Abstract: A laser device includes a seed laser, an amplifier, a detector, and an optical element arranged to direct radiation emitted by the seed laser towards a plasma generation site. The optical element is arranged to direct towards the detector amplified spontaneous emission radiation which has been emitted by the seed laser and has been reflected from a droplet of fuel material. The detector is arranged to trigger generation of a laser radiation pulse by the seed laser when the reflected amplified spontaneous emission radiation is detected.

Abstract: A method and an apparatus for determining at least one optical property of an imaging optical system which is designed to image an object disposed in an object plane of the optical system into an assigned image plane. The method includes disposing at least one test structure in the object plane of the optical system, disposing an image recording device in at least two different positions relative to the image plane of the optical system, in each of the at least two relative positions the image recording device being offset in relation to the image plane to such an extent that an image of the pupil of the optical system is produced respectively on the image recording device by the optical system by means of the test structure, and recording an image produced on the image recording device by the optical system by means of the test structure in each of the at least two relative positions by means of the image recording device.

Abstract: An exposure apparatus for exposing a wafer to light through a pattern of a mask. The apparatus includes a projection optical system configured to project the pattern onto the wafer, a first barometer configured to measure pressure of an atmosphere in the apparatus, a second barometer configured to measure the pressure at a speed higher than that at which the first barometer measures the pressure, a calibration unit configured to calibrate an output of the second barometer based on an output of the first barometer, and an aberration correction unit configured to correct aberration of the projection optical system based on the calibrated output.

Abstract: There is provided an optical characteristic measuring method for measuring an optical characteristic of an optical system which forms, on a second plane, an image of an object arranged on a first plane, the optical characteristic measuring method including: arranging at least one phase pattern on the first plane; illuminating the arranged phase pattern, with a light having a predetermined wavelength; extracting a partial image of a pattern image formed via the phase pattern and the optical system; and detecting information about the light in relation to the extracted partial image.

Abstract: An illumination apparatus and an exposure apparatus that achieves higher quality exposure to light and higher operating speed even where the ratio Hx/Hy between the transverse dimension Hx and the longitudinal dimension Hy of the plane of optical modulation of a two-dimensional optical space modulator is 1.5 or above, for instance, are to be provided. The focal distance fx in an x-direction and the focal distance fy in a y-direction of a second optical system that guides light emitted from an integrator to a two-dimensional optical space modulator are made different, in a ratio of fx/fy=1.6, for instance. In this way, the number of rod lenses in the integrator can be made equal between transverse and longitudinal directions and the value of Hx/Hy can be made 2.5 by bringing the aspect ratio dx:dy of rod lenses to 1.6:1, close to 1.

Abstract: A method of structuring a photosensitive material is disclosed. The method includes illuminating a first object structure and projecting a pattern of the first object structure onto a photosensitive material such that the projected pattern of the first object structure is focussed at a first focus position with respect to the photosensitive material. The method also includes illuminating a second object structure and projecting a pattern of the second object structure onto the photosensitive material such that the projected pattern of the second object structure is focussed at a second focus position with respect to the photosensitive material. The respective patterns are projected in the same projection direction.

Abstract: A lithographic apparatus, includes a support structure configured to hold a patterning device, the patterning device configured to impart a beam of radiation with a pattern in its cross-section; a substrate table configured to hold a substrate; a projection system configured to project the patterned beam onto a target portion of the substrate; a liquid supply system configured to provide liquid to a space between the projection system and the substrate table; a sensor configured to measure an exposure parameter using a measuring beam projected through the liquid; and a correction system configured to determine an offset based on a change of a physical property impacting a measurement made using the measuring beam to at least partly correct the measured exposure parameter.

Abstract: A method for exposing a resist layer on a substrate to an image of a pattern on a mask is disclosed whereby, after starting exposure and before completing exposure, a controlled amount of contrast loss is introduced by a controller in the image at the resist layer by changing during exposure the position of the substrate holder. The contrast loss affects the pitch dependency of the resolution of a lithographic projection apparatus, and its control is used to match pitch dependency of resolution between different lithographic projection apparatus.

