Method for determining the height of a sample surface and structured optical microscope

Abstract

This invention provides a method for determining the local height of a location on the surface of a sample. [Solution] A structured optical microscope (1) is provided to determine the local height of a position on the sample surface, and includes an optical sensor (2), a sample holder (3) that holds the sample surface (5), a projector (4), and a processor (6). The procedure includes the steps of projecting an optical pattern, moving the sample surface, obtaining a contrast-focus position relationship, determining a local tilt angle, obtaining a height correction value, and obtaining the local height. The structured optical microscope (1) also includes a computer-readable data carrier containing a computer program to be executed on the processor.

Description

Technical Field

[0001] The present invention relates to a method for determining the local height of a position on a sample surface. The present invention further relates to a structured optical microscope for determining the local height of a position on a sample surface. The present invention further relates to a computer-readable data carrier including a computer program which, when executed on a processor of the structured optical microscope according to the present invention, causes the structured optical microscope to execute the method according to the present invention.

Background Art

[0002] A structured optical microscope projects an optical pattern onto a sample surface and measures the contrast at a position on the sample surface when the sample surface is at different measurement positions relative to the microscope along its optical axis, to obtain a contrast-through-focus relation. The maximum value of the contrast-through-focus relation can be associated with the local height of the position on the sample surface. A height map of the sample surface can be obtained by performing these measurements for a plurality of positions on the sample surface.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The optical system is affected by aberrations. Aberrations can be defined as deviations of the wavefront from an ideal shape. In a structured optical microscope, aberrations can distort the image in the lateral direction, for example, in a direction perpendicular to the optical axis, and aberrations can also distort the shape of the obtained contrast-through-focus relation, which can displace its maximum value. Therefore, aberrations lead to measurement errors in height measurements.

[0004] Generally, the effects of aberrations can be minimized by using multiple optical surfaces. In the case of structured optical microscopy, minimizing the effects of aberrations is complex because the sample has a three-dimensional shape. The way the sample reflects the optical pattern depends on the sample's shape and affects height measurements through system aberrations. For example, this can result in obtaining a non-planar height map for a flat sample surface.

[0005] The object of the present invention is to provide a method for reducing the influence of aberrations on height maps obtained by structured optical microscopy. [Means for solving the problem]

[0006] The object of the present invention is achieved by the method described in claim 1.

[0007] The method of the present invention makes it possible to determine the local height of a location on the sample surface. The local height may be, for example, the local height relative to another location on the sample surface, such as a baseline point. By collecting multiple local heights for multiple locations on the sample surface, a height map of the sample surface can be obtained. For each location on the sample surface, the corresponding local height can be obtained using the method of the present invention.

[0008] The location on the sample surface may also be referred to as the sample surface position in this specification. The sample surface position may be associated with a pixel or group of pixels on a structured optical microscope.

[0009] The sample surface may be the surface of a semiconductor or an optical element. The sample surface may also be a product obtained from a manufacturing process. The method of the present invention can be used in quality control of a manufacturing process.

[0010] This method involves projecting an optical pattern onto the surface of a sample and moving the sample surface relative to the structured optical microscope between multiple measurement positions along the optical axis of the structured optical microscope. The structured optical microscope may comprise a projector for projecting the optical pattern and an optical sensor for measuring the light reflected from the sample surface.

[0011] The sample surface may be held in a sample holder during measurement. The sample surface can be moved between multiple measurement positions. A structured optical microscope or a part thereof, such as an optical sensor or the lens of an optical sensor, can be moved relative to the sample surface between different measurement positions. The effective distance between the sample surface and the optical sensor may differ at different measurement positions. Since the measured contrast or focus of the optical pattern projected onto the sample surface depends on the effective distance, the measured contrast may differ between different measurement positions. The maximum contrast of the optical pattern, i.e., when the optical pattern is at focus, may be related to the height of the sample surface.

