Measuring apparatus, scanning probe microscope, and methods for testing the measured samples.

Abstract

This invention relates to a measuring device, a scanning probe microscope, and a method for testing a sample. The measuring device for a scanning probe microscope includes: a sample receiving portion configured to receive a sample to be tested; a measuring probe disposed on a probe holder and having a probe tip, the sample being measured using the probe tip; a displacement device configured to move the measuring probe and the sample receiving portion relative to each other for measuring the sample, such that the measuring probe performs a scanning motion relative to the sample in at least one spatial direction for measuring the sample; a control device connected to the displacement device and controlling the relative motion between the measuring probe and the sample receiving portion; and a sensor device configured to detect a motion measurement signal of the actual motion of the measuring probe and / or the sample receiving portion and transmit the motion measurement signal to the control device.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to German Patent Application No. 10 2019131 421.6, filed on 21 November 2019 with the German Patent and Trademark Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a measuring device for a scanning probe microscope, a scanning probe microscope, and a method for performing scanning probe microscopy testing on a sample using a scanning probe microscope. Background Technology

[0004] Such scanning probe microscopes are known in various different embodiments. These microscopes are used to scan probes to microscopically test and measure samples. Here, in order to scan the sample, relative movement occurs between the probe tip and the sample container, on which the sample to be tested is placed. The probe and the sample container move relative to each other by means of a displacement device. The probe tip and the sample interact. A measurement signal is detected through this interaction.

[0005] This atomic force microscope can have a lever arm that can bend elastically, with the probe tip located at the end of the lever arm. The displacement device has an actuator for achieving relative displacement between the probe tip and the sample to be tested; in scanning microscopy, a piezoelectric actuator is used as the actuator, for example. Additionally, a detection unit is provided for measuring the force on the lever arm. Depending on the specific embodiment, the components can be fixed to one or more supports. For example, when the actuator performs periodic vibrational motion during measurement, the actuator's motion may be independent of its inherent resonant characteristics, resulting in unplanned motion due to mechanical coupling of different axes of motion, or exciting the corresponding support structure to vibrate internally. This can lead to imaging distortion of the sample surface or the surface properties of the sample, because the trajectory generated by the targeted manipulation of the actuator is not consistent with the actual relative motion between the probe tip and the sample.

[0006] In probe microscopy, the sample is scanned by a measuring probe (probe tip). It's important to note that the actual scan performed by the measuring probe corresponds to a pre-defined and planned grid pattern for the measurement technique, ensuring that the resulting image of the sample is not distorted during scanning. In known scanning probe microscopy, problems can arise in this case when the piezoelectric element used in the displacement device causes nonlinear motion. Additionally, so-called creep can occur, causing the measuring probe and sample, for example, which may be designed as cantilevered, to move relative to each other during the scanning motion. Typically, the offset between the two components is measured by a sensor, where the displacement device moves one component while the other remains stationary. In this case, it is generally assumed during measurement data analysis that the connection between the displacement device (and its housing) and the point of interaction between the measuring probe and the sample is rigid. At higher scanning or probing speeds (scanning frequency), this assumption usually no longer holds, resulting in image distortion that the sensor can no longer detect or eliminate. Summary of the Invention

[0007] The purpose of this invention is to provide a measuring device for a scanning probe microscope, a scanning probe microscope, and a method for performing scanning probe microscopy testing on a measurement sample using a scanning probe microscope, wherein the measurement sample testing can be performed with higher precision.

[0008] According to one aspect, a measuring device for a scanning probe microscope is proposed, the measuring device having the following features: a sample receiving portion configured to receive a measurement sample to be tested; a measuring probe disposed on a probe holder and having a probe tip, the probe tip being capable of measuring the measurement sample; a displacement device configured to move the measuring probe and the sample receiving portion relative to each other for measuring the measurement sample, such that the measuring probe performs a scanning motion relative to the measurement sample in at least one spatial direction for measuring the measurement sample; a control device connected to the displacement device and controlling the relative motion between the measuring probe and the sample receiving portion; and a sensor device configured to detect a motion measurement signal of the actual motion of the measuring probe and / or the sample receiving portion and send the motion measurement signal to the control device, the actual motion being performed when the measuring probe and the sample receiving portion move relative to each other for measuring the measurement sample, the motion measurement signal indicating a first motion component of interfering scanning motion along a first spatial direction and a second motion component of interfering scanning motion along a second spatial direction extending transversely to the first spatial direction. Furthermore, the control device is configured to control the relative movement between the measuring probe and the sample container according to the motion measurement signal, such that the control device applies a compensating control signal component to the displacement device, the control signal component realizing a first reverse movement and / or a second reverse movement for the movement of the measuring probe and / or the sample container, the first reverse movement substantially compensating for the first motion component that interferes along the first spatial direction, and the second reverse movement substantially compensating for the second motion component that interferes along the second spatial direction.