Abstract: A test photomask includes a first mask pattern and a second mask pattern formed at a center portion of the first mask pattern thereon. The first mask pattern is a pattern with light condensing effect and a nature in which an exposure-dose amount to a transfer object varies in dependence on a focus variation, which is a two-dimensional Fresnel zone pattern here.

Abstract: A method for improving critical dimension uniformity of a wafer includes exposing a plurality of mask patterns on a first plurality of substrates at predetermined locations with common splits conditions of focus and exposure dose for each of the first plurality of substrates to form a plurality of perturbed wafers; measuring a critical dimension of the plurality of mask patterns at each of the predetermined locations for each of the plurality of perturbed wafers; averaging the critical dimension measured at each of the predetermined locations over the plurality of perturbed wafers to form a perturbed critical dimension map; measuring a sidewall angle of the plurality of mask patterns; averaging the sidewall angle measured to form a perturbed sidewall angle map; and providing the perturbed critical dimension map and the perturbed sidewall angle map to an exposure tool.

Abstract: An exposure apparatus projects a pattern of an original plate onto a substrate through a projection optical system to expose the substrate to the pattern. The exposure apparatus includes a supporting member configured to support an optical element of the projection optical system along the direction of gravitational force, and position adjustment mechanisms disposed at least two different positions on the supporting member and configured to press the optical element to displace the optical element relative to the supporting member. The pressing force of the position adjustment mechanisms against the optical element is changed to move contact positions between the position adjustment mechanisms and the optical element to displace the optical element relative to the supporting member. Thus, optical performance adjustment of the optical element is performed, and then all the position adjustment mechanisms are made in non-contact state with the optical element.

Abstract: Several embodiments of photolithography devices and associated methods of focal calibration are disclosed herein. In one embodiment, a method for determining a focus shift in a photolithography system include placing a microelectronic substrate on a substrate support of the photolithography system and producing first and second refraction patterns on the photoresist layer corresponding to first and second grating patterns, respectively, of a single reticle by illuminating the first and second grating patterns with an asymmetric monopole source perpendicular to the first and second grating patterns. The method further includes measuring an image shift between the first and second refraction patterns on the photoresist layer and determining a defocus shift of the illumination source based on the image shift.

Abstract: high performance and high quality micro devices, etc. are produced highly efficiently at a high throughput. Before transferring a wafer W to an exposure apparatus 200 for exposing the wafer W, marks formed on the wafer W is measured by an in-line measurement device 400 and a measurement result and/or a result of performing calculation processing on the measurement result is notified to the exposure apparatus 200. In the exposure apparatus 200, a measurement condition is optimized based on the notified result and an alignment processing and other processing are performed.

Abstract: A driving apparatus of the present invention is a driving apparatus which adjusts a position of a member to be driven. The driving apparatus comprises a driving member connected with the member to be driven and made of an elastic member, a female screw provided so as to penetrate the driving member, and a taper-shaped male screw configured to be screwed into the female screw. The driving member is provided with a cutting portion which penetrates in an axis direction of the female screw so that an inner circumference of the female screw is discontinuous, and the driving member is configured to move in an axis direction of the male screw in a state where the male screw is screwed into the female screw to displace the member to be driven in a direction orthogonal to the axis direction of the male screw.

Abstract: A method is described that includes illuminating a patterning device pattern with a radiation beam having a symmetric illumination mode, the patterning device pattern comprising a first pattern feature that substantially diffracts radiation of the radiation beam, and a second pattern feature that does not substantially diffract radiation of the radiation beam, introducing an asymmetry, relative to an optical axis, in the substantially diffracted radiation using a phase modulation element, illuminating a radiation beam receiving element with radiation emanating from the phase modulation element to form a receiving element pattern that is related to the patterning device pattern, the receiving element pattern having first and second receiving element pattern features related to the first and second pattern features respectively, and determining information at least indicative of a focal property from positional information regarding the relative positions of the first and second receiving element pattern featur

Abstract: A projection exposure apparatus includes an optical element, and projects a pattern formed on a first object onto a second object to be exposed through a projection optical system for correcting imaging characteristics by controlling the optical element. The projection exposure apparatus includes: a displacement measurement unit configured to measure a displacement of the optical element; a storage unit configured to store a measurement criterion of the displacement measurement unit; an imaging characteristics measurement unit configured to measure imaging characteristics of the projection optical system; and a calibration unit configured to calibrate the measurement criterion based on a result of measurement by the imaging characteristics measurement unit.

