Atomic force microscope with probe distancer
Patent Information
- Application Number
- NL2039058
- Authority / Receiving Office
- NL · NL
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-11-12
- Publication Date
- 2026-06-09
- Estimated Expiration
- 2044-11-11
Smart Images
Figure 00000028_0000 
Figure 00000028_0001 
Figure 00000029_0000
Abstract
Description
l P 137501NL00 Title: Atomic force microscope with probe distancer The invention relates to a probe tip for an atomic force microscope for measuring high aspect ratio structures on a surface of a sample, an atomic force microscope and a method ofscanning a surface ofa sample using an atomic force microscope. Scanning probe microscopy is a widespread class ofmicroscopy methods that is based upon the scanning ofa surface by means a probe tip in continuous or periodic, i.e. intermittent, contact with the surface. The method enables the detection and mapping ofsurface features e.g. trenches, dimples, edges, roughness, etcetera on the surface of a sample andbelow the surface of a sample with great accuracy and at high resolution. Measurements below the surface are performed using ultrasound in combination with scanning the surface using a probe. The high resolution enables the detection ofeven nanometer sized structures, and as a result of this high resolution has become very popular for example as a tool in the production ofsemiconductor elements. However, scanning probe microscopy is used in many other applications as well, for example the imaging and analysis of soft tissue or biological samples. Atomic force microscopy is a type ofscanning probe microscopy that uses a sharp tip attached to a cantilever to scan the surface ofa sample and measure the forces between the tip and the sample's surface atoms. The cantilever's motion is monitored and used to produce high-resolution images ofthe on-surface and sub-surface features and topography ofthe sample, with a resolution on the order ofa few nanometers. Atomic force microscopy can be used in a variety ofenvironments, including vacuum, air, and liquids, and can provide information on a wide range ofsample properties, including mechanical, electrical, and magnetic properties. The surface of a sample to be mappedby atomic force microscopy may comprise high aspect ratio structures.A high aspect ratio structure is a shape or feature on the surface ofthe sample that is relatively high, or deep, compared to its width and / or length. As an example, a small and high structure, viewedfrom a side ofthe surface, can be considered a structure having a high aspect ratio. High aspect ratio structures are commonly measured, or mapped, using probe tips that are cylindrical, conical or spike- shaped and are more thin than a conventional probe tip. These shapes may be inserted in between high aspect ratio structures, thus allowing the high aspect ratio structures to be measured where a conventional probe tip would not be able to. A downside ofusing cylindrical, conical or spike-shaped probe tips, i.e. commonly used probe tips for high aspect ratio structure measurements, is that there may be a high interaction between the surface ofthe probe tip and the high aspect ratio structure, specifically the sidewall ofthe structure. As a result, it is necessary to use higher forces to measure the surface while the lifetime ofthe probe, and specifically the probe tip, is limited. At the same times artifacts, e.g. incorrectly measured andmapped structures, may be created. For example, the depth between two structures may not correctly be measured as a result ofthe high interaction between the surface ofthe probe tip and the structures. Furthermore, lateral dimensions ofthe high aspect ratio structures may not be reliably measured due to the formation of artifacts as a result ofthe side wall ofthe probe tip coming in to contact with the side wall ofthe structure instead ofthe end of the probe tip coming in to contact with the surface ofthe sample, adjacent the structure. The invention aims to counteract the above disadvantages, preferably while retaining the advantages. More specically, the invention aims to provide for method and an atomic force microscope that is able to more accurately measure andmap the surface ofa sample having high aspect ratio structures, in particular the depth ofan high aspect ratio structure, e.g. measure andmap the surface ofthe sample while producing less artifacts, and increase the lifetime ofthe probe tip ofthe atomic force microscope. Therefore, the invention provides for a method ofmeasuring a dimension of a high aspect ratio structure of a sample using a scanning probe microscope, e.g. an atomic force microscope, in particular the method according to claim 1. The high aspect ratio structure ofthe method comprises a recess having a height dimension in a direction transverse to the surface and a lateral dimension in a direction parallel to the surface. In the context ofthe invention, a high aspect ratio structure should be understood as a structure having a height dimension that is greater than the lateral dimension. The method comprises the steps of: scanning the surface ofthe sample in a scanning direction parallel to the surface by a probe including a probe tip attached to the scanning probe microscope, and lowering, during the step of scanning, the probe tip into the recess such as to determine the dimension ofthe high aspect ratio structure, preferably at least the height ofthe high aspect ratio structure by lowering the probe tip ofthe scanning probe microscope in the recess until the probe tip reaches the bottom ofsaid recess; wherein the recess comprises a recess width between at least two opposing sidewalls in a direction parallel to the scanning direction; wherein the probe tip, which is lowered into the recess, comprises a base, an apex at an end ofthe base arranged to interface with the surface ofthe sample, and a distancer, wherein said base extends parallel to a longitudinal axis ofthe probe tip and wherein the distancer extends from the base such as to extend radially outward for defining a width ofthe probe tip including the distancer; and wherein the width ofthe probe tip is smaller than the recess width. For example, the width ofthe probe tip can be between 0.3 and 1 times the recess width. Advantageously, by providing a distancer that extends, or protrudes, radially outward, interfacingbetween the probe tip and the surface ofthe sample can be better controlled. Since the distancer locally broadens the probe tip at the end ofthe base, it may be prevented that a side ofan structure on the surface comes in to