[0012] This method involves obtaining a contrast-focus position relationship corresponding to a sample surface position by measuring the contrast of the optical pattern at each measurement position. The contrast-focus position relationship can relate the effective distance to the measured contrast. The contrast-focus position relationship may also be a list of data points. Each data point includes the effective distance and the corresponding contrast. The contrast-focus position relationship may also be an interpolated relationship based on the measured contrast. For example, the contrast-focus position relationship may be a curve based on the measured values.

[0013] The local tilt angle of the sample surface position (i.e., the position on the sample surface) is determined by comparing the acquired contrast-focus position relationship with several calibrated contrast-focus position relationships, and then selecting one of the calibrated contrast-focus position relationships based on the comparison results. Here, each of the calibrated contrast-focus position relationships is associated with a tilt angle.

[0014] The local tilt angle may also be the local deviation of the local orientation of the sample surface relative to the horizontal. For example, the local tilt angle may also be the local tilt, and the local tilt angle is associated with the sample surface position. The local tilt angle can be expressed in Cartesian coordinates, polar coordinates, and / or azimuthal coordinates. The local tilt angle may also be expressed as a vector having, for example, x and y components.

[0015] For example, the tilt angle may increase from -10° to 10° in both the x and y directions. For each set of tilt angles, for example, the set where the x-angle is 5° and the y-angle is 0°, the corresponding calibrated contrast-focus position relationship is known.

[0016] Each calibrated contrast-focus relationship is associated with a tilt angle. The calibrated contrast-focus relationships and their corresponding tilt angles may be provided in a calibration table corresponding to a structured optical microscope. The calibrated contrast-focus relationships and their corresponding tilt angles can be obtained as disclosed herein. In other embodiments, the calibrated contrast-focus relationships and tilt angles may be obtained from a calibration table.

[0017] The determined local tilt angle may be equal to the tilt angle corresponding to the selected calibrated contrast-focus position relationship. The determined local tilt angle may be based on, or derived from, the tilt angle corresponding to the selected calibrated contrast-focus position relationship. For example, in embodiments of the present disclosure, the local tilt angle may be based on a weighted average of the tilt angles corresponding to the calibrated contrast-focus position relationship.

[0018] The selected calibrated contrast-focus relationship may be chosen based on its resemblance to the acquired contrast-focus relationship, for example, using means such as correlation.

[0019] The method further includes the step of obtaining a height correction value for a location based on the acquired local tilt angle. For example, each calibrated contrast-focus position relationship and the corresponding tilt angle may be further associated with a height correction value, and the corresponding height correction value may be acquired. In such embodiments, the calibrated contrast-focus position relationship, the corresponding tilt angle, and the corresponding height correction value may be included in a calibration table. The calibrated contrast-focus position relationship, the corresponding tilt angle, and the corresponding height correction value may be acquired as disclosed herein. In other embodiments, the calibrated contrast-focus position relationship, the corresponding tilt angle, and the corresponding height correction value may be provided in combination with the structured optical microscope used in the method. The calibrated contrast-focus position relationship, the corresponding tilt angle, and the corresponding height correction value may be specific to the structured optical microscope used, or specific to the type of structured optical microscope used.

[0020] This method includes the steps of obtaining a local height by determining the focal position of an optical pattern along the optical axis, for example, the position along the optical axis where the contrast of the optical pattern is highest, for example, the position with the maximum contrast; and correcting the obtained height with a height correction value in order to obtain the local height. For example, this can be obtained by adding or subtracting the height correction value from the height obtained in this way.

[0021] The method of the present invention makes it possible to correct the obtained height for errors caused by aberrations in structured optical microscopy. The inventors have found that since the actual inaccuracy of height measurement depends on the local tilt angle of the sample surface, it is not sufficient to measure a flat surface to obtain inaccuracy and then correct any measured height with the obtained inaccuracy. Importantly, the local tilt angle may not be directly obtained from the sample surface because the shape of the sample surface is not measured. Therefore, the local tilt angle is obtained by comparing the contrast-focus position relationship with a calibrated contrast-focus position relationship. The method comprises, firstly, the step of determining the local tilt angle, and secondly, the step of correcting the measured height with a height correction value corresponding to the local tilt angle, for example, the height correction value depending on the local tilt angle.

