Scanning probe microscope error correction

Abstract

A method of imaging a sample with a scanning probe microscope, the scanning probe microscope comprising: a probe comprising a cantilever and a probe tip extending from the cantilever; a lateral scanning system; and a support structure comprising a sample support which supports a sample and a probe support which supports the probe. the method comprises: generating a lateral scanning motion between the probe and the sample with the lateral scanning system so that the probe tip interacts with the sample across a region of the sample; monitoring the probe to obtain sample data from the region of the sample; during the lateral scanning motion, measuring a lateral position of the sample support or the probe support to obtain a lateral error signal, wherein the lateral error signal is obtained by: reflecting a beam from a measurement point to generate a reflection of the beam, and performing an interferometric measurement based on the reflection of the beam, wherein the measurement point is not moved by the lateral scanning system so the lateral error signal does not include the lateral scanning motion; and performing a correction based on the lateral error signal.

Description

[0001] SCANNING PROBE MICROSCOPE ERROR CORRECTION

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method of obtaining sample data with a scanning probe microscope, and a scanning probe microscope configured to perform such a method.

[0004] BACKGROUND OF THE INVENTION

[0005] In US8402560A a scanning probe microscope compensates for relative drift between its upper structure that includes a probe and a scanner that scans the probe in a straight line and a lower structure that includes a sample stage and a scanner that scans the sample stage in a plane. A light beam from the upper structure is initially aligned with a center of a position sensitive photo detector (PSPD) disposed on the lower structure at a predetermined position of the sample stage and any subsequent misalignments of the light beam with the center of the PSPD at the predetermined position of the sample stage are determined to be caused by drift and compensated by the scanning probe microscope.

[0006] A first problem with the arrangement in US8402560A is that the position sensitive photo detector (PSPD) is moved by the scanner so the signal from the PSPD will include the lateral scanning motion. Hence the lateral scanning motion must be removed from the signal from the PSPD in order to determine the drift.

[0007] A second problem with the arrangement in US8402560A is that it is not well suited for imaging a large sample, such as a 300mm semiconductor wafer, where it may be desirable to obtain images from a number of imaging sites which are spaced apart by some distance. This unsuitability is for two reasons. Firstly, the PSPD must be accurately aligned with the light beam at all times, which prevents large movements of the PSPD (or equivalently the light beam) when the wafer (or equivalently the probe) is moved laterally between imaging sites. Secondly, the PSPD occupies space on the upper surface of the sample stage, which may prevent a large sample from being accommodated on the sample stage.

[0008] SUMMARY OF THE INVENTION A first aspect of the invention provides a method according to claim 1 . Optional features are set out in the dependent claims.

[0009] A further aspect of the invention provides a scanning probe microscope according to claim 27. Optional features are set out in the dependent claims.

[0010] A further aspect of the invention provides a scanning probe microscope according to claim 30.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0013] Figure 1 shows a scanning probe microscope;

[0014] Figure 2a shows the microscope of Figure 1 imaging a first site of a sample;

[0015] Figure 2b shows the microscope of Figure 1 imaging a second site of the sample;

[0016] Figure 3 shows a probe head;

[0017] Figure 4 is a plan view of an XY scanner;

[0018] Figure 5 is a side view of the XY scanner;

[0019] Figure 6 shows first and second mirrors;

[0020] Figure 7 shows a scanning probe microscope with a scanning sample;

[0021] Figure 8 shows a scanning probe microscope with only a single measurement point, on the probe support; and

[0022] Figure 9 shows a scanning probe microscope with only a single measurement point, on the sample support.

[0023] DETAILED DESCRIPTION OF EMBODIMENT(S)

[0024] The scanning probe microscope 1 of Figure 1 comprises a probe comprising a cantilever 5 and a probe tip 6 extending from the cantilever.

[0025] The cantilever 5 is carried by a Z-actuator 20 which can drive the cantilever 5 up and down, typically over a range of about 7 micron. The Z-actuator 20 is configured to adjust a height of the proximal end of the cantilever by moving the cantilever under control of a height control signal. The Z-actuator 20 may comprise a piezoelectric actuator for example.

