Method for measuring the sample and microscope for performing this method

Abstract

The present invention relates to a method (200) for measuring a sample (100) using a microscope, the method comprising the steps of measuring (S210) a tilt (131, 132) of the sample (100), correcting (S220) an orientation of the sample (100) based on the tilt (131, 132), and scanning (S230) the sample.

Description

Technical Field

[0001] The first aspect of the present invention generally relates to a method for measuring a sample using a microscope and a microscope for implementing the above method. More specifically, the method enables the inclination of the positioning of the sample to be compensated or corrected.

[0002] This application claims the priority of U.S. Patent Application No. 17 / 501,238, which is incorporated herein by reference.

Background Art

[0003] In various technical fields, it is often necessary to investigate a sample not only on its surface but also throughout its vertical depth. In some cases, this is possible by an imaging device that enables viewing through the sample. In some cases, this is not possible, for example, due to the complexity of the sample and its material.

[0004] As an example, semiconductor devices with vertical structures are known. The structures can be, for example, vertical continuations or capacitor arrays of so-called high aspect ratio (HAR) structure configurations. In many cases, there is an interest in investigating how those structures develop along their vertical directions.

[0005] FIG. 1A shows an example of such a structure. In particular, FIG. 1A schematically shows a cross-section of a sample 100A that can be, for example, a part of a semiconductor wafer. The sample 100A is provided with an upper surface 101 that is usually substantially flat. One or more channels 102A to 102N are implemented in the sample. The channels 102A to 102N can be etched and left empty for subsequent measurements or filled with one or more various layers as shown. When realizing such deep and narrow channels, it is difficult to control their vertical orientations across the wafer.

[0006] It will be understood that other functional elements of sample 100A are not illustrated for clarity of representation. For example, sample 100A may include multiple horizontal layers 107A-107N that implement various electronic components such as transistors, resistors, or capacitors. One exemplary function of channels 102A-102N is, for example, that they are filled with conductive material and provide interconnection between two or more of such layers 107A-107N. Therefore, it is important that the orientation of the channels matches with sufficient precision to the intended orientation, which is not limited to but is usually perpendicular to the wafer surface. Otherwise, referring to the exemplary functions above, it will not be possible to correctly establish the required contact to the functional units above or below. In another example, channels may be used to implement a capacitor plate, and as a result, channel mismatch may result in a capacitance different from the desired value.

[0007] Therefore, controlling the orientation of channels 102A to 102N is important and has a dramatic causal relationship with the yield of the manufactured devices. The longer the channels 102A to 102N are, the more important it becomes to precisely control their characteristics.

[0008] For example, Figure 1B schematically shows a cross-section of sample 100B where channels 102A-102N exist at an angle 103 with respect to the vertical direction Y. To more accurately control and / or correct the manufacturing process, the manufacturer wants to know whether the situation in Figure 1A or Figure 1B arises from those processes. Although the angle 103 is shown with respect to the vertical direction Y, the top surface 101 of sample 100 may be, for example, the wafer surface. In some cases, this surface can be considered a reference plane, and the channel inclination with respect to it can be measured using the method described below.

[0009] Therefore, methods have been developed to evaluate the vertical expansion of such channels 102A-102N. As schematically shown in Figure 1C, at least a portion of the top surface 101 of sample 100B can be removed by using etching or milling means 110. The etching or milling means 110 can be any known type of etching or milling device, such as a focused ion beam (FIB). The newly exposed top surface of sample 100B can then be scanned by scanning means 120, such as a scanning electron microscope (SEM), a helium ion microscope (HIM), or generally an electron beam from a charged particle microscope. Alternatively, or in addition, the scanning means can be any known type of scanning means capable of scanning the surface of a sample, such as the tip of an atomic force microscope (AFM), or more generally. Although the milling is shown substantially parallel to the top surface 101 in Figure 1C, the present invention is not limited thereto, and the plane along which the milling is performed can be oblique to the top surface 101.

[0010] By repeating the milling and scanning procedures, it is possible to obtain various images of sample 100B at various vertical locations in a stepwise manner. By reconstructing the model based on these images, it is possible to determine the vertical expansion of channels 102A to 102N.

[0011] However, in order to ensure accurate measurement, it is necessary that the sample 100 be precisely positioned. For example, as shown in Figure 1D, sample 100A, in which channels 102A to 102N are substantially vertically aligned, can be positioned such that its upper surface 101 exhibits an angle 132 with respect to the vertical plane X, for example, due to the presence of dust particles 130.

[0012] If this is not taken into consideration, performing the milling and scanning methods described above will result in the situation shown in Figure 1D, and the reconstruction model from the scanning and milling methods will show that channels 102A to 102N exhibit an angle of 131 with respect to the vertical. [Overview of the project]

[0013] Therefore, it is necessary to provide a method that enables the microscope to detect the situation shown in Figure 1D in order to allow for the correct volume reconstruction of the image sample 100.

[0014] This need is met by the features of the independent claim. The features of the dependent claim specify further embodiments.

