A Measurement Positioning and Coordinate Transformation Method for a White-Light Interferometric Atomic Force Probe System

Abstract

This invention discloses a measurement positioning and coordinate transformation method for a white-light interferometric atomic force probe system. This method is applied to a dual-mode, multi-scale measurement system for white-light interferometric atomic force probes and includes the following steps: obtaining a transformation matrix P1 representing the positional relationship between the atomic force scanning probe tip and the cantilever tip; in the atomic force probe contact measurement mode, obtaining the position coordinates of the cantilever tip; and calculating the position coordinates p of the atomic force scanning probe tip based on the transformation matrix P1. nw The measurement positioning and coordinate transformation method of the white light interferometric atomic force probe system of this invention enables rapid and accurate automatic positioning of the atomic force probe tip appearing in the CCD field of view after mode switching, obtaining the precise coordinates of the atomic force probe tip, and obtaining the coordinate transformation relationship between the two measurement modes. This allows for flexible selection of measurement methods in different target areas, improving measurement accuracy and speed.

Description

Technical Field

[0001] This invention belongs to the field of ultra-precision surface topography measurement technology, and more specifically, relates to a measurement positioning and coordinate transformation method for a white light interferometric atomic force probe system. Background Technology

[0002] White-light interferometric atomic force scanning probe microscopy (AFM) uses the zero-order fringes of white light to quantify the deformation of the AFM probe, thereby indirectly obtaining the height of the workpiece surface. The principle behind the deformation of the AFM probe is the van der Waals force between atoms. During measurement, the tip of the AFM probe is equivalent to an atom, and an atom on the surface of the sample being measured interacts with the tip of the AFM probe, causing deformation of the cantilever of the AFM probe. The white-light interference fringes formed on the cantilever will then shift accordingly. The amount of deformation of the AFM probe can be calculated based on the amount of shift of the zero-order white-light interference fringes.

[0003] The principle of white light interferometry is based on the extremely short coherence length of the white light source. White light contains spectral components across the entire visible spectrum, forming a continuous spectrum. During interference, each wavelength produces its own set of interference fringes, and the distributions of their respective interference intensities are superimposed on the final interference image. When the optical path difference of the coherent light is zero, the zero-order fringes of each wavelength completely overlap, resulting in the strongest interference contrast. As the optical path difference and interference order increase, the interference fringes of each wavelength gradually shift apart. In obtaining three-dimensional surface information, white light interferometry utilizes the characteristic that the fringe contrast is most pronounced when two beams of white light with identical properties have zero optical path difference to determine the location of the zero optical path difference, thereby obtaining the three-dimensional surface morphology changes of the object under test.

[0004] The two measurement systems mentioned above are combined in the white-light interferometric atomic force dual-mode cross-scale measurement system. A pose adjustment mechanism enables switching between the two measurement modes. The former is used for scanning larger areas, such as 20mm*20mm, while the latter is used for scanning areas requiring higher precision. This allows for flexible selection of measurement methods for different target areas, improving both measurement accuracy and speed. However, during mode switching, rapid and accurate automatic positioning of the atomic force scanning probe tip is required, as well as coordinate transformation between the two measurement systems after mode switching. Therefore, a fast and accurate positioning and coordinate transformation method is needed. Summary of the Invention

[0005] To address at least one deficiency or improvement requirement in the prior art, this invention provides a measurement positioning and coordinate transformation method for a white light interferometric atomic force probe system. The purpose is to solve the problem of accurate positioning and coordinate transformation of the atomic force scanning probe in a white light interferometric atomic force dual-mode cross-scale measurement system.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for measurement positioning and coordinate transformation of a white-light interferometric atomic force probe system is provided. This method is applied to a two-mode, multi-scale measurement system for white-light interferometric atomic force, and is characterized by comprising the following steps:

[0007] Obtain the transformation matrix P1 for the positional relationship between the atomic force scanning probe tip and the cantilever tip;

[0008] In the atomic force probe contact measurement mode, the position coordinates of the cantilever tip are acquired, and the position coordinates p of the atomic force scanning probe tip are calculated based on the transformation matrix P1. nw .

[0009] Preferably, the transformation matrix P1 for obtaining the positional relationship between the atomic force scanning probe tip and the cantilever tip includes:

[0010] The distance Δx between the tip of the atomic force scanning probe and the tip of the cantilever is obtained on a plane parallel to the cantilever. The transformation matrix P1 is:

[0011]

[0012] Where P1 is the transformation matrix of the positional relationship between the atomic force scanning probe tip and the cantilever tip; h is the actual height of the atomic force scanning probe tip; and t is the thickness of the cantilever.