[0009] According to another aspect, a scanning probe microscope having the aforementioned measuring device is provided.

[0010] According to another aspect, a method for performing scanning probe microscopy on a measurement sample using a scanning probe microscope is provided. The method includes the steps of: placing the measurement sample on a sample receiving portion of the scanning probe microscope; and performing a probe microscopy test on the measurement sample using a probe, the measurement probe being disposed on a probe holder and having a probe tip. Here, a displacement device moves the measurement probe and the sample receiving portion relative to each other, such that the measurement probe performs a scanning motion relative to the measurement sample along at least one spatial direction. A control device is provided, connected to the displacement device and controlling the relative motion between the measurement probe and the sample receiving portion. A motion measurement signal is detected by a sensor device, and the motion is performed during the relative motion between the measurement probe and the sample receiving portion. The motion measurement signal indicates a first motion component interfering with the scanning motion along a first spatial direction and a second motion component interfering with the scanning motion along a second spatial direction, the second spatial direction extending transversely to the first spatial direction. The motion measurement signal is sent to the control device. The control device controls the relative movement between the measurement probe and the sample container according to the motion measurement signal, so that the control device loads a compensation control signal component onto the displacement device. The control signal component realizes a first reverse movement and / or a second reverse movement for the movement of the measurement probe and / or the sample container. The first reverse movement substantially compensates for the first motion component that interferes along the first spatial direction, and the second reverse movement substantially compensates for the second motion component that interferes along the second spatial direction.

[0011] The sensor device detects the actual movement performed by the measuring probe and / or the measuring sample disposed on the sample container and feeds it back to the control device, which can then generate control signals for a displacement device to move the measuring probe and the measuring sample relative to each other. If the actual movement performed by the measuring probe and the measuring sample during scanning or probing of the measuring sample differs from the pre-defined scanning movement for probe microscopy testing, this can be corrected. This ensures, in an improved manner, that the relative movement performed between the measuring probe and the sample container (scanning the measuring sample) during testing corresponds to the pre-defined movement for the test plan.

[0012] Within the scope of this disclosure, scanning motion (probing) is the relative motion between a measuring probe and a measuring sample, used to cause the measuring probe and the area of ​​the measuring sample to be tested to move relative to each other. Here, for example, a triangular motion can be performed in one lateral direction relative to the measuring sample, while a step function motion can be performed in another lateral direction, thereby scanning a quadrilateral region of the measuring sample.

[0013] The first or second spatial direction (spatial axis) may correspond to at least one spatial direction of the scanning motion.

[0014] The sensor device can be configured to detect motion measurement signals in the form of absolute measurements. Absolute measurement, within the scope of this disclosure, refers to measuring physical quantities based on an inertial system, meaning that the measurement is performed without any reference point, particularly neither on the measuring device nor in the surrounding environment of the measuring device, such as in a laboratory.

[0015] The sensor device can be configured to detect motion measurement signals for actual motion of the measuring probe and / or sample container, the motion measurement signals indicating a first motion component of the interfering scanning motion along the x-direction of the xy-plane of the sample container.

[0016] The motion measurement signal may include a first motion component for interfering scanning motion along a first spatial direction and a position measurement signal for a second motion component for interfering scanning motion along a second spatial direction.

[0017] The control device and the shifting device can be configured to perform a periodic scanning motion of the measuring probe relative to the measuring sample along at least one spatial direction when measuring the measuring sample. It can be configured that the periodic motion is a sinusoidal or triangular waveform along at least one spatial direction.

[0018] The control and shifting devices can be configured to control the periodic movement of the measuring probe relative to the measuring sample based on the amplitude and / or phase of the periodic movement according to the motion measurement signal during the measurement of the measuring sample. Based on motion signals detected, for example in an absolute measurement manner, for the movement of the measuring probe and / or the sample housing, a control signal is generated to control the vibratory movement used for scanning the measuring sample.