contact with the base ofthe probe tip, reducing interaction between the probe tip and the structure. In the context ofthe invention, interaction between the probe tip and the structure is to be understood as forces acting upon the probe tip and the structure as a result ofthem being in proximity ofeach other, e.g. in physical contact with each other, By providing a distancer, the contact area between the probe tip and the wall ofthe structure interacting with each othermay be reduced, reducing forces such as capillary forces and adhesive forces acting upon the probe tip and wall As a result lifetime ofthe probe tip may be increasedby reducing scraping or interference to diminish wearing ofthe probe tip. Also the risk of artifacts may be reduced that are normally caused as a result ofsuch interaction with a sidewall or other structure. Furthermore, less force may need to be applied for the probe tip to reach the bottom ofthe recess, because the probe tip more easily slides into the recess to reach the bottom. To elaborate on the above, as may be appreciated, by limiting contact with the sidewalls, wear and tear on the probe tip is reduced, resulting in an extended operational lifespan. This means fewer replacements and lower operational costs. The reduction in interaction also helps to reduce measurement artifacts, such as false readings or inaccurate dimensions, particularly in the measurement ofnarrow or deep structures. This allows for more precise mapping ofthe sample's surface, ensuring reliable data. Furthermore, because the distancer reduces (diminishes) direct contact with the sidewalls, less force is needed to lower the probe tip into the recess or structure. This reduces the risk ofdamaging sensitive structures on the sample. It allows the probe to smoothly reach the bottom ofthe recess without being hindered by unnecessary resistance.The smooth motion results in less artefacts. In addition to this, the reduction in direct contact not only results in less wear to the probe tip, but likewise to a reduction ofrisk ofdamage to the sample. In turn, since damage and wear to the sample results in remnants ofthe sample left behind, this likewise lowers the risk of contamination ofthe probe tip and / or the sample surface. The reduced level ofwear to or contamination ofthe probe tip also improves repeatability of measurements performed with a same probe more than once. Furthermore, by reducing unwanted lateral contact between the probe tip and the sidewalls ofhigh aspect ratio structures, the probe tip can maintain improved vertical positioning stability within a recess. Such an improved vertical positioning stabilitymay be achievedby due to the distancer providing a single andknown contact point between the probe tip and the sidewalls ofthe high aspect ratio structure. When the probe tip is lowered during measurements ofthe scanning probe microscope, only the distancer will interact with the sidewall ofthe high aspect ratio structure, while the rest ofthe probe tip does not interact with said sidewall.Aknown probe tip, not having a distancer, may have multiple contact points with the sidewall at the same time and / ormay have a contact point at an unknown height from the apex ofthe probe tip. Thismay negatively affect the measurement precision, as in both cases it is not known what point ofthe probe tip has been interacting with the surface such that it is not known at what vertical position the measurement data has been collected. As a result, stable positioning allows for increased vertical precision when measuring the depth ofnarrow or deep features, thereby enhancing the accuracy of depth profiles obtained from samples. Vertical positioning stability refers to the ability ofthe probe tip to maintain a consistent and precise vertical orientation relative to the sample surface while being lowered into and withdrawn from high aspect ratio structures. This stability ensures that the probe tips movements in the depth direction remain controlled, reducing the likelihood oflateral shifts or unintended contact with the structures sidewalls. Maintaining such stability is essential for accurate depth measurement, as even minor deviations in vertical alignment can introduce errors in the recorded depth and overall topography ofthe sample. Such vertical precision is especially benecial in applications where nanoscale accuracy is required, for example, in the production ofsemiconductor elements or in the structural analysis ofbiological samples. Consequently, the risk ofpositional deviation due to unintended sidewall interaction is minimized, supporting more reliable and accurate measurements ofhigh aspect ratio features with nanometer-level detail. The distancer, in some implementations, can have a stiffness such that, during said lowering upon an engagement ofthe distancer with one of said sidewalls, the distancer can engage the sidewall without a bending of the distancer. When a probe tip having a distancer is lowered into a recess of a high aspect ratio structure, the distancermay experience various forces acting upon it. For example, ifthe distancer interfaces directly with a sidewall, interaction forces and / or shear forces may act on the distancer. Bending or otherwise deforming ofthe distancermay result in inaccurately determining the dimensions ofthe high aspect ratio structure, such as the depth ofthe recess. When the distancer does not bend relative to the probe tip, more accurate measurements may be taken. This may be achievedby manufacturing the probe tip out of a sufficiently stiffmaterial. Additionally or alternatively, the distancer can be shaped such as to provide said stiffness in at least one direction sideways to a direction wherein the distancer extends from the base. The distancer can comprise a remote end away from the base of the probe tip, the remote end can include a rounded shape.A rounded end of the distancer, at a location away ofthe probe tip, i.e. a distal end ofthe distancer, reduces the amount of surface ofthe distancer that interfaces with the side wall ofthe a recess ofa high aspect ratio structure. For example, assuming that a probe tip that during operation has a horizontally provided distancer. When such a distancer has a rounded end at a remote end, it has an apex in the horizontal direction. When this probe tip is now lowered into a recess, only the apex ofthe distancermay interact with the sidewall. As a result, the rounded shape thus further reducing the interaction between the wall ofthe high aspect ratio structure and the probe tip. The distancer can be rotationally symmetric around the longitudinal