Abstract: An improved method for optimizing layer registration during lithography in the fabrication of a semiconductor device is disclosed. In one example, the method comprises optimizing contact layer registration of an SRAM device having a plurality of transistors having active and gate region features extending generally along a channel length (X) direction and a channel width (Y) direction, respectively. The method comprises aligning a contact layer to a gate layer in the channel length direction (X), using gate layer overlay marks to control the alignment of the contact layer in the channel length direction (X) of the semiconductor device. The method further includes aligning the contact layer to an active layer in the channel width direction (Y), using active layer overlay marks to control the alignment of the contact layer in the channel width direction (Y) of the semiconductor device.

Abstract: Systems and methodology for orienting the tip/tilt and vertical height of samples, preferably automated, as applied in ellipsometer and the like systems.

Abstract: A method of measuring a numerical aperture of an exposure machine is described. A control wafer having vernier marks thereon and an aberration mask having pinholes therein are provided, wherein each pinhole corresponds to a vernier mark in position. A lithography process using the exposure machine and the aberration mask is performed to the control wafer, so as to form over each vernier mark a photoresist pattern having the same shape of the illumination pattern of the light source of the exposure machine. The numerical aperture of the exposure machine is then derived from a graduation of the vernier mark corresponding to an outer edge of the photoresist pattern.

Abstract: In repeated processes (steps 201 to 213) of lot processing, an analytical apparatus detects abnormality of overlay, that is, deterioration of overlay accuracy in step 211 and optimizes an apparatus parameter of an exposure apparatus so that the abnormality is solved (so that the overlay accuracy is improved), and then the optimization result is promptly reflected in the exposure apparatus and a measurement/inspection instrument. Since such optimization is performed without stopping the lot processing, the productivity of devices is not lowered.

Abstract: A method of performing alignment of an array of probe tips of a probe card to corresponding contact pads for wafer probing applications by performing the steps of: obtaining a backside image of the wafer; overlaying a mapping of the contact pads over the backside image; selecting contact pads as landing points; obtaining an image of the probe tips array; comparing the landing points to corresponding positions of probe tips; and, if the positions of probe tips are not aligned with the landing point, rotating the probe card to align the positions of probe tips to the landing points.

Abstract: A reference microplate is described herein which can be used to help calibrate and troubleshoot an optical interrogation system. In one embodiment, the reference microplate has a frame with an array of wells each of which contains an optical biosensor and each optical biosensor is at least partially coated with a substance (e.g., elastomer, optical epoxy). In another embodiment, the reference microplate in addition to having its optical biosensors at least partially covered with a substance (e.g., elastomer, optical epoxy) also has a controllable heating device attached thereto which is used to heat the optical biosensors.

Abstract: Methods of optimizing optical alignment in an optical package are provided. In one embodiment, the optical package includes a laser diode, a wavelength conversion device, coupling optics positioned along an optical path extending from the laser diode to the wavelength conversion device, and one or more adaptive actuators. The method involves adjusting the optical alignment of the wavelength conversion device in a non-adaptive degree of freedom by referring to a thermally-dependent output intensity profile of the laser diode and a thermally-dependent coupling efficiency profile of the optical package.

Abstract: Alignment of layers during manufacture of a multi-layer sample is controlled by applying optical measurements to a measurement site in the sample. The measurement site includes two diffractive structures located one above the other in two different layers, respectively. The optical measurements include at least two measurements with different polarization states of incident light, each measurement including illuminating the measurement site so as to illuminate one of the diffractive structures through the other. The diffraction properties of the measurement site are indicative of a lateral shift between the diffractive structures. The diffraction properties detected are analyzed for the different polarization states of the incident light to determine an existing lateral shift between the layers.

Abstract: Apparatus for monitoring the alignment of marking lasers in a room for diagnosis and/or treatment in the radiation therapy, characterized by a housing, which is provided with holding means for the installation in the room and which has the following a linearly extending photosensor and an analyzing unit, which compares the position of the light generated by the laser on the photosensor with a reference position, and generates a corresponding signal upon a deviation of the measured position from the reference position.

