 0

In other words, it is assumed that the product of the transfer functions of the transimpedance amplifier 35 (HtiaGco)) and the amplifier 55 (HVA (jco)) assume a constant value G and are therefore not a function of the frequency. In addition, it is assumed that there is no offset voltage.

The output current iou-r (t) results in: iouT (t) = ip (t) -iN (t) = d / dt (cP (t) -up (t)) -d / dt (CN (t) -UN (t)) up (t) and Uhi (t) are the electrical excitation signals of the two capacitors: up (t) = UPsin (cot) UN (t) = UNsin (cot)

Cp (t) and Chi (t) correspond to the respective capacitance value at time t: cP (t) = e AP / (dp + e (t)) cN (t) = e AN / (dN-e (t))

Here, ε stands for the electrical permittivity, A for the active area of a respective plate capacitor and d for the spacing of the plates A, B or B, C. e (t) denotes the mechanical displacement of the middle plate B.

The reference signal λ (ί, φ0) is defined as follows: Ä (t, (p0) = sin (cüt + (p0)

The analysis signal A (t) results from the multiplication of UADc (t) with the reference signal λ (ί, φ0): A (t) = uADc (t) -Δ (t, (po) = iouT (t) G- sin (cot + (po)

Taking into account a few trigonometric relationships and the subsequent low-pass filtering (ideal low-pass filter with an infinitely high attenuation in the stopband above the cut-off frequency ω) it can be shown that:

ALp (t) = [1 / 2piCOs ((po) + 1 / 2cop2COs ((po)] G

Pi = Cp '(t) Up-Ci \ i' (t) Un P2 = Cp (t) Up-Ci \ i (t) Un

Cp (t), CN (t) are the respective capacitance values at time t and Cp '(t), CN' (t) correspond to the first derivative of Cp (t), CN (t) after time t.

It should be noted that the displacement signal of the probe body 7 is also included in the analysis signal ALp (t). Preferably, this influence should be kept as small as possible so that the Wegstreckensignal is not charged with speed-dependent contributions. This can be achieved, for example, by adapting the reference signal λ (ί, φ0) accordingly (in particular by phase-shifting by setting φ0).

By varying φ0, taking into account the phase position of the excitation signals, ALp (t) can be converted into an I component ALp, i (t) (in-phase component) and a Q component ALp, Q (t) (quadrature-phase component ) disassemble.

FIG. 10 shows a displacement device 80 for displacing a probe body 7 and a displacement measuring device 50 for measuring a displacement of a displacement of the probe body 7 by means of the displacement device 80 according to an exemplary embodiment of the invention. In particular, measuring probe 11 is shown in FIG. 10, which is set up to scan the surface of specimen body 6 in a scanning manner. The measuring probe 11 is formed from probe body 7 and measuring tip 5. A displacing device 80, which is advantageously designed as a piezoactuator, serves to displace the probe body 7 and is rigidly coupled both to the probe body 7 and to the displacement measuring device 50. Both the displacement device 80 and the path measuring device 50 may be mounted on a housing 71. If, by means of the displacement device 80, the probe body 7 is displaced toward or removed from a sample 6 to be measured, this results in a corresponding displacement of the coupling body 76 due to the rigid coupling of the displacement device 80 to the probe body 7 and to the displacement measuring device 50 76 deforms thereupon the at least partially deformable capacitor body 58 of the path measuring device 50. This deformation is capacitively detected and evaluated and allows a quantitative inference to path information of the probe body 7, for example, the displacement or the position of the probe body 70 in the z-direction, ie in according to Figure 10 vertical direction. More specifically, as shown in FIG. 10, the path measuring device 50 for measuring path information of the probe body 7 is formed and arranged in a vertical direction and perpendicular to a substantially horizontal scanning plane, respectively.

Exemplary application fields of the path measuring device 50 are, for example, an insert as a displacement measuring system for determining the vertical displacement of the probe body 7 in an atomic force microscope 1.

FIG. 11 shows a partially deformable or partially translationally movable capacitor body 58 with a rigid electrode 68 and bendable webs 70 of a path measuring device 50 according to an exemplary embodiment of the invention in an operating state in which the webs 70 are not bent. FIG. 12 shows the movable capacitor body 58 according to FIG. 11 in another operating state in which the webs 70 are bent. According to FIG. 11 and FIG. 12, the center electrode or the capacitor body 58 is subdivided into guide webs (see reference numeral 70) and electrode surface (see reference numeral 68). FIG. 11 and FIG. 12 compare the relative position of the webs 70 and the electrode 68 in the ground state (see FIG. 11) and on deflection (see FIG. 12) to a greatly exaggerated scale.

In addition, it should be noted that "having" does not exclude other elements or steps and "a" or "an" does not exclude a multitude. "It should also be noted that features or steps described with reference to one of the above embodiments also can be used in combination with other features or steps of other embodiments described above, and reference signs in the claims are not intended to be limiting.