[0013] Preferably, obtaining the position coordinates of the cantilever tip includes:

[0014] Acquire images of the cantilever and the tip of the atomic force scanning probe in the CCD field of view under atomic force scanning probe contact measurement mode;

[0015] The cantilever edge contour is extracted after processing the image;

[0016] The position coordinates of the cantilever tip are calculated based on the coordinates of the cantilever edge profile. The calculation formula is as follows:

[0017] x a =(x l +x r ) / 2

[0018] y a =min{y e}

[0019] Where, x a y a x represents the coordinates of the tip of the cantilever. l x r The x-coordinates of the two edges of the cantilever are respectively; the y-coordinates are respectively. e This is the set of y-coordinates of the extracted cantilever edge.

[0020] Preferably, the step of extracting the cantilever edge contour after processing the image includes:

[0021] The image is then subjected to grayscale conversion, Gaussian filtering, and contrast enhancement.

[0022] The Canny operator edge detection algorithm was used to extract the edge contour of the atomic force scanning probe cantilever from the processed image.

[0023] Preferred options also include:

[0024] Determine the target area for atomic force probe contact measurement in white light measurement mode;

[0025] Switch to atomic force probe contact measurement mode, obtain the horizontal displacement value of the atomic force scanning probe tip moving to the target area after the measurement mode switch, and then obtain the conversion matrix P2 between the white light measurement mode and the atomic force contact probe measurement mode data;

[0026] Based on the transformation matrix P1 and the transformation matrix P2, the data transformation relationship under the two measurement modes is obtained.

[0027] Preferably, the transformation matrix P2 between the data obtained from the white light measurement mode and the atomic force contact probe measurement mode is:

[0028]

[0029] Among them, s x This represents the displacement of the atomic force scanning probe in the x-direction after mode switching; s y This represents the displacement of the atomic force scanning probe in the y-direction after mode switching.

[0030] Preferably, the data conversion relationship between the two measurement modes is as follows:

[0031]

[0032] Where, p nw These are the coordinates of the atomic force scanning probe tip in white light measurement mode, p aa These are the coordinates of the atomic force scanning probe in the atomic force probe contact measurement mode.

[0033] It also includes constructing a correction matrix, including:

[0034] Obtain the set of coordinates of feature points on the surface of the workpiece under white light measurement mode {p w};

[0035] Obtain the coordinate set {p} of the feature points on the surface of the workpiece under atomic force contact measurement mode. a};

[0036] The correction matrix P is obtained by fitting the coordinate set data from the two measurement modes. mod The formula for the correction matrix is:

[0037] {p w}=P mod {p a}

[0038] Among them, {p w} is the set of coordinates of feature points on the surface of the workpiece under white light measurement mode, {p a} is the set of coordinates of feature points on the surface of the workpiece under atomic force contact measurement mode.

[0039] Preferably, the calculation formula for data conversion under the modified two measurement modes is as follows:

[0040]

[0041] Among them, {p w} is the set of coordinates of feature points on the surface of the workpiece under white light measurement mode, {p a} is the set of coordinates of feature points on the surface of the workpiece under atomic force contact measurement mode.

[0042] Preferably, when switching to the atomic force probe contact measurement mode, the horizontal angle between the atomic force scanning probe and the surface CCD measurement system is within ±1.5°.

[0043] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0044] (1) The measurement positioning and coordinate transformation method of the white light interferometric atomic force probe system provided by this invention is based on the principle that the relative position of the atomic force scanning probe tip and the cantilever remains unchanged under normal conditions. After the measurement system switches from the white light interferometric measurement mode to the atomic force probe contact measurement mode, a combination of physical measurement and image processing is used. The relative position of the atomic force scanning probe tip and the cantilever tip is determined by physical measurement, and then the atomic force probe tip appearing in the CCD field of view after the mode switch is quickly and accurately automatically positioned to obtain the precise coordinates of the atomic force probe tip. At the same time, relying on the horizontal displacement measurement module, the horizontal displacement of the probe position after the mode switch is recorded, thereby obtaining the transformation matrix of the measurement data in the two measurement modes. This realizes the precise positioning of the probe tip in the two measurement modes and the transformation of data in different coordinate systems, and enables flexible selection of measurement methods in different target measurement areas, improving measurement accuracy and measurement speed.