[0019] Furthermore, the control device and the shifting device can be configured to control the periodic movement of the measurement probe relative to the measurement sample based on the amplitude and / or phase of the periodic movement according to the motion measurement signal when measuring the measurement sample.

[0020] The sensor device can be configured to detect, in a time-related manner, a first motion measurement signal of the motion of the measuring probe or sample container, which moves to implement the relative motion between the measuring probe and the sample container, during the measurement of the sample. For this purpose, an accelerometer can be used, for example. The velocity and distance information of the motion of the measuring probe or sample container can be derived from the measurement signal provided by the sensor device through integration. The first motion signal is detected for the components of the measuring device that move during the measurement of the sample and during the relative motion between the measuring probe and the sample container implemented for this purpose.

[0021] The sensor device can be configured to detect, in a time-related manner, a second motion measurement signal for the measurement probe or sample container that does not move in order to implement the relative motion between the measurement probe and the sample container during the measurement of the sample. For this purpose, an accelerometer can be used, for example. Motion information can also be detected for the sample container or the measurement probe in this way. This additional and unplanned motion is particularly likely to occur at higher scanning or detection speeds, even for components of the measuring device that are not intentionally moving (for implementing the relative motion between the measurement probe and the sample container) and therefore occupy a stationary position in the prior art. Information regarding the absolute values ​​of the velocity and distance of the motion can be derived from the acceleration signal, for example, through integration.

[0022] The sensor device can be at least partially mounted on the probe holder. On the probe holder, the sensor device can be disposed adjacent to, particularly directly near, the support structure of the measuring probe on the probe holder. The sensor device can here be disposed on the outer surface of the probe holder. Alternatively, it is conceivable to integrate the sensor device into the housing or body of the probe holder. The sensor device can partially form part of the measuring probe. The sensor device can be at least partially mounted on the sample receiving portion. In conjunction with the fact that the sensor device is at least partially mounted on the sample receiving portion, the foregoing explanations regarding design options for the probe holder apply accordingly.

[0023] The sensor device may be a capacitive sensor device.

[0024] The control and shifting devices are configured to perform a scanning motion of the measuring probe relative to the measuring sample at a vibration frequency of at least about 100 Hz when measuring the sample. Vibration frequencies up to about 1 kHz are conceivable, alternatively up to about 20 kHz. Unexpectedly, it has been confirmed that vibration frequencies from about 100 Hz adversely affect measurement accuracy or even result in distorted measurement results. This is because additional movement occurs in the components or functional elements of the measuring device, which may be caused, for example, by resonance. In particular, improved measurement results can be achieved using the proposed technique for such vibration frequencies. It has been unexpectedly found that at vibration frequencies from about 100 Hz, measurement accuracy decreases or even distorted measurement results are obtained. This is because additional movement occurs in the components or functional elements of the measuring device, which may be caused, for example, by resonance. In particular, improved measurement results can be achieved using the proposed technique for such vibration frequencies.

[0025] Another sensor device can be configured to detect additional motion signals in the form of relative motion, particularly to measure and selectively compensate for slow motions that do not suffer from the problems described above, where the potential drawbacks of absolute measurement, such as high noise, are not permitted. The relative motion may be relative to the probe holder, for example, relative to the support member. The other sensor device can be configured, for example, on the support member housing the displacement device or on the probe holder. The other sensor device can have a distance sensor device configured to detect, in a time-dependent manner, the distance between the support member and the probe holder that changes due to the motion achieved by the displacement device during the measurement of the sample. Detecting this time-varying distance provides a scale for measuring the relative motion between the measuring probe and the sample housing during scanning probe microscopy testing of the sample. The distance sensor device can, for example, be formed by one or more distance sensors configured to mate with each other, one on the support member and the other on the displacement device. The other sensor device can, for example, be a capacitive sensor, strain gauge, differential transformer, or other relative sensor.

[0026] The sensor device can be constructed using a first sensor element on a probe holder and a second sensor element on a sample container that mates with the first sensor element. Relative measurements are achieved from the signals of the first and second sensor elements for each spatial direction without requiring complex orientation of the sensor elements. The first and second sensor elements can, for example, be positioned opposite each other.

[0027] The other sensor device can be used to control the relative movement between the measuring probe and the sample container during scanning and measuring the sample, with the first sensor device and, if necessary, the second sensor device correcting the control. This correction can be set, particularly for sinusoidal motion, to be used only from a threshold speed, for example, from approximately 100 Hz.