Claims (23)

claims Capacitive path measuring device (50) for measuring path information of a probe body (7), in particular for a scanning probe microscope (1), wherein the path measuring device (50) comprises: two at least partially electrically conductive, rigid and in their relative position mutually unchangeable capacitor body (54 , 56); an electrically conductive and at least partially deformable capacitor body (58) disposed between the rigid capacitor bodies (54, 56) and arranged to be deformed upon movement of the probe body (7); a detection device (60) for detecting electrical signals at at least one of the capacitor bodies (54, 56, 58); a determination device (62) for determining information indicative of the path information of the probe body (7) based on the detected electrical signals. 2. path measuring device (50) according to claim 1, wherein the rigid capacitor body (54, 56) and the at least partially deformable capacitor body (58) are arranged in a power-free state parallel to each other. The path measuring device (50) according to claim 1 or 2, wherein at least one of said rigid capacitor bodies (54, 56) comprises an electrically insulating substrate (64) and an electrode (66) deposited thereon. 4. path measuring device (50) according to one of claims 1 to 3, wherein the electrically conductive and at least partially deformable capacitor body (58) during operation at least partially undeformed electrode (68) and an adjoining and bent in operation area, in particular in Operation curved webs (70), comprising. 5. A distance measuring device (50) according to claim 4, wherein a surface of the electrode (68) is at least three times, in particular at least five times, a surface of a respective one of the webs (70). 6. path measuring device (50) according to one of claims 1 to 5, wherein the at least partially deformable capacitor body (58) is wholly or partially formed as an elastic membrane (72). 7. path measuring device (50) according to claim 6, wherein the membrane (72) is formed such that upon deformation as a result of movement of the probe body (7) a first region of the membrane (72) is less loaded than a second region of the membrane (72 ) and the first region of the membrane (72) remains substantially parallel to the rigid capacitor bodies (54, 56) when the probe body (7) moves. The path measuring device (50) according to claim 6 or 7, wherein the diaphragm (72) is formed so that, when deformed due to movement of the probe body (7), a diaphragm region substantially parallel to the rigid one compared to another diaphragm region of higher rigidity Capacitor bodies (54, 56) remains. 9. path measuring device (50) according to one of claims 1 to 8, wherein the at least partially deformable capacitor body (58) is integrally formed and / or einstoffig. 10. path measuring device (50) according to one of claims 1 to 9, wherein the at least partially deformable capacitor body (58) is formed when moving the probe body (7) in a central portion of the at least partially deformable capacitor body (58) to be deflected substantially free of deformation and deformed in an edge region of the at least partially deformable capacitor body (58). 11. A distance measuring device (50) according to any one of claims 1 to 10, wherein the determining means (62) for determining the information indicative of the path information of the probe body (7) is arranged by synchronous demodulation. 12. path measuring device (50) according to any one of claims 1 to 11, wherein the detecting means (60) for detecting the electrical signals in response to the application of an electrical excitation signal, in particular a respective electrical voltage, further generated in particular by means of a common signal source (74). , between a respective one of the rigid capacitor body (54, 56) and the at least partially deformable capacitor body (58) is arranged. 13. path measuring device (50) according to one of claims 1 to 12, comprising a coupling body (76), in particular a spherical coupling body, which is in operative connection with the at least partially deformable capacitor body (58) and in operative connection with the probe body (7), so upon movement of the probe body (7), the probe body (7) displaces the coupling body (76) and the coupling body (76) deforms and / or displaces the at least partially deformable capacitor body (58). 14. A distance measuring device (50) according to any one of claims 1 to 13, comprising a respective spacer (78, 79) between a respective one of the rigid capacitor body (54, 56) and the at least partially deformable capacitor body (58). 15. Distance measuring device (50) according to one of claims 1 to 14, wherein a distance (D) between the rigid capacitor bodies (54, 56) is at most 700 pm, in particular at most 500 pm. 16, path measuring device (50) according to one of claims 1 to 15, wherein a thickness (d) of the at least partially deformable capacitor body (58) is at most 500 pm, in particular at most 300 pm. 17. A distance measuring device (50) according to any one of claims 1 to 16, which is formed, an excitation signal to at least a part of the capacitor body (54, 56, 58), in particular to the rigid capacitor body (54, 56), on a first side of Capacitor body (54, 56, 58) apply and remove the electrical signals from at least a portion of the capacitor body (54, 56, 58), in particular of the at least partially deformable capacitor body (58), on a first side facing away from the second side. 18 scanning probe microscope (1) for determining surface information regarding a sample body (6) by scanning scanning a surface of the sample body (6), wherein the scanning probe microscope (1) comprises: a movable probe body (7) with a measuring tip (5) for scanning scanning the surface of the specimen (6); A capacitive displacement measuring device (50) according to any one of claims 1 to 17 for measuring displacement information of the probe body (7). 19. Scanning probe microscope (1) according to claim 18, designed as an atomic force microscope. 20, scanning probe microscope (1) according to claim 18 or 19, comprising a displacement device (80) which is adapted to move the probe body (7) and rigidly coupled to the probe body (7) and the Wegmessvorrichtung (50). 21 scanning probe microscope (1) according to claim 20, wherein the displacement device (80) is designed as a piezo actuator. 22, scanning probe microscope (1) according to any one of claims 16 to 19, wherein the path measuring device (50) for measuring a displacement information of the probe body (7) in a vertical direction and / or perpendicular to a scanning plane of the sample body (6) is arranged. 23. A method for capacitive measuring of a path information of a probe body (7), in particular a scanning probe microscope (1), wherein the method comprises: deforming an electrically conductive and at least partially deformable capacitor body (58) during movement of the probe body (7), which at least partially deformable capacitor body (58) between two at least partially electrically conductive, rigid and in their relative position to each other invariable capacitor bodies (54, 56) is arranged; Detecting electrical signals on at least one of the capacitor bodies (54, 56, 58); Determining an information indicative of the path information of the probe body (7) based on the detected electrical signals.