Patent Grant
10139429
N/A.
The invention related to scanning probe microscopy for scanning and probing a sample with multi-tip scanning probes.
A scanning probe microscope (SPM) is a type of microscope that forms images of a specimen using a physical probe that scans over the surface of the specimen. The scanned probe may react with the specimen through a variety of physical forces, including mechanical contact forces, van der Waals forces, capillary forces, chemical bonding forces, electrostatic forces, and magnetic forces. SPMs measure different forces to determine different properties of the specimen, and display the sample properties on an image.
Types of SPMs include the scanning tunneling microscope (STM), which measures conducting sample, and the atomic force microscope (AFM), which can measure various properties of non-conductive sample. AFMs are well known and are described, for example, in U.S. Pat. No. 6,185,991 to Hong et al. for “Method and Apparatus for Measuring Mechanical and Electrical Characteristics of a Surface Using Electrostatic Force Modulation Microscopy Which Operates in Contact Mode”, which is hereby incorporated by reference. An AFM can operate in a contact mode, a tapping mode, or a non-contact mode.
U.S. Pat. No. 6,951,130 to Hare, et al, issued Oct. 4, 2005 and titled “Software Synchronization of Multiple Scanning Probes,” which is commonly owned by the present assignee, describes a method and apparatus for scanning multiple scanning probe microscopes in close proximity. This allows the system to scan overlapping scan areas at the same time while avoiding collision. The techniques therein provide drive signals to a first Atomic Force Microscope (AFM) and calculated drive signals to additional AFMs based on the first drive signals and the relative position of the additional AFMs to the first AFM for consistent spaced motion. Scanning and Failure Analysis (FA) probing of multiple feature of interest using multiple APMs allows for reduced time for locating FA features to set up measurements. This prior patent is hereby incorporated by reference for all purposes.
When an AFM is operated in a mode to detect electrostatic force, it is referred to as an electrostatic force microscope (EFM). The EFM is a type of vibrating, non-contact AFM in which a force generated by applying an electrical potential difference between the probe tip and the sample is measured. An EFM is described, for example, in P. Girard, “Electrostatic Force Microscopy: Principles and Some Applications to Semiconductors,” Nanotechnology 12, 485 (2001). As described in Girard, a voltage difference between a sample and an AFM tip creates a force proportional to the change in capacitance with probe height and the square of the potential difference. U.S. Publication No. 20160231353, by Erickson et al., describes a scanning probe microscope includes a scanning probe and one or more additional local-potential-driving probes that provide one or more local electrical potentials on a nanometer scale structure on the sample. The local-potential-driving probes may provide a fixed potential, an alternating potential, or a combination of both in order to tailor the local electrical field distribution for maximum sensitivity and selectivity when measurement are performed by the scanning probe. By driving the potential at a local feature rather than through the bulk sample, the local feature can be differentiated on a potential map from neighboring features, which allows for a single line among closely spaced lines to be identified and allows for imaging using fainter signals, such as those from subsurface features. This is particularly useful to identify circuit defects.
As semiconductor circuits get smaller and the metal lines get closer together. The “pitch,” or distance between metal lines in modern integrated circuits varies with the fabrication process, but can be typically less than 100 nm, less than 80 nm, and even less than 40 nm. As the pitch becomes smaller in each new generation of fabrication processes, it becomes more difficult, time consuming, and labor intensive to calibrate a multi-tip AFM system for scanning and probing with probe tips at very close proximity. What is needed are improved systems and methods for operating multi-tip AFM probes to increase efficiency, precision, and throughput of such systems.
The present invention teaches a new approach to the calibration and scanning of multiple AFM probe heads used employed together for synchronous scanning. An automated calibration process is provided employing scan data from multiple AFM probe heads to automatically calibrate the system and position the probe heads at relative offset positions that are successively closer and more precise. Multiple heads are scanned simultaneously and synchronously to produce scan images, which are automatically evaluated to recognize a common feature in the scan images. From this, a relative offset of the images is calculated and the true position of each probe tip may be known. Using this knowledge, a position offset is applied to bring the probe tips closer together at a desired spatial relationship. The techniques may be repeated at two or more levels varying from coarse to fine, and may be repeated after probing or movement to a new region of interest.
Other aspects of the invention include computer readable media containing programming instructions for accomplishing the processes herein. Still further aspects involve a system including multiple AFM assemblies, control electronics, and programming for managing system workflow and conducting the processes described herein.
