Multi-head AFM for defect inspection and review

Abstract

A method for inspecting and reviewing defects in a substrate using a scanning probe microscope comprising a plurality of scanning heads and a substrate carrier, wherein each of the plurality of scanning heads comprises a probe including a probe tip positioned for scanning the substrate surface, the method comprising: - providing a substrate on a substrate carrier, wherein the substrate carrier is positioned to position the substrate for at least one of the plurality of scanning heads; - scanning the substrate surface in a first scanning mode using at least one first scanning head of the plurality of scanning heads; - scanning the substrate surface in a second scanning mode using at least one second scanning head of the plurality of scanning heads, wherein at least one first scanning head and at least one second scanning head are different scanning heads of the plurality of scanning heads, the method for inspecting and reviewing defects, wherein the first scanning mode has a lower scanning resolution than the second scanning mode.

Description

Technical Field

[0001] The present invention relates to a method for inspecting and reviewing defects, and a scanning probe microscope for inspecting and reviewing defects.

Background Art

[0002] Scanning probe microscopy is a popular class of microscopy based on scanning a surface with a probe tip that contacts the surface continuously or periodically, i.e., intermittently. This method enables the detection and mapping of surface features on and below the surface of a sample, such as grooves, depressions, edges, roughness, etc., with high precision and high resolution. Subsurface measurements are performed using ultrasound in combination with scanning the surface using a probe. High resolution enables the detection of even nanometer-sized structures, and as a result, high resolution is very popular as a tool in, for example, the production of semiconductor devices. However, scanning probe microscopes are also used in many other applications, such as imaging and analyzing soft tissue or biological samples.

[0003] Atomic force microscopy is a type of scanning probe microscopy that uses a sharp tip attached to a cantilever to scan the surface of a sample and measures the force between the tip and the surface atoms of the sample. The movement of the cantilever is monitored and used to generate high-resolution images of surface and subsurface features and the topography of the sample with a resolution of about a few nanometers. Atomic force microscopes can be used in various environments including vacuum, air, and liquid, and can provide information on a wide range of sample characteristics including mechanical, electrical, and magnetic properties.

[0004] Generally, to reduce scanning time, only predetermined sections of the sample are scanned. These predetermined sections may be selected for various reasons, such as a relatively higher risk of manufacturing defects compared to other sections. A section is scanned by first inspecting and then reviewing it. During inspection, images and data generated by the atomic force microscope are analyzed to identify features and patterns on the sample surface and to determine the characteristics of the sample. In this process, the results are evaluated to ensure that the data is accurate, consistent, and reliable. For example, this may involve verifying that the atomic force microscopy measurements were performed correctly. Verification is important to ensure the validity of the results of atomic force microscopy and to provide reliability for the information obtained from the measurements.

[0005] A drawback of atomic microscopy is its relatively low scanning speed compared to other imaging techniques. Scanning speed depends on several factors, such as the size of the scanning area, the required resolution, and the cantilever oscillation frequency. For example, a large scanning area with high resolution may take several hours to scan, while a small area with low resolution can be scanned in minutes. While recent developments have aimed to improve scanning speed, such as parallel imaging techniques that use multiple cantilevers to scan a sample simultaneously, the scanning speed is still considered relatively slow. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention aims to offset the above-mentioned drawbacks while preferably retaining the advantages. More specifically, the present invention aims to reduce the overall scanning time required to scan a sample before it can be determined whether or not the sample has any defects.

[0007] Accordingly, the present invention provides a method for inspecting and reviewing defects using a scanning probe microscope comprising a plurality of scanning heads and a substrate carrier, in particular the method according to claim 1. Each of the plurality of scanning heads comprises a probe including a probe tip positioned for scanning the substrate surface. The method is as follows: - To provide a substrate on a substrate carrier, wherein the substrate carrier is arranged to position the substrate with respect to at least one of a plurality of scanning heads. - Scanning the substrate surface in a first scanning mode using at least one first scanning head among multiple scanning heads. - Scanning the substrate surface in a second scanning mode using at least one second scanning head among a plurality of scanning heads, wherein at least one first scanning head and at least one second scanning head are different scanning heads among the plurality of scanning heads. The first scanning mode has a lower scanning resolution than the second scanning mode.

