AUTOMATED LANDING METHOD AND SYSTEM USING SAME - Patent application

Abstract

The present disclosure relates to a method of operating an SPM system comprising a landing procedure, the landing procedure comprising a first landing stage comprising applying a first translation by a coarse translation means over a first working distance to bring a probe tip held by an SPM head from an initial separation distance from a substrate to be probed to a more proximal second separation distance defined by a characteristic transient response of the probe tip in close proximity to the substrate. Following the first translation, a second landing stage is applied comprising applying a second translation by a fine translation means over a second working distance under feedback control to bring the probe tip to the working separation distance. Prior to applying the first (coarse) working distance, an initial optical distance indicative of the initial separation distance is measured using a detector, preferably a mark sensor. The measured initial optical distance is related to a reference distance to determine a deviation. The first working distance corresponds to the reference distance and the deviation. The present disclosure also relates to an SPM system and software product configured to implement the landing method.

Description

[Technical field]

[0001] The present disclosure relates to an automated landing method and apparatus for a scanning probe microscope (SPM) that provides efficient and reliable landing. More specifically, the present disclosure relates to an automated landing method for a scanning probe microscope (SPM) and an SPM system using the same. [Background technology]

[0002] Scanning probe microscopes are widely used to characterize properties of samples by the interaction of a probe device with the sample. The probe can be mounted in a scanning probe microscope (e.g., an atomic force microscope). Typically, a cantilever-based probe is used, which may have a probe tip located near the end of the cantilever to locally probe and measure one or more properties of the sample. Probe-based systems can characterize small-scale sample features by monitoring the interaction between the sample and the tip of the associated probe device.

[0003] The landing procedure in which the probe tip is brought to a working distance (working separation) from the substrate typically involves two steps or stages. Specifically, the probe is typically brought from an initial separation distance to an approximate distance from the substrate, from which the probe is then precisely guided to the sample location.

[0004] In a semi-automated landing or approach method, the first stage typically involves coarse movements, typically via a user's manual operation and experience, such as via an image information display. The second stage is typically an automated process using fine movements, where the probe is automatically driven until a desired condition, such as resonant amplitude, is met, for example by monitoring conditions during the drive process. Obviously, the duration and overall efficiency of a semi-automated landing procedure depends on the user's skill level.

[0005] In the automated landing method, manual operation during the first stage is eliminated by providing automated coarse motion until the desired transition condition is met by periodic comparison of the cantilever response signal to a set point at regular intervals at each step during the coarse motion stage.

[0006] Compared to the semi-automated landing method, which can be driven quickly by an experienced user in the coarse movement, the landing speed in the automated landing method is limited by the feedback control required during the coarse movement, regardless of the initial separation distance between the sample and the probe tip. Summary of the Invention [Problem to be solved by the invention]

[0007] It is therefore an object of the present disclosure to provide a less time consuming landing method that can effectively achieve uniform speed and / or effective landing regardless of the apparent initial separation distance between the probe and the target.

[0008] Another object of the present disclosure is to provide an SPM system and / or software product arranged to implement the landing method. [Means for solving the problem]

[0009] Aspects of the present disclosure relate to methods of operating an SPM system, particularly methods involving a landing procedure, and to an SPM system configured to carry out the methods.

[0010] The SPM system comprises an SPM head for probing a substrate to be probed with a probe tip held on the SPM head, a controller, and translation means for adjusting a separation distance between the probe tip and the substrate, the translation means being communicatively connected to the controller, and comprising coarse translation means for bringing the probe tip from an initial separation distance from the substrate to a closer separation distance, and fine translation means for bringing the probe tip to an operating separation distance.

[0011] A method of operating an SPM system includes a landing procedure comprising a first landing step, the first landing step comprising applying a first translation by a coarse translation means over a first working distance to bring a probe tip held by an SPM head from an initial separation distance from a substrate to be probed to a proximal second separation distance defined by a characteristic transient response of the probe tip in close proximity to the substrate, and a second landing step, the second landing step comprising applying a second translation by a fine translation means under feedback control over a second working distance following the first (coarse) translation to bring the probe tip to the working separation distance; and the steps comprising measuring an initial optical distance indicative of the initial separation distance with a detector, and relating the measured initial optical distance to a reference distance to determine a deviation; where the first working distance corresponds to the reference distance and the deviation.