The various aspects provide the benefits of much greater efficiency and accuracy in calibrating and using AFM systems with multiple scanning and probing tips scanned synchronously. The improved calibration also provides ability to perform lengthy calibration procedures required to bring tips into very close proximity for synchronous scanning with multiple tips of samples with very small feature sizes.
According to one aspect of the invention, a method is provided for operating an atomic force microscope (AFM) system under control of a processor, the AFM system including multiple AFM assemblies positioned for scanning a common sample area, each having a cantilever supporting a probe head with at least one tip. The method includes positioning the multiple AFM probe heads with their respective tips at a first predetermined relationship to each other. Then it automatically performing a first scan including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image. The method automatically processes the scan images to recognize a feature appearing in all the scan images having desired spatial characteristics. From this, it automatically designates the recognized feature as a common feature and overlays the scan images together to determine a relative offset for each of the scanning tips. Based on the relative offset, the method automatically positions the scan tips at a second predetermined relationship to each other, the second relationship placing the tips relatively closer to each other than the first relationship. After positioning the scan tips at the second predetermined relationship, automatically performing a region of interest scan including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image.
In some embodiments, the desired spatial characteristics of the recognized feature include a designated minimum feature pitch between two feature structures. The second predetermined relationship may also have greater precision than the first predetermined relationship with regard to control of the position. The method may, after positioning the scan tips at the second predetermined relationship, automatically reconfigure the AFM system for scanning at an increased resolution.
In some embodiments, the second predetermined relationship places the tips along the circumference of an imaginary calibration circle. The calibration circle may be centered around the common feature of the first scan.
The method may be employed with an AFM system including multiple AFM assemblies, for example a number n of least two, three, four, or eight AFM assemblies.
The method may further include, before performing the region of interest scan, performing a second, fine probe reference scan which proceeds similarly to the coarse probe reference scan but repositions the probe tips at a closer proximity, for example positioning the probe tips along circumference of an imaginary fine calibration circle.
According to another aspect, the invention may be embodied as an atomic force microscope (AFM) system including at least three AFM assemblies positioned for scanning a common sample area, each including a cantilever supporting a probe head with at least one tip, a 3-axis actuator mechanically coupled to the cantilever, control electronics operably coupled to a feedback position sensor for providing calibrated scanning of the probe head, and a deflection sensor positioned to sense deflection of the cantilever. The system includes an electronic controller coupled to the control electronics of the AFM assemblies, and operable to generate a scan waveform for each respective AFM assembly. Coupled to the controller is tangible, non-transitory computer readable memory coupled to the electronic controller and containing program code executable by the electronic controller performing the methods herein.
According to another aspect, the invention may be embodied as program code stored on computer readable media executable by a controller to operate an atomic force microscope (AFM) system, the system having at least three AFM assemblies positioned for scanning a common sample area, the program product containing program code executable for performing the methods described herein.
Other objects and advantages appear hereinafter in the following description and claims. The accompanying drawings show, for example purposes without limiting the scope of the present invention or the appended claims, certain practical embodiments of the present invention.
The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing.
Several variations of the subject invention are now described in order to illustrate the salient features of the invention. The examples are chosen to illustrate how the beneficial features of invention, including the use of automated calibration processes for multiple scanning AFM heads employed together, facilitates improvements for processing and automating scanning and probing of samples. Not all of the innovative elements are employed in each of the illustrated examples.
The depicted system in
During the scanning of each probe tip, forces between the sample 108 and the cantilevers 404 with probe tip 402 cause a deflection of cantilever 404. A laser 116 directs a beam of light 117 towards a reflective surface on cantilever 404 near tip 402, and the reflected light 120 is detected by a position sensitive photon detector 122, which produces an electrical output signal corresponding to the position of the tip. The output signal from each detector 122 is processed by a signal processor 124 to determine the deflection of tip 402 over time. The cantilever oscillation, and therefore the signal output from photon detector 122, is essential sinusoidal and characterized by a frequency, amplitude, and phase. The various forces between the probe and the sample will affect these sinusoidal properties. Signal processor 124 may include one or more lock-in amplifiers 126 to extract signals corresponding to specific frequencies from other signals and noise present in the output signal from detector 122. In various applications, the amplitude, frequency, and/or phase of the cantilever vibration are detected and used to determine a local property of the sample.