[0045] (2) The measurement positioning and coordinate transformation method of the white light interferometric atomic force probe system provided by the present invention constructs a repair matrix by means of data comparison, corrects the data transformation of the coordinate system under different measurement modes, improves its accuracy, and reduces the offset, rotation and other errors generated during mode switching and measurement. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the structure of the white light interferometric atomic force dual-mode cross-scale measurement system provided in an embodiment of the present invention;

[0047] Figure 2 This is a flowchart of the measurement, positioning, and coordinate transformation method of the white light interferometric atomic force probe system provided in this embodiment of the invention;

[0048] Figure 3 This is a schematic diagram showing the positional relationship between the atomic force scanning probe and the cantilever provided in an embodiment of the present invention; Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0050] This invention provides a measurement positioning and coordinate transformation method for a white-light interferometric atomic force probe system. This method is applied to a dual-mode, multi-scale measurement system for white-light interferometric atomic forces, such as... Figure 1 The diagram shows the structure of the dual-mode cross-scale measurement system for white-light interferometry atomic force measurement involved in this method. It includes a cantilever 1, an atomic force scanning probe 2, a white-light interferometry system 3, a vertical piezoelectric ceramic PZT4, a displacement measurement system 5, a surface CCD measurement system 6, and a measurement and control system 7. The atomic force scanning probe 2 is mounted on the cantilever, and the vertical piezoelectric ceramic PZT4, under the control of the measurement and control system 7, finely adjusts the vertical displacement of the atomic force scanning probe 2. In white-light measurement mode, the atomic force scanning probe 2 is retracted and not appearing in the field of view of the surface CCD measurement system 6. After the measurement system switches to atomic force probe contact measurement mode, the horizontal imaging area of ​​the surface CCD measurement system 6 remains stationary, but is vertically moved upwards by a motor. Under the control of the mode switching mechanism, the atomic force scanning probe 2 rotates from the side of the surface CCD measurement system 6 into the field of view.

[0051] like Figure 2The diagram shows a flowchart of a measurement, positioning, and coordinate transformation method for a white-light interferometric atomic force probe system provided by this invention. The method includes the following steps:

[0052] S1: The transformation matrix P1 is used to obtain the positional relationship between the tip of atomic force scanning probe 2 and the tip of cantilever 1;

[0053] Specifically, the transformation matrix P1 for obtaining the positional relationship between the atomic force scanning probe tip 2 and the tip of the cantilever 1 includes:

[0054] The atomic force scanning probe 2 is mounted onto the cantilever 1, as follows: Figure 3 The diagram shows the positional relationship between the atomic force scanning probe 2 and the cantilever 1. The dimensions are measured using a scanning electron microscope (SEM). The SEM resolution is up to 1 nm, meaning the error in measuring the horizontal distance between the tip of the atomic force scanning probe 2 and the tip of the cantilever 1 is no more than 1 nm. The actual distances Δx and Δy between the tip of the probe 2 and the tip of the cantilever 1 on a plane parallel to the surface of the cantilever 1 are directly measured. Δy is a very small value and can be ignored. The sum of the actual height h of the tip of the atomic force scanning probe 2 and the thickness t of the cantilever 1 is taken as the z-axis distance between the tip of the probe 2 and the tip of the cantilever 1, thus obtaining the relative positional relationship between the tip of the atomic force scanning probe 2 and the tip of the cantilever 1. The transformation matrix P1 between the tip 2 and the tip of the cantilever 1 is:

[0055]

[0056] Where P1 is the transformation matrix of the positional relationship between the atomic force scanning probe tip 2 and the tip of the cantilever 1; h is the actual height of the atomic force scanning probe tip 2; and t is the thickness of the cantilever 1.

[0057] The scanning electron microscope in step (I) has a resolution of up to 1 nm, meaning that the error in measuring the horizontal distance between the tip of the atomic force scanning probe 2 and the tip of the probe cantilever 1 does not exceed 1 nm.

[0058] S2: In the atomic force probe contact measurement mode, obtain the position coordinates of the tip of cantilever 1, and calculate the position coordinates p of the tip of atomic force scanning probe 2 according to the transformation matrix P1. nw .