Abstract: A lithographic apparatus includes an illumination system configured to condition a radiation beam, a support for a patterning device, a substrate table for a substrate, a projection system, and a control system. The patterning device is capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam. The projection system is configured to project the patterned radiation beam as an image onto a target portion of the substrate along a scan path. The scan path is defined by a trajectory in a scanning direction of an exposure field of the lithographic apparatus. The control system is coupled to the support, the substrate table and the projection system for controlling an action of the support, the substrate table and the projection system, respectively. The control system is configured to correct a local distortion of the image in a region along the scan path by a temporal adjustment of the image in that region, hereby reducing the intra-field overlay errors.

Abstract: The via chain conduction failure due to non-conduction caused by insufficient etching in a contact plug/via plug forming process can be detected precisely in a short time. For its achievement, a defect is detected at high speed by taking advantage of characteristics of a potential contrast method using a via chain defect inspection structure and an electron beam defect detection apparatus which can perform continuous inspection while changing an inspection direction without rotating a wafer. Accordingly, the capturing efficiency of a critical electric defect and search efficiency of a defect point can be improved.

Abstract: An alignment unit includes a measurement unit configured to measure a coordinate of a center position of an alignment mark transferred to each layer that is located under an uppermost layer of a substrate, and a controller configured to determine a target coordinate of the center position of the alignment mark transferred to the uppermost layer of the substrate based on a result of a weighted average that is made by weighting the coordinate of the center position of the alignment mark of each layer of the substrate measured by the measurement unit using as a weight a function inversely proportional to a minimum critical dimension of the pattern of an original formed on each layer of the substrate.

Abstract: In one embodiment, a metrology target for determining a relative shift between two or more successive layers of a substrate may comprise; an first structure on a first layer of a substrate and an second structure on a successive layer to the first layer of the substrate arranged to determine relative shifts in alignment in both the x and y directions of the substrate by analyzing the first structure and second structure overlay.

Abstract: An inspection method for an illumination optical system of an exposure tool includes coating a surface of an exposure target substrate with a resist film; placing a plurality of imaging components deviating from an optical conjugate plane of a surface of the resist film; generating a plurality of inspection patterns of the resist film having a plurality of openings, by projecting exposure beams output from a plurality of effective light sources onto the resist film via the imaging components; measuring one of the inspection patterns as a reference image, and processing the reference image so as to provide reference image data; and determining an abnormal inspection image by measuring inspection images of the inspection patterns and comparing a plurality of inspection image data provided by processing the inspection images with the reference image data.

Abstract: An exposure method includes the steps of (a) calculating a pupil transmittance distribution in a projection optical system based on a first effective light source distribution of the projection optical system acquired by a measuring apparatus of an exposure apparatus, and a second effective light source distribution derived from a pupil plane light intensity distribution measured on a plate plane using light that has passed the projection optical system without a reticle, (b) calculating an imaging performance by using a result of the pupil transmittance distribution calculating step and the first or second effective light source distributions, (c) adjusting at least one of the effective light source distribution or the projection optical system by using the imaging performance, and (d) exposing the plate based on at least one of the effective light source distribution and the projection optical system that have been adjusted.

Abstract: The invention provides for an imaging apparatus for imaging integrated circuits and a respective integrated circuit carrier. This enables positional analysis to be carried out on the integrated circuits and respective carrier. The imaging apparatus includes a support structure, and a bed mounted on the support structure and displaceable along an operatively horizontal axis, the bed being configured to support a nest assembly that operatively retains the integrated circuit carrier and respective integrated circuits. Also included is a support assembly operatively mountable with respect to a bed on which the integrated circuit carrier and integrated circuits are supported, in use. The apparatus further includes an image recordal device mounted on the support assembly and configured to record an image representing the integrated circuit carrier and integrated circuits, the support assembly including an adjustment mechanism to enable adjustment of a position of the image recordal device relative to the bed.

Abstract: Measuring an aerial image with an aerial image measuring device having a light detector and a light blocking layer for separating polarization components of light incident thereon. The light blocking layer has first and second apertures structured differently from each other, wherein the different structures transmit at least one of the polarization components differently. The detector provides separate samples for light transmitted through the first and second apertures. Separate image profiles for each polarization component of the aerial image are generated using the samples provided by the detector. Image recovery for each of the generated image profiles is performed to generate estimated image profiles for each polarization component of the aerial image that exclude the effects of transmission through the first and second apertures of the aerial image measuring device.