axis ofthe probe tip. This may allow, in particular in relatively narrow recesses of a high aspect ratio structure, for the forces action upon the distancer to act symmetrically around the probe tip. When forces acting upon the distancer are equal, bending ofthe probe tip and / or the distancer may be mitigated. In an implementation, the distancer can be spherically, or ovoid, shaped such that it has a rounded cross-section, preferably the center ofthe spherically shaped distancer can coincide with the longitudinal axis of the probe tip. The distancer thus protrudes in all directions equally, e.g. by forming a disc-shaped distancer, when viewed in a direction parallel to the longitudinal axis. This may ensure that, regardless ofthe orientation ofthe probe tip relative to the surface of a sample, the distancer interfaces with the surface instead ofthe base ofthe probe tip. As an example, when the distancer is a at disc and the probe tip is lowered in the center ofa high aspect ratio structure, forces acting upon the distancer by the walls ofthe high aspect ratio structure are equal, and thus the probe tip will not bend as a result. In case the distancer is only provided partially around the base of the probe tip, e.g. at a single side ofthe probe tip, forces may act upon one side ofthe probe tip andmay cause bending as a result. This may thus be preventedby a distancer that is rotationally symmetric around the longitudinal axis ofthe probe tip. In a further example ofprovided a rotationally symmetric distancer around the longitudinal axis ofthe probe tip is that the probe tip may be used in any direction and the benets ofthe distancermay still be achieved. Since the distancer is present in all directions in which the probe tip may move in lateral direction during scanning ofthe scanning probe microscope, the distancer will be positioned between the base ofthe probe tip and a wall ofa recess of a high aspect ratio structure when the probe tip is lowered in such a high aspect ratio structure. In an implementation, wherein the distancer is a spherical distancer provided at the tip ofthe probe such that the apex ofthe probe tip is located on the distancer, the distancer reduces the complexity ofdeconvolution during or after scanning ofthe surface. When the distancer is a spherical distancer, it has a constant radius. The midpoint can coincide with the longitudinal axis ofthe base, such that spherical distancer is rotational symmetric around the longitudinal axis ofthe base with a constant radius. Since the radius ofthe distancer is constant, angling ofthe probe tip or deformation ofthe probe tip can be conveniently accounted and corrected for. For example, ifthe probe tip is angled relative to its original position, the width and height ofthe spherical probe tip projected on the sample remains the same. Comparing this to the behavior ofnon-spherical apexes of a probe tip, angling or rotation ofthe probe tip mostly also affects the projection ofthe width and / or height ofthe probe tip on the surface ofthe sample. This may result in incorrect measurements, e.g. artifacts, or additional errors which may need to be corrected or accounted for.A spherical distancer provided at the tip ofthe probe alleviate this as it reduces the complexity ofdeconvolution during or after scanning. In particular, the spherical shape ofthe probe tip renders deconvolution to be independent ofthe angle ofthe probe relative to the surface ofthe sample, and will therefore result in less complexity and thus an advantage during deconvolution. Reduced complexity during processing ofmeasurement results is a clear advantage, especially for high throughput scanning probe microscopy applications e.g. in industrial environments. In further implementations, the distancer ofthe probe tip that can be used for lowering into the recess can be formed by a disc shape, star shape or bar shape such as to provide the distancer extending in more than a single direction. Such a distancer protrudes more than the other parts of the distancer or probe tip. As a result it may be more clearly dened where the structure on the surface ofthe sample interfaces, or comes in to contact with, the distancer. Therefore, accuracy ofmeasurement results may improve compared to conventional probe tips, or a probe tip having a sphering end. The distancer can be provided at the apex ofthe probe tip. This may advantageously facilitate that when the probe tip is lowered in the recess of a high aspect ratio structure, the distancer interfaces with a wall of the high aspect ratio structure instead ofthe apex the probe tip. When the walls ofthe high aspect ratio structure are sloped, uneven or otherwise not perpendicular to the surface ofthe sample, it may occur that the apex ofthe probe tip interfaces with, e.g. a sloped, wall before the distancer does. This wouldmean that the distancermay be bypassed and its aforementioned positive effects negated. Therefore, providing a distancer at the apex ofthe probe tip can facilitate the contact between the probe tip and the high aspect ratio structure in case the high aspect ratio is sloped, or uneven. The base can be tapered such that the base has a larger width than the distancer, measured in a direction transverse to the longitudinal axis, at a rst length from the end ofthe probe tip in a direction parallel to the longitudinal axis. Such tapering provides structural integrity and allows the probe tip to access narrow recesses while maintaining stability. By having the distancer protrudingmore radially outward than the width of the base, e.g. when the length is smaller than the first length, itmay be ensured that the distancer interfaces with the structures on the surface of the sample. The larger the first length is, the more suitable the probe tip may be to scan high resolution structures. Conversely, by having the side of the base ofthe probe tip opposite the apex being relatively wide compared to the width ofthe base ofthe probe tip between the apex and the first length, it may be facilitated that the probe tip may be conveniently attached to the scanning probe microscope. Additionally, a relatively wide probe tip may increase the structural integrity ofthe probe tip when exposed to forces acting upon the probe tip when scanning. Thus, the skilled person will need to consider the advantages ofhaving a relatively long first length to the advantages ofhaving a relatively short first length. For example, the rst length can be larger than 1 / 3 the length ofthe probe tip measured parallel to the longitudinal axis, such as 1 / 2 the length or 8 / 4 the length or