[0026] A lateral scanning system 10 is configured to generate a fine lateral scanning motion between the probe 5, 6 and a sample 2 in a horizontal (XY) plane so that the probe tip 6 interacts with the sample 2 across a selected region of the sample. In this case the relative scanning motion is achieved by motion of the probe 5, 6.

[0027] The lateral scanning system 10 may comprise a pair of piezoelectric actuators which each move the probe in a respective horizontal direction (X or Y). The lateral scanning system 10 is driven by scanning drive signals from a scan controller 13.

[0028] A detection system 30, such as an interferometer or optical lever, is used to monitor the probe during the lateral scanning motion to generate a height measurement signal 31 which is analysed to obtain sample data from the region of the sample. The sample data can then be used to obtain an image of the region of the sample, or other information about the region of the sample.

[0029] In the case of an interferometric detection system 30, a laser light source generates a detection beam which is steered onto the distal end of the cantilever by a steering mirror (not shown) and an objective lens 37. The distal end of the cantilever 5 reflects the detection beam to generate a return beam. An interferometric measurement is then performed to measure interference between the return beam and a height reference beam, thereby generating the height measurement signal 31. The detection system 30 is arranged to detect a path difference between the return beam and the height reference beam. The height measurement signal 31 is indicative of this path difference, and hence indicative of a height of the distal end of the cantilever. Further details of a suitable interferometric detection system are described in US11733265, the contents of which are incorporated herein by reference.

[0030] A signal processing system 32 is configured to monitor the height measurement signal 31 to obtain a series of topography measurements indicative of a topography of the sample. These topography measurements may be output as a topography measurement signal 33 to an image collection module 34. The image collection module 34 is configured to use the topography measurement signal 33 to obtain an image of the scanned region of the sample.

[0031] A laser 40 is configured to bend the cantilever by heating the cantilever with an actuation beam via the objective lens under control of an oscillation signal from an oscillation signal generator 42. The oscillation signal may be substantially sinusoidal, at a resonant frequency of the cantilever 5.

[0032] The Z-actuator 20 is configured to adjust a height of the proximal end of the cantilever by moving the cantilever under control of the topography measurement signal 33.

[0033] The image collection module 34 constructs an image on the basis of the topography measurement signal 33, and an XY position signal from the scan controller 13 which indicates the current XY position of the probe tip 6.

[0034] The lateral scanning motion may follow a two-dimensional scan pattern with a plurality of scan lines, such as a raster scan pattern. In this case the sample data can be used by the image collection module 34 to construct a two-dimensional image of the region of the sample. In other embodiments of the invention, rather than generating a two- dimensional image with the image collection module 34, the scanning probe microscope 1 may use the topography measurement signal 33 in some other way - for instance to measure a critical dimension of the sample (such as a wall height, wall angle, trench width, etc.). In this case a series of topography measurements may be measured with only a single line scan (for instance across a trench) rather than scanning in two-dimensions to generate a two-dimensional image.

[0035] Figure 2a shows a support structure of the scanning probe microscope 1. Certain elements of Figure 1 are omitted from Figure 2a to improve clarity. A lower part of the support structure is a sample support 70 which supports the sample 2; and an upper part of the support structure is a probe support 80 which supports the probe 5, 6.

[0036] In this case the sample support 70 supports the sample 2 from below (and hence is a lower part of the support structure) and the probe support 80 supports the probe 5, 6 from above (and hence is an upper part of the support structure). In other embodiments this arrangement may be inverted so the sample support 70 supports the sample 2 from above and the probe support 80 supports the probe 5, 6 from below. The sample support 70 comprises a platform 71 which contacts the sample 2; a substructure 72; and a lateral positioning system 73 (referred to hereinafter as an XY stage 73) which carries the platform 71. Hence the substructure 72 supports the platform 71 via the XY stage 73.