A controller 130 controls AFM system 100 in accordance with instructions input through user interface 132 or in accordance with program instructions stored in computer memory 134. Controller 130 also controls an imaging device 136, such as a computer display screen, to display sample images formed by AFM system 100. In some applications, controller 130 uses the tip deflection to provide feedback to positioner 406 to raise or lower the cantilever 404 to maintain a constant distance between the probe tip 402 and the sample surface. By “distance between the probe tip and the sample surface” is meant the distance from the local sample surface below the probe to the rest position of the probe. In other applications, the probes are scanned in a straight line, and so the height of the probe about the sample surface varies as the local surface topography.
A sample voltage source 140 may be included to apply a dc bias voltage, an ac voltage, or a combination of both to sample 108. As used herein, applying a dc bias voltage may include applying a zero voltage, that is, grounding an element.
When the AFM is being used to measure voltages, the sample may optionally positioned within a guard chuck which secures the sample and partly surrounds it with a conductive material to reduce stray electrical potentials that can affect the electrical measurements. The potential from sample voltage source 140 can be applied to the bulk sample through the guard chuck, or through a conventional chuck. The potential can also be applied to contact pads on the sample.
AFM 100 system of
Controller 130 may be a dedicated computer processor in specialized hardware having control interfaces for system 100, or may be a part of a standard laboratory personal computer, and is typically coupled to at least some form of memory 134 including one or more computer-readable media. Such computer-readable media, which may include both volatile and nonvolatile media, removable and non-removable media, may be any available medium that can be accessed by controller 130. By way of example and not limitation, computer-readable media comprise computer storage media and communication media. Computer storage media include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. For example, computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by controller 130. Memory 134 includes program memory can include computer storage media in the form of removable and/or non-removable, volatile and/or nonvolatile memory and can provide storage of computer-readable instructions, data structures, program modules and other data. Generally, controller 130 is programmed by means of instructions stored at different times in the various computer-readable storage media. The invention described herein includes these and other various types of computer-readable storage media when such media contain instructions or programs for implementing the steps described below in conjunction with a microprocessor or other data processor. The invention may also include the computer processor itself when programmed according to the methods and techniques described herein.
After probing, the process may go to block 340 to navigate to a new ROI, or may remain in the same ROI and go to block 342 to perform a reference ROI update scan to update the relative calibration of the multiple probe tips. Then more scanning and probing may be conducted until all desired features and tests have been probed.
Next at block 452, the process automatically processes the scan images to recognize a feature appearing in all the scan images having desired spatial characteristics, and automatically selects or designates the recognized feature as a common feature all the scanned images. The feature may be predetermined or may be selected automatically according to suitable criteria, as further described below. In some versions of the process, the desired spatial characteristics of the recognized feature include a designated minimum feature pitch between two feature structures. Next at block 454, the process automatically overlays the scan images together to determine a relative offset for each of the scanning tips. This may be performed with a plane-fit filtering technique or other suitable cross-correlation technique for measuring an offset between similar, but not identical, images. Note that head sizes may vary based on uneven wear, and so scan image properties may be different between the various acquired scan images. Based on the relative offset, the process next automatically positions the scan tips at a second predetermined relationship to each other, the second relationship placing the tips relatively closer to each other than the first relationship, such as at circle 203 or another suitable relative relationship. The second predetermined relationship preferably has greater precision than the first predetermined relationship for not only a closer configuration of the tips, but a more highly calibrated group of scan tips. Then the coarse reference scan ends at block 458. Following, the process may proceed with a fine reference scan or if the coarse reference scan is sufficiently calibrated, may proceed with automatically performing a second scan of a region of interest including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image for use in probing the region of interest. The process may further include, after positioning the scan tips at the second predetermined relationship, automatically reconfiguring the AFM system for scanning at an increased resolution. The second predetermined relationship may be a calibration circle that is centered around the common feature of the first scan. Such a relationship may be seen in the sequence of diagrams of
As discussed with regard to
Further, in some cases a third automatic reference scan may be employed after the fine reference scan to achieve an even smaller separation of the probe tips, depending on the system parameters such as tip size, desired scan resolution, and the precision with which the piezo-electric positioners 406 are controllable during movement. For example when system 100 is employed to scan semiconductor features from a 10 nm or smaller process, the fine calibration circle size of 350 nm may be too large for a particular desired high resolution scan, and third reference scan may be conducted to bring the tips to a closer relative spatial arrangement.