the full length ofthe probe tip. In some implementations ofthe present concept, in conjunction with the step ofscanning, the method further comprises a step ofmapping of said structures by moving the probe tip relative to the substrate surface and bringing the probe tip in contact with the surface, wherein for performing saidmapping ofthe structures the method comprises sensing a deection ofthe probe causedby interaction ofthe probe tip with a structure for obtaining a measurement signal, and performing a step of deconvolution ofthe measurement signal with a shape ofthe probe tip for establishing the shape ofthe structure, wherein the probe comprises a probe tip including a spherical shaped distancer forming the apex ofthe probe tip. The use ofa spherical shaped probe tip makes deconvolution invariant of the angle oforientation, thereby reducing the complexity ofthis process and increasing the accuracy ofthe calculated shape ofthe structure. In a second aspect ofthe invention, there is provided for a probe tip for a scanning probe microscope. The probe tip is arranged to be attached to a probe of a scanning probe microscope, e.g. an atomic force microscope. The probe tip comprises a base, an apex at an end ofthe base arranged to interface with the surface ofthe sample and a distancer. The base extends parallel to a longitudinal axis ofthe probe tip. The distancer extends from the base such as to extend radially outward for defining a width ofthe probe tip including the distancer. In an implementation, the distancer can be rotationally symmetric around the longitudinal axis ofthe probe tip and additionally or alternatively be provided away from the apex ofthe base. If it is known that the walls ofthe high aspect ratio are sufciently perpendicular to the surface ofthe sample, providing the distancer away from the probe tip, or at a distance from the probe tip, may allow for the scanning ofeven deeper recesses ofhigh aspect ratio structures, i.e. high aspect ratios ofwhich the lateral dimension is even further reduced. Ifthe ll distancer is provided at a distance chosen such that the interaction between the side wall ofthe high aspect ratio structure and the probe tip is sufciently low, e.g. by providing the distancer at 1 / 5th, 1 / 4th or even 1 / 3rd of the length ofthe probe tip measured from the apex, the interactionmay be still sufciently low to increase probe tip lifetime and reduce the forces needed by the scanning probe microscope to scan the surface and the high aspect ratio structure in particular. For example, ifthe distancer is provided at 1 / 5th de distance ofthe probe tip measuredfrom the apex, only 1 / 5th ofthe probe tip may be exposed to the side wall ofthe high aspect ratio structure before the movement into the recess is limitedby the distancer, as the distancermay interface with the surface ofthe sample, e.g. the top ofthe high aspect ratio structure, or the side wall ofthe high aspect ratio structure. Further advantageous aspects ofthe invention are set out in the description and appended claims. The technical features described in the paragraphs and sentences above can be isolatedfrom the context, and the isolated technical features from the different paragraphs and sentences can be combined. Such combinations are herewith specifically disclosed in this description. The invention will further be elucidated on the basis ofexemplary embodiments which are represented in the drawings. The exemplary embodiments are given by way ofnon-limitative illustration ofthe invention. In the drawings: Figs. 1A and 1B show a schematic view ofa probe tip scanning a surface of a sample according to the prior art; Fig. 2 shows a schematic view ofan example of a probe tip according to the invention; Figs. 3A and 3B show a schematic the probe tip according to Fig. 2 and a probe tip according to the prior art scanning a surface ofa sample respectively; Fig. 4 shows a schematic view of a further example of a probe tip according to the invention; Figs. 5A and 5B show a schematic view ofthe example ofthe probe tip according to Fig. 4 and a probe tip according to the prior art scanning a surface of a sample respectively; Figs. GA and GB depict a schematic view ofa probe tip according to another example ofthe invention, wherein in Fig. GB the probe tip ofFig. GA is angled; Figs. 7A 7C depict a schematic view of a further probe tip according to an example ofthe invention, wherein in Fig. 7B and 7C the probe tip of Fig. 7A is angled; and Figs. 8A 8C depict a schematic view ofan even further probe tip according to an example ofthe invention, wherein in Fig. 8B and 8C the probe tip of Fig. 8A is angled. Figure 9 schematically illustrates a system for executing a method according to the present concept. Figure 10A and 10B schematically illustrates a method in accordance with the third aspect. It is noted that the figures are only schematic representations that are given by way ofnon-limited examples. In the gures, the same or corresponding parts are designated with the same reference numerals. Figure 9 schematically illustrates a system for executing a method according to an embodiment ofthe invention. The system comprises a scanning probe microscopy device comprising a scan head 202 with a probe 203 including a probe tip 1. The scan head 202 cooperates with the substrate carrier 205, which supports the substrate 206, for mapping features on or below the substrate surface 261. The probe tip 1 includes a distancer 4, which will be further described in relation to the gures discussed in the description below. The distancer 4 at the apex ofthe probe tip 1 is to be brought in contact with the substrate surface 261. In the presently described invention, the scanning probe microscopy system is used in order to map high aspect ratio features on the surface. Mapping offeatures on surface 261 is performed by moving the probe tip 1 relative to the substrate surface 261 and bringing the probe 203 in contact with the substrate surface 261. This contactmay be established continuously, i.e. in contact mode ofthe system wherein the probe tip 1 remains in contact with the surface 261, or intermittently by vibrating the probe tip such that it impacts (i.e. taps) the surface regularly in tapping mode. The measurements are performed by monitoring the deection ofthe probe tip. To established the shape of surface features, a deconvolution step is to be performedbetween the measurement signal and the shape and orientation ofthe probe tip. In contact mode, for example, a constant force is maintained continuously between the probe tip 1 and the substrate surface 