[0037] The XY stage 73 can be operated to adjust a relative lateral position between the probe 5, 6 and the sample 2 by moving the platform 71 relative to the substructure 72. The XY stage 73 is configured to move the sample 2 in a horizontal (XY) plane before the lateral scanning motion so that the imaging space of the sample 2 becomes laterally aligned with the probe tip 6. The XY stage 73 may comprise a pair of motors which each move the sample in a respective horizontal direction (X or Y).

[0038] The platform 71 may be a vacuum chuck which grips the underside of the sample 2 by suction, or a magnetic clamp which grips the underside of the sample by magnetic force (in this case the sample is glued to a metal slab which is attracted to the magnetic clamp).

[0039] The probe support 80 comprises a support arm 81 , a Z-motor 82, a probe head 83, the lateral scanning system 10 and the Z-actuator 20. The probe head 83 is coupled to the support arm 81 by the Z-motor 82. The Z-motor 82 is a coarse actuator arranged to translate the probe head 83 in a vertical (Z) direction over a relatively large distance. The probe head 83 contains various components including the detection system 30 and the objective lens 37, as shown in Figure 3.

[0040] The sample support 70 is connected to the probe support 80 by an upright 90. The upright 90 extends upwardly from the substructure 72 and the support arm 81 extends laterally from the upright 90. The substructure 72, upright 90 and support arm 81 may be granite blocks joined to each other.

[0041] As shown in Figure 4, the XY-scanner 10 comprises a piezoelectric actuator (X-piezo) 47 which can be driven to move the probe in a lateral X-direction; and a piezoelectric actuator (Y-piezo) 48 which can be driven to move the probe in a lateral Y-direction. The X-piezo 47 and Y-piezo 48 may act between an inner frame 44 and an outer frame 45 so that each actuator 47, 48 causes the inner frame 44 to move laterally relative to the outer frame 45. The probe is connected to the inner frame 44 via the Z-actuator 20 so that lateral movement of the inner frame 44 will result in lateral movement of the probe. As shown in Figure 6, the outer frame 45 of the XY-scanner 10 is attached to an X-Y align actuator 16, which is attached in turn to the probe head 101. Hence the X-Y align actuator 16 and the outer frame 45 of the XY-scanner 10 are moved up and down together by the Z-motor 82.

[0042] The Z-actuator 20 is mounted at its upper end to the inner frame 44 by a support structure 49 (shown in Figure 5 but omitted in Figure 4 so the Z-actuator 20 is visible). The lower end of the Z-actuator 20 is connected to the probe. Hence as the X-piezo 47 and Y-piezo 48 are actuated to scan the inner frame 44 laterally, the Z-actuator 20 and probe 5, 6 move with the inner frame 44.

[0043] The inner frame 44 is connected to the outer frame 45 by flexures 42 or any other suitable means for holding the inner frame 44 while allowing movement relative to the outer frame 45. Flexures 42 are shown in only one of the four corners of the XY-scanner 10 in Figure 4, but typically there will be similar flexures at each corner.

[0044] The X-piezo 47 and the Y-piezo 48 together provide a lateral scanning system which can be operated to generate a lateral scanning motion between the probe 5, 6 and the sample 2, in this case by motion of the probe.

[0045] The Z-actuator 20 can be driven to move the probe up and down in a Z-direction perpendicular to the sample 2. The XY-scanner 10 and the Z-actuator 20 are arranged in a gap below the objective lens 37 as shown in Figure 5. The detection beam and the return beam pass through a small aperture 44a in the inner frame 44.

[0046] The X-Y align actuator 16, shown in Figure 3, is used to move the probe laterally relative to the objective lens 37 so that the detection beam falls onto the cantilever 5. A detection system focusing stage 109 can be also operated to move the detection system 30 and objective lens 37 up and down (in the Z direction) so that the focal plane of the objective lens 37 coincides with the cantilever 5.

[0047] Figures 2a and 2b show the microscope imaging first and second regions respectively of a sample 2, such as a semiconductor wafer. In a set-up phase, the XY stage 73 is operated to generate a lateral registration motion between the probe and the sample so that the probe becomes laterally aligned with a first imaging region of the sample as in Figure 2a. Typically the probe crosses a peripheral edge of the sample 2 during this lateral registration motion so the probe head 83 is held by the Z-motor 82 at some distance from the sample to avoid clash. In a second part of the set-up phase the Z-motor 82 is operated so that the probe head 83 moves down and brings the probe down to an operating distance in close proximity with the sample 2.