[0015] The present invention is generally based on the concept that the tilt of the orientation of a sample can be detected and, if necessary, corrected for the tilt. For example, the position of the sample can be corrected before scanning the sample, or the sample can be scanned, and then the volume reconstruction from the cross-sectional image can be corrected by taking the tilt into account. Alternatively, the sample can be etched and / or scanned along a plane corrected by taking the tilt into account.

[0016] One embodiment relates in particular to a method for measuring a sample using a microscope, the method comprising the steps of measuring the inclination 131, 132 of the sample, correcting the orientation of the sample based on the inclination, and scanning the sample.

[0017] This configuration has the advantage of allowing for correction of the sample position to compensate for measurement inclination.

[0018] In some embodiments, the method may further include a step of checking whether the incline falls within a predetermined interval.

[0019] This configuration has the advantage of allowing for the avoidance of correcting the sample position when correction is not necessary, and / or allowing for continued correction of the sample position if previous corrections were insufficient, and / or to implement a stepwise correction method.

[0020] One embodiment further relates to a method for measuring a sample using a microscope, the method comprising the steps of measuring the tilt of the sample, scanning the sample, and correcting the volume reconstruction from the scanned image based on the tilt.

[0021] This configuration advantageously allows for correction of the sample model created by volume reconstruction, taking the slope into account. As a result, the volume model of the sample, such as a 3D model, is unaffected by the slope.

[0022] One embodiment further relates to a method for measuring a sample using a microscope, the method comprising the steps of measuring the inclination of the sample, correcting the scanning plane based on the inclination, and scanning the sample.

[0023] This configuration advantageously allows for measuring the sample along a plane calculated based on the inclination, such as a plane parallel to the inclination, and as a result, the image obtained from the scan is corrected for the inclination.

[0024] In some embodiments, the inclination may include at least an angle formed by a predetermined surface and a predetermined plane of the sample.

[0025] In some embodiments, the predetermined surface can be the top surface, horizontal layer, side surface, or bottom surface, and the predetermined plane can be the scanning plane of the microscope.

[0026] With this configuration, advantageously, it is possible to measure the inclinations of a plurality of surfaces with respect to the scanning surface of the microscope as a reference. As a result, subsequent scanning can be performed along the scanning surface while correcting for the inclination as described above.

[0027] In some embodiments, the predetermined surface can be any one of the upper surface, horizontal layer, side surface, and bottom surface, and the predetermined plane can be the horizontal plane XZ.

[0028] With this configuration, advantageously, it is possible to measure the inclinations of a plurality of surfaces with respect to the horizontal plane as a reference. As a result, the horizontal plane can be advantageously used for positioning the sample.

[0029] In some embodiments, the measurement step can be performed by focusing a beam onto the sample and measuring the resulting focal length.

[0030] With this configuration, advantageously, it is possible to perform the measurement step easily and accurately.

[0031] In some embodiments, the beam can be the scanning beam that is also used in the scanning step.

[0032] With this configuration, advantageously, it is possible to use the same beam in the microscope for a plurality of steps.

[0033] In some embodiments, the focus can be directed to a focusing marker.

[0034] With this configuration, advantageously, it is possible to improve the focusing by appropriately selecting the characteristics of the marker. Moreover, the position of the marker can also be selected to achieve the measurement step at a predetermined location of the sample.

[0035] In some embodiments, the method may further include the step of realizing one or more focusing markers.

[0036] This configuration advantageously allows for the realization of markers at selected locations on the sample. Knowledge of the locations of these markers can then be advantageously used in the measurement steps.

[0037] In some embodiments, the measurement step can be performed by reflecting the beam onto the sample.

[0038] This configuration has the advantage of allowing for easy and reliable measurement of the sample's position. Furthermore, the detector receiving the reflected beam can be configured to directly indicate when the sample is in a predetermined position, and thus, the sample can be positioned in a predetermined location through stepwise correction, without the need to precisely measure the sample's position.

[0039] In some embodiments, the measurement step may include measuring at least three points on the sample.

[0040] This configuration advantageously allows for the detection of a plane corresponding to the incline, which is identified by three points.

[0041] In some embodiments, the method may further include the step of fitting the measurement point to a plane that identifies the inclination.

[0042] With this configuration, the inclined surface can be identified by the plane resulting from the fit.

[0043] In some embodiments, the measurement step may include measuring a predetermined number of points on a sample and fitting the measurement points to a plane.

[0044] This configuration has the advantage of reducing errors that may arise from one or more incorrect measurement points.

[0045] In some embodiments, the measurement step may include measuring multiple points on a sample, removing one or more of the measurement points based on a predetermined threshold, and fitting the measurement points, excluding the removed points, to a plane.

[0046] This configuration has the advantage of eliminating points resulting from erroneous measurements, and therefore increasing the accuracy of slope measurements.

[0047] In some embodiments, the scanning step may include removing at least a portion of the upper surface of the sample and scanning the sample.

[0048] This configuration advantageously allows for stepwise scanning of the sample at multiple different heights, thus enabling subsequent reconstruction of the sample model along its depth or vertical direction.