[0008] A scanning probe microscope can be an atomic force microscope, and the substrate or sample can include a wide range of products, such as polymers, nanoparticles such as nanotubes, biological samples, and semiconductors in particular. For example, silicon wafers and semiconductors such as GaAs can be analyzed using a scanning probe microscope to detect defects. The substrate is provided on a substrate carrier, which is capable of moving the substrate relative to a plurality of scanning heads, such as a movable stage, a piezoelectric stage, or an electromagnetic stage. Preferably, the movement provided by the substrate carrier is arranged to provide precise movement, for example, on a nanometer scale.

[0009] To facilitate the first and second scanning modes, multiple scanning heads are provided, i.e., each scanning mode may have a dedicated scanning head. Additionally or alternatively, the multiple scanning heads are preferably arranged to switch between the first and second operating modes when not scanning, thereby allowing the use of multiple scanning heads in both modes to facilitate configuration flexibility, which can speed up the inspection and review of defects in the substrate.

[0010] To further facilitate the speed at which substrates can be inspected and defects reviewed, the first scanning mode scans at a lower scanning resolution than the second scanning mode. In the context of this invention, resolution should be understood as a measure of the scanning probe microscope's ability to distinguish different features, more specifically defects, on the surface of the substrate. Additionally, resolution should also be understood to include lateral resolution, i.e., resolution in a plane parallel to the surface of the substrate, commonly referred to as the XY plane, and vertical resolution, i.e., resolution in a direction perpendicular to the plane of the substrate, commonly referred to as the Z direction. The resolution of a scanning probe microscope can be influenced by the shape and size of the probe tip, the stiffness of the cantilever provided to the scanning head positioned to hold the probe tip, and the precision of the control system used to move the probe tip toward or away from the substrate surface. In an example where a scanning probe microscope is used to scan the surface of a substrate in the scanning direction, and the scanning direction is a line in a plane parallel to the surface of the substrate, the measure of resolution may be the amount of lines scanned by the scanning probe microscope in a plane parallel to the surface of the substrate in a direction perpendicular to the scanning direction. Reducing the number of scan lines perpendicular to the scanning direction in the first scanning mode relative to the number of scan lines perpendicular to the scanning direction in the second scanning mode on the same surface results in a lower scanning resolution.

[0011] Advantageously, scanning at a lower scanning resolution can speed up the overall scanning process. In particular, the first scanning mode may be used to inspect the substrate surface, while the second scanning mode may be used to review any defects that may have been found by the first scanning mode. Thus, the relatively high speed of the first scanning mode compared to the second scanning mode may be used to identify potential defects, while the slower but more accurate second scanning mode may be used to verify whether a potential defect is actually a defect, and additionally, to clarify the type of defect. Using two different scanning modes, a fast scanning mode with low resolution and a slow scanning mode with high resolution can be used to complement each other and mitigate each other's shortcomings, thereby increasing the overall speed of the scanning probe microscope while maintaining its accuracy.

[0012] In the first scanning mode, at least one first scanning head can move relative to the scanning probe microscope while the substrate remains stationary relative to the scanning probe microscope. Because the first scanning mode scans at a lower resolution, the first scanning head can traverse a relatively larger distance while measuring compared to the second scanning mode. To facilitate the relatively larger distance and higher speed, it may be advantageous to activate the first scanning head and use a substrate carrier to keep the substrate stationary relative to the surroundings.

[0013] In the second scanning mode, at least one second scanning head can remain stationary relative to the surroundings while the substrate moves relative to the surroundings. To further enhance the relatively high accuracy of the measurements performed by the second scanning head in the second scanning mode, the scanning head can remain stationary while the substrate carrier moves the substrate relative to the second scanning head. Advantageously, the substrate carrier is positioned to perform precise and relatively small movements compared to the movements performed by the scanning head in the first scanning mode. Alternatively, in the second scanning mode, the probe of at least one second scanning head can move relative to the surroundings of the scanning probe microscope while both the substrate and at least one second scanning head remain stationary relative to the surroundings. Even more precise and smaller movements, further increasing scanning resolution, can be achieved simply by moving the probe tip of the second scanning head.