Abstract: Transducer modules for use in a blood analysis instrument and methods for analyzing a blood sample. The transducer modules presented generally include a light source, a focus-alignment system, a flow cell, and a light scatter detection system. Electrodes within the flow cell allow for the measurement of the DC impedance and RF conductivity of cells passing through a cell-interrogation zone in the flow cell. Light scatter from the cells passing through the cell-interrogation zone is measured by the light scatter detection system. The light scatter detection system measures the light scatter parameters of upper median light scatter, lower median angle light scatter, low angle light scatter, and axial light loss.

Abstract: A structure for overlay measurement is provided in the present invention, using the diffraction characteristics on the boundary portion between two microstructures formed on each of two material layers. The optical intensity distribution on the boundary portion between microstructures formed on the two overlaid material layers respectively are measured by an optical microscope to obtain the overlay error between the two overlaid material layers. In addition, the present invention also provides a method for overlay measurement using the structure for overlay measurement, wherein a merit relation based on the optical intensity distribution on the boundary portion between different microstructures is determined. The merit relation can be used to analyze the overlay error to improve the efficiency and accuracy of on-line error measurement.

Abstract: A method for loading a semiconductor wafer into a process unit comprises opening the process unit, inserting a wafer into the process unit, adjusting the position of the wafer in the process unit so that it is in a certain position in relation to markers, and inserting a camera into the process unit facing the markers. The camera acquires an image of the markers and of a part of the wafer, and displays on a display screen the image acquired. The position of the wafer is adjusted according to the position of the wafer in relation to the markers on the image displayed.

Abstract: A position finding system and method may be used to find an alignment position of a laser device relative to an optical fiber such as an angled optical fiber. The laser device may be positioned “off-axis” relative to the optical fiber such that light from the laser device is directed at an angle to an end of the optical fiber and coupled into the optical fiber. The position finding system and method may be used to find the alignment position by searching for relative high power positions at different angular orientations of the laser device and calculating coordinates of at least one alignment position from the coordinates of the relative high power positions. The relative high power positions may be positions at which the measured power coupled into the optical fiber by the laser is maximized.

Abstract: The invention relates to a detection device for identifying objects in a material stream, preferably a cullet stream. The device comprises several light sources, which emit light in a rectilinear manner, preferably diode light sources and which are combined to form at least one optical emitter, at least one receiver that contains a lens system and a photoelectric cell, in addition to a detection section, which is located between the emitter and the receiver and is traversed by the material stream. The aim of the invention is to provide a detection device, which eliminates to a great extent the error sources that are inherent in optical lens systems. To achieve this, the light sources of an emitter are directed onto the area of intersection of the optical axis of the lens system with the lens system of the receiver that is assigned to the emitter.

Abstract: Microchip testing device having a chip holder that can be exactly positioned and from which adhered sample liquid can be removed easily. The microchip testing device has a chip holder, with a cover and a box area, mounted on a measurement stage, a microchip that has an optical measurement chamber is housed in the chip holder, a light source that radiates light on the optical measurement chamber of the microchip, a detector that receives light that has passed through the optical measurement chamber, and a controller that controls the device. The chip holder has reference planes to position the microchip in two directions perpendicular to the optical axis of the optical measurement chamber and pushers that push the microchip against the reference planes, so that the microchip is positioned within the chip holder by closing the cover of the chip holder.

Abstract: A method for aligning a reticle is provided. A first patterned layer with a first alignment grid is formed. Sidewall layers are formed over the first patterned layer to perform a first shrink. The first alignment grid after shrink is etched into an etch layer to form an etched first alignment grid. The patterned layer is removed. An optical pattern of a second alignment grid aligned over the etched first alignment grid is measured. The optical pattern is used to determine whether the second alignment grid is aligned over the etched first alignment grid.

Abstract: Disclosed are apparatus and methods for determining overlay between a plurality of first structures in a first layer of a sample and a plurality of second structures in a second layer of the sample. Targets A, B, C and D that each include a portion of the first and second structures are provided. The target A is designed to have an offset Xa between its first and second structures portions; the target B is designed to have an offset Xb between its first and second structures portions; the target C is designed to have an offset Xc between its first and second structures portions; and the target D is designed to have an offset Xd between its first and second structures portions. Each of the offsets Xa, Xb, Xc and Xd is different from zero, and Xa is an opposite sign and differ from Xb. Offset Xc is an opposite sign and differs from Xd. The offsets Xa, Xb, Xc and Xd are selected so that an overlay error, including the respective offset, is within a linear region of overlay values.