[0028] The control can be configured to control the relative movement between the measuring probe and the sample container using coupling control or through coupling control based on the motion measurement signal. Here, considering the movement of the measuring probe and / or the sample container caused by the movement of the measuring probe and / or the sample container along the second spatial direction, a compensating control signal component is provided, which provides a first reverse movement along the first spatial direction in response to the movement of the measuring probe and / or the sample container. The movement along the second spatial direction causes or results in the movement along the first spatial direction.

[0029] The embodiments described above in conjunction with the measuring device can be correspondingly configured as methods for scanning probe microscopy and / or for performing scanning probe microscopy tests on the measured samples using a scanning probe microscope. Attached Figure Description

[0030] Further embodiments will now be described in detail with reference to the accompanying drawings. Here:

[0031] Figure 1 A schematic diagram of a measuring apparatus for a scanning probe microscope is shown.

[0032] Figure 2 A schematic diagram of the coupling control flowchart is shown, which is a control method in which different sensors detect and measure signals along all spatial directions;

[0033] Figure 3 A schematic diagram of one embodiment is shown, in which mechanical coupling to be suppressed is included;

[0034] Figure 4 A schematic diagram of one embodiment is shown, illustrating the internal vibration of the support structure to be considered; and

[0035] Figure 5 A schematic diagram of an embodiment in which an additional sensor is provided is shown. Detailed Implementation

[0036] Figure 1 A schematic diagram of a measuring device 1 for a scanning probe microscope is shown. Scanning probe microscopes are known in various embodiments of this type of microscope, for example, as atomic force microscopes (AFM). A measuring probe 2 is housed in a probe holder 3, specifically on the underside of the probe holder 3. This measuring probe can also be called a near-field probe and is, for example, a cantilever structure. In this scanning probe microscope, the interaction between the measuring probe 2 and the sample 6 being measured is detected. During the scanning process, the sample 6 to be tested is scanned point by point through the measuring probe 2. The measurements obtained for each individual point can then be combined into a digital image.

[0037] For probe microscopy testing, a probe or measuring tip 5 of a measuring probe 2 is positioned opposite a measuring sample 6, which is placed on a sample receiving portion 7, optionally on a sample support (not shown) provided on the sample receiving portion. A displacement device 8 housed on a support member 9 moves the probe holder 3, along with the measuring probe 2, relative to the sample receiving portion 7 with the measuring sample 6, in order to probe (scan) the measuring sample 6. A so-called force detection is used to detect the degree of interaction between the probe tip 5 and the measuring sample 6. Corresponding to this interaction, the probe tip 5, for example, shifts toward the measuring sample 6. This shift of the probe tip 5 can be detected, for example, according to the principle of optical levers. Here, for example, a measuring beam is aligned with a segment of the measuring probe 2 in a known manner and form, and the measuring beam is reflected here. The reflected beam is then detected using a photosensitive element, such as a photodiode. Such measurement principles are known in different embodiments and will therefore not be discussed further.

[0038] The motion measurement signal, detected by the sensor device 10, indicates the actual movement of the measuring probe 2 and / or the sample container 7. This actual movement is implemented when the measuring sample 6 undergoes relative movement between the measuring probe 2 and the sample container 7 in order to measure the relative movement of the measuring sample 6. The motion measurement signal is sent to the control device 11, indicating a first motion component of the scanning motion performed to measure the measuring sample 6 along a first spatial direction and a second motion component of the interfering scanning motion along a second spatial direction, the second spatial direction extending transversely to the first spatial direction.

[0039] In one exemplary embodiment, the sensor device 10 has two position sensors 20, 21 (see Figure 3 There is one position sensor for each spatial direction. To simplify the description, the following description is based on position sensors, and the content can be generally applied to other sensor types used to measure, for example, the time derivative of position, without significant expenditure.

[0040] For scanning probe microscopy, capacitive sensors can be used for the two position sensors 20 and 21, which measure the relative movement of the measuring probe 2 relative to the support member 9. Position sensors 20 and 21 may have two electrodes 22 and 23, which constitute a plate capacitor and their distance determines their capacitance. It is generally assumed that the position of the support member 9 does not move relative to the measured sample 6. The measuring device is mechanically and substantially isolated from external disturbances. However, position sensors 20 and 21 still measure a total motion 23, which is not predetermined by the manipulation of the displacement device 8 by the actuators 24 and 25, but is formed by the superposition of the actual trajectory (actual motion track) 26 intentionally generated by the measuring probe 2 and the motion 27 generated by coupling, thus the actual trajectory 23 relative to the measured sample 6 cannot be adequately corrected by independent adjustment of the two axes.