[0048] After the set-up phase, a sequence of two or more images of the sample is obtained, each image being obtained in a respective imaging phase. Each imaging phase comprises generating a lateral scanning motion between the probe and the platform with the XY scanner 10 so that the probe tip interacts with the sample across a respective region, expanding and contracting the Z-actuator 20 so that the probe moves towards and away from the platform 71 to react to topographic changes of the sample across the region, and monitoring the probe 5, 6 to obtain sample data from the region.

[0049] A variety of different types of imaging modes may be used in the imaging phases, for example the adaptive imaging mode described in US2014 / 0026263A1 ; or the dynamic imaging mode described in LIS2011 / 0247106A1. In each case the Z-actuator 20 expands and contracts so that the probe moves towards and away from the platform 71 to react to topographic changes of the sample across the imaging region. The image may be a two-dimensional image (based on a two-dimensional scan) or a onedimensional image (based on a single line scan).

[0050] In Figure 2a a first region of the sample is aligned with the probe tip 6. After the imaging phase of Figure 2a, the XY stage 73 is operated again to further adjust the relative lateral position between the probe and the sample so that a second region of the sample becomes laterally aligned with the probe tip 6 as in Figure 2b. An imaging phase is then performed at the second region - that is, a further lateral scanning motion between the probe and the sample is driven by the lateral scanning system 10 so that the probe tip 6 interacts with the sample across the second imaging region; and the probe is monitored by the detection system 30 to obtain further sample data from the second imaging region. A problem with the support structure of Figure 2a is that vibration and thermal drift in the support structure can cause an unwanted relative motion (in X, Y or Z) between the probe tip 6 and the sample 2. This relative motion can cause errors in the image or the critical dimension measurement.

[0051] The scanning probe microscope 1 incorporates an interferometric correction system 60 which is configured to correct for such unwanted relative motion. The correction system 60 is configured to measure a relative lateral position between the sample support 70 and the probe support 80 during the lateral scanning motion to obtain a lateral error signal 61 , which is then used to correct or compensate for the unwanted relative motion.

[0052] The interferometric correction system 60 comprises an interferometer system 62 which generates a first beam 63 which is directed onto a first measurement point on the probe support 80 to generate a reflection 64 of the first beam. The interferometer system 62 also generates a second beam 65 which is directed onto a second measurement point on the sample support 70 to generate a reflection 66 of the second beam.

[0053] In US8402560A the light beam is emitted from the upper structure (i.e. the probe head). Advantageously the interferometer system 62 is not carried by the probe head 83, which makes the probe head 83 lighter and less congested.

[0054] The interferometer system 62 may comprise a single interferometer which obtains the lateral error signal 61 by performing an interferometric measurement which measures interference between the reflections 64, 66 of the first and second beams. The interferometric measurement provides an indication of an optical path difference between the beams, which in turn indicates the relative position between the first and second measurement points.

[0055] Alternatively, the interferometer system 62 may comprise a first interferometer which performs a first interferometric measurement by measuring interference between the reflection 64 of the first beam and a reference beam (which provides an indication of an optical path difference between the first beam and the reference beam); and a second interferometer which performs a second interferometric measurement by measuring interference between the reflection 66 of the second beam and a reference beam (which provides an indication of an optical path difference between the second beam and the reference beam). In this case the interferometer system 62 obtains the lateral error signal 61 on a basis of a difference between the first and second interferometric measurements, which in turn indicates the relative position between the first and second measurement points. An example of a suitable interferometer for performing the second interferometric measurement is the RL10 plane mirror interferometer, disclosed at www.renishaw.com / en / rld10-differential-interferometer-- 6483 (13 December 2024).

[0056] In either case, the lateral error signal 61 provides an accurate indication of the relative lateral position between the sample support 70 and the probe support 80. The lateral error signal 61 may be indicative of a drift in the relative lateral position, for example thermal drift. The lateral error signal may also be indicative of vibrational noise or jitter in the relative lateral position.