Abstract: An apparatus, which scans an original and a substrate relative to light slit-shaped on the original and on the substrate, comprises an adjusting device configured to adjust a distribution of a width of the light slit-shaped, the width being a width in a scanning direction, the distribution being a distribution in a perpendicular direction perpendicular to the scanning direction, and a controller. The controller is configured to obtain information representing a relationship between a position on the substrate and a target dose, calculate a distribution of the target dose in the perpendicular direction with respect to each of the shot regions based on the relationship represented by the obtained information, and control the adjusting device so as to achieve the calculated distribution of the target dose with respect to each of the shot regions.

Abstract: An exposure apparatus includes: an optical system having an optical element on which a first exposure light and a second exposure light are incident, the first exposure light and the second exposure light from the optical element being irradiated onto a first exposure field and a second exposure field; and a detection device that detects at least one of the first exposure light and the second exposure light, which are from the optical element and are directed towards a different direction from directions towards the first and second exposure fields.

Abstract: An optical element for correcting aberrations in an optical apparatus has a casing. The casing is filled with liquid and has a support layer and a cover layer designed to pass light of a predetermined wavelength range. The casing accommodates several actuators. Each actuator has a first end supporting the cover layer and a second end supporting the support layer. Each actuator is able to locally change a local distance between the support layer and the cover layer to correct for local aberrations in a light beam directed to the optical element by providing local phase shifts. The optical element may be used in a lithographic apparatus.

Abstract: Several embodiments of photolithography systems and associated methods of overlay error correction are disclosed herein. In one embodiment, a method for correcting overlay errors in a photolithography system includes measuring a plurality of first overlay errors that individually correspond to a microelectronic substrate in a first batch of microelectronic substrates. The method also includes determining a relationship between the first overlay errors and a first sequence of the microelectronic substrates in the first batch. The method further includes correcting a second overlay error of individual microelectronic substrates in a second batch based on a second sequence of the microelectronic substrates in the second batch and the determined relationship.

Abstract: Aberration control capabilities of sophisticated lithography tools may be exploited in order to locally adapt the focal surface of the optical system. That is, higher order correction terms may be incorporated in the design of the local surface in addition to the conventionally used first order corrections, thereby enhancing uniformity of the lithography process and thus of corresponding microstructure devices.

Abstract: Several embodiments of photolithography systems and associated methods of focus correction are disclosed herein. In one embodiment, a method for characterizing focus errors in a photolithography system includes placing a microelectronic substrate onto a substrate support of the photolithography system. The microelectronic substrate is divided into a plurality of fields individually partitioned into a plurality of regions. The method also includes developing a raw focus error map that has a focus error corresponding to the individual regions of the plurality of fields and deriving at least one of an inter-field focus error map and an intra-field focus error map based on the raw focus error map. The inter-field focus error map has an inter-field focus error corresponding to the individual fields, and the intra-field focus error map has an intra-field focus error corresponding to the individual regions.

Abstract: A measurement apparatus for measuring wavefront aberration of an optical system to be measured comprises a pinhole mask having a pinhole, an illumination optical system configured to illuminate the pinhole mask, a test pattern disposed between the pinhole mask and the optical system to be measured, a detector configured to detect an image formed on an image plane of the optical system to be measured by light having passed through the pinhole, the test pattern, and the optical system to be measured, and an optical member which is disposed or inserted in the illumination optical system, and configured to control an illuminance distribution in a pupil region of the optical system to be measured so that a peripheral portion in the pupil region includes a portion having an illuminance higher than an illuminance in a central portion in the pupil region.

Abstract: The optical element supporting device of the present invention includes a first supporting member that supports the optical element, a second supporting member that supports the first supporting member at a plurality of locations, a plate spring fastened to the first supporting member and having a plate thickness extending in the optical axis direction of the optical element, and a force supplying unit, which is provided on the first supporting member, configured to provide a force in the optical axis direction applied to the plate spring at a location different from the plurality of locations, wherein the force supplying unit elastically deforms the first supporting member by receiving the reactive force generated by the force applied to the plate spring to thereby adjust the position of the optical element.