[0059] Specifically, the measurement system is switched to atomic force probe contact measurement mode, the surface CCD measurement system 6 is kept stationary in the horizontal direction and moved upward in the vertical direction, the atomic force scanning probe 2 is switched from the retracted posture to the usage posture, and images of the atomic force scanning probe 2 and cantilever 1 in the field of view are captured.

[0060] After further image processing, the edge contour of cantilever 1 is extracted. In order to accurately extract the edge contour of cantilever 1 in the image, image processing and data comparison are required.

[0061] Specifically, this includes: performing grayscale processing on the image to increase the image resolution; Gaussian filtering to remove pixel impurities; and contrast enhancement processing to further increase the resolution of the cantilever edge contour.

[0062] The Canny operator edge detection algorithm with adaptive thresholding is then used on the processed image to extract the edge contours of atomic force scanning probe 2 and cantilever 1.

[0063] After obtaining the coordinates of the edge contour of cantilever 1 through the above processing, the position coordinates of the tip of cantilever 1 are calculated based on the coordinates of the edge contour of cantilever 1. The calculation formula is as follows:

[0064] x a =(x l +x r ) / 2

[0065] y a =min{y e}

[0066] Where, x a y a x is the coordinate of the tip of cantilever 1; l x r The x-coordinates of the two edges of cantilever 1 are respectively; the y-coordinates are respectively. e This is the set of y-coordinates of the extracted edge of cantilever 1.

[0067] After calculating the coordinates of the cantilever 1, the position coordinates of the atomic force scanning probe 2 tip are calculated based on the transformation matrix P1 obtained in step S1, which determines the relative position relationship between the tip of the atomic force scanning probe 2 and the tip of the cantilever 1, thereby achieving rapid and accurate positioning of the tip of the atomic force scanning probe 2.

[0068] In another embodiment, the present invention also calculates the coordinate data transformation relationship between the two measurement systems. The specific steps are as follows:

[0069] Determine the target area for atomic force probe contact measurement in white light measurement mode;

[0070] Switching to the atomic force probe contact measurement mode, the atomic force scanning probe 2 is moved to the target area via the displacement measurement system 5 of the horizontal moving platform. The horizontal displacement value of the tip of the atomic force scanning probe 2 after the measurement mode switch is obtained. Based on the recorded x and y direction displacement values ​​s... x s y The transformation matrix P2 between the white light measurement mode and the atomic force contact measurement mode data can be obtained. The transformation matrix P2 is:

[0071]

[0072] Among them, s x This represents the displacement of atomic force scanning probe 2 in the x-direction after mode switching; s y This represents the displacement of the atomic force scanning probe 2 in the y-direction after mode switching. The data conversion relationship between the two measurement modes is obtained based on the transformation matrices P1 and P2.

[0073] Therefore, the data conversion relationship between the two measurement modes is as follows:

[0074]

[0075] Where, p nw These are the coordinates of the tip of the atomic force scanning probe 2 in white light measurement mode, p aa These are the coordinates of the atomic force scanning probe 2 in the atomic force probe contact measurement mode.

[0076] Furthermore, during the comparison and fusion of data obtained from atomic force contact measurement mode and white light scanning measurement mode, a slight offset and rotation of the measured morphological features were found. Therefore, a correction matrix is ​​needed to correct the final coordinate system transformation result. The correction matrix P mod This is achieved by comparing the features of two sets of data obtained from measuring the same test sample using white light scanning measurement mode and atomic force probe contact measurement mode. The two sets of data obtained during the experiment are fused, and based on the surface feature points of the tested sample, the two sets of data are correlated, and a transformation matrix between the two sets is fitted.

[0077] Specifically, the coordinate set {p} of the feature points on the surface of the workpiece under white light measurement mode is obtained. w};

[0078] Obtain the coordinate set {p} of the feature points on the surface of the workpiece under atomic force contact measurement mode. a};

[0079] The correction matrix P is obtained by fitting the coordinate set data from the two measurement modes. mod The formula for the correction matrix is:

[0080] {p w}=P mod {p a}

[0081] Among them, {p w} is the set of coordinates of feature points on the surface of the workpiece under white light measurement mode, {p a} is the set of coordinates of feature points on the surface of the workpiece under atomic force contact measurement mode.