[0014] In a further advantageous embodiment, scanning in the first scanning mode and scanning in the second scanning mode can be performed simultaneously. This may allow the first scanning head to rapidly scan a relatively large area, while the second scanning head is used to verify the results of the first scanning head. Preferably, multiple scanning heads are distributed to the first and second scanning heads in such a manner that the first and second scanning heads complete inspection and review of substrate defects substantially almost simultaneously, thereby reducing the time spent scanning.

[0015] The probe tip of at least one first scan head of a plurality of scan heads may be of a first tip type, and the probe tip of at least one second scan head of a plurality of scan heads may be of a second tip type, the second tip type may be sharper compared to the first tip type. The relatively sharp tip type can be used, for example, in a second scanning mode for measurements that require relatively high resolution. The sharp tip type may provide more accurate measurements but is also more susceptible to defects or breakage. In particular to increase the reliability of the first scan head, a relatively blunt tip type can be used on the first scan head. Relatively low resolution may not be considered so difficult in the first scanning mode because this scanning mode operates at a relatively lower resolution compared to the second scanning mode, so that the relatively blunt tip does not limit the scanning resolution.

[0016] In the first scanning mode, the substrate surface can be scanned parallel to a first direction in a plane parallel to the substrate surface. In the second scanning mode, the substrate surface can be scanned parallel to a second direction in a plane parallel to the substrate surface, and the first direction may be perpendicular to the second direction. In certain advantageous embodiments, the first scanning mode can be used to scan in a first direction, preferably parallel to the deposited material on the substrate. The resolution of the first scanning mode can be further reduced without significantly reducing the likelihood of missing defects during the inspection stage, by ensuring that the relatively low resolution of the first scanning mode follows the deposited material on the substrate. When reviewing potential defects in the second stage, a second scanning mode can be used, having a scanning direction perpendicular to the deposited material on the substrate and a scanning direction of the first scanning head, which increases accuracy.

[0017] Furthermore, the present invention provides a scanning probe microscope for inspecting and reviewing defects in a substrate, comprising a plurality of scanning heads, each scanning head comprising a probe including a probe tip positioned for scanning the substrate surface. The scanning probe microscope further provides a substrate carrier positioned to position the substrate for at least one of the plurality of scanning heads. The plurality of scanning heads includes at least one first scanning head. The probe tip of the first scanning head is of a first tip type. The plurality of scanning heads includes at least one second scanning head. The probe tip of the first scanning head is of a second tip type. The probe tip of the second tip type is sharper than the probe tip of the first tip type. The scanning probe microscope is configured to scan the substrate surface using at least one first scanning head and at least one second scanning head simultaneously during use.

[0018] The first scanning head can be positioned to scan the substrate surface in a plane parallel to the substrate carrier surface and parallel to a first direction. The second scanning head can be positioned to scan the substrate surface in a plane parallel to the substrate carrier surface and parallel to a second direction. The first direction may be perpendicular to the second direction.

[0019] The scanning probe microscope may further include a moving means for moving at least one first scanning head relative to the scanning probe microscope while keeping the substrate carrier stationary relative to the scanning probe microscope in a first scanning mode.

[0020] In addition, the scanning probe microscope may further include a moving means for moving a substrate carrier relative to the scanning probe microscope while keeping at least one second scanning head stationary relative to the scanning probe microscope in a second scanning mode.

[0021] At least one second scanning head further comprises moving means for moving the probe tip relative to the periphery of the scanning probe microscope while keeping the substrate carrier stationary relative to the periphery of the scanning probe microscope in a second scanning mode.

[0022] In addition, the present invention provides a computer program product including instructions that enable a controller of the scanning probe microscope to execute the above-described method when loaded into the memory of the scanning probe microscope.

[0023] Further advantageous aspects of the present invention are described in the present specification and the appended claims.

[0024] The technical features described in the above paragraphs and sentences can be separated from the context, and the technical features separated from different paragraphs and sentences can be combined. Thereby, such combinations are specifically disclosed herein.

[0025] The present invention is further clarified based on the exemplary embodiments shown in the drawings. The exemplary embodiments are given by way of non-limiting illustration of the present invention.