[0022] In this embodiment, a plurality of calibrated contrast-focus position relationships, corresponding tilt angles, and corresponding height correction values ​​are obtained as follows: - A step of obtaining multiple calibrated contrast-focus position relationships by measuring the contrast of an optical pattern on a flat test surface having a known height using a structured optical microscope at each of multiple measurement positions, wherein different calibrated contrast-focus position relationships are obtained by positioning the test surface at different inclination angles with respect to the optical axis. - For each calibrated contrast-focus position relationship, the steps include determining the height of the flat test surface based on the corresponding calibrated contrast-focus position relationship and obtaining the corresponding height correction value by calculating the difference of the known height of the flat test surface from the determined height, - A step of storing the calibrated contrast-focus position relationship, the corresponding tilt angle, and the corresponding height correction value.

[0023] A flat test surface can be obtained using an expensive and / or labor-intensive process that is not suitable for manufacturing a sample surface whose local height can be determined. Since the flat surface has a known height, the difference between the measured height and the known height is an error of measurement that can be used as a height correction value. By storing the obtained height correction value, the contrast-focus position relationship, and the corresponding tilt angle, a calibrated contrast-focus position relationship, the corresponding tilt angle, and the corresponding height correction value can be obtained by performing a plurality of steps for different tilt angles.

[0024] For example, the flat surface may be tilted at angles of 0°, 1°, 2°, ···, 45° in the vertical direction to obtain different calibrated contrast-focus position relationships.

[0025] In an embodiment, a plurality of calibrated contrast-focus position relationships, the corresponding tilt angles, and the corresponding height correction values are obtained as follows: - Measuring the contrast of an optical pattern on a test surface having a known three-dimensional shape with a known height profile at each of a plurality of measurement positions using a structured optical microscope to obtain a plurality of calibrated contrast-focus position relationships, wherein the different calibrated contrast-focus position relationships are obtained by positioning the test surface at different lateral positions with respect to the optical axis; - For each of the calibrated contrast-focus position relationships, obtaining the corresponding height correction value by determining the height of the flat test surface based on the corresponding calibrated contrast-focus position relationship and calculating the difference in the height of the test surface from the determined height; - Storing the calibrated contrast-focus position relationship, the corresponding tilt angle, and the corresponding height correction value.

[0026] For example, a test surface having a known three-dimensional shape with a known height profile may be a test surface having dome-shaped elements located thereon. This makes it possible to obtain a calibrated contrast-focus position relationship for different tilt angles by moving the test surface laterally with respect to the optical axis.

[0027] The above two embodiments are examples of methods for performing a reference measurement or a calibration measurement to obtain a calibrated contrast-focus position relationship in which a tilt angle and a height correction value are associated. The reference measurement may have to be performed once for a structured optical microscope. If two or more structured optical microscopes are sufficiently similar or if quality criteria permit, one of the structured optical microscopes can be used to obtain reference measurement values for both or all of the structured optical microscopes according to the above embodiments.

[0028] In an embodiment, the step of comparing the obtained contrast-focus position relationship with a plurality of calibrated contrast-focus position relationships and selecting one of the plurality of calibrated contrast-focus position relationships based on the comparison includes determining a similarity between the obtained contrast-focus position relationship and each of the plurality of calibrated contrast-focus position relationships, and selecting one of the plurality of calibrated contrast-focus position relationships based on the determined similarity. For example, the similarity is a correlation relationship. For example, the selected calibrated contrast-focus position relationship is selected based on having the highest similarity with the calibrated contrast-focus position relationship.