[0012] Providing the first (coarse) translation over a working distance corresponding to the reference distance and the determined deviation advantageously reduces the time spent in the first stage of the landing procedure, i.e., the time required to bring the probe tip from an initial separation distance to a more proximal second separation distance from the substrate to be probed. It has been found that the method provides reliable landing by setting the coarse translation distance depending on a measured initial optical distance and a trained predetermined reference distance. It has been found that the method provides a significant reduction in landing time, since the first translation distance at a given target measurement position along the substrate can be determined by a limited number of input signals (typically including a single optical measurement at a target sampling position). Among other things, this allows essentially the complete first working distance to be covered by applying a single coarse operating parameter, in contrast to known methods that rely on feedback control, i.e., monitoring the response following the application of each coarse translation step.

[0013] Advantageously, the method allows for iterative application of the landing procedure, including a first coarse translational movement depending on the reference distance and the deviation, for multiple target measurement areas along the substrate to be probed, thus reducing the overall time required to address the multiple target areas. The improvement in overall time may be considered particularly relevant for large substrates and / or for substrates having a spread in the apparent initial separation distance between tip and substrate between target measurement areas, for example due to variations in substrate thickness or variations due to warping.

[0014] The separation distance between the probe tip and the substrate can be correlated with the determined optical distance using a suitably positioned detector. Typically, the detector is provided at a fixed relation, at a fixed lateral offset from the means for mounting the probe, along a position for holding the probe tip, e.g., the SPM head, so that the determined optical distance between the substrate and the detector can indicate the separation distance between the substrate and the probe tip. By using optical detection principles, the separation distance can be determined in a fast and reliable manner, advantageously independent of the physical properties of the probe and / or substrate, e.g., electrical conductivity or capacitance.

[0015] The reference distance is determined in a calibration routine before the first landing stage. The calibration routine includes: a) measuring a reference optical distance associated with the probe tip held by the SPM head positioned at a reference separation distance from a reference; and b) determining the reference distance by recording the working distance required to bring the probe tip from the reference separation distance to a closer second reference separation distance as defined by an observed characteristic transient response of the probe tip close to the reference, e.g., as defined by monitoring the phase transition of a driven cantilever beam as the probe tip approaches the substrate. The calibration routine can be understood as a training performed on a reference to provide a safe coarse working distance (reference distance), which is thereby related to the reference optical distance and, via the reference optical distance, to the corresponding separation distance between the substrate and a given probe tip. The time spent determining the safe coarse operating distance can be understood to be comparable to the coarse translation step of an automated lancing procedure, in that the calibration or training routine does not need to be supplemented by a fine translation step.

[0016] In a preferred embodiment, determining the reference distance includes recording an operating parameter for the coarse translation means associated with the required working distance, for example by counting the number of coarse translation steps for a stepper motor, and the measured optical distance is correlated with the number of steps from the stepper motor.

[0017] The difference between the reference optical distance and the optical distance measured at the target landing site is used to determine the safe coarse working distance for the target landing area, for example by adding the difference to the predetermined reference. The determined safe distance can be advantageously used during the first landing phase, for example by activating the coarse translation means to reduce the separation by the distance, for example by applying an operating parameter for the coarse translation means associated with the required working distance. Advantageously, the coarse translation towards the substrate can be performed without feedback control, while still effectively bringing the probe tip from an initial separation from the substrate to a separation corresponding to the second, more proximal separation.

[0018] Typically, the detector is part of the SPM system, for example integrated with or along the SPM head. It will be appreciated that the detector does not have to be an integrated part of the head, and does not have to be the head. The optical distance can be measured at the detector at another location, for example using a suitably positioned mirror. Preferably, measuring the optical distance is performed using an optical distance sensor. In a preferred embodiment, the optical distance is correlated to the focus condition of the optical distance sensor, for example by maximizing the optical contrast in the optical image of the reference.