261. As the probe tip 1 moves across the substrate surface 261, variations in surface topography cause changes in the interaction forces between the probe and the substrate.A light source 207 emits a lightbeam 209 onto the back ofthe probe 203, typically onto a specular reective surface on the back ofprobe tip 1. Changes in the interaction forces between the probe 203 and substrate 206 will cause a deection ofthe probe tip 1. These deections will cause the lightbeam 209 to be reected by the probe 203 at a changed angle. This change is detectedby an optical sensor 210 and used by a controller 2 1 1 to correct the probe position on the substrate 261. This correction may be done using a correction signal from the controller 2 1 1, or based on the deection signal detectedby the sensor 2 10, or by a combination ofboth signals. The correction is used to determine a dimension ofan on-surface feature on the substrate 206 and to generate an image ofthe features on the substrate surface 26 1. Alternatively to contact mode, in tappingmode the probe tip 1 oscillates at high frequencies near its resonant frequency, such that contact between the rounded shape 241 and the substrate surface 261 is made intermittently. As the rounded shape 241 taps on the substrate surface 261, changes in amplitude, phase, or frequency ofthe oscillatory movement are monitored to detect variations in the topography ofthe substrate surface 261 and used to generate an image thereof. The method using a probe 203 and probe tip 1 can also be used for mapping features below the substrate surface 261, including buried interfaces oflayers, or subsurface defects or inclusions such as the subsurface feature 2 12. This would involve applying an acoustic vibration 213 to the probe 203 or to the substrate 206. This vibration 213 then propagates through the substrate 206 andhas signal components which can be detected again at the substrate surface 261. For example, the vibration may have signal components with high frequencies (for example above 100 MHz), or signal components with lower frequencies (for example below 100 MHz). In the case ofhigher frequencies, the vibration 213 propagates through the substrate 206 and scatters from the feature 2 12. Some ofthe scattered vibration propagates back to the surface; this backscattered output signalmay then be detectedby the probe 203. In the case oflower frequencies, the feature 212 may be detectedbased on a mechanical response ofthe probe-substrate interaction caused by the vibration 2 13. For example, the substrate 206 may deform less when the vibration 213 is applied directly above the feature 212 than it wouldwhen the vibration 213 would be applied elsewhere on the substrate surface 261. In both cases, the probe will detect a signal component that has a frequency equal to the difference between two signal components ofthe applied acoustic vibration 2 13. In the present concept, a system such as briey described above and illustrated in figure 9 will be used for mapping high aspect ratio structures.A high aspect ratio structure, as referred to herein, is a structure ofwhich the height dimensions (transverse to the surface) are typically more pronounced (i.e. larger) than the width dimensions (in the directions parallel to the surface). Figs. 1A and 1B show a schematic example ofa probe tip 100 scanning a surface 101 of a sample 102 according to the prior art. The surface 101 comprises an structure 103, specifically a high aspect ratio structure 103 being a recess. The structure 103 is considered to be a high aspect ratio structure as the structure 103 is relatively high, in a height direction H, compared to its width in a width direction W. Specifically, the object has a height dimension in the height directionH being larger than a lateral dimension in the width direction W. The probe tip 100, which is mounted to a probe ofan atomic force microscope (not depicted) is used to scan the surface 101. This may be done by dragging the probe tip 100 over the surface, i.e. having a minimal amount ofmovement in the height directionH while moving in a direction parallel to the width direction W, or may be done by tapping the surface 101, i.e. by also significantly moving in the height directionH while moving in the direction parallel to the width direction W. In the shown example ofFigs. 1A and 1B, the surface 101 is scanned by a tapping movement. The probe tip 100 is a conventional probe tip, being rotational symmetric around a longitudinal axis A1, being tapered along the longitudinal axis A1 towards an end 104 ofthe probe tip 100. Turning to Fig. 1A, the probe tip 100 taps the surface 101, and is lowered in the high aspect ratio structure 103 and reaches the surface 101 at the bottom ofthe high aspect ratio structure 103 where the end 104 ofthe probe tip 100 interfaces with said surface 101. As can be seen from the schematic image, this is indeed the surface 101 and as a result data ofthe surface is correctly registered by the atomic force microscope to which the probe tip 100 is mounted. Turning to Fig. 1B, the same probe tip 100 as in Fig. 1A attempts to interface with the surface 101 again, however the tapered probe tip 100 comes in to contact with the high aspect ratio structure 103. As a result, the probe tip 100 experiences a signicant amount ofinteraction with the high aspect ratio structure 103, which may result in increased wear on the probe tip ormay prevent the probe tip 100 from moving further down and not registering it still has a distanceD to bridge before the actual surface 10 1 is reached. As a result, the atomic force microscope to which the probe tip 100 is attached incorrectly registers that the surface 101 is at the end ofthe probe tip 104 and the atomic force microscope incorrectly registers the surface data. Turning to Figs. 2, 3A and 3B, a schematic view illustrates an example ofa probe tip 1 according to the invention. The probe tip 1 is designed to provide a probe tip of a probe ofan atomic force microscope (not depicted). The probe tip comprises a base 3 and an apex 5 at an end ofthe base 3 arranged to interface with a surface of a sample. The probe tip 1 further comprises a distancer 4, in the shown example the distancer 4 is provided at the apex 5 ofthe probe tip 1. As a result, the distancer 4 in the shown example is arranged to scan a surface 11 ofa sample 10. The base 3 extends parallel to a longitudinal axisA ofthe probe tip 1. In this example, the base 3 is tapered towards the apex 5 ofthe probe tip 1. Such tapering provides structural integrity and allows the probe tip to access narrow recesses while maintaining