[0057] A correction based on the lateral error signal 61 can be performed in different ways. In a first example the correction is performed by operating the XY scanner 10 to adjust the lateral scanning motion in real time during image acquisition. In this case, a scan correction module 63a determines a scan correction based on the lateral error signal 61 and the scan controller 13 applies the scan correction accordingly to remove drift, noise or jitter. That is, the scan controller 13 modifies the scanning drive signals to correct the motion of the lateral scanning system 10 and counteract the drift, noise or jitter. In other words, the correction is applied by operating the lateral scanning system 10 to adjust the lateral scanning motion based on the lateral error signal 61. In a second example, the correction is performed in post-processing after the sample data has been obtained, by applying a correction to the sample data. In this case, an image correction module 64a determines an image correction based on the lateral error signal 61 and the image collection module 34 applies the image correction accordingly to remove image artefacts caused by drift, noise or jitter.

[0058] Each beam 63, 65 is reflected from a respective mirror 67, 68 as shown in Figure 6. The first beam 63 is reflected from a first mirror 67 which is mounted on a side of the outer frame 45 of the XY-scanner 10. The second beam 65 is reflected from a second mirror 68 which is mounted on a side of the platform 3.

[0059] Ideally the first mirror 67 is perfectly vertical, aligned with the drive axis of the Z-motor 82. So when the first mirror 67 is driven up or down by the Z-motor 82, the motion has no effect on the path length of the reflected beam 64. Any deviation from vertical of the first mirror 67 can be measured and accounted for by mapping motion of the Z-motor 82 to change in path length of the reflected beam, and compensating accordingly.

[0060] It would be theoretically possible for the second beam 65 to be reflected from the edge of the sample 2, but this is not preferred because it would require the second beam 65 to be set up for each sample 2, and would require a sample with a reflective edge.

[0061] The second mirror 68 is elongated in the Y direction (out of the plane of Figure 6) so when the platform 71 is driven in the Y-direction by the XY stage 73 the second beam 35 still falls on the mirror 68 and the motion has no effect on the path length of the reflected beam 66. Any deviation from being perfectly aligned in the Y-direction of the second mirror 68 can be measured and accounted for by mapping motion of the XY stage 73 to change in path length of the reflected beam 66, and compensating accordingly.

[0062] In US8402560A the PSPD occupies space on the upper surface of the sample stage, which may prevent a large sample from being accommodated on the sample stage. Mounting the second mirror 68 on the side of the platform 71 , rather than the upper surface of the platform 71 , leaves the upper surface free to carry a large sample 2, such as a 300mm semiconductor wafer.

[0063] In US8402560A the center of the PSPD must be accurately aligned with the light beam. The use of an interferometer as in Figure 6 is advantageous because accurate alignment is not necessary in the case of either the first mirror 67 or the second mirror 68 - it is only necessary that the beam 63, 65 falls on the mirror 67, 68 at some point.

[0064] Note that the interferometric correction system 60 only measures and corrects for motion in a single lateral direction (X) and a second similar interferometric correction system (not shown) may also be provided which measures and corrects for motion in the orthogonal lateral direction (Y).

[0065] The XY stage 73 is used to adjust a relative lateral position between the probe 5, 6 and the sample 2 before the lateral scanning motion in the imaging phase, so that a region of the sample to be imaged becomes laterally aligned with the probe tip 6. In Figure 2a the probe is scanning a first region of the sample 2, and in Figure 2b the sample has been moved to the left so that a second region of the sample can be scanned. The second region is lower than the first region, so the Z-motor 82 has driven the probe head 83 down compared with Figure 2a to bring the probe tip 6 in contact with the sample. As shown by comparison of Figures 2a and 2b, the second measurement point on the sample support (i.e. the second mirror 68) is moved to the left by the XY stage 73 as it adjusts the relative lateral position between the probe and the sample. However the XY stage 73 is inactive during imaging, and the platform 71 and the second mirror 68 are not moved by the XY scanner 10. Hence the second mirror 68 does not move during imaging. This ensures that the lateral error signal 61 does not include the lateral scanning motion, but only includes undesirable motion caused by drift, noise, jitter etc.