[0049] In some embodiments, the method may further include the step of measuring the vertical structure in the sample.

[0050] This configuration advantageously allows for determining whether vertical structures in the sample are oriented as expected, without introducing errors due to inclination.

[0051] In some embodiments, the sample can be a semiconductor wafer or a portion thereof.

[0052] This configuration is advantageous in that it is possible to measure the development of vertical structures within a semiconductor wafer, preferably a semiconductor wafer or a portion thereof such as a coupon.

[0053] One embodiment may further relate to a microscope comprising a processor and memory, the memory storing instructions configured to cause the processor to control the microscope to perform the method described in any preceding item.

[0054] This configuration allows for the control of the microscope to achieve any of the advantages mentioned above.

[0055] One embodiment may further relate to a computer program that, when executed by a processor, includes instructions configured to cause the processor to control a microscope to perform the method described in any preceding term.

[0056] Throughout this specification, drawings are referenced for ease of understanding, and similar reference numerals represent similar elements. [Brief explanation of the drawing]

[0057] [Figure 1A] This is a schematic perspective view of sample 100 to illustrate the steps of the method for measuring the sample according to the current state of technology. [Figure 1B] This is a schematic perspective view of sample 100 to illustrate the steps of the method for measuring the sample according to the current state of technology. [Figure 1C] This is a schematic perspective view of sample 100 to illustrate the steps of the method for measuring the sample according to the current state of technology. [Figure 1D] This is a schematic perspective view of sample 100 to illustrate the steps of the method for measuring the sample according to the current state of technology. [Figure 2A] This is a schematic diagram of measurement method 200. [Figure 2B] This is a schematic top view of sample 100. [Figure 2C] This is a schematic side view of sample 100. [Figure 3] This is a schematic diagram illustrating measurement method 300. [Figure 4] This is a schematic diagram illustrating measurement method 400. [Figure 5] This is a schematic diagram illustrating measurement method 500. [Figure 6] This is a schematic side view of sample 100 and the components for measuring the position of the sample. [Figure 7] This is a schematic diagram showing measurement step 710. [Figure 8] This is a schematic diagram showing measurement step 810. [Figure 9] This is a schematic diagram showing scanning step 930. [Figure 10] This is a schematic diagram illustrating measurement method 1000. [Figure 11] This is a schematic diagram showing microscope 1100. [Modes for carrying out the invention]

[0058] Some examples of this disclosure generally provide multiple circuits or other electrical devices. All references to circuits and other electrical devices and the functions provided by each are not intended to be limited to those illustrated and described herein. Certain labels may be assigned to various circuits or other electrical devices disclosed, but such labels are not intended to limit the scope of operation of the circuits and other electrical devices. Such circuits and other electrical devices may be combined with and / or separated from each other in any way based on a desired particular type of electrical embodiment. It is recognized that any circuit or other electrical device disclosed herein may include any number of microprocessors, graphics processor units (GPUs), integrated circuits, memory devices (e.g., flash, random access memory (RAM), read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other suitable variations thereof), and software that cooperate with each other to perform the operations disclosed herein. In addition, one or more of the electrical devices may be configured to execute program code embodied in a non-temporary computer-readable medium that is programmed to perform any number of functions as disclosed.

[0059] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the following description of embodiments should not be construed as limiting. The scope of the present invention is not intended to be limited by the embodiments described below or by the drawings, and should be construed as illustrative only.

[0060] Drawings should be considered as schematic representations, and the elements shown in the drawings are not necessarily shown to scale. Rather, the various elements are represented in a way that makes their function and general purpose clear to those skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by indirect connection or coupling. Coupling between components may also be established via wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

[0061] Figure 2A schematically illustrates the measurement method 200. Figures 2B and 2C schematically show top and side views, respectively, of the sample 100 to further illustrate the method 200 and some optional features.

[0062] Method 200 is generally based on the concept of measuring the tilt of sample 100 and correcting the orientation of the sample based on the tilt before scanning the sample. In some embodiments, sample 100 can be understood as a portion of a semiconductor wafer cut from a wafer for analysis. This can be referred to as a coupon.

[0063] In particular, method 200 includes step S210 of measuring the inclination 132 of the sample 100. Generally, inclination can be understood as any numerical index that identifies how much the surface of the sample differs from a given plane. Thus, the sample can include at least one angle formed by a given surface of the sample 100 and a given plane. For example, as seen in Figure 1D, inclination 132 can be understood as the angle between the horizontal plane XZ and the top surface 101 or bottom surface 106 of the sample 100. In the context of this application, the top surface 101 can be understood as the surface that is substantially aligned with the horizontal plane and is on top of the sample 100 when the sample is positioned in a microscope. Preferably, the top surface 101 can be understood as a portion of the top surface that has not yet undergone etching, milling, or scanning for the purpose of scanning by a microscope, as described, for example, with reference to step S932 in Figure 9. However, the present invention is not limited thereto, and as can be seen in Figure 1D, the inclination 131 can be understood as the angle between the vertical plane YZ and the sides 104, 105 of the sample 100. It is clear that the inclination can be expressed as an angle having a given orientation, or as a combination of angles. For example, the inclination 132 can be described as an angle with respect to the horizontal XZ plane along a given direction in the XZ plane. Alternatively, or in addition, the inclination 132 can be described as a combination of a first angle with respect to the XZ plane along the X direction and a second angle with respect to the horizontal XZ plane along the Z direction. Alternatively, or in addition, the inclination 132 can be described as a plane.