Abstract: A measurement apparatus includes a measurement unit configured to execute first measurement at each of a plurality of measurement points on a substrate, which are juxtaposed in one of a direction perpendicular to a scanning direction and an oblique direction with respect to the scanning direction, and to execute a second measurement at each of the plurality of measurement points, while the substrate is shifted in a direction different from the scanning direction and a processing unit configured to select some measurement points from the plurality of measurement points on the basis of a change in a measurement value at each measurement point, which is obtained by the first measurement and the second measurement.

Abstract: An imaging device in a projection exposure machine for microlithography has at least one optical element and at least one manipulator, having a linear drive, for manipulating the position of the optical element. The linear drive has a driven subregion and a nondriven subregion, which are movable relative to one another in the direction of a movement axis. The subregions are interconnected at least temporarily via functional elements with an active axis and via functional elements with an active direction at least approximately parallel to the movement axis.

Abstract: The present invention presents an exposure device, which includes an optical source for emitting a UV ray, a first lighting system for shaping the UV ray into a collimated light beam, an aperture member for producing rectangular first and second light beams based on the light beam from first lighting system by using the first and second rectangular windows, first and second spatial light modulators for spatially modulating the first and second light beams, respectively, and first and second projection lighting systems for guiding the modulated first and second light beams to the object.

Abstract: A wafer surface level detection method includes a first level measurement step of measuring a level of a surface of a substrate having a plurality of shot regions, a position measurement step of measuring a position along the surface of the substrate, a first movement step of moving the substrate in at least a vertical direction on the basis of the measurement result obtained in the first level measurement step and the measurement result obtained in the position measurement step, and a second level measurement step of measuring the level of the surface of the substrate after the first movement step, wherein each of the plurality of shot regions has a measurement region. In the first movement step, the substrate is moved such that a relative position of the measurement region of each of the plurality of shot regions and each of the plurality of shot regions along the surface is constant, and, in the second level measurement step, the measurement region of each of the plurality of shot regions is measured.

Abstract: An exposure apparatus is equipped with a laser unit that emits a laser beam, a memory that stores a first information which shows a first relation indicating a relation between a linewidth error of a pattern formed on a wafer and a spectral characteristic of the laser beam emitted from the laser unit, and a main controller that controls the spectral width of the laser beam via a laser controller, based on the first information and on information related to a reticle that is to be used. Main controller performs spectral width control of the laser beam so as to suppress linewidth error, based on the first information and on the information related to the reticle that is to be used.

Abstract: In a method of determining a focus position for a substrate exposure process and a substrate exposure apparatus capable of performing the same, a reticle having a light-transmitting region may be illuminated by an off-axis illumination light. A projected light, which is transmitted through the reticle and a projection optical system, may be detected by a light sensor disposed on a substrate stage. An intensity of the projected light measured at a light-receiving surface of the light sensor may vary in accordance with positions of the light-receiving surface. The focus position may be determined based on the variations in the intensity of the projected light.

Abstract: A projection optical system comprises eight reflectors and forms a reduced image of a first surface (4) onto a second surface (7). It comprises a first reflective imaging optical system (G1) for forming an intermediate image of the first surface and a second reflective imaging optical system (G2) for forming an image of the intermediate image onto the second surface. The first reflective imaging optical system includes a first reflector (M1), a second reflector (M2), a third reflector (M3), and a fourth reflector (M4) successively as light enters from the first surface side. The second reflective imaging optical system includes a fifth reflector (M5), a sixth reflector (M6), a seventh reflector (M7), and an eighth reflector (M8) successively as light enters from the first surface side. This realizes a reflective projection optical system which can favorably correct aberrations while having a favorable reflection characteristic with respect to X-rays and keeping the reflectors from becoming bulky.

Abstract: A method for photolithography in semiconductor device manufacturing comprises defining test critical dimension target for a photolithography mask, measuring a mask critical dimension, comparing mask critical dimension to the test critical dimension target and determining a critical dimension deviation, determining a photolithography light base energy in response to the critical dimension deviation, and exposing the wafer according to the photolithography light base energy.