stability. In the example, to minimize contact with sidewalls and ensure compatibility with high aspect ratio structures, the distancer 4 is spherically shaped, with a rounded cross-section, and is rotationally symmetric around the longitudinal axis A. The distancer 4 extends from the base 3 such as to extend radially outward and dening a widthW2 ofthe probe tip 1, said widthW2 including the distancer 4. In the shown example, the distancer 4 furthermore protrudes radially in a direction transverse to the longitudinal axis A. Specically, the distancer 4 is spherically shaped, such that it has a rounded cross-section. The center C ofthe spherically shaped distancer 4 coincides with the longitudinal axisA ofthe probe tip 1. The base 3 is tapered such that the base 3 has a larger widthW1 than the distancer W2, measured in a direction transverse to the longitudinal axis A, at a first length L from the end 5 ofthe probe tip 1 in a direction parallel to the longitudinal axis A. The distancer 4 has a first dimension D1 parallel to the longitudinal axisA and a second dimension, in the example corresponding to the widthW2 ofthe distancer 4, transverse to the first dimension D1. The second dimension, or widthW2 ofthe distancer 4 is larger than the rst dimensionD 1, effectively causing the distancer element 4 to be relatively thin in a direction parallel to the longitudinal axis A, comparable to a disc-shape. Turning to Figs. 3A and 3B, the probe tip 1 according to an example ofthe invention and a probe tip 100 according to the state ofthe art are shown respectively. Both probe tips 1, 100 are used by an atomic force microscope (not depicted) in a tappingmode to scan the surface 1 1 ofa sample 10 on which a high aspect ratio structure 12 is provided. In both Figs. 3A and 3B, the corresponding probe tip 1, 100 is lowered, during the tapping motion ofthe atomic force microscope, at the same position relative to the high aspect ratio structure 12 measured from the most distal end 13, 13 ofboth probe tips 1, 100, e.g. at the bottom ofthe corresponding probe tip 1, 100. Comparing the surface ofthe probe tip 1, 100 ofthe example ofthe invention and the prior art interfacing with the wall 14 ofthe high aspect ratio structure 12, it can be seen that the probe tip 1 according to the invention has signicantly less surface interfacing with the wall 14 compared to the probe tip 100 ofthe prior art. In particular, the distancer element 4 in the inventive probe limits lateral contact, ensuring that only a small section ofthe probe tip interacts with the sidewall. As a result, the probe tip 1 ofthe invention will have less interaction with the high aspect ratio structure 103 than the commonly used probe tip 100, which leads to an increased probe tip lifetime, a reduced chance of artifacts, and greater accuracy in depth and lateral measurements ofthe high aspect ratio structure. Additionally, by reducing unwanted lateral contact between the probe tip 1 and sidewalls 14 ofthe high-aspect-ratio structure 12, the probe tip 1 maintains improved vertical stability within the high-aspect ratio structure 12. This stability is achieved as the distancer 4 ensures a single, known contact point with the sidewall 14. During measurements, only the distancer 4 contacts the sidewall 14, leaving the rest ofthe probe tip 1 unaffected. In contrast, probes without a distancermay have multiple or variable-height contact points, reducing measurement precision. Turning to Fig. 4 a schematic side view of a probe tip 1 according to a further example ofthe invention is depicted. The probe tip 1 comprises a base 3, an apex 5 at an end ofthe base, and a distancer 4 positioned away from the apex 5. The apex 5 is arranged to interface with a surface of a sample. The distancer 4 ofthe probe tip 1 extends from the base 3 such as to extend radially outward for dening a widthW2 ofthe probe tip 1 including the distancer 4. The distancer 4 is rotationally symmetric around a longitudinal axisA ofthe probe tip 1, in the shown example the distancer is spherically shaped, forming a disc-like structure having its center C coincide with the longitudinal axis A. In further implementations, the distancer 4 may take on alternative shapes or positions along the probe tip, allowing customization based on specic sample or structural characteristics. The distancer is provided away from the apex 5 ofthe base 3, i.e. the distancer is provided at a distance D2 from the apex 5 ofthe probe tip. By positioning the distancer at the distance D2 from the apex 5, the probe tip 1 is kept narrow and sharp, providing a very small contact point, whereas advantages ofthe distancer 4 such as reducing the contact area with the sidewalls are maintained. In Figs. 5A and 5B the use ofthe probe tip 1 according to the example ofFig. 4 has been shown. Specically, Fig. 5A depicts the probe of Fig. 4 scanning a surface 1 1 of a sample 10 comprising high aspect ratio structure 12. In Fig. 5B a probe tip 100 according to the prior art is depicted scanning the surface 11 ofthe same sample 10 as shown in Fig. 5A. As can be seen, both probe tips 1, 100 interface with the wall 14 ofthe high aspect ratio structure 12. However, the probe tip 1 ofFig. 5A is limited in height direction by the distancer 4 and as a result cannot be moved down further. Alternatively, the probe tip 1 may deform slightly or slip over the surface 1 1 ofthe sample 10 such that the probe tip 1 can move down the recess formed by the high aspect ratio structure 12. When moving down the recess 12 in such a situation, the distancer 4 interfaces with the wall 14 ofthe high aspect ratio structure, and not the base ofthe probe tip 100 as will be the case in the example depicted in Fig. 5B. The probe tip 1 according to an example ofthe invention however either cannot move down further without lateral movement in the scan directionW or will slip such that the distancer 4 prevents the base 3 ofthe probe tip 1 from interfacing with the wall 14. Thus, compared to the conventionally used probe tip depicted in Fig. 5B, the probe tip 1 according to the invention interacts less with the side wall 14 of the high aspect ratio structure 12 and as a result has less interaction with the probe tip 1. The rounded, spherically shaped distancer which is for example depicted in Figs. 2 and 4 provides additional advantages by minimizing the contact area between the distancer and the sidewalls ofhigh aspect ratio structures. By limiting contact primarily to the apex ofthe distancers rounded shape, interaction between the probe tip 1 and the sidewalls is signicantly reduced. This design