[0064] In general, the inclination can be understood as an indicator of the misalignment of a given surface of sample 100 with respect to a given plane in the coordinate system of the microscope. In some preferred embodiments, the given surface of sample 100 may be the top surface 101, and the given plane may be the scanning plane of the microscope. The scanning plane can be understood as the plane along which the scanning means 120 is focused by the microscope during each scanning operation. Alternatively, or in addition, the given surface may be the top surface 101, and the given plane may be the horizontal plane XZ. These embodiments have the advantage that the top surface 101 is used as the reference plane of sample 100. This is particularly advantageous because sample 100 is generally positioned within the microscope so that the top surface 101 can be measured. However, the present invention is not limited thereto, and it will be understood that any of the sides 104, 105, or other surfaces such as the bottom surface 106 may be used as the reference plane in the sample.

[0065] Therefore, the measurement step S210 makes it possible to generally measure the inclination 131, 132, i.e., misalignment, of a predetermined surface of the sample 100 with respect to a predetermined plane. Various methods for measuring such inclination are known to those skilled in the art. Two particularly advantageous possible embodiments are described below with reference to Figures 2B, 2C, and 6. For the sake of clarity of the examples and descriptions, the description will be made in terms of inclination measurement based on the top surface 101, but those skilled in the art will understand that similar embodiments can be obtained for any other surface of the sample 100.

[0066] As shown in Figure 2C, the measurement step S210 can be performed by focusing a beam, such as the beam of the scanning means 120, onto the sample 100 and measuring each focusing position or focal length, such as the focusing height when the top surface 100 is used as the measuring surface. If a slope exists, the beam will be focused at different points along the vertical Y direction at corresponding different locations XZ across the sample 100, as indicated by beams 120A and 120B. In some embodiments, the absolute value of the focusing height can be measured to calculate the slope. Alternatively, or in addition, in some embodiments, the slope can be derived by the difference between at least two focusing points, such as indicated by ΔH. This latter method has the advantage that the focusing height does not need to be calibrated to an exact given zero value, as any value chosen as zero is compensated for when calculating the height difference between various points.

[0067] In some preferred embodiments, the beam used for focusing and measurement can be the same scanning beam 120 that is also used in the subsequent scanning step S230. This has the advantage that a single instrument within the microscope can be used for both the calculation in the measurement step S210 and the execution of the scanning step S230.

[0068] In some preferred embodiments, as shown in Figure 2B, the focal point, i.e., the point where the focused beam is focused, can be directed toward a focusing marker 240. The focusing marker 240 is generally a structure having shape and / or other physical properties such as material, surface reflectivity, surface roughness, etc., which enable or enhance the automated focusing procedure. Thus, by using one or more focusing markers 240, it is advantageously possible to provide a more accurate and / or faster reading of the sample at the corresponding location. Furthermore, by positioning the markers 240 at a given location, as will be described in more detail below with reference to Figure 5, a given location can be placed in a given coordinate system. Knowledge of those coordinates can advantageously be used to determine the subsequent inclination. Precise positioning can be achieved by automatically focusing the beam 120 onto each marker whose position is precisely known, thereby avoiding the need for precise measurement of the lateral position of the beam 120 along the XZ plane.

[0069] The above description is given with respect to a light beam 120 used to determine the height of various sample points and, therefore, the tilt of the sample 100, but it will be apparent to those skilled in the art that the present invention is not limited thereto. The above description is particularly advantageous for microscopes that utilize the beam 120 as a scanning means, such as scanning electron microscopes (SEMs), helium ion microscopes (HIMs), or generally charged particle microscopes. However, the present invention is not limited thereto, and the tilt of the sample can be obtained, for example, by measuring the height of the sample 100 through contact with the tip of an atomic force microscope (AFM) instead of focusing the beam 120.

[0070] Alternatively, or in addition, in some embodiments, the measurement step S210 can be performed by reflecting the beam 651 onto the sample 100. For example, as shown in Figure 6, a beam emitter 650 can emit the measurement beam 651 toward the sample 100. For example, a surface of the sample, such as the top surface 101, can reflect the measurement beam 651 toward a detector 660. The detector 660 can be, for example, a multi-quadrant position sensor such as a four-quadrant position sensor, or more generally, any detector that allows determining the incoming direction and / or position of the reflected measurement beam 651.

[0071] As will become clear, by appropriately controlling the beam emitter 650 and the detector 660, the heights of various points along the upper surface 101 can be measured in this way. Alternatively, or in addition, the orientation of the upper surface 101 can be advantageously measured by the beam emitter 650 and the detector 660, and therefore, as a result, the inclination can be determined directly.