[0029] For example, the similarity between the obtained contrast-focus position relationship and the calibrated contrast-focus position relationship can be obtained based on one or more of the following: - Comparing features of a contrast-focus position curve representing a contrast-focus position relationship as follows 〇 The width of the curve, for example, the full width at a value that is half of the maximum value 〇 The position of one or more of the extreme values, for example, the position of the first minimum or maximum value on the left and right sides of the overall maximum value ○ The values ​​of the curve at one or more of the extreme values, for example, the first minimum values ​​to the left and right of the overall maximum value. ○ The width of the first side robes to the right and / or left of the main robe, for example, the robe containing the overall maximum value. 〇 The maximum value of the whole - An artificial neural network trained to compare contrast-focus relationships. -Cross-correlation between contrast and focal position, e.g., cross-correlation between contrast and focal position excluding the main lobe.

[0030] In the embodiment, the similarity between the acquired contrast-focus position relationship and a plurality of calibrated contrast-focus position relationships is based on the contrast-focus position curve associated with each contrast-focus position relationship, for example, by comparing the positions of their extreme values ​​or by comparing their size and / or shape.

[0031] In the embodiment, the step of determining the local tilt angle of the sample surface at a location includes calculating a weighted average of a first tilt angle corresponding to a calibrated contrast-focus position relationship having the highest similarity to the acquired contrast-focus position relationship, and a second tilt angle. The second tilt angle is associated with a calibrated contrast-focus position relationship adjacent to the first tilt angle and having the second highest similarity to the calibrated contrast-focus position relationship corresponding to the tilt angle adjacent to the first tilt angle, and the weights of the weighted average are based on the determined similarity.

[0032] For example, the tilt angles corresponding to the calibrated contrast-focus position relationship may be ordered by a matrix in which, for instance, the change in the x-component of the angle occurs in the columns of the matrix and the change in the y-component of the angle occurs in the rows of the matrix. For example, in a one-dimensional example, the tilt angles could be 0°, 1°, 2°, 3°, and 4°. Angles 2° and 4° can be considered adjacent to 3°, but 0° and 1° are not.

[0033] Therefore, one calibrated contrast-focus relationship can be selected based on its highest similarity to the acquired contrast-focus relationship, and the corresponding tilt angle is the first tilt angle. Adjacent tilt angles of the first tilt angle are selected, and the similarity between the corresponding calibrated contrast-focus relationship and the acquired contrast-focus relationship is determined. The second tilt angle is associated with the calibrated contrast-focus relationship that has the highest similarity among those considered.

[0034] For example, the local slope angle is, JPEG2026082692000002.jpg15170 Here, s1 is the similarity between the calibrated contrast-focus position relationships corresponding to the first tilt angle, A1 is the first tilt angle, s2 is the similarity between the calibrated contrast-focus position relationships corresponding to the second tilt angle, and A2 is the second tilt angle.

[0035] In the embodiment, the step of determining the height correction value includes calculating a weighted average of the height correction values ​​corresponding to the first and second inclination angles, where the weights of the weighted average are based on the determined similarity. For example, the height correction value may be determined using an equation similar to the one described above.

[0036] The present invention further relates to a structured optical microscope for determining the local height of a location on a sample surface, wherein the structured optical microscope: - A projector that projects an optical pattern onto the surface of the sample, - An optical sensor for obtaining the contrast of the optical pattern projected onto the sample surface, - A sample holder for holding the sample surface at different measurement positions relative to the optical sensor along the optical axis of a structured optical microscope, -It comprises an optical sensor, a sample holder, and a processor functionally connected to a projector, and the processor is - Based on the contrast of the optical pattern projected onto the sample surface by the projector, measured by an optical sensor at each of multiple measurement positions, the contrast-focus position relationship corresponding to the position on the sample surface is obtained. - The acquired contrast-focus position relationship is compared with multiple calibrated contrast-focus position relationships, and based on this comparison, one of the multiple calibrated contrast-focus position relationships is selected to determine the local tilt angle of the sample surface at that position, and each of the calibrated contrast-focus position relationships is associated with the tilt angle. - Based on the acquired local tilt angle, obtain a height correction value for the position, - The system is configured to determine the focus position of the optical pattern along the optical axis and obtain the local height by correcting it with a height correction value.