Abstract: Disclosed are methods and apparatus for determining overlay error. Radiation that is scattered from each of a plurality of cells of a target is measured. Each cell includes at least a first grating structure formed by a first process and a second grating structure formed by a second process and wherein each cell has a predefined offset between such each cell's first and second grating structures. The first and second grating structures of the different cells have different predefined offsets, and each predefined offset of each cell is selected to cause one or more terms to be cancelled from a periodic function that represents radiation scattered and measured from each cell. The scattered radiation of each cell is represented with a periodic function having a plurality of unknowns parameters, including an unknown overlay error, and the unknown overlay error is determined based on the plurality of periodic functions for the plurality of cells.

Abstract: A method includes measuring spectral responses of at least first and second sections of a measurement mark. In the first section, individual ones of primary lines of a first width are arranged at a first pitch and in alternating order with secondary lines spaced from the primary lines at a first distance. In the second section, individual ones of further primary lines of a second, different width are arranged at the first pitch and in alternating order with further secondary lines that are spaced from the further primary lines at the first distance. From at least the first and second spectra, information on a difference between target and actual widths of the primary and secondary lines may be obtained.

Abstract: A position aligning apparatus performs position alignment of a pattern in a current process of a pattern exposure process by using a pattern formed before the current process. The position aligning apparatus includes: a correction calculating section configured to calculate a correction value set of a current lot about each of misalignments in scale and rotation of a pattern in a chip in the current process based on a correction value set in an immediately-preceding lot in the current process, a completeness value set in the immediately-preceding lot in the current process, a summation of completeness value sets in the immediately-preceding lot to a process immediately-preceding to the current process, and a summation of completeness value sets in the current lot to the immediately-preceding process; and a correction control unit configured to control correction of the scale and the rotation of the pattern in the chip by using the correction value sets.

Abstract: An alignment apparatus includes first and second alignment devices (1) and means (9) for mounting each of the first and second alignment devices in spaced relationship one behind the other and such that one alignment device is at a higher level than the other alignment device. Each alignment device (1) includes a plate member having a surface comprising at least one area of reflective material and at least one area (3, 5) of non-reflective material. The areas of reflective material and of non-reflective material are configured such that, when an elongate beam of electromagnetic radiation is incident on both of the first and second alignment devices, the pattern of reflected radiation varies according to whether both of the first and second alignment devices are aligned with the beam.

Abstract: The invention provides a liquid ejecting head alignment apparatus that is used for positional determination and adhesion of nozzle plates and a fixation member, each of the nozzle plates having nozzle openings through which each of a plurality of liquid ejecting heads ejects liquid and further having alignment marks for positional alignment, the fixation member holding the nozzle-plate side of the plurality of liquid ejecting heads.

Abstract: A lithographic apparatus includes a displacement measuring system to measure a position of a moveable object with respect to a reference frame of the lithographic apparatus, in at least three coplanar degrees of freedom (x, y, Rz) of an orthogonal x-y-z coordinate system centered in the center of the moveable object. The moveable object includes a support structure configured to support a patterning device or a substrate table configured to support a substrate. The displacement measuring system includes at least three sensor heads, each sensor head being positioned with a measuring direction substantially coplanar with the x-y plane of the coordinate system and each sensor head being furthermore positioned with the measuring direction substantially perpendicular to a connection line connecting the sensor head with the center of the movable object and extending coplanar with the x-y plane.

Abstract: A resultant image of a grating target may be obtained by dividing an image of the target into first and second portions and optically modifying the first and/or second portion such that a final image formed from their combination is characterized by a Moiré pattern. The resultant image may be analyzed to determine a shift in the grating target from a shift in the Moiré pattern. Optical alignment apparatus may include a first beam splitter, an image transformation element optically coupled to the first beam splitter, and a second beam splitter. The first beam splitter divides an image of a grating target into first and second portions. The second beam splitter combines the first portion and the second portion. The image transformation element optically modifies the first and/or second portion such that a final image formed from their combination is characterized by a Moiré pattern.

Abstract: An apparatus for aligning semiconductor wafers includes equipment for positioning a first surface of a first semiconductor wafer directly opposite to a first surface of a second semiconductor wafer and equipment for aligning a first structure on the first semiconductor wafer with a second structure on the first surface of the second semiconductor wafer. The aligning equipment comprises at least one movable alignment device configured to be moved during alignment and to be inserted between the first surface of the first semiconductor wafer and the first surface of the second semiconductor wafer. The positioning equipment are vibrationally and mechanically isolated from the alignment device motion.