Brief Description of the Drawings

[0026] [Figure 1] A schematic side view of a scanning probe microscope according to an embodiment of the invention is shown. [Figure 2] A schematic top view of a substrate scanned according to an embodiment of the present invention is shown. [Figure 3A] A schematic side view of a second scanning head is shown. [Figure 3B] A schematic side view of a first scanning head is shown. [Figure 3C] A schematic side view of a substrate being scanned by the scanning heads of FIGS. 3A and 3B is shown. [Figure 4] A flowchart of a method for detecting and reviewing defects in a substrate is depicted.

Mode for Carrying Out the Invention

[0027] Please note that the diagram is merely a general representation given as a non-limiting example. In the diagram, the same or corresponding parts are indicated by the same reference number.

[0028] Referring to Figure 1, a scanning probe microscope 1, preferably the scanning probe microscope described in claim 1, is depicted. The scanning probe microscope 1 comprises a plurality of scanning heads 2. In the example shown, two scanning heads 2 are presented, but it will be understood by those skilled in the art that any number of scanning heads 2 can be used. Each scanning head 2 comprises a probe 3 including a probe tip 4 positioned to scan the surface 5 of a substrate 6. The scanning probe microscope 1 further comprises a substrate carrier 7 positioned to support and position the substrate 6 with respect to at least one of the plurality of scanning heads 2. In the embodiment shown, the substrate carrier 7 is an XY stage positioned to move the substrate 6 in a plane parallel to the surface 5.

[0029] Each of the multiple scanning heads 2 comprises at least one first scanning head 8, the probe tip 4 of the first tip type 4A. Each of the multiple scanning heads 2 further comprises at least one second type scanning head 9, the probe tip 4 of the second scanning head 9 of the second tip type 4B. The probe tip of the second tip type 4B is sharper than the probe tip of the first tip type 4A.

[0030] In a first scanning mode, a moving means 10 is provided to facilitate the movement of the first scanning head 8 relative to the scanning probe microscope 1 while keeping the substrate carrier 7 stationary relative to the scanning probe microscope 1. In the shown embodiment, the moving means 10 is an actuator positioned to move the first scanning head 8 via an arm 16. In a second scanning mode, the scanning probe microscope 1 further includes a moving means 11 for moving the substrate carrier 7 relative to the surroundings while keeping at least one second scanning head 9 stationary relative to the surroundings via an actuator 11. Additionally, at least one second scanning head further includes a moving means 12, which is a piezoelectric element in the illustrated example, for moving the probe tip 4B relative to the surroundings while keeping the substrate carrier 7 stationary relative to the surroundings in a second scanning mode. The scanning probe microscope 1 is configured to scan the surface 5 of a substrate 6 using at least one first scanning head 8 and at least one second scanning head 9 simultaneously during use. In the embodiment shown, this can be achieved by first defining the motion of a second scanning mode, i.e., a low-resolution scanning mode with relatively large movements, provided by acting on at least one second scanning head 9 via the arm 16, while first defining the motion of a second scanning mode, i.e., a high-resolution scanning mode with relatively small movements provided by the XY stage 7 via the actuator 11. The motion of at least one second scanning head 9 accounts for the relatively small movement of the XY stage 7 via the controller 32.

[0031] Referring to Figure 2, a schematic top view of an example of the surface 5 of a substrate 6 is depicted. A series of materials are deposited on the surface 5. As an example, two inspection areas 14 are predetermined to be scanned. A first scanning head 8 is positioned to scan the inspection areas 14 on the substrate surface 5 in a plane P parallel to the substrate surface 5, parallel to a first direction I. When the first scanning head 8 detects an anomaly, i.e., a gap or bridge, the location of such a possible anomaly is called a review area 15. Such a review area 15 can be scanned by a second scanning head 9 to more accurately scan and verify whether a gap or bridge actually exists. It will be obvious to those skilled in the art that the review area 15 is a smaller area compared to the inspection area 14, since the review area 15 includes only the possible defect and the immediate periphery of the possible defect. The review area 15 in Figure 2 is depicted relatively large for illustrative purposes. A second scanning head 9 is positioned to scan the substrate surface 5 in a plane P parallel to the surface 5, parallel to a second direction II. The first direction I is perpendicular to the second direction II.