[0019] In some embodiments, the calibration or training routine is performed on a reference area of ​​the substrate to be probed. In a preferred embodiment, the reference distance is defined relative to a fixed reference, such as a fiducial provided on a stage for holding the substrate. The fiducial is preferably characterized by having a property, such as a surface pattern property, that allows it to be registered optically, such as by an optical distance sensor. The reference is preferably further characterized by having, for example, the following properties, such as a suitable surface finish or structure that allows it to be contacted or scanned by the probe tip. Performing the calibration routine on a fiducial provided on or along a stage for holding the substrate allows the reference distance and / or corresponding operating parameters to be determined under controlled conditions. By performing a calibration routine on a fiducial provided on or along the sample stage, the calibration is performed in the direct vicinity of the substrate, thus reducing the time spent on lateral and / or vertical translation.

[0020] In some embodiments, the calibration routine further includes determining a second reference distance by recording the fine translation distance required to bring the probe tip from the second reference separation distance, which is closer, to the working separation distance from the reference (fiducial). In other words, the need for the calibration or training routine is supplemented by a fine translation step to determine a second reference distance corresponding to the fine translation distance required to bring the probe tip into contact with the reference or fiducial. As with determining the coarse reference distance, the required fine translation can be correlated to an operating parameter for the fine translation means, e.g., a potential to be applied to a piezo transducer or Z-stage associated with the SPM head. The second reference distance, or an operating parameter for the fine translation means, can be used to further reduce the landing time by at least partially reducing the distance that needs to be covered under feedback control, e.g., by covering at least a portion of the fine translation distance without feedback control. Thus, in some embodiments, the method includes an intermediate translation between the first translation and the second translation, wherein the intermediate translation includes intermediate translation by the fine translation means without feedback control, and the intermediate translation is provided over a distance corresponding to a fraction, for example 0 to about 80%, or 10 to 60%, for example about 50% of the second reference distance.

[0021] In a particularly preferred embodiment, the method further comprises the step of recording an optical height map of the substrate to be probed. The height map comprises optical height records covering each one of a number of target measurement areas along the substrate relative to a marker, preferably a fiducial, having a fixed relationship to the substrate to be probed. The marker can in principle be any specific area, for example a reference area on the substrate to be probed, but the records are preferably associated with the fiducial. By determining the optical height map of the substrate to be probed, the need to perform optical measurements during each of the subsequent landing procedures is eliminated, thereby allowing a further reduction in overall process time, especially as the number of target measurement areas along a given substrate increases, since less time is spent switching (activating / deactivating) the optical measurement sensor and / or lateral translation.

[0022] Determining an optical height map of the substrate can have the additional advantage of reducing the risk of tip and / or sample damage during lateral translation since potential variations in substrate height are pre-determined. Alternatively or in addition, determining an optical height map of the substrate can have the advantage of allowing a relatively low safe travel height during lateral translation, thereby reducing the time between landings, e.g. the number of coarse translation steps.

[0023] Additionally, and importantly, by determining an optical height map of the substrate and relating height records to the marker, preferably the fiducial, the robustness of the method is increased and / or the idle time of the system is reduced, for example after a probe change. Since the optical height information is relative to a fixed reference point, for example the fiducial, the optical height once determined can be used even after a probe change, for example by performing a new calibration procedure on the fiducial. The optical measurement can be understood as a one-time calibration (referring to the relationship between optical distance and coarse translation), which only needs to be recalibrated if the fiducial and / or the approach motor are changed.

[0024] In addition, the optical height map may be used to particular advantage in SPM systems that include individually addressable ones of the SPM heads, for example, where each head is individually translatable by corresponding ones of the coarse and fine translation means. By using multiple individually addressable SPM heads of the SPM heads, larger substrates may be analyzed in shorter parallel runs, with each head addressing a specific region of the substrate. By relating the height records in the map to a fixed reference point, e.g., the fiducial, each head may benefit from a single set of data, for example by performing a calibration procedure on the reference point.

[0025] According to another or further aspect, the present disclosure relates to an SPM system and / or software product arranged to implement the operational method including the landing method.

[0026] The SPM system comprises an SPM head for probing a substrate to be probed with a probe tip held by the SPM head, a controller, and translation means for adjusting a separation distance between the probe tip and the substrate, the translation means being communicatively connected to the controller, and comprising coarse translation means for bringing the probe tip from an initial separation distance from the substrate to a closer separation distance, and fine translation means for bringing the probe tip to an working separation distance, wherein the SPM system applies a first translation by the coarse translation means over a first working distance to bring the probe tip held by the SPM head into contact with the substrate. the probe tip being adapted to land on a substrate to be probed, the probe tip being adapted to land on the substrate and adapted to receive the probe tip from the substrate and to receive the probe tip from the substrate and adapted ...

