Abstract: A system and method are used to compensate for distortions or aberrations in an image formed in a projection system. Pattern data is generated corresponding to features to be formed on a substrate. At least one of aberrations and distortions of a projection optical system are measured. The pattern data is altered based on the measuring step. The altered pattern data is transmitted to a patterning device to control individually controllable elements coupled to the patterning device. Non uniformities in one or both of a field and pupil of an illumination system can also be measured and used to alter the pattern data.

Abstract: Provided are systems and methods for overcoming optical errors occurring from reticle and other hardware usage in a semiconductor fabrication apparatus. The systems and methods minimize optical errors, such as those resulting from gravitational sag on a reticle or mask, for a pattern being projected onto a wafer. The reduced errors allow larger reticles and masks to be used—while maintaining optical accuracy; and also improve optical budget management.

Abstract: A semiconductor wafer is exposed with a pattern from a mask or reticle in an exposure tool. The exposure tool has an adjustable lens system and a light source, which is tunable in wavelength. A first exposure is performed with a tuned first wavelength and a first setting of the lenses. Prior to performing a second exposure onto the same wafer and into the same resist layer, the wavelength of the light source is varied to a second wavelength in order to mimic a focus offset. A resulting image shift at the slit edges of the scanning system due to chromatic aberration is then corrected for by setting the lens system in dependence of the difference between the tuned first and second wavelength. Having tuned second wavelength of the light source and having set the lens system, the second exposure is performed. A continuous adjustment of the lens system based upon a continuously varying light source wavelength can be accomplished.

Abstract: An in-situ interferometer includes an image modifying optic that produces light ray bundles. The light ray bundles are projected onto a reticle with a plurality of measurement fiducials encoded onto a face of the reticle. The measurement fiducials are exposed onto a sensing plane and their locations measured. Aberrations in the projection system are determined from the measurements of the exposed reticles.

Abstract: An in-situ interferometer includes an image modifying optic that produces light ray bundles. The light ray bundles are projected onto a reticle with a plurality of measurement fiducials encoded onto a face of the reticle. The measurement fiducials are exposed onto a sensing plane and their locations measured. Aberrations in the projection system are determined from the measurements of the exposed reticles.

Abstract: A lithographic apparatus includes an illumination system configured to provide a beam of radiation of radiation; a support configured to support a patterning device configured to impart a pattern to the beam of radiation; a substrate table configured to hold a substrate; a projection system configured to project the patterned beam onto a target portion of the substrate, the projection system and/or illumination system including a focusing element; a plurality of stop discs each having an aperture therethrough different from the size and/or shape of the apertures of the other stop discs; and a mechanism configured to exchangeably place a selected one of the stop discs adjacent to the focusing element.

Abstract: An image correction processing apparatus for correcting a pixel value of each pixel constituting image data obtained from an original image affected by the peripheral light-off is disclosed. The apparatus includes a pixel coordinate transforming unit for converting a distance between each pixel of a group of pixels which have an equal amount of peripheral light amount reduction and which are located on a common contour line of an oval about a predetermined reference pixel located at the center thereof and said predetermined reference pixel into a radius of a true circle having a diameter corresponding to the major axis of the oval; a cos4 calculating unit for obtaining, for each pixel, an angle value thereof in proportion to the radius obtained by the conversion and then obtaining a cos4 value of the angle value; and a correction calculating unit for multiplying an inverse of said cos4 value obtained for each pixel by a pixel value of this pixel, thereby to obtain a corrected pixel value for the pixel.

Abstract: Techniques for determining wafer stage grid and yaw in a projection imaging tool are described. The techniques include exposing an overlay reticle onto a substrate having a recording media, thereby creating a plurality of printed fields on the substrate. The overlay reticle is then positioned such that when the reticle is exposed again completed alignment attributes are created in at least two sites in a first and a second printed field. The substrate is then rotated relative to the reticle by a desired amount. The overlay reticle is then positioned such that when the reticle is again exposed, completed alignment attributes are created in at least two sites in the first and a third printed field. Measurements of the complementary alignment attribute and a dynamic intra-field lens distortion are then used to reconstruct wafer stage grid and yaw error of the projection imaging system.