ensures that only a minimal portion ofthe distancer interacts with the structure, facilitating smoother movement of the probe tip within narrow recesses and thereby further enhancing measurement accuracy while reducing wear. In addition to reducing wear on the probe tip itself, this limited contact minimizes potential damage to delicate samples and lowers the risk ofsample and probe tip contamination. The limited sidewall interaction further enables the probe tip to maintain stable vertical positioning within a recess, contributing to more accurate depth measurements. By ensuring consistent orientation and reducing probe deformation, the design also enhances repeatability across multiple measurements, allowing for more reliable results when scanning similar structures with the same probe. Turning to Figs. GA and GB, an example ofa probe tip 1 according to the invention is depicted. The distancer 4 is a spherical distancer 4 provided at the tip 5 ofthe probe 1 such that the apex ofthe probe tip 1 is located on the distancer 5. The spherical distancer 4 has a constant radius, and its midpoint coincides with the longitudinal axis ofthe base 3 such that the distancer 4 is rotational symmetric around the longitudinal axis ofthe probe tip 1. In Fig. 6A the probe tip 1 is in an upright position, in Fig. GB the probe tip 1 is angled. This anglingmay be the result ofthe suspension from the scan head ofthe scanning probe microscope, a periodic motion of the probe tip 1, or of external forces acting upon the probe tip 1. Comparing Fig. 6A and 6B, it can be seen that the projected width ofthe probe tip, WO andw1 of Fig. 6A and GB respectively, is the same. As a result, the spherical distancer 4 renders deconvolution to be independent ofthe angle ofthe probe relative to the surface ofthe sample. As a result, the process of deconvolution is less complex. In Figs. 7A-7C and 8A-8C a comparison is given with different probe tip 4 shapes. Turning to Figs. 7A-7C and 8A-8C further examples ofthe probe tip 1 according to the invention have been depicted. As an example, the spherical distancer 4 ofFigs. 6A and GB has been replaced by a square probe tip 4 (in Figs. 7A 7C) and a ovoid shaped distancer 4 in Figs. 8A 8C. In Figs. 7A and 8A, the probe tip 1 is in an upright position, having a projected width ofWO on the surface of a sample during use. In Figs. 7B and 8B, the probe tip 1 has been angled relative to the upright position over an angle a. Due to the angling, it can be seen that both probe tips 1 of Figs. 7B and 8B tilt, andhave a displacement height dz and a projected width ofw1. The projected width w1 in Figs. 7B and 8B is larger than the projected width WO of Figs. 7A and8A due to the tilting. The incorrect projected width w1 needs to be corrected for, ofwhich an example is shown in Figs. 7C and 8C. The incorrect projected width w1 is the sum ofthe projected width WO and the displacement width dx. Although, it is possible to deconvolute the angled probe tip 1 ofFigs. 7B and 8B, doing so will result in an error ofvalue dx in x-direction and dz in z-direction. The displacement width dx and height dz ofthe probe tip ofFigs. 7A 7C can be determined using the following equations respectively: dx : hO * cos (a) and dz : WO * sin (a), in Which h1 is the length ofthe probe tip 1. For Figs. 8A-8C, the displacement width dx and height dz ofthe probe tip 1 can be determined using the following equations respectively: dx : 4r (Zr + Zr * cos(a)) and dz : Zr * sin (a).Hence, in either case ofgures 7 and 8, the angle must be determined in order for the correction to be carried out. Comparing to the spherically shaped probe tip 1 of Figs. 6A and 6B, it can be seen that the deconvolution process is less complex and results in less error when a spherical distancer 4 is used. Figure 10A schematically illustrates a probe 203 scanning a substrate surface 261 as the spherical shape 241 ofthe probe tip 1 makes contact with a sidewall 262 ofan on-surface feature 264. The direction ofthe probe 203 relative to the surface 261 is indicatedby arrow 266. The probe 203 in gure 10A is oriented at an angle 6 With respect to the substrate surface 261. As the probe tip 1 moves over the feature 264, the probe tip 1 will encounter the edge 265 thereof. Upon going over the edge 265, the probe 203 will be deected, resulting in a deection signal being measured. An example ofresultingmeasurement data 300, in the form ofa deection signal u against a horizontal probe position x is depicted in figure 10B. The measurement data 300 are deconvolved with probe tip shape data associated with the shape at the end ofprobe tip 1. In embodiments ofthe first aspect ofthe invention where the rounded shape is spherical, and in the method according to the third aspect ofthe invention, the deconvolution is invariant with respect to the angling 6 ofthe probe 208 because the constant radius ofthe spherical shape 241 ofthe probe tip 1. Therefore, the measurement signal 300 of deection u will be invariant to angle 6. The shape ofedge 265 can be obtainedby deconvolving the round shape 801 of the measurement signal thereofWith the shape ofthe probe tip 1. In other embodiments, the probe tip may be provided with partially spherical rounded shapes, such as hemi-spherical shapes. Ifthe probe tip 1 were instead provided with a non-spherical shape, such as elliptical shape 243, scanning the substrate surface 261 with that probe will result in a measurement signal that is dependent on the orientation angle 6 ofthe probe 203, which is therefore more difficult to deconvolve. This is an example ofhow the deconvolution ofthe measurement data 300 would be more complex than when a probe tip 1 with a spherically shaped tip is used, because additional uncertainties are contained within the measurement data. The rotational symmetry ofspherical shapes alleviates these effects, signicantly simplifying the deconvolution process. Many variations will be apparent to the skilled person in the art. For example, the base ofthe probe tip may have a different cross-sectional shape than shown in the examples, i.e. round, for example triangular, square or hexagonal. As may be appreciated by the skilled person, additional implementations not explicitly depicted in the drawings are possible, wherein the distancers dimensions, shape, and positioningmay be varied to achieve similar advantages. Furthermore, it will be apparent to the skilled person that the disclosed probe tip can be used on various surfaces to detect structures having various, preferably high aspect ratio structures, and not merely a at surface and a rectangular structure.