Using the techniques above, a ‘four circles’ calibration process may be automated entirely or almost entirely, allowing technicians to setup the process and then leave the system 100 to automatically conduct calibration through the reference scans. In some cases the coarse optical alignment step, for example positioning at circle 201 (block 334,
Table 1 below includes an example automated workflow for conducting a scanning phase including three calibration adjustments. With regard to the preferred embodiment diagrammed in
While these example setting are provided, this is not limiting and any suitable settings may be employed for the sizes, resolutions, speed, and the sizes of calibration circles or other virtual shapes used to align the probe tips. For example, the sizes of circles 201-204 in
Beginning at block 1102, it is assumed that the tips have been arranged in a desired arrangement such as at the circumference of a circle approximately 2 microns in radius by the user visually, or automatically via feedback through image recognition, using the optical camera on the tool. The goal of the overlay and auto-offset is generally to subsequently go beyond reasonably achievable optical accuracy by using AFM scanning to achieve closer and more precise offsets for the AFM tips in iterative overlay and auto-offset steps, for example first to a 0.7 microns radius and then to a 0.35 microns radius circular positioning of all tips. This is achieved by scanning with each tip over an overlapping area with at least one unique feature that is common, i.e. partially visible in all of the overlapping scans, and employing the scan data in the process of
Next at block 1104, the process calculates a set of pairwise shifts between each pairwise combination of images (and therefore tips which acquired the respective images). Each pair of images has a subset of image data that is overlapping so the algorithm(s) for this stage are provided to accurately calculate the translation in X and Y axes to align these overlapping subsets, as further described below. Next at block 1106 the process adjusts for noise and error in the offset measurements by checking for a transitive consistency in the shifts produced by block 1104. This block is performed to reduce the error in each measurement and provides a global coordinate system for all the tip locations as further described below. Finally at block 1108, the process employs the corrected shift locations and global coordinate system from block 1106 to produce the tip offset movements needed to move the tips to new locations to fit the desired shape, such as a circle, and moves the tips according to the offsets. The desired shape may be other suitable shapes such as a grid, oval, square, etc., as discussed above. At this point the overlay and auto-offset process is complete, and the tips can be navigated or scanned as desired, depending on whether the overlay/auto-offset process was a coarse, fine, or update process as discussed above.
The process begins at block 1202 with the multiple partially overlapping scan images provided from a scan of the AFM tips. An example of such an image is shown in
After block 1406, the process calculates one or more sets of offsets using a respective one or more offset calculation algorithms, each set preferably including offset calculations for all respective pairwise combinations to be considered as discussed above. There are multiple methods of calculating offsets between two images that have a common sub-area. Generally the process is restricted to those that use linear offsets in X and Y, although this is not limiting and other suitable techniques may be employed in various embodiments. As depicted, three categories of calculation algorithms are provided that yield linear offsets in X and Y. Block 1408 provides autocorrelation based algorithms, block 1410 provides information-theoretic algorithms, and block 1412 provides feature-tracking based algorithms. Within each category there are many specific implementations and variants that may be used alone or in combination with other algorithms and variants within the category or from other categories. The selection of suitable algorithms may be adjusted based on the application. For scanning semiconductor samples, the present inventors tested multiple algorithms from all three categories. In particular, block 1408 provides three known autocorrelation based algorithms. The first shown is normalized cross correlation on the images directly, using the intensity values. The second is normalized cross correlation on the gradient images, where the gradient of an image may be calculated in multiple ways. The presently preferred implementation of this algorithm calculates the gradient using a modified version of the Kirsch operator. The third technique is phase auto-correlation. Additionally, at block 1410, in parallel to using one or more of the techniques of block 1408, offsets may also be calculated using information-theoretic matching in order to account for scanning variations caused by variation in tip shape and size among the multiple AFM tips. The method used is based on cross cumulative residual entropy which has been shown to be more robust and accurate than mutual information based metrics. A specific correction as defined in Cahill, et al. (Overlap Invariance of Cumulative Residual Entropy Measures for Multimodal Image Alignment, Cahill et al, SPIE, February 2009) is employed to account for reduced accuracy in large shifts.