Abstract: A process for providing illumination source conditions for the accurate determination Zernike tilt coefficients in the presence of coma is described. Large feature-shift coma sensitivity is simulated for a range of illumination conditions. The resulting source sensitivity data is modeled and a practical array of source shapes, each of which is optimized to eliminate the effects of transverse distortion due to third-order coma, is identified. The optimized set of source shapes can be used to more accurately determine Zernike terms a2 and a3 using a variety of methods. Knowledge of the lens distortion data in the absence of coma induced shifts can be entered into more traditional overlay regression routines to better identify systematic and random error.

Abstract: A lithographic projection apparatus includes a measurement system for measuring changes in projection system aberrations with time, and a predictive control system for predicting variation of projection system aberrations with time on the basis of model parameters and for generating a control signal for compensating a time-varying property of the apparatus, such as the OVL values (X-Y adjustment) and the FOC values (Z adjustment) of a lens of the projection system for example. An inline model identification system is provided for estimating model parameter errors on the basis of projection system aberration values provided by the predictive control system and measured projection system aberration values provided by the measurement system, and an updating system utilizes the model parameter errors for updating the model parameters of the predictive control system in order to maintain the time-varying property within acceptable performance criteria.

Abstract: In an exposure apparatus, in which exposure data necessary for direct exposure is sequentially supplied to an exposure engine having a plurality of exposure devices and, based on the supplied exposure data, the exposure engine forms an exposure pattern on an exposure target substrate which moves relative to the exposure engine, lights respectively produced from the exposure device groups based on the identical exposure data supplied to each of the plurality of exposure device groups, are projected via optics so as to be superimposed one on top of another on the same area on the exposure target substrate.

Abstract: In one method of compensating for the distortion of front-to-backside alignment optics, a displacement vector between the estimated position of a substrate mark and the actual position of a substrate mark is calculated. An optical correction array is also calculated by moving a reference substrate by a fixed amount and comparing how far an image of a point on the back side of a reference substrate moves to how far a corresponding point on the front side of the substrate moves. The displacement vector and optical correction array may then be used to accurately calculate the position of further substrates.

Abstract: Exposure equipment having a wafer pre-alignment apparatus and a wafer pre-alignment method using the same reduce wafer pre-alignment errors. The exposure equipment comprises a plurality of exposure units in which lots of wafers are loaded, respectively, and a central control unit. The exposure units are constituted by an alignment apparatus that can detect the relative angular orientation of each wafer transferred to the apparatus and thus, sense any misalignment of the wafers. The central control unit calculates inherent error values for the exposure units based on data transmitted to the central control unit from the alignment apparatus. The central control unit also controls the equipment based on the inherent error values of the exposure units to compensate for the misalignment of the wafers in the exposure units.

Abstract: A photolithography mask critical dimension metrology system is provided. The system includes a radiation source, a holder operable to securely hold at least one mask oriented to receive radiation emitted from the radiation source, a projection system operable to direct radiation passing through the at least one mask, and an image capture system operable to receive radiation directed by the projection system and capture a projected image of the at least one mask.

Abstract: A method for correcting structure-size-dependent positioning errors during the photolithographic projection by an exposure apparatus and the use thereof includes providing an exposure apparatus for exposing a plurality of exposure fields and a simulation model of the exposure apparatus for specifying correction values for intra-field errors, providing a first pattern with first structure elements and first measurement marks, which, in the case of a projection, are beset by a first positioning error and a second positioning error dependent on the dimensions and the position in the exposure field, providing a correction function suitable for specifying the first and the second positioning error, determining an average relative positioning error including the first and the second positioning error, calculating correction values for the control of the exposure apparatus, and transmitting the correction values to the exposure apparatus so that subsequent exposures are performed with an improved overlay.