[0027] The present disclosure is further directed to a computer program product including instructions, for example computer readable instructions stored on a non-transitory computer readable medium, that can be loaded into a memory of a scanning probe microscope system according to the present disclosure to enable the controller of the system to perform an operational method including a landing method.

[0028] These and other features, aspects, and advantages of the devices, systems, and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawings. [Brief description of the drawings]

[0029] [Figure 1A] FIG. 1A illustrates a schematic of an SPM system and aspects of a known two-stage landing procedure. [Figure 1B] FIG. 1B illustrates a schematic of an SPM system and aspects of a known two-stage landing procedure. [Figure 2A] FIG. 2A illustrates a schematic of a method of operation of an SPM system, including a landing procedure and system, in accordance with the present disclosure. [Figure 2B] FIG. 2B illustrates a schematic of a method of operation of an SPM system, including a landing procedure and system, in accordance with the present disclosure. [Figure 3A] FIG. 3A shows a schematic of the system at various stages during the landing procedure. [Figure 3B] FIG. 3B shows a schematic of the system at various stages during the landing procedure. [Figure 4A] FIG. 4A illustrates the calibration routine diagrammatically. [Figure 4B] FIG. 4B shows a schematic of the system at various stages during the calibration routine. [Figure 5A] FIG. 5A shows a schematic view of measuring distance. [Figure 5B] FIG. 5B shows a schematic view of measuring distance. [Figure 6A] FIG. 6A shows a schematic of an SPM system and a method for manipulating a height map. [Figure 6B] FIG. 6B shows a schematic of the SPM system and the method of manipulating the height map. [Figure 7] FIG. 7 shows a schematic of an SPM system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The terms used to describe particular embodiments are not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise. The word "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that the words "comprises" and "comprising" specify the presence of the stated features but do not exclude the presence or addition of one or more other features. When a particular step of a method is referred to as following another step, it will be further understood that the other step may follow directly, or one or more intermediate steps may be performed before performing the particular step, unless otherwise specified. Similarly, when a connection between structures or components is described, it will be understood that the connection may be established directly or through an intermediate structure or component, unless otherwise specified.

[0031] The present invention is described in more detail below with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, absolute and relative sizes of systems, components, layers and regions may be exaggerated for clarity. The embodiments may be described with reference to schematic and / or cross-sectional illustrations of possibly idealized embodiments and intermediate structures of the invention. In this specification and the drawings, like numbers refer to like elements throughout. Relative terms and their derivatives should be construed to refer to the orientation shown in the drawings currently being described or discussed. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation, unless otherwise specified.

[0032] For ease of understanding, a known automated two-stage landing procedure will be explained with reference to Figures 1A and 1B. Figure 1A shows an SPM head 10 equipped with coarse and fine movement means 11, 12 for providing a relative movement between a substrate 50 and the tip 21 of a probe 20 held by the head, as well as a controller. Figure 1B shows a schematic way of operating an SPM system, comprising a landing procedure comprising a first landing stage L1, comprising a coarse translational movement, a second landing stage L2, comprising a fine translational movement, and a scanning stage S following the landing procedure. Before probing and sampling the substrate, the tip needs to be brought to an operating separation distance Sw from the substrate, for example a distance allowing intermittent contact. Figure 1A illustrates the system with the probe tip positioned at an initial separation distance S0 far away from the substrate, i.e. at the start of the landing procedure L1.

[0033] The first stage of the automated landing procedure involves a coarse motion to bring the tip from an initial separation distance to a closer separation distance. To avoid the tip colliding with the substrate, the coarse motion is applied stepwise under continuous monitoring of the response signal R. When the probe and the substrate are close to each other, the coarse motion is stopped when a desired condition is achieved, e.g., an observed phase shift. From this position, also referred to as the transition separation distance, the probe is precisely guided to a sampling position in a second landing phase L2, which involves using a fine translation, e.g., a fine translation by a piezo scanner.

[0034] 2A and 2B respectively show generally a method 1000 of operating an SPM system according to the present disclosure and an SPM system 1 configured to perform the method.