Abstract: A lithographic apparatus arranged to transfer a pattern from a patterning device onto a substrate includes a reference set of gratings provided in the substrate, the reference set including two reference gratings having line elements in a first direction and one reference grating having line elements in a second, perpendicular, direction. A measurement set of gratings is provided on top of the reference set of gratings, the measurement set comprising three measurement gratings similar to the reference gratings. Two of the measurement gratings are oppositely biased in the second direction relative to the respective reference gratings. An overlay measurement device is provided to measure asymmetry of the three gratings in the reference set and the measurement set, and to derive from the measured asymmetry the overlay in both the first and second direction.

Abstract: A method for evaluating an optical module, the optical module including a light emitting element and a supporting member for supporting an end of an optical fiber for communications, by which relative positions of the light emitting element and the supporting member are evaluated, the method including the steps of: (a) supporting an end of an optical fiber for evaluation at the supporting member; (b) propagating light emitted from the light emitting element through the optical fiber for evaluation; and (c) detecting the amount of only a portion of components of light including an optical axis thereof emitted from the light emitting element by a photodetector provided at the other end of the optical fiber for evaluation.

Abstract: This application describes, among others, wafer designs, testing systems and techniques for wafer-level optical testing by coupling probe light from top of the wafer.

Abstract: A position adjustment mechanism for laser optics includes a fixed mount, a fastening member, and a position regulation device. The fixed mount is connected to a heat-dissipating mount and positioned near the optics mount. The fastening member penetrates the fixed mount and the optics mount to connect the fixed mount with the optics mount and maintains a gap between the fixed mount and the optics mount. The position regulation device is positioned in the vicinity of the fastening member and in the gap between the fixed mount and the optics mount. The position regulation device presses against the optics mount to adjust the position of the reflective element relative to the light-emitting device.

Abstract: A system and method of use thereof that enables determining and setting sample alignment based on the location of, and geometric attributes of a monitored image formed by reflection of an electromagnetic beam from a sample and into an image monitor, which beam is directed to be incident onto the sample along a locus which is substantially normal to the surface of the sample.

Abstract: An alignment target with geometry designs provides a desired alignment offset for processes (both symmetric and asymmetric) on a wafer substrate. The alignment target includes one or more sub-targets, where each sub-target is defined as having a left portion and a right portion having a different geometric pattern, and where the left portion has a geometry density and the right portion has a geometry density.

Abstract: A microfluidic apparatus having a one-dimensional or two-dimensional hydrodynamic flow system to control stable and proper digitally coded bead orientation through the optical detection area of a bioanalysis system. The hydrodynamic system include one core flow, which carries the rectangular barcode beads, and sheath flows, on the sides of or about or around the outer periphery of the core flow, pull the core flow into a proper orientation. The sheath flows, at much higher flow speed but lower volume flow rate, can be pushed or pulled by vacuum, gravity, or pressure. By this method, the coded bead will align themselves in line and flow reliably, without wobbling or flipping, in the core flow channel through the detection zone. By adjusting the relative flow rate of core flow and sheath flows, the coded beads flow reliably in the flow system, thus it can be decoded and detected by an optical system accurately.

Abstract: A detection apparatus detecting predetermined positions of a member includes: n (n?2) sensors one-dimensionally disposed at a sensor pitch equal to or greater than a distance D; and a member to be detected having m (2?m?n) parts to be detected, the m parts to be detected being formed in k respective positions (k?nCm) in respective patterns of disposition which are unique with respect to each other.

Abstract: Techniques are described for the detection of multiple target species in real-time PCR (polymerase chain reaction). For example, a system comprises a data acquisition device and a detection device coupled to the data acquisition device. The detection device includes a rotating disk having a plurality of process chambers having a plurality of species that emit fluorescent light at different wavelengths. The device further includes a plurality of removable optical modules that are optically configured to excite the species and capture fluorescent light emitted by the species at different wavelengths. A fiber optic bundle coupled to the plurality of removable optical modules conveys the fluorescent light from the optical modules to a single detector. In addition, the device may control the flow of fluid in the disk by locating and selectively opening valves separating chambers by heating the valves with a laser.