Abstract: A focus monitor method comprising preparing a mask comprising a first and second focus monitor patterns and an exposure monitor pattern, the focus monitor patterns being used to form first and second focus monitor marks on a wafer, and the exposure monitor pattern being used to form exposure meters on the wafer, obtaining a exposure dependency of a relationship between a dimensions of the focus monitor marks and the defocus amount, forming the focus monitor marks and exposure monitor mark on the wafer, measuring a dimension of the exposure monitor mark to obtain an effective exposure, selecting a relationship between the dimensions of the focus monitor marks and the defocus amount corresponding to the effective exposure, measuring a dimensions of the first and second focus monitor marks, and obtaining a defocus amount in accordance with the measured dimensions of the focus monitor marks and the selected relationship.

Abstract: An apparatus for forming a pattern has a light-modulating unit, a scanner, a pattern data processor, a light modulating controller, a position-error detector, and a correction value calculator. The pattern data processor generates band-pattern data corresponding to each scanning band on the basis of pattern data matching a preceding pattern that is repeatedly and regularly formed on the photo-sensitive material. The position-error detector detects a position-error of the preceding pattern relative to a pattern area. The correction value calculator calculates an alignment correction value in each pattern area on the basis of the position-error, so as to overlay the pattern on the preceding pattern. The pattern data processor corrects the band-pattern data in accordance with the alignment correction value while classifying each exposure data of the band-pattern data into a corresponding pattern area.

Abstract: A lithographic system includes an illumination system for providing a projection beam of radiation, a mask table for supporting a mask, the mask serving to impart the projection beam with a pattern in its cross-section, a substrate table for holding a substrate, and a projection system for projecting the patterned beam onto a target portion of the substrate. The system also comprises a processor arranged to calculate overlay corrections using a reference height map representing a surface of the substrate table or the mask table. Feed forward correction of non-flatness induced wafer grid distortion is allowed during alignment and during exposure, thereby reducing overlay errors caused by differences in flatness characteristics. It provides an indirect qualification method for overlay accuracy related to exposure chuck flatness based on height map information.

Abstract: Provided are an off-axis illumination apparatus, an exposure apparatus, and an off-axis illumination method. The off-axis illumination apparatus may include a mask, a light source for emitting light to the mask, and an incident angle varying section for varying an incident angle of the light. The exposure apparatus may include the off-axis illumination apparatus in addition to a wafer stage and an optical detector. The off-axis illumination method may include irradiating light from the light source to a mask, and moving positions of the light source and the mask to vary an incident angle of the light to the mask.

Abstract: An exposure method of forming pattern on object via projection optical system, including deciding optimal adjustment amount of adjustment device which adjusts image forming property of the projection optical system to optimize the image forming property under pattern to be formed and exposure condition of the pattern, based on information related to wavefront aberration of the projection optical system, Zernike Sensitivity Chart corresponding to the pattern and the exposure condition, wavefront aberration variation table that denotes relation between adjustment amount of the adjustment device and change in coefficients of terms in the Zernike polynomial, and restraint condition with respect to the adjustment amount of the adjustment device, and exposing the pattern on the object under the exposure condition via the projection optical system of which the image forming property is adjusted by the adjustment device based on the decided optimal adjustment amount.

Abstract: An exposure apparatus for transferring a pattern onto an object via a projection optical system, including a moving body arranged on an image plane side with respect to the projection optical system, a wave-front measuring unit at least a part of which is arranged in the moving body, and which measures wave-front information of the projection optical system, an adjusting unit that adjusts a state of an image of a projected pattern generated on the object via the projection optical system, and a controller that controls the adjusting unit using the wave-front information and Zernike Sensitivity corresponding to exposure conditions of the object.

Abstract: A lithographic projection apparatus is presented, which includes a housing, which comprises therein a first exposure system that has at least one movable part (e.g. a movable first substrate holder or a movable second substrate holder in a twin stage apparatus). The apparatus also includes a position disturbance correction system for correcting a position of the first substrate holder with respect to the patterned projection beam due to the influence of gas pressure differences or gas movements, caused by movements of the movable part. A related device manufacturing method is also presented in which, during the exposure of a first substrate, the position thereof is corrected by means of position disturbance correction system.