[0032] The scanning probe microscope 1 further comprises a computer program product that, when loaded into the memory 31 of the scanning probe microscope 1, includes instructions that enable the scanning probe controller 32 to control the moving means 10, 11, and 12. Preferably, the controller 32 operates the moving means 10, 11, and 12 such that the total time spent scanning the substrate is minimized. In the shown embodiment, this means that at least one scanning head 2 operating in a first scanning mode scans most of the surface 5 of the substrate 6, while at least one scanning head 2 operating in a second scanning mode scans for defects that may have been found by the scanning head 2 operating in the first scanning mode. Preferably, the scanning head 2 operating in the second scanning mode and the scanning head 2 operating in the first scanning mode are relatively close to each other and more preferably complete scanning simultaneously. The controller 32 is connected to the various moving means 10, 11, and 12 via information transport cables 33.

[0033] In a particular example, the first direction I is parallel to the deposited line so that the tip 4 of the first scanning head 8 is provided on the deposited line 13 and follows the deposited line 13. In a particular advantageous example, the first scanning head 8 scans only where the deposited line is expected to be deposited, according to the expected pattern of the deposited line. By scanning only by following the expected pattern of the deposited line in the first scanning mode, the amount of scanning time of the first scanning head 8 can be minimized.

[0034] Referring to Figures 3A and 3B, schematic side views of the first scan head 8 and the second scan head 9 are depicted. In the example shown, the difference in tip types between the first scan head 8 and the second scan head 9 is further highlighted. The tip 4B of the second scan head 9 is relatively sharper compared to the tip 4A of the first scan head 8; for example, the end of the tip 4A of the first scan head 8 has a more convex shape. Referring to Figure 3C, which depicts the surface 5 of a substrate on which material 13 is deposited, the effect of the tip types can be seen. The relatively sharp tip 4B can fit into smaller gaps between lines of deposited material 13. The relatively blunt tip 4A of the first scan head 8 has a more robust shape and can therefore move faster across the surface 5 of the substrate. Moving the relatively sharp tip 4B of the second scan head 9 at the same speed may result in tip damage, as the tip may be more fragile and more easily snagged between lines of deposited material 13.

[0035] Figure 4 illustrates a flowchart of an example of a method for inspecting and reviewing defects in a substrate according to the present invention. First, a substrate is provided, and preferably, a predetermined area for scanning is identified. A first scanner head 8 is moved to a position, i.e., the location of the predetermined area that needs to be scanned. The first scanner head 8 scans in a first scanning mode. If no potential defects are found, the first scanner head 8 continues scanning in the first scanning mode until the scanning area is complete, and then the results are saved. If a potential defect is found, a second scanner head 9 can be used in a second scanning mode to verify the results. Optionally, the second scanning mode is delayed, for example, if it is physically impossible for the first scanner head 8 to reach the location of the potential defect while the first scanner head 8 is still scanning nearby. The location of the defect, e.g., the X and Y coordinates on the substrate, is determined, and then the second scanner head moves to that location and begins scanning. Once the area of ​​potential defects has been scanned by the second scanner head 9, the results are saved.

[0036] Many variations will be apparent to those skilled in the art. For example, although only two scanning heads 2 are depicted, it will be obvious to those skilled in the art that any number of scanning heads 2 can be used. In addition, although the shown example has equal amounts of first scanner heads 8 and second scanner heads 9, this is not necessary, and it will be understood that any number of first and second scanner heads can be used in a scanning probe microscope. Furthermore, although the deposited material on the substrate is linear in the shown example, any shape of deposited material can be used. Such variations will be understood to fall within the scope of the invention as defined in the appended claims.