[0041] Furthermore, for the rapid periodic scanning or probing motion of the measuring probe 2, the sensor support 6 may no longer be spatially rigid relative to the measuring probe 6, for example, due to mechanical resonance 28 caused by the excitation of the measuring device.

[0042] In this situation, when the position sensor is installed inside the measuring device, the total motion 23 (actual movement) of the probe tip 5 relative to the measured sample 6 can no longer be measured with sufficient accuracy. In this case, another sensor 29 is used, which additionally measures the motion of the support structure or the total motion 23 of the probe tip 5, that is, the superposition of the support motion and the actual trajectory 26 generated by the actuators 24 and 25. The closer the other sensor 29 is positioned to the probe tip 5, the more accurately the deviation of the probe tip 5 from the specified motion can be determined, and thus corrections can be made.

[0043] The desired motion of the measuring or probe tip 5 at time t can be described in the following form.

[0044]

[0045] here, It is a reference point in space. It is a velocity vector used to describe continuous scanning motion along an axis. Under normal circumstances, this is motion in the slow scanning direction, such as the advancement of a (scanning) line. The periodic motion with angular frequency ω and high harmonics up to order N can be expressed in complex form as follows:

[0046]

[0047] In a conventional adjustment loop, the entire curve is tentatively adjusted. Adjustment / closed-loop control is performed. This adjustment provides rapid correction to the gradually increasing deviation from the prescribed trajectory; therefore, a feedforward control is used instead. Unlike the adjustment process that adjusts the input at various times based on the deviation in the output, here multiple measurements are considered along a trajectory to correct the coefficients of the entire input. This method is also known as "iterative learning control".

[0048] In one possible embodiment, the adjustment is divided into two parts (see...). Figure 2 ): Constant and linear components There is a normal slow control loop adjustment. This adjustment can be configured to regulate only the component ω. This can be achieved, for example, using a low-pass filter 11. The faster periodic motion of a single spatial axis (whose amplitude is also allowed to be zero in principle) is regulated by feedforward control 12, which is further explained below.

[0049] The following describes an embodiment for a control loop.

[0050] The Definitive Movement of Hope The motion is transmitted to the probe tip 5 via drivers 24 and 25. Due to the response function of the system consisting of the probe tip 5, drivers 24 and 25, shifting device 8, and other electronic components, the resulting measurement or motion of the probe tip 5 does not precisely correspond to the desired motion, especially since the actual motion may have a time delay. If the actual motion of the probe tip 5 is continuously measured, the control function of the shifting device 8 via drivers 24 and 25 can be adapted using an iterative method (feedforward control) so that the desired periodic motion is achieved with sufficient accuracy after several iterations.

[0051] At this point, the following problems may arise, which could at least hinder the realization of the desired movement:

[0052] - Mechanical and electronic coupling / crosstalk: This type of interference cannot be adequately eliminated when adjusting individual spatial axes separately, because a change in control in one direction will result in a change in the other direction.

[0053] - The measuring instrument, consisting of the control device, probe tip 5, and sensor device, vibrates relative to the measured sample as a whole: Due to the motion superimposed on the motion of the support structure, the position measurement by the position sensor installed inside the measuring instrument does not allow the actual motion to be sufficiently adjusted to the specified motion of the probe tip 5 relative to the measured sample 6.

[0054] - An external, constant periodic disturbance, which corresponds to the fundamental frequency ω of the internal vibration or to a higher harmonic, and excites the occurrence of said harmonic.

[0055] - The nonlinearity of the response function, which, when excited at a certain frequency, also excites its harmonic oscillations.

[0056] The known control loops for scanning probe microscopy adjust each axis independently. Here, it's important to distinguish between model-based and model-free algorithms. For model-based algorithms, the system is modeled, and an attempt is made to find the inverse function of the response function, adjusting the manipulation so that the output signal corresponds to the desired signal.