[0035] As illustrated diagrammatically in FIG. 2A, the method includes at least a landing procedure 200. Following the landing procedure, there may be one or more measurement or probe phases 300, in which one or more regions of interest of one or more substrates are probed. The landing procedure 200 includes a first (coarse) landing phase 210, a second (fine) landing phase 220, and before them a step 201 of measuring an initial optical distance and a step 202 of relating the measured initial optical distance to a reference distance to determine a deviation. The reference distance and the deviation are used to determine the working distance covered during the first coarse landing phase. The reference distance is a parameter determined in a prior training (or calibration) routine 100. It will be appreciated that once the reference distance is determined, the training or calibration routine 100 does not have to be repeated before each and every probe phase 300. Once determined, the reference parameters can be used repeatedly, e.g., for multiple measurement regions along the substrate of interest and / or for multiple substrates, regardless of variations in the initial separation distance between the probe tip and the target measurement region, e.g., due to variations in substrate roughness and / or apparent substrate thickness.

[0036] FIG. 2B shows an SPM system 1 configured to carry out a method according to the present disclosure. The system comprises an SPM head 10 including means for holding a probe 20 having a probe tip 21 for probing a substrate 50 to be probed. The illustrated system further comprises a sample stage for holding the substrate, a fiducial 4 mounted on the sample stage, and a controller 60. The controller is communicatively connected to translation means including fine translation means 12 and coarse translation means 11 for providing relative motion between the probe tip and the substrate. As shown, the method and system further comprises a detector 30, a means for optically determining the distance (optical distance) to the substrate. As will be apparent, the method and system can be used to particular advantage with a variety of samples, such as large samples, such as full size wafers, or samples with variations in apparent height (shown with exaggerated relief for clarity), providing improved landing. These and further aspects of corresponding features of the present method and system will be elucidated in more detail with reference to FIGS.

[0037] 3A and 3B show a schematic representation of the SPM system in various stages during a landing procedure. FIG. 3A shows the system in a state where the probe tip is still away from the substrate, such as before starting a first coarse landing stage. Using a lateral translation, the head is positioned across the relevant first landing 50-1 area along the substrate to be probed. Before applying the first coarse translation, the optical distance OD0 between the substrate and the detector 30 is measured. Since the optical distance to the substrate is determined from a position having a fixed relationship to the means for holding the probe, the optical distance can be related to the separation between the substrate and the probe tip, i.e. the initial separation distance S0 in this case. As will be explained in relation to FIGS. 5A and 5B, the optical distance is preferably determined by determining the focus condition of an optical distance sensor provided on the SPM head 10. In a preferred embodiment, the optical distance sensor can be understood to be associated with the mark sensor 31, as shown for example in FIG. 5A. As used herein, a mark sensor may be understood to relate to a miniature microscope system or an integrated microscope system.

[0038] 3B shows the same system after application of the first coarse translation over a working distance D1. For ease of understanding, the applied working distance is represented by a corresponding nominal increased dimension of the coarse translation means 11.

[0039] Typically, the translation means 11 comprises a stepper motor, providing a constant translation at each applied step. It will be understood that the translation distance can be provided by an alternative or combination of translation means, e.g. a screw drive. It will be understood that the translation can be equally effective by translating the substrate. The first working distance D1 corresponds to a reference distance and deviation corresponding to the distance required to bring the probe to a transitional separation distance St from the substrate. Details regarding the determination of the reference distance and the deviation will be explained in relation to FIG. 4. In contrast to conventional landing methods, the first (coarse) translation distance D1 can be safely applied without the need for manual or automated feedback control during the coarse translation to monitor the response as the probe tip is brought close to the substrate, for example by instructing the coarse translation means 12 to apply a specified distance at a time. After providing the coarse translational motion, a second landing step can be initiated to precisely contact the probe with the substrate at a desired location.

[0040] Figure 4A shows a schematic of the calibration routine, and Figure 4B shows a schematic of the SPM system at various stages during the calibration routine.

[0041] The calibration or training routine 100 includes at least a step 102 of determining a reference optical distance ROD0. This reference optical distance can be related to a reference separation distance RS0 (see FIG. 4B, left) between the probe tip and a fiducial 4. In the illustrated embodiment, the fiducial is formed by a fiducial 4 provided on the sample stage 40 at a position in direct proximity to the position of the sample 50.