[0037] In this way, the method of the present invention can be carried out using a structured optical microscope.

[0038] In this embodiment, the structured optical microscope is configured to acquire multiple calibrated contrast-focus position relationships, corresponding tilt angles, and corresponding height correction values ​​by the following process: - A step of obtaining multiple calibrated contrast-focus position relationships by measuring the contrast of an optical pattern on a flat test surface having a known height using optical sensors at each of multiple measurement positions, wherein different calibrated contrast-focus position relationships are obtained by positioning the test surface in a sample holder at different inclination angles with respect to the optical axis. - The processor determines the height of the flat test surface based on the corresponding calibrated contrast-focus position relationship for each calibrated contrast-focus position relationship, and obtains a corresponding height correction value by calculating the difference of the known height of the flat test surface from the determined height. - The processor stores the calibrated contrast-focus position relationship, the corresponding tilt angle, and the corresponding height correction value.

[0039] In this embodiment, the structured optical microscope is configured to acquire multiple calibrated contrast-focus position relationships, corresponding tilt angles, and corresponding height correction values ​​by the following process: - A step of obtaining multiple calibrated contrast-focus position relationships by measuring the contrast of an optical pattern on a test surface having a known three-dimensional shape and a known height profile using optical sensors at each of multiple measurement positions, wherein different calibrated contrast-focus position relationships are obtained by positioning the test surface at different lateral positions with respect to the optical axis using a sample holder. - The processor determines the height of a flat test surface based on the corresponding calibrated contrast-focus position relationship for each calibrated contrast-focus position relationship, and obtains a corresponding height correction value by calculating the difference in height of the test surface from the determined height. - The processor stores the calibrated contrast-focus position relationship, the corresponding tilt angle, and the corresponding height correction value.

[0040] In the embodiment, the processor is further configured to compare the acquired contrast-focus relationship with a plurality of calibrated contrast-focus relationships, and the step of selecting one of the plurality of calibrated contrast-focus relationships based on the comparison includes the steps of determining the similarity between the acquired contrast-focus relationship and each of the plurality of calibrated contrast-focus relationships, and selecting one of the plurality of calibrated contrast-focus relationships based on the determined similarity. For example, the similarity is the correlation.

[0041] In the embodiment, the processor is configured to determine the similarity between an acquired contrast-focus position relationship and a plurality of calibrated contrast-focus position relationships based on the contrast-focus position curve corresponding to each contrast-focus position relationship, for example, by comparing the positions of extreme values ​​or by comparing their size and / or shape.

[0042] In the embodiment, the processor is further configured to determine the local tilt angle of the sample surface at a location by calculating a weighted average of a first tilt angle and a second tilt angle, corresponding to a calibrated contrast-focus position relationship that has the highest similarity to the acquired contrast-focus position relationship. The second tilt angle is associated with a calibrated contrast-focus position relationship adjacent to the first tilt angle and having the second highest similarity to the calibrated contrast-focus position relationship corresponding to the calibrated contrast-focus position relationship adjacent to the first tilt angle, and the weights of the weighted average are based on the determined similarities.

[0043] In the embodiment, the processor is further configured to determine the height correction value by calculating a weighted average of the height correction values ​​corresponding to the first and second tilt angles, the weights of the weighted average being based on the determined similarity.

[0044] The present invention further relates to a computer-readable data carrier which, when executed on a processor of a structured optical microscope according to the present invention, includes a computer program that causes the structured optical microscope to perform the method according to the present invention.

[0045] Herein, embodiments of the present invention will be described by reference to the accompanying drawings, where corresponding reference numerals indicate corresponding parts, merely as examples. [Brief explanation of the drawing]

[0046] [Figure 1] Figure 1 shows three contrast-focus position curves corresponding to different tilt angles. [Figure 2] Figure 2 shows a method for obtaining a calibrated contrast-focus position relationship with corresponding tilt angle and height correction values. [Figure 3] Figure 3 shows a structured optical microscope. [Modes for carrying out the invention]

[0047] Figure 1 shows three different contrast-focus position curves corresponding to three different local tilt angles. The local tilt angles are 0, 1.25, and 2.5 in the x-direction. The x-axis in the figure represents the position along the optical axis of the structured optical microscope. The y-axis in the figure represents the contrast in arbitrary units, such that the maximum contrast is normalized to 1.