[0057] Model-free algorithms typically refer to iterative methods, which calculate the inverse response function iteratively and, if necessary, adapt it to the time-varying response function. A coupled model-free method is explained below, which, with the aid of measurement data from sensor devices, particularly position sensors 20 and 21, achieves a significant improvement in the adjustment of the actual motion of the measuring probe 2 relative to the measuring sample 6 towards a predetermined motion, even in the presence of the aforementioned disturbances.

[0058] The periodic scanning or probing motion is decomposed into Fourier coefficients by spectral analysis of the values ​​measured by position sensors 20 and 21 over at least one period. If a position sensor is used that measures the derivative determined by the scanning motion, the Fourier coefficients must be corrected accordingly. For velocity sensors, this refers to a 90° phase adjustment and a coefficient of ω. -1 The amplitude is adjusted. Then, all the coefficients obtained in this way can be used to dynamically and adaptively adjust the adjustment for the shifting device 8 so that the actual movement of the measuring or probe tip 5 is very close to the specified movement after a few cycles.

[0059] Different sensor types have different advantages and disadvantages:

[0060] -Sensor Type 1- Position sensors, such as capacitive sensors: These sensors typically allow for very precise position determination for slow motion. For fast, periodic measurement motions, the measured value of the relative position of the measuring probe relative to the sample may be systematically distorted due to the inherent vibration of the measuring instrument.

[0061] -Sensor Type 2- Velocity or acceleration sensors, or sensors that determine higher-order derivatives for instantaneous position: These sensors can measure velocity / acceleration very accurately for sufficiently fast periodic motion. Determining the absolute global position of the measuring probe relative to the sample by integration is more difficult for slow or low-frequency translations.

[0062] For scanning motion (detecting motion) at frequencies where only mechanical or electronic coupling occurs, corrections to bring the actual trajectory (actual motion path) closer to a predetermined trajectory (prescribed motion path) can be achieved, for example, by using a position sensor (sensor type 1). For other disturbances, for example, another position sensor can be provided that measures the motion of the support structure and incorporates it into the adjustment, or a type 2 sensor can be used.

[0063] By assigning the adjustment task to these sensor types, the accuracy of the adjustment can be significantly improved. When the line rate exceeds a threshold frequency (related to sensor quality and internal vibrations of the measuring instrument), data from sensor type 2 is additionally used for adjustment. This data may contain information about the vibrational motion of the support structure, which may occur when the measurement data is decomposed into Fourier coefficients and can thus be corrected by the adjustment algorithm. To maintain a constant absolute global position in the scanned area, the zero-order spectral coefficients of sensor type 1 are used in an external, slow control loop. Figure 2 This adjustment is illustrated in the example.

[0064] Figure 2 A schematic diagram of a flowchart for coupling control is shown, wherein various different sensors detect measurement signals along all spatial directions. A low-pass filter 11 is used to filter sensor type I... The measured signals (measurement data) are fed into the normal control loop. All periodic measurement signals (sensor data) can be used in feedforward control 12 to calculate the inverse function of the system response. During the iteration of feedforward control 12, an attempt is made to adjust the measured periodic components to a specified value. The periodic components.

[0065] The following describes a method for feedforward adjustment involving coupling of one or all spatial axes or spatial directions, with reference to one embodiment. Here, processing is performed in frequency space, whereby all parameters are explicitly frequency-dependent and complex. The combination of system 13 and measuring instrument 14 (see...) Figure 2 That is to say, for example Figure 1 The measuring device 1 in the middle will input signal Converted into measurement signal This can be written as:

[0066]

[0067] Generally speaking, G is a non-linear operator ( (A nonlinear function). Depending on the type of sensor used, a measurement value proportional to the offset is obtained. (Type 1) or its time derivative, such as acceleration (Type 2). The latter can be converted into a signal proportional to the offset through appropriate transformation.

[0068] The term "system" as used here refers to the effective voltages on drivers 24 and 25 and the mechanical characteristics of the shifting device. Coupling along a spatial axis or direction is a consequence of the shifting device's structural design.

[0069] The goal of feedforward control is to achieve the following in each (scan) line: The previous adaptation adjustments made it possible for subsequent operations. As close as possible to the prescribed movement Assuming linearity, we transform G into a matrix and simplify the problem to computing the inverse of G and applying it to... The desired form:

[0070]

[0071] In general, the order of matrix G is N×d, where N is the maximum order of the Fourier coefficients in equation (2), and d is the number of coupled axes. For the following derivation, it is assumed for simplicity that the different frequency terms are not coupled to each other.