A set of shifts, again preferably using all pairwise combinations, may also be calculated using feature tracking based offset calculations at block 1413. The process may use feature based technique employing a contour detector to generate features as described in Desolneux et al. (Edge Detection by Helmholtz Principle, Desolneux et al, Journal of Mathematical Imaging and Vision, 2001) with RANSAC (random sample consensus) used to determine shifts. Other methods to extract features like Scale-invariant feature transform (SIFT), speeded up robust features (SURF), or histogram of oriented gradients (HOG), for example, may also be used. For semiconductor scanning applications, the three autocorrelation-based algorithms were determined through experimentation by the present inventors to be the most effective and are combined in the preferred implementation.
In embodiments where two or more algorithms are used to calculate the offsets, the results must be combined in some manner, or the preferred result selected from among the two or more results. As shown at block 1416, in this embodiment the results are combined with normalized addition to produce a single set of pairwise offsets that best reflects the offsets of the images and therefore the actual offset positions of the AFM tips. Note that while there are many ways of combining results from multiple algorithms (i.e. median, highest confidence, weighted by other means, etc), a normalized addition of the results across all possible shifts provided the best performance in experiments with semiconductor scanning data sets.
To achieve the transitive consistency check, several different known algorithms are available which may be employed to the offsets as used herein. The present inventors implemented and tested three suitable algorithms for this process, however this is not limiting and other suitable algorithms may be employed to check for and correct transitive consistency errors in the offsets. In some versions, more than one algorithm may be employed and the best performing results selected afterward.
For the sake of completeness, two alternative algorithms are also described. As depicted at block 1510, the process may alternatively perform a stepwise refinement of the offsets in triplet groups. One suitable algorithm that may be employed for this is the In this section we formulate an iteratively reweighted least squares (IRLS) solver as found in Ozyseli et al. (Robust Camera Location Estimation by Convex Programming, Ozyseli, O., and Singer, A., arXiv:1412.0165v2, 4 Jun. 2015), which is hereby incorporated by reference for all purposes. The corrected offsets are then provided at block 1518 and the consistency check is ended. A third alternative algorithm for the global consistency check is given at block 1512-1516. This solution starting at block 1512 performs a rigid body analysis, such as that given provided in Kennedy et al. (Identifying maximal rigid components in bearing-based localization, Kennedy et al, IEEE/RSJ International Conference on Intelligent Robots and Systems, October 2012), which is hereby incorporated by reference for all purposes. The process identifies a subset of offsets that conform to the rigid body analysis and those that do not. Then at block 1516 the non-conforming values are either corrected or excluded from the analysis.
Some embodiment of the invention provide a method of operating an atomic force microscope (AFM) system under control of a processor, the AFM system including multiple AFM assemblies positioned for scanning a common sample area, each having a cantilever supporting a probe head with at least one tip comprising: positioning the multiple AFM probe heads with their respective tips at a first predetermined relationship to each other; automatically performing a first scan including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image; automatically processing the scan images to recognize a feature appearing in all the scan images having desired spatial characteristics; automatically designating the recognized feature as a common feature and overlaying the scan images together to determine a relative offset for each of the scanning tips; based on the relative offset, automatically positioning the scan tips at a second predetermined relationship to each other, the second relationship placing the tips relatively closer to each other than the first relationship; and after positioning the scan tips at the second predetermined relationship, automatically performing a region of interest scan including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image.
In some embodiments, the desired spatial characteristics of the recognized feature include a designated minimum feature pitch between two feature structures.
In some embodiments, the second predetermined relationship has greater precision than the first predetermined relationship.
Some embodiments further comprise after, positioning the scan tips at the second predetermined relationship, automatically reconfiguring the AFM system for scanning at an increased resolution.
In some embodiments, the second predetermined relationship places the tips along the circumference of an imaginary calibration circle.
In some embodiments, the calibration circle is centered around the common feature of the first scan.
In some embodiments, the AFM system includes at least four AFM assemblies.
Some embodiments further comprise, before performing the region of interest scan: performing a second, fine probe reference scan; automatically processing the scan images of the second scan to recognize a feature appearing in all the scan images having desired spatial characteristics, which may be the designated common feature of the second scan or another feature; automatically designating the recognized feature of the second scan as a common feature and overlaying the scan images of the second scan together to determine a relative offset for each of the scanning tips; based on the relative offset, automatically positioning the scan tips at a third predetermined relationship to each other, the third relationship placing the tips relatively closer to each other than the second relationship; after positioning the scan tips at the second predetermined relationship, performing a third scan including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image.