[0048] As can be seen from Figure 1, the shape of the curve and the position of the extrema depend on the local tilt angle of the sample. Therefore, the corresponding tilt angle can be determined using the shape of the contrast-focus position relationship.

[0049] Figure 2 shows a method for obtaining a calibrated contrast-focus position relationship with corresponding tilt angle and height correction values. The figure shows two three-dimensional graphs with squares in the xy plane representing different positions on a flat test surface. The method of the present invention can be carried out for each position. As can be seen from the figure, the upper graph represents a test surface with a tilt angle of (0°,0°), and the lower graph represents a test surface with a tilt angle of (2°,0°).

[0050] Each square has the corresponding contrast-focus position relationship and determined height correction value shown. As can be seen by comparing the upper graph with the lower graph, both the contrast-focus position relationship and the corresponding height correction value for a given position depend on the tilt angle. For example, the left square representing the position has a height correction value of 50 nm when the tilt angle is (0°,0°) and a height correction value of 70 nm when the tilt angle is (2°,0°).

[0051] The calibrated contrast-focus position relationship can, in principle, be obtained by measuring the contrast-focus position relationship for each position and determining height correction values ​​for different inclination angles of the flat test surface.

[0052] Figure 3 shows a structured optical microscope 1 comprising an optical sensor 2, a sample holder 3 for holding a sample surface 5, a projector 4, and a processor 6. The optical sensor 2 is configured to acquire the contrast of an optical pattern projected onto the sample surface 3 by the projector 4.

[0053] The sample holder 3 is configured to hold the sample surface 3 at different measurement positions relative to the optical sensor 2 along the optical axis of the structured optical microscope 1. The sample holder 3 may be movable relative to the optical sensor 2, or the optical sensor 2 or a part thereof such as a lens may be movable relative to the sample holder 3 so that the effective distance between the sample surface 5 and the optical sensor 2 can be changed.

[0054] The processor 6 is functionally connected to the optical sensor 2, the sample holder 3, and the projector 4, and the processor is, - Based on the contrast measured by the optical sensor at each of the multiple measurement positions of the optical pattern projected onto the sample surface by the projector 4, the contrast-focus position relationship corresponding to the position on the sample surface 5 is obtained. - The acquired contrast-focus position relationship is compared with multiple calibrated contrast-focus position relationships, and based on the comparison, the local tilt angle of the sample surface 5 at that position is determined by selecting one of the multiple calibrated contrast-focus position relationships that corresponds to the tilt angle of each of the contrast-focus position relationships. - Based on the acquired local tilt angle, obtain a height correction value for the position, - The focus position of the optical pattern along the optical axis is determined, and the local height is obtained by correcting it with a height correction value.

[0055] The present invention, as disclosed herein, makes it possible to reduce the influence of aberrations on height maps or local heights obtained by a structured optical microscope 1.

Claims

1. A method for determining the local height of a position on the surface of a sample, The steps include projecting an optical pattern onto the surface of the sample, The steps include moving the sample surface relative to the structured optical microscope between multiple measurement positions along the optical axis of the structured optical microscope, The steps include: obtaining a contrast-focus position relationship corresponding to the position on the sample surface by measuring the contrast of the optical pattern at each of the plurality of measurement positions on the sample surface; The steps include determining the local tilt angle of the sample surface at the position by comparing the acquired contrast-focus position relationship with a plurality of calibrated contrast-focus position relationships, each associated with a tilt angle, and selecting one of the plurality of calibrated contrast-focus position relationships based on the comparison, A step of obtaining a height correction value for the position based on the acquired local tilt angle, The steps include determining the focus position of the optical pattern along the optical axis and obtaining the local height by correcting it with the height correction value, A method of having.