Abstract: An immersion lithography system that compensating for any displacement of the optical caused by the immersion fluid. The system includes an optical assembly (14) to project an image defined by the reticle (12) onto the wafer (20). The optical assembly includes a final optical element (16) spaced from the wafer by a gap (24). An immersion element (22) is provided to supply an immersion fluid into the gap and to recover any immersion fluid that escapes the gap. A fluid compensation system is provided for the force on the final optical element of the optical assembly caused by pressure variations of the immersion fluid. The resulting force created by the varying pressure may cause final optical element to become displaced. The fluid compensation system is configured to provide a substantially equal, but opposite force on the optical assembly, to prevent the displacement of the final optical element.

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: A photo mask includes an asymmetrical diffraction grating pattern in which diffraction efficiencies of plus primary diffracted light and minus primary diffracted light are different, the asymmetrical diffraction grating pattern including a shielding portion which shields light, a first transmitting portion which transmits light, and a second transmitting portion which transmits light, a ratio of widths of the shielding portion, the first transmitting portion, and the second transmitting portion being n11 where n is a positive real number except 2, the asymmetrical diffraction grating pattern approximately satisfying 163°?360°/(n+2)+??197° where ? (?90°) indicates an absolute value of a difference between a phase of the light transmitted through the first transmitting portion and that of the light transmitted through the second transmitting portion, and a reference pattern for obtaining an image as a reference for measuring a shift of an image of the asymmetrical diffraction grating pattern.

Abstract: A method for optical proximity correction (OPC) of a desired pattern for a substrate is disclosed in which a plurality of variable shaped beam (VSB) shots are determined which can form on a surface an OPC-corrected version of the desired substrate pattern. Shots within the plurality of VSB shots are allowed to overlap each other. Dosages of the shots may also be allowed to vary with respect to each other. The union of the plurality of shots may deviate from the OPC-corrected version of the desired pattern for the substrate. In some embodiments, optimization may be used to minimize shot count. In other embodiments, the plurality of shots may be optionally selected from one or more pre-computed VSB shots or groups of VSB shots, that is, glyphs. A method for creating glyphs is also disclosed, in which patterns that would result on a surface from one or a group of VSB shots are pre-calculated.

Abstract: A method for implementing discrete superpositioning of two or more defocal wafer images at different defocal positions in a lithographic step and scan projection system. The method includes tilting one of a mask and a wafer with respect to a scanning direction and splitting an illumination beam into at least two illumination areas which are in different defocus zones of the mask.

Abstract: A method of illuminating at least two illumination points by means of at least one spatial light modulator, said at least one spatial light modulator comprising a plurality of light modulators, whereby a predefined amount of energy transmitted to said points is at least partly controlled by varying the number of said light modulators illuminating said point.

Abstract: A system and method for calibrating the focal position of the imaging plane of a sequential lateral solidification (SLS) system. A test pattern is formed on a test substrate while varying the z-position of the focal position. Information concerning the z-position of the focal position is stored by a data processing system for various positions in the test pattern. An inspection light beam is directed onto the test pattern at a predetermined angle. The reflection of the inspection light beam is detected by an optical detector. The data processing system analyzes the reflection and determines whether the reflected light is substantially specular or substantially scattered. The data processing system uses the analysis of the reflected light and the information concerning the z-position of the focal position to select an optimal focal position for calibrating the SLS system.

Abstract: A positioning system adjusts a position of an optical element within an optical device, such as a variable-zoom lens system. A frame supports the optical element, and an elongated surface of each of one or more elongated support structures supports the frame. The frame also supports one or more piezoelectric actuators that, respectively, engage one of the elongated support structures. A controller supplies a control signal to activate each of the one or more actuator modules. Upon activation, a piezoelectric element of each of the activated actuator modules applies a combination of a first force and a second force to an elongated surface of the respective elongated support structures to position the frame along the elongated surface. The combination of forces applied by the piezoelectric element advances the piezoelectric actuator module along the elongated support structure.

Abstract: An exposure apparatus including an illumination optical system to illuminate an original with exposure light of plural wavelengths, a projection optical system to project an image of a pattern of the original onto a substrate, an original-side reference pattern provided at an original side of the projection optical system, a substrate-side reference pattern provided at a substrate side of the projection optical system, and an image plane detecting system configured so that the original-side reference pattern is illuminated with the exposure light or light equivalent to the exposure light with respect to a wavelength component rate.