[0072] Therefore, equation (3) becomes:

[0073]

[0074] The order of matrix G is reduced to d. The exponent ω is omitted below. Thus, equation (4) can be written iteratively for iteration k as follows:

[0075]

[0076] or

[0077]

[0078] In this example, the adjustment of the two axes is And we get:

[0079]

[0080] If we now multiply equation (3) on the right side... Right now The transpose-conjugate vector is then obtained.

[0081]

[0082] Alternatively, it can be written using iterative k expansion as follows:

[0083]

[0084] Let u represent the complex conjugate of u. Now, calculate the average value <·> of all recorded data points:

[0085]

[0086] As long as the average is linear across all components and satisfies the relation 1 = 1, any average can be used here. For example, here are the exponential smoothing, moving average, or arithmetic mean for all recorded measurement points.

[0087] Based on this G -1 It can be represented as follows:

[0088]

[0089] In order for the actual motion to fully converge to the prescribed motion, the determinant of the second matrix in equation (12) is very small. The minimum value of this determinant can be determined, and from this minimum value, G in equation (7)... -1 It can be set to zero and the calculation according to equation (12) can be omitted.

[0090] Noise in the measurement data prevents the determinant from precisely reaching zero. Additionally, the initial values ​​for the iterations are chosen in such a way that the algorithm runs stably.

[0091] The feedforward control, chosen in this manner, reliably converges in a few iterations, thereby obtaining an optimized trajectory of the measurement probe 2 relative to the measurement sample 6 in a short time. For example, the manipulation produced by the actuators 24 and 25, constructed using piezoelectric actuators, is adapted to accommodate all coupling and interference effects of the measurement device.

[0092] Coupled control is employed here, which will be further explained below. The term "coupled control" here means that the control takes into account coupled motions along different spatial axes / directions. This control / regulation considers a motion along one spatial axis / direction that arises or is caused by, at least due to, motion occurring along another spatial axis / direction. The proposed regulation treats or considers said motion as a coupled component. The spatial axes / directions are therefore not regulated independently, but rather regulated in a coupled manner.

[0093] Adaptive adjustment to dynamic regulation (recalculation of G) -1 This adaptation doesn't need to be continuous; it can be done only occasionally or just once before the actual measurements begin. In this case, a limitation arises: other dynamic, emerging disturbances cannot be suppressed.

[0094] To extend this regulation with an external constant periodic disturbance, it can be set as follows: For the derivation, the extended model is used instead of the model in equation (5). in For a fixed frequency ω, which is constant, we get the following equation:

[0095]

[0096] If the potential nonlinear frequency coupling is small, this model offers the possibility of tuning it with only a small increase in cost.

[0097] If all frequency couplings need to be adjusted, the complete matrix can be obtained from equation (4) and its inverse can be taken. For fast feedforward control, position signals can be combined from data of different sensor types of the sensor device to further reduce measurement errors.

[0098] The features disclosed in the foregoing description, claims and drawings are important individually and in any combination for implementing different embodiments.

Claims

1. A measuring device for a scanning probe microscope, having - A sample receiving section, the sample receiving section being configured to receive a measurement sample to be tested; - A measurement probe, which is mounted on a probe holder and has a probe tip, and the measurement sample can be measured using the probe tip; - A displacement device, the displacement device being configured to move the measuring probe and the sample receiving portion relative to each other in order to measure the measuring sample, such that the measuring probe performs a scanning motion relative to the measuring sample in at least one spatial direction in order to measure the measuring sample; - A control device, which is connected to the displacement device and controls the relative movement between the measuring probe and the sample container; as well as - A sensor device configured to detect motion measurement signals of actual movement of the measuring probe and / or the sample container and send the motion measurement signals to the control device, wherein the actual movement is performed when the measuring probe and the sample container move relative to each other in order to measure the measuring sample, wherein the motion measurement signals indicate a first motion component of interfering scanning motion along a first spatial direction and a second motion component of interfering scanning motion along a second spatial direction, the second spatial direction extending transversely to the first spatial direction; In this context, the first motion component and the second motion component of the interfering scanning motion correspond to a coupled motion, wherein the second motion component of the interfering scanning motion is caused by the first motion component of the interfering scanning motion. The control device is further configured to control the relative movement between the measurement probe and the sample container through coupling control based on the motion measurement signal for the coupled motion, such that the control device loads a compensating control signal component onto the displacement device, the control signal component realizing a first reverse motion and / or a second reverse motion for the motion of the measurement probe and / or the sample container, the first reverse motion substantially compensating for the first motion component that interferes along the first spatial direction, and the second reverse motion substantially compensating for the second motion component that interferes along the second spatial direction.