2. The plurality of calibrated contrast-focus position relationships, the corresponding tilt angles, and the corresponding height correction values ​​are, By measuring the contrast of an optical pattern on a flat test surface having a known height using a structured optical microscope at each of the aforementioned multiple measurement positions, and by positioning the test surface at different inclination angles with respect to the optical axis, a plurality of different calibrated contrast-focus position relationships are obtained. For each of the plurality of calibrated contrast-focus position relationships, the height of the flat test surface is determined based on the corresponding calibrated contrast-focus position relationship, and the corresponding height correction value is obtained by calculating the difference between the determined height and the known height of the flat test surface. The plurality of calibrated contrast-focus position relationships, the corresponding tilt angle, and the corresponding height correction value are stored. Characterized by being obtained by, The method according to claim 1.

3. The plurality of calibrated contrast-focus position relationships, the corresponding tilt angles, and the corresponding height correction values ​​are, By using the structured optical microscope at each of the plurality of measurement positions, the contrast of an optical pattern on a test surface having a known three-dimensional shape with a known height profile is measured, and by positioning the test surface at different lateral positions with respect to the optical axis, a plurality of different calibrated contrast-focus position relationships are obtained. For each of the plurality of calibrated contrast-focus position relationships, the height of the flat test surface is determined based on the corresponding calibrated contrast-focus position relationship, and the corresponding height correction value is obtained by calculating the difference in height of the test surface from the determined height. The plurality of calibrated contrast-focus position relationships, the corresponding tilt angle, and the corresponding height correction value are stored. Characterized by being obtained by, The method according to claim 1.

4. The step of comparing the acquired contrast-focus position relationship with the plurality of calibrated contrast-focus position relationships and selecting one of the plurality of calibrated contrast-focus position relationships based on the comparison is: The steps include determining the similarity between the acquired contrast-focus position relationship and each of the plurality of calibrated contrast-focus position relationships, The steps include selecting one of the plurality of calibrated contrast-focus position relationships based on the determined similarity, It includes, for example, the similarity being characterized by correlation, The method according to one or more of the preceding claims.

5. The similarity between the acquired contrast-focus position relationship and the plurality of calibrated contrast-focus position relationships is characterized by being based on the contrast-focus position curve associated with each of the contrast-focus position relationships, for example, by comparing the positions of their extreme values ​​or by comparing their size and / or shape. The method according to claim 4.

6. The step of determining the local tilt angle of the sample surface at the position includes calculating a weighted average of a first tilt angle and a second tilt angle, the first being the calibrated contrast-focus position relationship having the highest similarity to the acquired contrast-focus position relationship, wherein the second tilt angle is adjacent to the first tilt angle and is associated with the calibrated contrast-focus position relationship having the second highest similarity among the plurality of calibrated contrast-focus position relationships corresponding to tilt angles adjacent to the first tilt angle, and the weights of the weighted average are based on the determined similarity. The method according to one or more of claims 4 and 5.

7. The step of determining the height correction value includes calculating a weighted average of the height correction values ​​corresponding to the first and second inclination angles, wherein the weights of the weighted average are based on the determined similarity. The method according to claim 6.

8. A structured optical microscope for determining the local height of a position on the surface of a sample, A projector that projects an optical pattern onto the surface of the sample, An optical sensor for obtaining the contrast of the optical pattern projected onto the surface of the sample, A sample holder that holds the sample surface at multiple different measurement positions relative to the optical sensor along the optical axis of the structured optical microscope, A processor functionally connected to the optical sensor, the sample holder, and the projector, It has, The aforementioned processor, A step of obtaining a contrast-focus position relationship corresponding to the position on the sample surface based on the contrast of the optical pattern projected onto the sample surface by the projector, measured by the optical sensor at each of the plurality of measurement positions, The steps include comparing the acquired contrast-focus position relationship with a plurality of calibrated contrast-focus position relationships, The steps include determining a local tilt angle at a location on the sample surface, based on a comparison, by selecting one of the plurality of calibrated contrast-focus position relationships, each associated with a tilt angle, A step of obtaining a height correction value for the position on the sample surface based on the acquired local tilt angle, The steps include determining the focus position of the optical pattern along the optical axis and obtaining the local height by correcting it with the height correction value, A structured optical microscope characterized by performing the following:

9. The aforementioned structured optical microscope is By using the optical sensor at each of the multiple measurement positions, a flat test surface having a known height is positioned on the sample holder at different inclination angles with respect to the optical axis of the optical sensor, thereby measuring the contrast of the optical pattern on the test surface and obtaining the multiple calibrated contrast-focus position relationships. The processor determines the height of the flat test surface based on the corresponding calibrated contrast-focus position relationship for each of the plurality of calibrated contrast-focus position relationships, and obtains a corresponding height correction value by calculating the difference between the determined height and the known height of the flat test surface. The processor stores the plurality of calibrated contrast-focus position relationships, the corresponding tilt angles, and the corresponding height correction values, The system is configured to acquire the plurality of calibrated contrast-focus position relationships, the corresponding tilt angle, and the corresponding height correction value. The structured optical microscope according to claim 8.

10. The aforementioned structured optical microscope is At each of the plurality of measurement positions, the contrast of the optical pattern on the test surface having a known three-dimensional shape with a known height profile is measured using the optical sensor, and by positioning the test surface at different lateral positions with respect to the optical axis using the sample holder, a plurality of different calibrated contrast-focus position relationships are obtained. The processor determines the height of the flat test surface based on the corresponding calibrated contrast-focus position relationship for each of the plurality of calibrated contrast-focus position relationships, and obtains the corresponding height correction value by calculating the difference between the determined height and the known height of the flat test surface. The processor is configured to acquire the plurality of calibrated contrast-focus position relationships, corresponding tilt angles, and corresponding height correction values ​​by storing the plurality of calibrated contrast-focus position relationships, corresponding tilt angles, and corresponding height correction values. The structured optical microscope according to claim 8.

11. The process by which the processor compares the acquired contrast-focus relationship with the plurality of calibrated contrast-focus relationships and selects one of the plurality of calibrated contrast-focus relationships based on the comparison includes determining the similarity between the acquired contrast-focus relationship and each of the plurality of calibrated contrast-focus relationships, and selecting one of the plurality of calibrated contrast-focus relationships based on the determined similarity, wherein, for example, the similarity is a correlation. A structured optical microscope according to one or more of claims 8 to 10.

12. The processor is configured to determine the similarity between the acquired contrast-focus position relationship and the plurality of calibrated contrast-focus position relationships based on, for example, the position of the extreme values ​​of the contrast-focus position curves corresponding to each of the contrast-focus position relationships, or by comparing their size and / or shape. The structured optical microscope according to claim 11.

13. The processor is further configured to determine the local tilt angle of the sample surface at the position by calculating a weighted average of a first tilt angle and a second tilt angle corresponding to the calibrated contrast-focus position relationship having the highest similarity to the acquired contrast-focus position relationship. The second tilt angle is adjacent to the first tilt angle and is associated with the calibrated contrast-focus position relationship having the second highest similarity in the calibrated contrast-focus position relationship corresponding to the tilt angle adjacent to the first tilt angle. The weights of the aforementioned weighted average are characterized by being based on the determined similarity. A structured optical microscope according to one or more of claims 11 and 12.

14. The processor is further configured to determine the height correction value by calculating the weighted average of the height correction values ​​corresponding to the first tilt angle and the second tilt angle, The weights of the aforementioned weighted average are characterized by being based on the determined similarity. A structured optical microscope according to one or more of claims 11 to 13.

15. A computer-readable data carrier comprising a computer program, which, when executed on the processor of the structured optical microscope according to one or more of claims 8 to 14, causes the structured optical microscope to perform the method according to one or more of claims 1 to 7.

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