Abstract: A lithographic apparatus and method, in an embodiment for immersion lithography, are disclosed with a single stage in which leveling and exposure are performed simultaneously.

Abstract: A lithography exposure device is provided which includes a mounting device for the layer sensitive to light, an exposure unit with several laser radiation sources, an optical focusing means associated with the laser radiation sources, a movement unit for generating a relative movement between the optical focusing means and the mounting device, and a control for controlling intensity and position of exposure spots so that exposed structures which are as precisely structured as possible can be produced. A laser radiation field propagating in the direction of the light-sensitive layer generates each of the exposure spots from respective focal points and has a power density which leads in the conversion area in the light-sensitive layer to formation of a channel penetrating the light-sensitive layer with an index of refraction increased in relation to its surroundings by the Kerr effect and which guides the laser radiation field in a spatially limited manner.

Abstract: This invention discloses an immersion exposure method which executes immersion exposure for an exposure target film by transferring an image of a pattern formed on a mask onto the exposure target film through an immersion medium. A first vapor pressure as the target value in an immersion exposure atmosphere which surrounds the immersion medium is set. A second vapor pressure in the immersion exposure atmosphere is measured. The first vapor pressure is compared with the second vapor pressure. Whether to adjust the vapor pressure in the immersion exposure atmosphere is selected in accordance with the comparison result.

Abstract: A lens array plate of long-size or large area is provided reducing deterioration of optical performance. A lengthy lens array plate (10), which is based on manufacturing process in accordance with the present invention, is formed by connecting a plurality of planar-shaped lens array plates (1) in the longer direction thereof, the planar-shaped lens array plate (1) including a plurality of lens portions that are regularly arranged. The connecting portion (3) is linearly formed at the position other than the plurality of lens portions. Thereby, a lengthy lens array plate with any length may be formed.

Abstract: An optical apparatus includes a laser light source for emitting a beam of light, an integrator for dividing the beam of light into plural beams of light, and a light focusing optical system for focusing the beams of light passed through the integrator. The optical apparatus also includes a stage, on which the light concentrated by the light focusing optical system is irradiated and on which an object may be placed, and includes a projecting optical system for projecting the light transmitted through the object. The following conditions satisfy the following numerical formula (1). The projecting optical system has a visual field including an effective visual field, and the integrator has a division number N corresponding to a predetermined direction in a predetermined effective visual field. A ghost image is formed in the effective visual field in the predetermined direction and has contrast ?.

Abstract: A level sensor for a lithographic projection apparatus according to one embodiment of the invention includes a light source, a first reflector, a second reflector and a detector. The first reflector is positioned to direct light from the light source towards a wafer surface, and the second reflector is positioned to direct light reflected from the wafer surface to the detector. The first and second reflectors are selected to incur a minimal process dependent apparent surface depression.

Abstract: An optical system is used in a detection unit of an exposure apparatus that projects an original pattern by exposure onto a substrate via a projection optical system. The detection unit detects a position of the substrate in the optical axis direction of the projection optical system. The optical system includes a first imaging optical system configured to form an object image in the measurement region of the substrate by oblique light incidence, and a second imaging optical system configured to focus the object image onto a light receiving unit. The following relationship is satisfied: (??1)×(??1)>0 where ? represents an absolute value of a magnification of the first imaging optical system, ?×L2 represents an image distance, ?/? represents an absolute value of a magnification of the second imaging optical system, L2 represents an object distance, and ? and ? are positive real numbers.

Abstract: A photolithography system using an optical microscope is provided that can form various types of selective patterns at a low cost in small-scale research using unit-size silicon substrates which is not targeted for mass production, without requiring an expensive photomask.

Abstract: Focus monitoring for a photolithographic applications is provided by illuminating a photoresist layer with a light beam transmitted through a first binary mask to define a circuit pattern on an underlying substrate and then illuminating the photoresist layer with an unbalanced off-axis light beam transmitted through a second binary mask. The second mask contains a shifting feature configuration in one portion, while another portion blocks light transmission to the chip design area of the photoresist. After development of the photoresist layer, the pattern formed by illumination of the second mask can be compared with a predefined reference feature on the photoresist layer to determine whether a shift, if any, is within acceptable focus limits.