[0066] Since the first measurement point (the first mirror 67) is mounted on a fixed part of the XY-scanner 10 (the outer frame 45) it is also not moved by the XY scanner 10 during scanning. This further ensures that the lateral error signal 61 does not include the lateral scanning motion.

[0067] The first measurement point (first mirror 67) on the probe support 80 is positioned as close as possible to the probe, so it is exposed to the same drift, noise and jitter as the probe. In this example the first mirror 67 is mounted to the XY scanner 10, but in other embodiments the first mirror 67 may be mounted to the X-Y align actuator 16, the probe head 83 or any other part of the probe support 80.

[0068] The second measurement point (second mirror 68) on the sample support 70 is positioned as close as possible to the sample 2, so it is exposed to the same drift, noise and jitter as the sample. In this example the second mirror 68 is mounted to the platform 71 , but in other embodiments the second mirror 68 may be mounted to the XY stage 73 or any other part of the sample support 70.

[0069] The second measurement point (second mirror 68) is moved by the lateral positioning system (XY stage 73) as it adjusts the relative lateral position between the probe and the sample. This is advantageous, because it enables the lateral error signal 61 to pick up drift in the XY stage 73.

[0070] In the embodiments above the lateral scanning motion is caused by movement of the probe, driven by the XY scanner 10. Figure 7 shows an alternative probe microscope 1a, in which the lateral scanning motion between the probe and the sample is caused by motion of the sample 2, rather than motion of the probe. Hence the XY scanner 10 carrying the probe is omitted, and replaced by a lateral scanning system (XY scanner 10a) between the XY stage 73 and the platform 71.

[0071] The first measurement point (first mirror 67) is on the probe head 83, as close as possible to the probe 5, 6. Since the platform 71 moves laterally during imaging, the second measurement point (second mirror 68) cannot be mounted on the side of the platform 71 , so instead it is mounted on a side of the XY stage 73. This is less preferred than the arrangement of Figure 2a, because the mirror 68 is positioned further from the sample 2.

[0072] Figure 8 shows an alternative probe microscope 1b, in which the second beam 65 is omitted. In this case the interferometric correction system 60 is configured to correct for unwanted motion of the probe support 80, without reference to motion of the sample support 70. Hence the correction system 60 is configured to measure a lateral position of only the probe support 80 to obtain the lateral error signal 61. The lateral error signal 61 is obtained by reflecting beam 63 from a measurement point on the XY scanner 10 to generate a reflection 64 of the beam, and performing an interferometric measurement which measures interference between the reflection 64 and a reference beam.

[0073] Figure 9 shows an alternative probe microscope 1c, in which the first beam 63 is omitted. In this case the interferometric correction system 60 is configured to correct for unwanted motion of the sample support 70, without reference to motion of the probe support 80. Hence the correction system 60 is configured to measure a lateral position of only the sample support 70 to obtain the lateral error signal 61. The lateral error signal 61 is obtained by reflecting beam 65 from a measurement point on the platform 71 to generate a reflection 66 of the beam, and performing an interferometric measurement which measures interference between the reflection 66 and a reference beam.

[0074] In the embodiments above, a lateral error signal 61 is obtained by: reflecting a beam from a measurement point to generate a reflection of the beam, and performing an interferometric measurement based on the reflection of the beam. The measurement point is not moved by the lateral scanning system 10, 10a so the lateral error signal does not include the lateral scanning motion. The lateral scanning motion caused by the XY scanner 10, 10a can generate air turbulence which negatively impacts the interferometric measurements taken by the interferometric correction system 60. To reduce the impact of such turbulence, the method may be carried out with the XY scanner 10, sample 2, and probe 5, 6 in a vacuum. Alternatively, the beams 63, 65 may be shielded so they pass through less turbulent air.