2. The measuring device according to claim 1, characterized in that, The sensor device is configured to detect the motion measurement signal in an absolute measurement manner.

3. The measuring device according to claim 1 or 2, characterized in that, The sensor device is configured to detect motion measurement signals for actual motion of the measurement probe and / or the sample container, the motion measurement signals indicating a first motion component of the interfering scanning motion along the x-direction of the xy-plane of the sample container.

4. The measuring device according to claim 1 or 2, characterized in that, The motion measurement signal includes a first motion component for interfering scanning motion along the first spatial direction and a position measurement signal for a second motion component for interfering scanning motion along the second spatial direction.

5. The measuring device according to claim 1 or 2, characterized in that, The control device and the displacement device are configured to perform a scanning motion of the measurement probe relative to the measurement sample as a periodic motion along at least one spatial direction when measuring the measurement sample.

6. The measuring device according to claim 5, characterized in that, The control device and the shifting device are configured to control the periodic motion of the measuring probe relative to the measuring sample based on the amplitude and / or phase of the periodic motion according to the motion measurement signal when measuring the measuring sample.

7. The measuring device according to claim 1 or 2, characterized in that, The sensor device is configured to, when measuring the measurement sample, detect, in a time-related manner, a first motion measurement signal of the motion of the measurement probe or the sample container for implementing relative motion between the measurement probe and the sample container.

8. The measuring device according to claim 1 or 2, characterized in that, The sensor device is configured to, when measuring the measurement sample, detect, in a time-related manner, a second motion measurement signal that indicates that the measurement probe or the sample container is not moving in order to implement the relative motion between the measurement probe and the sample container.

9. The measuring device according to claim 1 or 2, characterized in that, The sensor device is a capacitive sensor device.

10. The measuring device according to claim 1 or 2, characterized in that, The sensor device is at least partially comprised of at least one of the following device components: a probe holder and a sample container.

11. The measuring device according to claim 1 or 2, characterized in that, The measurement probe is configured to have a cantilever.

12. The measuring device according to claim 1 or 2, characterized in that, The control device and the displacement device are configured to perform a scanning motion of the measurement probe relative to the measurement sample at a vibration frequency of at least about 100 Hz when measuring the measurement sample.

13. The measuring device according to claim 1 or 2, characterized in that, An additional sensor device is provided, which is configured to detect a further motion signal in the form of relative motion.

14. A scanning probe microscope for performing scanning probe microscopy tests on a sample, comprising a measuring device according to any one of claims 1 to 13.

15. A method for performing scanning probe microscopy on a sample for measurement, comprising: - Place the measurement sample on the sample container of the scanning probe microscope; as well as - The measurement sample is tested by probe microscopy using a measuring probe, which is mounted on a probe holder and has a probe tip; in, - The measuring probe and the sample container are moved relative to each other by a shifting device, so that the measuring probe performs a scanning motion relative to the measuring sample in at least one spatial direction; - A control device is provided, which is connected to the displacement device and controls the relative movement between the measuring probe and the sample receiving part; - Motion measurement signals are detected by a sensor device for the movement of the measuring probe and / or the sample container, the movement of the measuring probe and / or the movement of the sample container being implemented during relative movement between the measuring probe and the sample container, the motion measurement signals indicating a first motion component of interfering scanning motion along a first spatial direction and a second motion component of interfering scanning motion along a second spatial direction extending transversely to the first spatial direction; and - Send the motion measurement signal to the control device; In this context, the first motion component and the second motion component of the interfering scanning motion correspond to a coupled motion, wherein the second motion component of the interfering scanning motion is caused by the first motion component of the interfering scanning motion. The control device controls the relative movement between the measurement probe and the sample container through coupling control based on the motion measurement signal for the coupled motion, such that the control device loads a compensating control signal component onto the displacement device. The control signal component realizes a first reverse motion and / or a second reverse motion for the motion of the measurement probe and / or the sample container. The first reverse motion substantially compensates for the first motion component that interferes along a first spatial direction, and the second reverse motion substantially compensates for the second motion component that interferes along a second spatial direction.

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