In some embodiments, the third predetermined relationship has greater precision than the second predetermined relationship.
Some embodiments further comprise, after positioning the scan tips at the third predetermined relationship, automatically reconfiguring the AFM system for scanning at an increased resolution.
In some embodiments, the third predetermined relationship places the tips along the circumference of an imaginary fine calibration circle.
In some embodiments, the fine calibration circle is centered at the common feature of the second scan.
In some embodiments, the fine calibration circle is about 0.35 μm or less in diameter.
In some embodiments, overlaying the scan images of the second scan together to determine a relative offset for each of the scanning tips and based on the relative offset, automatically positioning the scan tips at a third predetermined relationship to each other further comprises pre-processing the scan images of the second scan to remove outlier data and scan artifacts; after the pre-processing, calculating a set of pairwise shifts between respective combinations of the scan images; after calculating the pairwise shifts, adjusting for error by checking for global transitive consistency of the calculated pairwise shifts and applying any resulting adjustments to their respective tip coordinates; after adjusting for error, fitting the tip locations to a desired shape for the third predetermined relationship.
In some embodiments, overlaying the scan images together to determine a relative offset for each of the scanning tips and based on the relative offset, automatically positioning the scan tips at a second predetermined relationship to each other further comprises pre-processing the scan images of the first scan to remove outlier data and scan artifacts; after the pre-processing, calculating a set of pairwise shifts between respective combinations of the scan images; after calculating the pairwise shifts, adjusting for error by checking for global transitive consistency of the calculated pairwise shifts and applying any resulting adjustments to their respective tip coordinates; and after adjusting for error, fitting the tip locations to a desired shape for the second predetermined relationship.
Some embodiments comprise an atomic force microscope (AFM) system, comprising: at least three AFM assemblies positioned for scanning a common sample area, each including a cantilever supporting a probe head with at least one tip, a 3-axis actuator mechanically coupled to the cantilever, control electronics operably coupled to a feedback position sensor for providing calibrated scanning of the probe head, and a deflection sensor positioned to sense deflection of the cantilever; an electronic controller coupled to the control electronics of the AFM assemblies, and operable to generate a scan waveform for each respective AFM assembly; tangible, non-transitory computer readable memory coupled to the electronic controller and containing program code executable by the electronic controller for: automatically performing a first scan, starting from an initial position in which the AFM probe heads are positioned with their respective tips at a first predetermined relationship to each other, the first scan including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image; automatically processing the scan images to recognize a feature appearing in all the scan images having desired spatial characteristics; automatically designating the recognized feature as a common feature and overlaying the scan images together to determine a relative offset for each of the scanning tips; based on the relative offset, automatically positioning the scan tips at a second predetermined relationship to each other, the second relationship placing the tips relatively closer to each other than the first relationship; after positioning the scan tips at the second predetermined relationship, automatically performing a second scan including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image.
Some embodiments comprises one or more tangible, non-transitory computer readable media containing a program product executable by a controller to operate an atomic force microscope (AFM) system, the system having at least three AFM assemblies positioned for scanning a common sample area, the program product containing program code executable for: automatically performing a first scan, starting from an initial position in which the AFM probe heads are positioned with their respective tips at a first predetermined relationship to each other, the first scan including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image; automatically processing the scan images to recognize a feature appearing in all the scan images having desired spatial characteristics; automatically designating the recognized feature as a common feature and overlaying the scan images together to determine a relative offset for each of the scanning tips; based on the relative offset, automatically positioning the scan tips at a second predetermined relationship to each other, the second relationship placing the tips relatively closer to each other than the first relationship; after positioning the scan tips at the second predetermined relationship, automatically performing a second scan including scanning the tips in synchronicity across a surface and creating, for each tip, a scan image.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. The combinations of features described herein should not be interpreted to be limiting, and the features herein may be used in any working combination or sub-combination according to the invention. This description should therefore be interpreted as providing written support, under U.S. patent law and any relevant foreign patent laws, for any working combination or some sub-combination of the features herein.
Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
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| Number | Date | Country | |
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| 20180275165 A1 | Sep 2018 | US |
| Number | Date | Country | |
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| 62476548 | Mar 2017 | US |