Abstract: An exposure apparatus includes a barometer for detecting air pressure, a lens driving unit for driving a lens of a projection optical system, a light-source-wavelength changing unit for changing a wavelength of an exposure light source, and a stage driving unit for driving a wafer stage in an optical-axis direction. The apparatus can correct an aberration caused by a change in air pressure by utilizing the lens driving unit, the light-source-wavelength changing unit, and the stage driving unit. During a shot of an exposure of the exposure apparatus, the lens driving unit and/or the stage driving unit are employed to correct the aberration. In the non-exposure state (shot interval), the light-source-wavelength changing unit and/or the lens driving unit as well as the stage driving unit are employed to correct the aberration.

Abstract: A device and a method for testing an exposure apparatus is disclosed. A testing device includes a substrate, and a plurality of block patterns, each of which has a top area varying with an area of a shot region of the exposure apparatus, having at least two different heights located on the substrate. Additionally, the method for testing an exposure apparatus includes using the exposure apparatus to perform an exposure process on the testing device or on the testing device having a photoresist layer thereon, and testing the performance of the exposure apparatus through comparing surface information of the testing device computed by the exposure apparatus with actual surface information of the testing device or through examining photoresist patterns formed on the testing device.

Abstract: Aberrations in an optical system can be detected and measured using a method comprised of a test target in the object plane of a projection system and imaging a photoresist film with the system. The test target comprises at least one open figure which comprises a multiple component array of phase zones, where the multiple zones are arranged within the open figure so that their response to lens aberration is interrelated and the zones respond uniquely to specific aberrations depending on their location within the figure. The method detects aberration types including coma, spherical, astigmatism, and three-point through the exposure of a photoresist material placed in the image plane of the system and the evaluation of these images.

Abstract: A reticle stage grid and yaw in a projection imaging tool is determined by exposing a first portion of a reticle pattern onto a substrate with a recording media thereby producing a first exposure. The first portion of the reticle pattern includes at least two arrays of alignment attribute that have features complementary to each other. The reticle stage is then shifted and a second portion of the reticle pattern is exposed. The first and second exposures overlap and interlock to create completed alignment attributes. Measurements of positional offsets of the completed alignment attributes are used to determine the reticle stage grid and yaw.

Abstract: A lithographic apparatus having a projection system that includes a plurality of mirrors arranged to project the patterned radiation beam onto a target portion of the substrate. The lithographic apparatus further includes an autofocus system having a light source, a position sensitive detector, and a light directing arrangement for directing a first portion of light from the light source to the position sensitive detector. The light directing arrangement further directs a second portion of light from the light source into the projection system and, after the second portion of light has traveled through the projection system to the substrate and back through the projection system to the light directing arrangement, the second portion of light is directed onto the position sensitive detector.

Abstract: A method and system are provided for printing a pattern on a photosensitive surface using a spatial light modulator (SLM). An exemplary method includes defining two or more exposure areas on the photosensitive surface, the exposure areas overlapping along respective edge portions of the exposure areas to form an overlap zone therebetween. Two or more exposure areas are exposed to print an image therein, the exposing extending through the overlap zone. The exposing within the overlap zone is then attenuated.

Abstract: A method of manufacturing first and second substrates that are coupled together, e.g., an active and passive plate of a flat panel display. The active plate is formed according to a standard pattern and inspected. The passive plate is then formed by modifying the pattern data for the passive plate according to the actual pattern formed on the active plate to ensure that the patterns formed on the active and passive plates correspond closely.

Abstract: A radiation system includes a radiation generator to generate radiation, a source, and an illumination system configured to receive the radiation and provide a beam of radiation. The illumination system includes a beam measuring system configured measure at least one of position and tilt of the beam of radiation relative to the illumination system and a projecting device configured to redirect only a part of a cross section of the beam of radiation to the beam measuring system. The beam measuring system may include several position sensors, the readouts of which can be used to determine incorrect alignment of the radiation source with respect to the illumination system. Diaphragms are connected to the collector of the radiation generator, so that in addition to X, Y, and Z corrections, Rx, Ry and Rz corrections are possible.