[0072] Thus, various methods for performing the measurement step S210 are described, which enable the identification of the inclination of the sample with respect to a predetermined orientation.

[0073] The method 200 may then further include step S220 of correcting the orientation of the sample 100 based on the measured tilt. In particular, the sample may be placed on a support whose orientation can be controlled to compensate for the measured tilt.

[0074] In some embodiments using the structure shown in Figure 6, the measurement beam 651 may include a laser or focused or collimated LED beam having a predetermined wavelength. In particular, the wavelength can be set as a function of the pitch of channels 102A to 102N. More specifically, the wavelength can be at least 0.2 μm, preferably at least 0.5 μm, greater than the channel pitch, which can be, for example, less than 0.1 μm. In some embodiments, the measurement beam may have a diameter larger than the channel pitch, preferably at least 5 times larger, and even more preferably at least 10 times larger. By using a beam with a wavelength larger than the channel pitch, the beam will no longer sample the fine structure but will detect the surface as a kind of effective refractive index. The main signal is specular reflection directed towards the detector 660. When using a multi-quadrant detector 660, the sample can be tilted until all quadrants measure reflected light of substantially the same intensity. This ensures that the surface from which the beam is reflected is oriented in a predetermined direction with respect to a known coordinate system associated with the emitter 650 and / or detector 660.

[0075] While the above provides a specific description of how to configure the optical signal so that the reflected light collides with two or more quadrants at that point, it is clear to those skilled in the art that several alternative forms can be implemented, in particular, depending on the configuration of the sample 100. Generally, it is sufficient to configure the emitters 650 and / or 660 so that when the reflective surface of the sample is positioned in a predetermined orientation, the light beam reflected from the sample 100 can cover two or more quadrants, preferably at least three, and more preferably at least four, of the multi-quadrant detector 660. More generally, it is sufficient to configure the emitters 650 and / or detector 660 so that the light beam reflected from the sample 100 can be detected by the detector 660, so that the detector 660 can determine the orientation of the sample 100 from the detected signal.

[0076] This predetermined orientation of the reflective surface can be calibrated against a known reference orientation, such as a horizontal plane or the focusing plane of a microscope, before or after the measurement step S210. It is therefore clear that the predetermined orientation can then be used to calculate the inclination relative to any reference orientation. Alternatively, or in addition, if the radiator 650 and detector 660 are configured such that the predetermined orientation corresponds to the position of a sample without inclination relative to the selected predetermined orientation, this allows both the measurement and correction of the inclination to be performed in a single step, and thus both steps S210 and S230 can be carried out.

[0077] For example, the emitter 650 and detector 660 can be calibrated so as to ensure that the upper surface of the sample is positioned parallel to a predetermined plane when multiple quadrants on the detector 660 receive substantially equal amounts of light per quadrant. For example, by using a predetermined plane or a plane parallel thereto as the scanning plane, the scanning means 120 can also be calibrated to the same predetermined plane, so it is not necessary to know the exact orientation of the predetermined plane. Therefore, by using the predetermined plane as a common reference between the coordinate system of the emitter 650 and detector 660 combination and the scanning means, the sample can be positioned so as to ensure that its orientation is not tilted for the operation of the scanning means 120.

[0078] In this way, we have explained how the sample can be positioned without any inclination relative to a predetermined plane. This makes it possible to correctly position the sample 100 relative to the predetermined plane for subsequent scanning steps, even if dust 130 is present or if there are any other unexpected causes of inclination of the sample 100 in general.

[0079] Therefore, method 200 may further include a step S230 of scanning the sample 100. The scanning step can be carried out using any known technique, such as a scanning means 120 utilizing a SEM, a helium ion microscope (HIM), or generally a charged particle microscope (AFM). By positioning the sample 100 without inclination relative to a predetermined plane, and by using the predetermined plane as a reference for the scanning step S230, it is possible to correctly reconstruct the vertical position of vertical structures in the sample 100, such as channels 102A to 102N.

[0080] In some embodiments, as shown in Figure 3, for example, Method 200 can be modified to include an additional step S340 for checking the inclination value. In particular, after measuring the inclination in step S210, step S340 can check whether the inclination value of the sample falls within a predetermined interval, such as an acceptable inclination range. If the determination is that the inclination of the sample falls within a predetermined acceptable range, Method 300 can proceed to scanning step S230.

[0081] On the other hand, if the determination is that the tilt of the sample is outside a predetermined acceptable range, the method can proceed to step S220, which corrects the position of the sample based on the measured tilt. In some embodiments, after the correction step S220, the method 300 can then proceed to the scanning step S230. Alternatively, after the correction step S220, the method 300 can return to the measurement step S210. Thus, this latter method can ensure that the measurement and correction steps are repeated until the measured tilt falls within the acceptable range. This provides the additional advantage that possible errors during the repositioning of the sample in the correction step S220 can be compensated for. This may be the case, for example, if the device used to reposition the sample in the correction step S220 is not functioning properly or is out of specification. Alternatively, or in addition, the sample 100 may move slightly during repositioning, or dust 130 may do so, and thus the tilt may change in an unexpected manner.