[0042] Starting with the probe tip at a reference separation distance RS0 (see FIG. 4B, left), the probe is brought closer to the substrate in a second step 102. In the second step, a reference distance RD is determined by recording the working distance AD ​​required to bring the probe tip 21 from the reference separation distance RS0 to a more proximal second reference separation distance St, as defined by an observed characteristic transient response of the probe tip close to a reference 4 (see FIG. 4B), for example by stepwise actuating the stepper motor 11 while monitoring a response signal (R, see FIG. 1) until a particular characteristic transient response is observed. While it may be preferred to perform the calibration or routine on a fiducial, it will be appreciated that it is also envisaged to perform the calibration or training routine at a reference position along the substrate to be probed, or at a fixed position along the system, for example on a part of a metro frame that serves as a mount for the sample stage and / or SPM head.

[0043] In some embodiments, for example as shown in FIG. 4A, the calibration or training routine further includes determining a second reference distance (step 103) by recording the fine translation distance required to bring the probe tip from a more proximal second reference separation distance St to the working separation distance from the reference.

[0044] In other or further embodiments, determining the reference distance (or the second reference distance) includes recording an operating parameter for the coarse translation means (or the fine translation means) associated with the required actuation distance. For example, if the coarse translation is provided by a stepper motor, the translation distance can be correlated to applied, e.g. counted, translation steps. Alternatively or additionally, depending on the type of translation means, the translation distance can be correlated to a drive potential or actuation time.

[0045] By determining which safe coarse working distance (reference distance) is appropriate for a given corresponding reference optical distance and training the system, the determined reference distance can be appropriately applied and adjusted at a given target sample position by measuring the corresponding optical distance for that position. If the corresponding optical distance OD0 at a particular measurement position matches the reference optical distance ROD0 (i.e., there is no deviation), the corresponding reference distance can be directly applied. If there is a deviation, for example 10%, the corresponding first working distance can be adjusted accordingly, for example by multiplying the operating parameter, for example the number of coarse translation steps, by a factor of 1.1.

[0046] The calibration routine or the training routine is performed at least once before performing the first measurement routine for a given first substrate to be probed. In some embodiments, the calibration routine or the training routine is performed once for each substrate to be probed. Alternatively or additionally, the calibration routine or the training routine can be repeatedly performed between successive measurements for each of a plurality of target measurement areas on the substrate to be probed, for example, to increase the confidence level or to correct for time-dependent changes.

[0047] Preferably, measuring the optical distance comprises determining a focus condition of an optical distance sensor provided. Preferably, the optical distance sensor is configured to determine the focus condition by automatically adjusting the focal length to move its focal plane. Alternatively or additionally, the optical distance can be determined using alternative optical principles, such as the optical principles mentioned above including interferometry, and / or by measuring the time of light, such as a laser pulse.

[0048] In some embodiments, as shown in FIG. 5A, the optical distance sensor is a mark sensor 31, e.g., a registration mark sensor, with an objective lens that can be automatically adjusted relative to the camera sensor to determine the best focus condition by checking image sharpness. Thus, the best focus condition, e.g., the position of the objective lens, can be correlated to the optical distance. The deviation between the initial optical distance measured at the fiducial and the initial optical distance measured at the sample position can be related to the deviation in focus condition (see FIG. 5B and the position of the objective lens).

[0049] The mark sensor 31 comprises a miniature camera unit 32 having a field of view 33 through its sensor aperture 34. The optical sensor 31 further comprises an aperture 35, adjustable focusing optics 36 (typically comprising an objective lens 36a and a tubular lens 36b), and an actuator 37 for adjusting the distance between the camera 32 and the focusing optics 36 to enable focusing of the image of the fiducial 4 and / or substrate.

[0050] Preferably, the mark sensor 31 is equipped with a redirection mirror 39 at a π / 4 angle with respect to the longitudinal axis through the sensor 30 to optimize the available parallel space within the head by orienting the imaging plane onto the surface of the substrate.