Claims

1. A method for inspecting and reviewing defects in a substrate using a scanning probe microscope equipped with multiple scanning heads and substrate carriers, Each of the plurality of scanning heads is equipped with a probe including a probe tip positioned for scanning the substrate surface, The method described above is - To provide the substrate on the substrate carrier, wherein the substrate carrier is arranged to position the substrate with respect to at least one of the plurality of scanning heads, - Scanning the substrate surface in a first scanning mode using at least one first scanning head among the plurality of scanning heads, - Scanning the substrate surface in a second scanning mode using at least one second scanning head among the plurality of scanning heads, wherein the at least one first scanning head and the at least one second scanning head are different scanning heads among the plurality of scanning heads. - A method for inspecting and reviewing defects, wherein the first scanning mode has a lower scanning resolution than the second scanning mode.

2. A method for inspecting and reviewing defects according to claim 1, wherein in the first scanning mode, the substrate remains stationary relative to the periphery of the scanning probe microscope, while the at least one first scanning head moves relative to the periphery.

3. In the second scanning mode, while the substrate moves relative to the surroundings, the at least one second scanning head remains stationary relative to the surroundings, or A method for inspecting and reviewing defects according to claim 1 or 2, wherein in the second scanning mode, the probe of the at least one second scanning head is moved relative to the surroundings of the scanning probe microscope while both the substrate and the at least one second scanning head remain stationary relative to the surroundings.

4. A method for inspecting and reviewing defects according to any one of the prior claims, wherein scanning in the first scanning mode and scanning in the second scanning mode are performed simultaneously.

5. A method for inspecting and reviewing defects, wherein the probe tip of at least one first scanning head of the plurality of scanning heads is of a first tip type, and the probe tip of at least one second scanning head of the plurality of scanning heads is of a second tip type, wherein the second tip type is sharper than the first tip type.

6. A method for inspecting and reviewing defects, wherein in a first scanning mode, the surface of the substrate is scanned parallel to a first direction in a plane parallel to the surface of the substrate, and in a second scanning mode, the surface of the substrate is scanned parallel to a second direction in a plane parallel to the surface of the substrate, and the first direction is perpendicular to the second direction.

7. A method for inspecting and reviewing defects, wherein a first scanning mode is used to identify a potential defect, and a second scanning mode is used to verify whether the potential defect is a defect.

8. A method for inspecting and reviewing defects, wherein scanning in a first scanning mode includes inspecting the substrate, and scanning in a second scanning mode includes reviewing defects found during the first scanning mode.

9. A scanning probe microscope for inspecting and reviewing defects in a substrate, - A plurality of scanning heads, each scanning head comprising a probe including a probe tip positioned for scanning the surface of a substrate, - A substrate carrier positioned to position the substrate with respect to at least one of the plurality of scanning heads, - The plurality of scanning heads include at least one first scanning head, the probe tip of the first scanning head being of a first tip type, and the plurality of scanning heads include at least one second scanning head, the probe tip of the second scanning head being of a second tip type, - The tip of the second tip type probe is sharper than the tip of the first tip type probe, - A scanning probe microscope, wherein the scanning probe microscope is configured to scan the surface of a substrate by simultaneously using the at least one first scanning head and the at least one second scanning head during use.

10. The scanning probe microscope according to claim 9, wherein the first scanning head is arranged to scan the substrate surface in a plane parallel to the surface of the substrate carrier in a direction parallel to a first direction, and the second scanning head is arranged to scan the substrate surface in a plane parallel to the surface of the substrate carrier in a direction parallel to a second direction, and the first direction is perpendicular to the second direction.

11. The scanning probe microscope according to claim 9 or 10, further comprising a moving means for moving the at least one first scanning head relative to the surroundings while keeping the substrate carrier stationary relative to the surroundings of the scanning probe microscope in a first scanning mode.

12. A scanning probe microscope according to any one or more of claims 9 to 11, further comprising, in a second scanning mode, a moving means for moving the substrate carrier relative to the surroundings while keeping the at least one second scanning head stationary relative to the surroundings of the scanning probe microscope.

13. The scanning probe microscope according to any one or more of claims 9 to 12, wherein the at least one second scanning head further comprises a moving means for moving the probe tip relative to the surroundings while keeping the substrate carrier stationary relative to the surroundings of the scanning probe microscope in the second scanning mode.

14. A computer program product comprising instructions that, when loaded into the memory of a scanning probe microscope according to any one of claims 9 to 13, enable the controller of the scanning probe microscope to perform the method according to any one of claims 1 to 7.

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