[0082] Therefore, the calculation formula for data conversion under the two measurement modes after correction is obtained as follows:

[0083]

[0084] In summary, the measurement positioning and coordinate transformation method of the white light interferometric atomic force probe system provided by this invention, after the measurement system switches from white light interferometric measurement mode to atomic force probe contact measurement mode, firstly determines the relative position of the atomic force scanning probe tip and the cantilever tip through physical measurement; then, it uses image processing to quickly and accurately automatically position the atomic force probe tip appearing in the CCD field of view after the mode switch, obtaining the precise coordinates of the atomic force probe tip; simultaneously, relying on the horizontal displacement measurement module, it records the horizontal displacement of the probe position after the mode switch, thereby obtaining the transformation matrix of measurement data in the two measurement modes; then, it constructs a correction matrix through data comparison to correct the transformation of coordinate system data in the two measurement modes, further improving accuracy and reducing errors such as offset and rotation generated during mode switching and measurement.

[0085] The measurement positioning and coordinate transformation method of this invention enables flexible switching between different measurement modes in different target measurement areas, and allows for rapid and accurate automatic positioning and coordinate data transformation of the atomic force probe tip, thereby improving measurement accuracy and speed.

[0086] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measurement positioning and coordinate conversion of a white light interferometric atomic force probe system, the method being applied to a white light interferometric atomic force dual-mode cross-scale measurement system, characterized in that, It comprises the following steps: Conversion matrix for acquiring the position relationship between the tip of an atomic force scanning probe and the tip of a cantilever , comprising: acquiring a distance measurement of the tip of an atomic force scanning probe from the tip of a cantilever in a plane parallel to the cantilever , the conversion matrix ; In the atomic force probe contact measurement mode, the position coordinates of the cantilever tip are obtained, comprising: obtaining images of the cantilever and the atomic force scanning probe tip in the CCD field of view in the atomic force scanning probe contact measurement mode; extracting the cantilever edge profile after processing the images; and calculating the position coordinates of the cantilever tip according to the coordinates of the cantilever edge profile, the calculation formula being: ; ; Determine a target region of atomic force probe contact measurement in a white light measurement mode; switch to an atomic force probe contact measurement mode, acquire a horizontal displacement value of a tip of an atomic force scanning probe moving to the target region after the measurement mode switching, and then obtain a conversion matrix between the white light measurement mode and the atomic force contact probe measurement mode data ; the conversion matrix ; According to the conversion matrix And the conversion matrix The data conversion relationship under two measurement modes is obtained, and the position coordinates of the atomic force scanning probe needle tip are calculated ; , wherein, is the actual height of the AFM probe tip; is the thickness of the cantilever; , is the coordinate of the cantilever tip; are the coordinates of the two edges of the cantilever, respectively; is the set of extracted coordinates of the cantilever edges; is the displacement value of the AFM probe in the x direction after mode switching; is the displacement value of the AFM probe in the y direction after mode switching; is the coordinate of the AFM probe tip in the white light measurement mode, is the coordinate of the AFM probe in the AFM probe contact measurement mode.​​​​ 2. The method of claim 1, wherein the white light interferometric atomic force probe system is a Veeco® Dimension® 3100 atomic force microscope. The extracting the cantilever edge profile after processing the image comprises: The image is processed by graying, Gaussian filtering and improving contrast; The Canny operator edge detection algorithm is used to the processed image to extract the cantilever edge profile of the atomic force scanning probe.

3. The method of claim 1, wherein the white light interferometric atomic force probe system is a Veeco® Dimension® 3100 atomic force microscope. It also comprises constructing a correction matrix, comprising: Acquiring a coordinate set of a feature point on a surface of an object under measurement in a white light measurement mode ; Acquiring a coordinate set of a surface feature point of the measured piece in an atomic force contact measurement mode ; The coordinate set data in two measurement modes are fitted to obtain a correction matrix The correction matrix formula is: wherein, is a set of coordinates of the surface feature points of the measured piece in the white light measurement mode, is a set of coordinates of the surface feature points of the measured piece in the atomic force contact measurement mode.

4. The method of claim 3, wherein the white light interferometric atomic force probe system is a Veeco® Dimension® 3100® atomic force microscope. The calculation formula of the data conversion of the two measurement modes after the correction is: 。 5. The method of claim 1, wherein the white light interferometric atomic force probe system is a Veeco® Dimension® 3100® atomic force microscope. Switching to the atomic force probe contact measurement mode, the horizontal angle between the atomic force scanning probe and the surface CCD measurement system is within ±1.5°.

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