[0051] The camera 32 must be accurate enough to recognize the fiducial marks 4a. The size of such marks is typically between 20*20 micrometers and 50*50 micrometers, but of course the size of these marks may vary and may become smaller over time. The resolution of the image features of the alignment marks may typically be up to 1 micrometer, which may also vary (i.e., decrease) over time. The camera 32 may be adapted accordingly depending on the size and / or resolution of the alignment marks and must be able to identify the image features required to perform its task. For example, the pixel resolution of the camera 32 at the object plane (e.g., the surface to be read) may be 2 micrometers or less, preferably 1.0 micrometers or less, more preferably 0.5 micrometers or less. Moreover, the magnification of the camera may be between 5 and 100 times, preferably 10 and 50 times, and the camera may be capable of operating at at least two magnifications: low and high.

[0052] In a preferred embodiment, as shown, for example, in Figures 6A and 6B, the method includes a step 150 of recording an optical height map 151, which includes mapping an optical height record for each of a plurality of target measurement areas along the substrate 40.

[0053] The height map includes optical height records RD covering each of a plurality of target measurement regions along the substrate 50 (50-1, 50-2, ..., 50-n, see Figure 7) relative to a marker, preferably a fiducial, having a fixed relationship to the substrate to be probed.

[0054] Typically, the optical height is determined by scanning a head, such as the head described above including an optical distance sensor, over the substrate and recording the best focus condition to cover each of the target measurement areas relative to the marker. In this way, a first translational movement by the coarse translation means over a first working distance RD can be mapped for each of a plurality of target measurement areas.

[0055] It will be appreciated that depending on expected variations in the sensor's field of view and / or surface height, the optical distance need not be measured at each target measurement area, and at least a portion of the optical height recording can be extrapolated from one or more adjacent measurement points.

[0056] Figure 7 shows diagrammatically an embodiment of an SPM system 1 comprising a plurality of individually addressable SPM heads 10, such as that shown in Figure 2B. The heads (10-1 to 10-n) are provided with respective fine and coarse translation means connected to a controller 60. A system comprising multiple SPM heads can advantageously address multiple target measurement areas (50-1, 50-2 to 50-n) simultaneously, for example on a large substrate and / or on multiple adjacently arranged substrates.

[0057] In one embodiment, for example as shown, the head is positioned along a first end 7a of a support frame (metro frame) opposite a second end 7b of the frame supporting the substrate carrier 40 and fiducials 4. Positioning the head across the associated target along the opposite end of the frame (containing the substrate 50 and fiducials 4) allows for parallel operation of the method according to the present disclosure. In a preferred embodiment, the system includes one or more robotic arms (7c) for accurately positioning the head at a target location along the frame 7a, for example along a reference grid provided thereon. A reference distance for each of a plurality of heads can be determined by sequentially positioning each head on the opposite side of the fiducial. Optionally, the system can be equipped with a plurality of fiducials, for example positioned along the periphery of the substrate to be probed to minimize lateral translation time between the fiducials.

[0058] Advantageously, the height map can be determined by providing appropriate lateral translational movements by one or more of the multiple heads, for example by scanning a head equipped with a mark sensor along the substrate by a robotic arm, and advantageously, because the reference heights are relative to a constant reference point, the height records determined in the map can be advantageously applied for each of the multiple heads.

[0059] Although for clarity and conciseness of description, features are described herein as part of the same or separate embodiments, it will be understood that the scope of the invention may include embodiments having all or a partial combination of the described features.

[0060] In interpreting the appended claims, the word "comprising" does not exclude the presence of other elements or acts than those recited in a given claim; the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements; any reference sign in a claim does not limit its scope; a plurality of "means" may be represented by the same or different items or by structure or function implemented; it should be understood that the disclosed device or parts thereof may be combined together or divided into further parts, unless specifically stated otherwise. When a claim refers to another claim, this may indicate synergistic advantages achieved by the combination of the respective features. However, the mere fact that certain means are recited in mutually different claims does not indicate that a combination of these means cannot also be advantageously used. Thus, the present embodiment may include all possible combinations of claims, where each claim may in principle refer to the preceding claim, unless clearly excluded by the context.