[0082] This embodiment is also particularly advantageous when the measurement step S210 is not configured to output an exact numerical value of the slope, but only an index. For example, referring to Figure 2C, the measurement step may indicate that the point corresponding to beam 120A is higher than the point corresponding to beam 120B, without indicating exactly how much the difference is, but only indicating that the difference is outside the acceptable range. This can then be corrected by gradually raising the right portion of the sample 100 until the measured slope falls within the acceptable range, and then measuring the slope again.

[0083] In the above description, it is assumed that the tilt can be corrected before performing the scanning step S230. In an alternative embodiment, such as the one illustrated by method 400 in Figure 4, the tilt can be measured in step S210 as described above. However, instead of repositioning the sample to correct the tilt, method 400 can proceed to scanning step S230, which scans the sample with its tilt downward.

[0084] In these embodiments, the tilt value can then be used in step S450 to correct the volume reconstruction based on the image obtained from scanning step S230. That is, instead of correcting the position of the sample, the volume reconstruction, or reconstruction of the model of the sample, based on images obtained from multiple scans, can be corrected to compensate for the measured tilt. It will be apparent to those skilled in the art that various image transformations and / or geometric scans of image and / or image synthesis can be performed to compensate for the measured tilt. These embodiments have the advantage that repositioning of the sample is not required to correct the tilt.

[0085] Alternatively, referring to Method 200, instead of correcting the orientation of the sample based on the inclination in step S220, the scanning surface and / or the etched or milled surface can be corrected based on the inclination.

[0086] In particular, the scanning plane can be corrected to compensate for the inclination. For example, the scanning plane can be set to be parallel to a plane defined by the inclination. In a particular embodiment, the scanning plane can be set to be parallel to an inclined top surface 101. Alternatively, the scanning plane does not necessarily have to be parallel to the top surface 101, but can be oblique to the top surface 101, or set to be parallel to a plane along which the top surface 101 is milled. The scanning plane can be understood as the plane along which the microscope scans the sample 100. For example, in the case of an optical microscope, the scanning plane can be the plane corresponding to the focal position of the microscope when the sample is scanned. Alternatively, or in addition, in the case of an atomic force microscope, the scanning plane can be the plane corresponding to the zero reference position of the measuring tip.

[0087] In some embodiments, the sample can be milled along a plane calculated based on the inclination, either as an alternative to or in addition to the correction of the scanning surface based on the inclination. For example, the milled surface can be set to be parallel to the plane defined by the inclination. In certain embodiments, the milled surface can be corrected to compensate for the inclination. More specifically, in some embodiments, the milled surface can be set to be parallel to the inclined top surface 101, but the present invention is not limited to this configuration, and the milled surface can instead be oblique to the inclined top surface 101. The milled surface can then be understood as a plane along which at least a portion of the top surface of the sample 100 is etched for the purpose of scanning the sample at different depths, as discussed with reference to Figure 1C.

[0088] Therefore, various possible embodiments can be performed to obtain a reconstructed model of the sample from multiple scans based on the measured tilt of the sample, thereby compensating for the tilt by repositioning the sample and correcting the scanning plane or model reconstruction. In some cases, two or more of these techniques can be performed together, partially using the first technique and partially using the second technique, or using more techniques to compensate for the tilt.

[0089] Therefore, the present invention can provide reliable imaging of the development of vertical structures such as channels 102A-102N along the vertical direction Y of sample 100. For example, as shown in Figure 10, method 1000 may differ from method 200 due to the presence of a further step S1060 for measuring the vertical structures 102A-102N in sample 100. It is also apparent that step S1060, shown in Figure 10 as being performed in relation to method 200, may also be performed in relation to method 300, or more generally, in relation to any other method described throughout this application.

[0090] Whether by correcting the position, focusing, and / or milled surface, image, or image reconstruction of the sample 100, the problems discussed in the prior art can be avoided by performing step S1060 based on the inclination after the inclination has been corrected.

[0091] Figure 5 shows a further method 500 based on a different method 200, resulting from the implementation of step S560, which realizes one or more focusing markers 240 as described above. By enabling the focusing markers 240 to be implemented before the measurement step S210, it is possible to implement focusing markers having properties that enable more efficient automatic focusing of the beam 120 or desired reflection of the beam 651. In this case as well, although method 500 is described as being based on method 200 for the sake of ease of explanation, it will be apparent that step S560 can be combined with any other method described throughout this application.

[0092] In the above description, the measurement step S210 is described based on various technical embodiments, without specifically limiting the number of points of the sample 100 to be measured.

[0093] In some embodiments, the measurement step S210 can be carried out by measuring at least three points on the sample 100. In some embodiments, the method may further include the step of fitting the measurement points to a plane that identifies inclinations 131, 132. This makes it possible to determine a plane defined by the inclinations that passes through at least three points.

[0094] Furthermore, as shown in Figure 7, the measurement step S710 may include a step S711 of measuring a predetermined number of points on the sample 100 and a step S712 of fitting the measurement points to a plane. In a preferred embodiment, the fitting step S712 may include fitting the measurement points to a plane that identifies the inclination, i.e., calculating the plane that best fits the measurement points, based on any known fitting algorithm. This method allows for the correct measurement of the inclined surface defined by the fitting, even if some measurements are incorrect.