Abstract: Methods, apparatuses and systems for monitoring a stage alignment in a processing system are disclosed. A method for monitoring a stage alignment in a processing system may include providing a calibration target on a surface of the stage; measuring an angle of incident of a light beam to the calibration target; and monitoring the stage alignment based on the determined angle of incidence.

Abstract: An article and a method for testing the assembly of that article are disclosed. The article includes a plurality of modules, at least two of the modules are capable of being placed in two different positions in the article, each module having a correct position in the article. Each module includes an aperture at a location determined by the desired position for that module in the article. The apertures are placed such that the apertures will be aligned to form a transparent channel when the modules are arranged in a predetermined pattern with respect to one another, but not when arranged in any of the possible incorrect orders. The article can be tested for assembly errors by transmitting a test light signal into the first end and testing for light that traversed all of said first transparent channel.

Abstract: A system comprises the step for applying a mark in advance in a reference position in which attachment of a lens holder is anticipated on a convex lens surface of a reference lens; the step for attaching the lens holder to the convex lens surface of the reference lens by using a holder attachment apparatus; and the step for comparing a position in which the lens holder is actually attached and a reference position in which the mark is applied on the lens. A cavity-shaped hole is formed in the holder so that a position of the mark on the reference lens can be observed when the lens holder is attached to the lens. In the comparison step, a toolmaker's microscope is used to observe the mark through the hole in the lens holder from a direction of the convex lens surface of the lens, an actual attachment position of the holder is compared to the reference position of the reference lens, and an attachment accuracy of the holder is verified.

Abstract: Provided is a wafer lens aligning method including the steps of: preparing a lens mold that has a lens forming portion formed in the central portion thereof and a groove formed around the lens forming portion; preparing a wafer that has two or more position recognition patterns formed at arbitrary positions thereof and a plurality of minute patterns formed in array at lens formation positions; loading the wafer, searching the position recognition patterns, and setting a coordinate system; causing the coordinate system of the wafer to coincide with the coordinate system of the lens mold; causing the center among the minute patterns formed on the wafer to coincide with the center of the lens mold so as to align the wafer with the lens mold; and forming a master lens in the lens formation positions arranged on the wafer.

Abstract: At Step 602, the grid of a wafer loaded into an exposure apparatus is approximated by a mathematical function fitting up to, for example, a cubic function, and at Step 612, the magnitude of a residual error between the position of a sample shot area obtained by the function and an actually measured position is compared with a predetermined threshold value. GCM measurement is performed in a mathematical function mode in a subroutine 616, or it is performed in a map mode in a subroutine 616, on the basis of the result of the comparison. In addition, it is determined whether to extract non-linear components from the wafer in each lot on the basis of a variation in the temperature of the wafer (Step 622) and a variation in random error between the wafers (Step 624).

Abstract: A paste dispenser and a method for controlling the same are disclosed. The paste dispenser includes a stage having a substrate mounted thereon, at least one nozzle dispensing a paste on the substrate by relative movement between the nozzle and the substrate, a measuring means provided at a position facing into an outlet of the nozzle and directly measuring a position of an exchange nozzle, and a controller converting a compensation value in accordance with a displacement of the exchange nozzle based on data measured by the measuring means.

Abstract: An apparatus including a stage configured to be moved. A first laser interferometer measures a position of the stage in a first direction. A second laser interferometer measures a position of the stage in the first direction. A control unit (i) obtains a position of the stage based on an output of one of the first and second laser interferometers, (ii) controls a position of the stage based on the obtained position of the stage, (iii) performs switching of one of the first and second laser interferometers to the other of the first and second laser interferometers while the stage is moved at a constant velocity in the first direction, (iv) calculates a distance by which the stage is to be moved during a time interval, and (v) sets an initial value of the other of the first and second laser interferometers after the switching, based on a position measured by the one of the first and second laser interferometers at a start time of the time interval and the calculated distance.

Abstract: A method for focusing a charged particle beam, the method includes: (a) altering a focal point of a charged particle beam according to a first focal pattern while scanning a first area of a sample and collecting a first set of detection signals; (b) altering a focal point of a charged particle bean according to a second focal pattern while scanning a second area that is ideally identical to the first area and collecting a second set of detection signals; and (c) processing the first and second set of detection signals to determine a focal characteristic; whereas the first focal pattern and the second focal pattern differ by the location of an optimal focal point.