Claims
1. Procedure for measuring a dimension of a structure with a high aspect ratio of a sample using a scanning measuring probe microscope, where the aspect ratio includes a recess with a height dimension in a direction perpendicular to the surface and a lateral dimension in a direction parallel to the surface, where the height- dimension is larger than the lateral dimension; where the method the steps includes: - scanning the surface of the sample in a scanning direction parallel to the surface by a measuring probe comprising a measuring probe point attached to the scanning measuring probe microscope, and lowering, during the scanning step, of the measuring probe tip in the recess to the dimension of to determine the structure with a high aspect ratio; - where the recess comprises a recess width between ten at least two opposite side walls in a direction parallel to the scan direction; - whereby the measuring probe tip, which is lowered into the recess, a base comprises, an apex at one end of the base arranged to make contact make with the surface of the sample, and a spacer, whereby the base extends parallel to a longitudinal axis of the probe tip and where the spacer extends from the base to radially outwards to serve to define a width of the measuring probe tip including the spacer; and - where the width of the probe tip is smaller than the recess width.
2. Method according to claim 1, where the spacer a stiffness is such that, during lowering at a contact of the spacer with one of the side walls, the spacer touches the side wall without the spacer bending.
3. Method in accordance with claim 2, whereby the spacer is such that formed to provide the stated stiffness in at least one direction laterally with respect to a direction in which the spacer extends from the ground up.
4. Method of working in accordance with one of the preceding claims, whereby the width of the measuring probe tip is between 0.3 and 1 times the recess width.
5. Method of working in accordance with one of the preceding claims, whereby the spacer one end at a distance from the base of the measuring probe tip includes, where the end has a rounded shape at a distance.
6. Method of working in accordance with one of the preceding claims, whereby the spacer is rotationally symmetrical about the longitudinal axis of the measuring probe point.
7. Method of working in accordance with one of the preceding claims, whereby the spacer of the measuring probe tip used for lowering in The recess is formed by a disc, star, or rod shape to the to allow the spacer to extend in more than one direction.
8. Method of working in accordance with one of the preceding claims, whereby the A spacer is provided at the apex of the measuring probe tip.
9. Method of working in accordance with one of the preceding claims, whereby the spacer is spherical or elliptical, such that it has a rounded has a cross-section.
10. Method of working in accordance with one of the preceding conclusions, whereby the base tapers so that the base has a greater width than the spacer, measured in the direction of movement, at a first length from the end of the probe tip in a direction parallel to the longitudinal axis. 1 1. Method of working in accordance with one or more of the preceding claims, whereby in combination with the scanning step, the method furthermore a step of in mapping of said structures encompassed by the probe tip at to move relative to the substrate surface and the measuring probe tip in to bring into contact with the surface, whereby for carrying out mentioned mapping of the structures the methodology includes the detecting a deflection of the measuring probe caused by interaction of the measuring probe tip with a structure for obtaining a measurement signal, and performing a deconvolution step of the measurement signal with a shape of the measuring probe tip for determining the shape of the structure, where the measuring probe comprises a measuring probe tip including a spherical spacer that forms the apex of the measuring probe tip.
12. Probe tip configured for a scanning probe microscope to be attached to a measuring probe of a scanning measuring probe microscope, comprising a base, an apex at one end of the base designed to make contact with a surface of a sample, and a spacer, where the base extends parallel to a longitudinal axis of the measuring probe tip and where the spacer extends from the basis to extend radially outwards to define a width of the measuring probe tip including the spacer.
13. Probe tip for a scanning probe microscope according to conclusion 12, where the spacer is rotationally symmetrical around the longitudinal axis of the measuring probe tip.
14. Measuring probe point according to claim 12 or 13, where the spacer is provided at a distance from the apex of the base.
15. Method for measuring a dimension of a structure with a high aspect ratio of a sample using a scanning measuring probe microscope, where the structure with a high aspect ratio a recess encompasses with a height dimension in a direction perpendicular to the surface and a lateral dimension in a direction parallel to the surface, where the height dimension is greater than the lateral dimension; where the method the steps include: - scanning the surface of the sample in a scanning direction parallel to the surface by a measuring probe comprising a measuring probe point attached to the scanning measuring probe microscope, and lowering, during the scanning step, of the measuring probe tip in the recess to the dimension of to determine the structure with a high aspect ratio; - where the recess comprises a recess width between ten at least two opposite side walls in a direction parallel to the scan direction; - whereby the measuring probe tip, which is lowered into the recess, a base comprises, an apex at one end of the base arranged to make contact make with the surface of the sample, and a spacer, whereby the base extends parallel to a longitudinal axis of the probe tip and where the spacer extends from the base to radially outwards to serve to define a width of the measuring probe tip including the spacer; and - where the width of the probe tip is smaller than the recess width. 5