[0075] Another solution to the air turbulence problem is to replace the interferometric correction system 60 with a non-interferometric measurement system, such as a quadrant photodiode correction system as described in US8402560A, which is configured to correct for unwanted relative motion in a similar way. Such a quadrant photodiode correction system can be configured to measure a relative lateral position between the sample support 70 and the probe support 80 during the lateral scanning motion to obtain a lateral error signal 61 , which is then used to correct or compensate for the unwanted relative motion. A beam is directed downwardly from the probe support 80 onto a quadrant photodiode on the platform 71 , and the position of the beam on the quadrant photodiode is used to measure the lateral position of the sample support 70 relative to the sample support 80. This is then used to obtain a lateral error signal, and a correction is performed based on the lateral error signal.

[0076] Note that such a quadrant photodiode correction system can be implemented in the system of Figure 1 (in which the lateral scanning motion is achieved by motion of the probe 5,6) but not in the system of Figure 7 (in which the lateral scanning motion is achieved by motion of the sample 2). This is because when implemented in the system of Figure 7 the quadrant photodiode is moved by the lateral scanning system, so the lateral error signal includes the lateral scanning motion. When implemented in the system of Figure 1 the quadrant photodiode is not moved by the lateral scanning system, so the lateral error signal does not include the lateral scanning motion.

[0077] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims

Claims

CLAIMS1. A method of obtaining sample data with a scanning probe microscope, the scanning probe microscope comprising: a probe comprising a cantilever and a probe tip extending from the cantilever; a lateral scanning system; and a support structure comprising a sample support which supports a sample and a probe support which supports the probe, the method comprising: generating a lateral scanning motion between the probe and the sample with the lateral scanning system so that the probe tip interacts with the sample across a region of the sample; monitoring the probe to obtain sample data from the region of the sample; during the lateral scanning motion, measuring a lateral position of the sample support or the probe support to obtain a lateral error signal, wherein the lateral error signal does not include the lateral scanning motion; and performing a correction based on the lateral error signal.

2. A method according to claim 1 , wherein the lateral error signal is obtained by: reflecting a beam from a measurement point to generate a reflection of the beam, and performing an interferometric measurement based on the reflection of the beam, wherein the measurement point is not moved by the lateral scanning system so the lateral error signal does not include the lateral scanning motion.

3. A method according to claim 2, wherein the measured lateral position of the sample support or the probe support comprises a relative lateral position between the sample support and the probe support; and the lateral error signal is obtained by: reflecting a first beam from a first measurement point to generate a reflection of the first beam, reflecting a second beam from a second measurement point to generate a reflection of the second beam, and performing one or more interferometric measurements based on the reflections of the first and second beams, wherein the first and second measurement points are not moved by the lateral scanning system so the lateral error signal does not include the lateral scanning motion.

4. A method according to claim 3, wherein the lateral error signal is obtained by performing an interferometric measurement which measures interference between the reflections of the first and second beams.

5. A method according to claim 3, wherein the lateral error signal is obtained by performing a first interferometric measurement which measures interference between the reflection of the first beam and a first reference beam; performing a second interferometric measurement which measures interference between thereflection of the second beam and a second reference beam; and obtaining the lateral error signal on a basis of the first and second interferometric measurements.

6. A method according to any of claims 3 to 5, wherein the first measurement point is on the probe support and the second measurement point is on the sample support.

7. A method according to claim 2, wherein the measurement point is on the sample support, typically on a platform which contacts the sample.

8. A method according to claim 2, wherein the measurement point is on the probe support, typically on the lateral scanning system.

9. A method according to any preceding claim, wherein the scanning probe microscope further comprises a lateral positioning system, and the method further comprises: operating the lateral positioning system to adjust a relative lateral position between the probe and the sample before the lateral scanning motion so that the region of the sample becomes laterally aligned with the probe tip.

10. A method according to claim 9 and claim 2, wherein the measurement point is moved by the lateral positioning system as it adjusts the relative lateral position between the probe and the sample.