[0095] In general, increasing the predetermined number of points increases the accuracy of the measurement step S711. When measuring the Y coordinates of N points subject to a stochastic error ΔY, the error Δtlit of the fitted slope from two points decreases approximately as a function of Δtilt / sqrt(N). Therefore, in some embodiments, a predetermined number of points N can be selected such that a desired error level is satisfied. In practical embodiments, the multiple points N may include an array of points that are preferably not collinear and more preferably extend into a plane of the maximum enclosing circle diameter. In some embodiments, the array may include at least 3 × 3 points.

[0096] In some embodiments, the result of fitting step S712 can also provide an index of the error of the measurement point relative to the plane being fitted. For example, the error can be the average distance of the point from the plane being fitted, but it will be clear that the index of error can be calculated in various ways. If the error is found to be higher than a predetermined number, it can be concluded that the surface being measured is not sufficiently flat. This index can advantageously be used as a warning that the sample is unsuitable for measurement or that a measurement problem exists.

[0097] Furthermore, as shown in Figure 8, step S810 may further include step S813, which removes one or more of a plurality of measurement points based on a predetermined threshold. This allows points outside a predetermined range to be excluded from the fit. This can be referred to as outlier filtering, and various algorithms are known for its implementation. Such techniques may be particularly useful in allowing the removal of points that are due to measurement errors and therefore differ by a large amount from the remaining points. It will be apparent that a number of statistical methods can be employed to determine which points should be removed. For example, the standard deviation of the measurement points from the fitting plane can be calculated, and points that are more than a predetermined multiple of the standard deviation away from such a plane can be removed. As an alternative, the Random Sample Consensus (RANSAC) algorithm can be used to implement step S813. Method 800 can then proceed by step S712, which fits the measurement points excluding the removed points.

[0098] In the above description, the scanning step S230 is described as being based on various technical embodiments, such as through SEM, HIM, or AFM. As shown in Figure 9, in some embodiments, the scanning step S930 may include a step S931 to remove at least a portion of the top surface 101 of the sample 100, and a step S932 to scan the sample 100 through, for example, SEM, HIM, or AFM measurement. The removal, etching, or milling step can be performed by any known etching or milling equipment such that the removed, etched, or milled surface can be parallel to the top surface as shown, or at an angle, as shown, for example, as shown in Figure 1C, resulting in the removal of at least a portion of the top surface. By repeating steps S931 and S932, the scanning step S930 makes it possible to evaluate the vertical unfolding of the structure throughout the depth or vertical direction of the sample 100.

[0099] In a preferred embodiment, the surface removal performed in step S931, as shown in Figure 1C, for example, can be limited to an area forming less than 50% of the upper surface 101 of the sample. This has the advantage that a flat surface remains around the etched area, sufficient for subsequent and / or periodic checks of the sample's inclination.

[0100] Therefore, in some embodiments, any of the methods described for correcting the tilt can be combined with method 900. More specifically, a method for correcting the tilt may be performed at each predetermined number of cycles of steps S931 and S932.

[0101] Although the present invention has been described as a method, it will be clear that embodiments of the present invention can also be carried out in other forms.

[0102] In particular, as shown in Figure 11, the microscope 1100 may include a processor 1170 and a memory 1171. The memory 1171 can store instructions configured to cause the processor 1170 to control the microscope 1100 to perform any step of any of the methods described above. In some embodiments, the microscope may further include any of the scanning means 120, emitter 650, and detector 660, as shown.

[0103] Furthermore, the present invention can be embodied by a computer program that includes instructions configured to cause the processor, when executed by a processor such as a processor 1170, to control a microscope, such as a microscope 1100, to perform the method 200, 400, 400, 500 according to any one of claims 1 to 16.

[0104] Thus, we have described how a microscope and / or a method for controlling the microscope can be used to facilitate the reconstruction of a sample model based on multiple scanning images obtained along the depth of the sample. The embodiments described enable the elimination of tilt in sample positioning, in particular, to result in a reliable scanning workflow.

[0105] Although the present invention has been illustrated and described in relation to certain preferred embodiments, equivalents and modifications will be conceivable to those skilled in the art upon reading and understanding this specification. The present invention includes all such equivalents and modifications and is limited only by the scope of the appended claims. [Explanation of Symbols]

[0106] 100 samples 101 Top surface 102A~102N Channels 103 angle 104, 105 Side view 106 Bottom 107A, 107N horizontal layer 110 Etching means 120 Scanning means 130 Dust and Debris 131 angle 132 Slope Method for measuring 200 samples S210 Measuring the incline S220 Correct the sample S230 Scan the sample 240 Focusing Markers Method for measuring 300 samples Check the slope value of S340. Method for measuring 400 samples Correcting S450 volume reconstruction 650 Beam emitter 651 Beam 660 detectors S710 for measuring incline Measure point S711 S712 Compatible S810 for measuring incline S811 Point Measurement S813 Outlier Filtering S930 Scan the sample S931 Remove a portion of the top surface S932 Scan the sample 1100 Microscope 1170 Processor 1171 memory Method for measuring 1000 samples S1060 Measuring Vertical Structures