Claims

1. A method for operating a scanning probe microscope (SPM) system, including a landing procedure, wherein the landing procedure comprises: A first landing stage, comprising applying a first translational movement over a first working distance by a coarse translational movement means to bring the probe tip held by the SPM head from an initial separation distance from the substrate to be probed to a more proximal second separation distance defined by the characteristic transient response of the probe tip closer to the substrate, A second landing stage, the second landing stage comprising applying a second translational movement over a second working distance by a micro-translational movement means under feedback control, following the first translational movement, to bring the probe tip to the working separation distance, and The initial optical distance, which indicates the initial separation distance, is measured using a detector, and, The measured initial optical distance is related to the reference distance to determine the deviation. Includes, Here, the first working distance corresponds to the reference distance and the deviation, The aforementioned method.

2. The method according to claim 1, wherein measuring the initial optical distance using the detector includes determining the focal condition of the optical distance sensor provided on the SPM head.

3. The method includes a pre-calibration routine for determining the reference distance, the routine being: Measuring the reference optical distance associated with the probe tip held by the SPM head positioned at a reference distance from the reference, and Determining a reference distance defined by the recorded working distance required to move the probe tip from the reference separation distance to a second, more proximal reference separation distance defined by the observed characteristic transient response of the probe tip closer to the reference. The method according to claim 1 or 2, including the method described in claim 1 or 2.

4. The method according to claim 3, wherein determining the reference distance includes recording an operating parameter for the coarse translational moving means associated with the required operating distance.

5. The method according to claim 3 or 4, further comprising determining a second reference distance by recording the fine working distance required to bring the probe tip from a more proximal second reference distance to an operating distance from the reference.

6. The method according to any one of claims 1 to 5, wherein the reference distance is defined relative to a fiducial provided on a stage for holding the substrate.

7. The method according to any one of claims 1 to 6, further comprising recording an optical height map including optical height records for each of a plurality of target measurement regions along the substrate relative to a marker.

8. The method according to claim 7, which is dependent on claim 6, wherein the marker is fiducial.

9. The method according to any one of claims 1 to 8, wherein the SPM system comprises a plurality of individually addressable SPM heads, each SPM head being individually translatable by a corresponding coarse translational movement means and a fine translational movement means, and the landing procedure is applied to each of the plurality of SPM heads.

10. The method according to claim 5, wherein the method includes an intermediate translation between the first translation and the second translation, the intermediate translation includes an intermediate translation by the fine translation means without feedback control, wherein the intermediate translation is provided over a distance corresponding to a portion of the second reference distance.

11. A scanning probe microscope (SPM) system comprising an SPM head for probe a substrate to be probed by a probe tip, a controller, and translational movement means for adjusting the distance between the probe tip and the substrate, The translational movement means is communicably connected to the controller, and comprises a coarse translational movement means for bringing the probe tip from an initial separation distance from the substrate to a more proximal separation distance, and a fine translational movement means for bringing the probe tip to an operating separation distance. Here, the SPM system is The coarse translational movement means applies a first translational movement over a first working distance to bring the probe tip held by the SPM head from an initial separation distance from the substrate to be probed to a more proximal second separation distance defined by the characteristic transient response of the probe tip closer to the substrate, and Following the first translational movement, a second translational movement is applied over a second working distance by a fine translational movement means under feedback control to bring the probe tip to the working separation distance, and The initial optical distance, which represents the initial separation distance, is measured using a detector, and the deviation is determined by relating the measured initial optical distance to the reference distance. It is configured to perform landing procedures that include, Here, the first working distance corresponds to a predetermined reference working distance associated with the reference distance and the deviation, The aforementioned scanning probe microscope (SPM) system.

12. The SPM system according to claim 11, wherein the detector is an optical distance sensor provided on the SPM head configured to determine the focal condition.

13. The SPM system according to claim 11 or 12, wherein the SPM system comprises a fiducial provided on a stage for holding the substrate.

14. The SPM system according to any one of claims 11 to 13, further configured to record an optical height map including optical height records for each of a plurality of target measurement regions along the substrate relative to a marker.

15. The SPM system according to claim 14, dependent on claim 13, wherein the marker is the fiducial.

16. The SPM system according to any one of claims 11 to 15, comprising a plurality of individually addressable SPM heads.

17. A computer program product comprising instructions that, when loaded into the memory of a scanning probe microscope system according to any one of claims 11 to 16, enables the system's controller to execute an operation method including the landing method according to any one of claims 1 to 10.

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