11. A method according to claim 9 or 10, further comprising: operating the lateral positioning system to further adjust the relative lateral position between the probe and the sample after the lateral scanning motion so that a second region of the sample becomes laterally aligned with the probe tip, wherein the measurement point is moved further by the lateral positioning system as it further adjusts the relative lateral position between the probe and the sample; generating a further lateral scanning motion between the probe and the sample with the lateral scanning system so that the probe tip interacts with the sample across the second imaging region; and monitoring the probe to obtain further sample data from the second imaging region.

12. The method according to claim 9, 10 or 11 , wherein the lateral positioning system adjusts the relative lateral position between the probe and the sample by moving the sample.

13. A method according to claim 10, wherein the sample support comprises a platform which is not moved by the lateral scanning system during the lateral scanning motion, and a substructure which supports the platform; and the lateral positioning system adjusts the relative lateral position between the probe and the sample bymoving the platform relative to the substructure, wherein the measurement point is on the platform.

14. A method according to any of claims 9 to 13, wherein the lateral error signal changes as the lateral positioning system adjusts the relative lateral position between the probe and the sample.

15. The method according to any preceding claim, wherein the correction is performed by operating the lateral scanning system to adjust the lateral scanning motion.

16. The method according to any preceding claim, wherein the correction is performed after the sample data has been obtained.

17. The method according to any preceding claim, wherein the correction comprises applying a correction to the sample data.

18. The method according to any preceding claim, wherein the lateral error signal is indicative of a drift in the lateral position.

19. The method according to claim 18, wherein the drift is thermal drift.

20. The method according to any preceding claim, wherein the lateral error signal is indicative of vibrational noise or jitter in the lateral position.21 . The method according to any preceding claim, wherein the lateral scanning motion is caused by movement of the probe.

22. The method according to any of claims 1 to 20, wherein the lateral scanning motion is caused by movement of the sample.

23. The method according to any preceding claim, wherein the lateral scanning motion follows a scan pattern with a plurality of scan lines.

24. The method according to any preceding claim, wherein the lateral scanning system comprises one or more piezoelectric actuators.

25. The method according to any preceding claim, wherein the sample support supports the sample from below.

26. The method according to any preceding claim, wherein the probe support supports the probe from above.

27. A scanning probe microscope configured to perform a method according to any preceding claim, the scanning probe microscope comprising: a probe comprising a cantilever and a probe tip extending from the cantilever; a support structure comprising: a sample support configured to support a sample and a probe support which supports the probe; a lateral scanning system configured to generate a lateral scanning motion between the probe and the sample so that the probe tip interacts with the sample across a region of the sample;a detection system configured to monitor the probe to obtain sample data from the region of the sample; and a correction system configured to measure a lateral position of the sample support or the probe support during the lateral scanning motion to obtain a lateral error signal, wherein the lateral error signal does not include the lateral scanning motion, and wherein the correction system is further configured to perform a correction based on the lateral error signal.

28. A scanning probe microscope according to claim 27, wherein the correction system is configured to obtain the lateral error signal by: reflecting a beam from a measurement point to generate a reflection of the beam, and performing an interferometric measurement based on the reflection of the beam, wherein the measurement point is not moved by the lateral scanning system so the lateral error signal does not include the lateral scanning motion.

29. A scanning probe microscope according to claim 28, further comprising a mirror mounted to the support structure at the measurement point.

30. A scanning probe microscope configured to perform a method according to any preceding method claim, the scanning probe microscope comprising: a probe comprising a cantilever and a probe tip extending from the cantilever; a support structure comprising: a sample support configured to support a sample and a probe support which supports the probe; a lateral scanning system configured to generate a lateral scanning motion between the probe and the sample so that the probe tip interacts with the sample across a region of the sample; a detection system configured to monitor the probe to obtain sample data from the region of the sample; and a correction system configured to measure a lateral position of the sample support or the probe support during the lateral scanning motion to obtain a lateral error signal, wherein the lateral error signal is obtained by: reflecting a beam from a measurement point to generate a reflection of the beam, and performing an interferometric measurement based on the reflection of the beam, wherein the measurement point is not moved by the lateral scanning system so the lateral error signal does not include the lateral scanning motion, and wherein the correction system is further configured to perform a correction based on the lateral error signal.

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