Claims

1. A method (200, 300, 500, 1000) for measuring a sample (100) using a microscope, The steps include measuring the inclination (131, 132) of the sample (100) (S210, S710, S810), Step (S220) of correcting the orientation of the sample (100) based on the inclination (131, 132), The steps include scanning the sample (S230, S930), The steps include: after the correction, measuring the vertical structure (102A to 102N) in the sample (100) (S1060); Based on the aforementioned inclination (131, 132), the step (S450) corrects the volume reconstruction from the scanning images (S230, S930) and Methods including (200, 300, 500, 1000).

2. The method according to claim 1 (300), further comprising the step (S340) of checking whether the inclines (131, 132) fall within a predetermined interval.

3. A method (400, 500, 1000) for measuring a sample (100) using a microscope, The steps include measuring the inclination (131, 132) of the sample (100) (S210, S710, S810), The steps include scanning the sample (S230, S930), Based on the aforementioned inclination (131, 132), the step (S450) corrects the volume reconstruction from the scanning images (S230, S930) and Methods including (400, 500, 1000).

4. A method (200, 300, 500, 1000) for measuring a sample (100) using a microscope, The steps include measuring the inclination (131, 132) of the sample (100) (S210, S710, S810), The steps include correcting the scanning plane based on the aforementioned inclination (131, 132), The steps include scanning the sample (S230, S930), The steps include: after the correction, measuring the vertical structure (102A to 102N) in the sample (100) (S1060); Based on the aforementioned inclination (131, 132), the step (S450) corrects the volume reconstruction from the scanning images (S230, S930) and Methods including (200, 300, 500, 1000).

5. The method according to claim 1 or 2 (200, 300, 400, 500), wherein the inclination (131, 132) includes an angle formed by a predetermined surface and a predetermined plane of the sample (100), the predetermined surface being any of the top surface (101), horizontal layers (107A to 107N), side surfaces (104, 105), and bottom surface (106), and the predetermined plane being the scanning plane of the microscope.

6. The method according to claim 1 or 2 (200, 300, 400, 500, 1000), wherein the inclination (131, 132) includes an angle formed by a predetermined surface and a predetermined plane of the sample (100), the predetermined surface being any of the top surface (101), horizontal layers (107A to 107N), side surfaces (104, 105), and bottom surface (106), and the predetermined plane being a horizontal plane (XZ).

7. The method according to claim 1 or 2 (200, 300, 400, 500, 1000), wherein the measurement step (S210, S710, S810) is performed by focusing the beam onto the sample (100) and measuring the resulting focal length.

8. The method according to claim 7 (200, 300, 400, 500, 1000), wherein the beam is a scanning beam (120) also used in the scanning steps (S230, S930).

9. The method according to claim 7 (200, 300, 400, 500, 1000), wherein the focus is directed toward a focusing marker (240).

10. The method according to claim 7 (500), further comprising the step (S560) of realizing one or more focusing markers (240).

11. The method according to claim 1 or 2 (200, 300, 400, 500, 1000), wherein the measurement steps (S210, S710, S810) are performed by reflecting the beam (651) over the sample (100).

12. The method according to claim 1 or 2 (200, 300, 400, 500, 1000), wherein the measurement step (S210, S710, S810) includes measuring at least three points of the sample (100).

13. The method according to claim 12 (200, 300, 400, 500, 1000), further comprising the step (S712) of fitting the measured points to a plane that identifies the inclination (131, 132).

14. The measurement step (S710) is, Step (S711) of measuring a predetermined number of points on the sample (100), Step (S712) to fit the measured point to a plane. The method according to claim 1 or 2, including (200, 300, 400, 500, 1000).

15. The measurement step (S810) is, Step (S711) of measuring multiple points on the sample (100), Step (S812): Remove one or more of the measured points based on a predetermined threshold. Step (S712): To fit the measured points to a plane, excluding the removed points. The method according to claim 1 or 2, including (200, 300, 400, 500, 1000).

16. The scanning step (S930) is, The step (S931) of removing at least a portion of the upper surface (101) of the sample (100), The step of scanning the sample (100) (S932) The method according to claim 1 or 2, including (200, 300, 400, 500, 1000).

17. The method according to claim 1 or 2 (200, 300, 400, 500, 1000), wherein the sample (100) is a semiconductor wafer or a part of the semiconductor wafer.

18. A microscope (1100), Processor (1170), Memory (1171) and Equipped with, The microscope (1100) has a memory (1171) that stores instructions configured to cause the processor (1170) to control the microscope (1100) to perform the method according to claim 1 or 2 (200, 300, 400, 400, 500, 1000).

19. A computer program comprising instructions, when executed by a processor (1170), configured to cause the processor (1170) to control a microscope (1100) to perform the method according to claim 1 or 2 (200, 400, 400, 500).

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