Abstract: A zero power identical pair of oppositely-oriented meniscus lens elements mounted in the projection light path, serves as curved mask support while compensating for optical anomalies such as beam shift and beam deviations produced by other transparent supports for the curved mask. The zero-power meniscus lens pair, without affecting the transmission beam characteristics, lets the beam diffract as efficiently as does a regular planar mask, thus preserving the partial coherence effects and resolution concepts of projection lithography. This simple but novel optics device is not only expected to clear several barriers for curved mask projection lithography but also find place in other applications where collimated or converging light beams have to travel extra paths without significant aberration.

Abstract: The invention provides an optical transceiver which makes it possible to simplify a production process. An optical transceiver of the present invention includes an optical socket to mount an optical plug disposed at one end portion of an optical fiber); a light-condensing device; and an optical element to emit light in accordance with a supplied electrical signal and an optical element to generate an electrical signal in accordance with a received light signal; and a light-transmissive substrate to support the optical socket, the light-condensing device, and the optical elements so that the optical fiber, the light-condensing device, and the optical elements are aligned on an optical axis of the optical transceiver.

Abstract: Provided are systems and methods for overcoming optical errors occurring from reticle and other hardware usage in a semiconductor fabrication apparatus. The systems and methods minimize optical errors, such as those resulting from gravitational sag on a reticle or mask, for a pattern being projected onto a wafer. The reduced errors allow larger reticles and masks to be used—while maintaining optical accuracy; and also improve optical budget management.

Abstract: An exposure method for projecting, through a projection optical system, a predetermined pattern formed on a mask onto an object to be exposed. The exposure method includes the steps of dividing an effective light source area for illuminating the mask into plural point light sources, calculating a Zernike sensitivity coefficient that represents a sensitivity of a change of image quality of the predetermined pattern to a change of a Zernike coefficient, when wave front aberration in the projection optical system is developed into a Zernike polynomial for all divided point light sources, determining an effective light source distribution based on a combination of Zernike sensitivity coefficient of all divided point light sources, and forming the effective light source distribution by intensity of each point light source.

Abstract: A system and method is used to pattern a substrate. A projection beam received from a radiation system is patterned using an array of individually controllable elements. A portion of the projection beam is directed directly onto one of the individually controllable elements and collecting radiation reflected therefrom using each one of a first array of focusing elements. An image of the first array of focusing elements is projected onto a second array of focusing elements using a projection system, such that radiation reflected from one of the individually controllable elements is projected via one of the focusing elements in the first array of focusing elements and the projection system to one of the focusing elements in the second array which focuses the radiation onto a spot on the substrate.

Abstract: A method for manufacturing a semiconductor device, including obtaining a first dimension difference or ratio which shows a dimension difference or ratio of a latent images of a first and a second focus monitor marks, or a dimension difference or ratio of a first and a second focus monitor marks, calculating a first defocus value based on the first dimension difference or ratio, obtaining second characteristic showing defocus value characteristic for a pressure inside a chamber based on pairs of the pressure and defocus value, measuring the pressure, predicting the defocus value based on the measured pressure and the second characteristic, correcting the relationship between a focus position of an exposure light and a position on the optical axis of the second resist film in accordance with the predicted defocus value, and forming the latent image of the circuit pattern on the second photo resist film.

Abstract: A lithographic apparatus includes an illumination system for providing a beam of radiation. The lithographic apparatus further includes: a support structure for supporting patterning device, the patterning device serving to impart the beam with a pattern in its cross-section; a substrate table for holding a substrate; and a projection system for projecting the patterned beam onto a target portion of the substrate. The lithographic apparatus includes a vacuum system in which at least the illumination system and the substrate table are present. The vacuum system includes at least two separate vacuum modules. A first vacuum module includes at least the projection system and/or the illumination system. A second vacuum module includes the substrate table. At least two of the vacuum modules are connected to each other via a closable connection.

Abstract: A projection exposure apparatus includes a diaphragm controlling unit controlling one or more of an diaphragm, an iris diaphragm, and a relay lens system. In addition, the projection exposure apparatus also includes a line width calculator which calculates a bias, which is a difference between a line width in a dense part and a line width in an isolated part, based on information regarding a mask pattern, the wavefront aberration of a lens, the effective light source of an illumination optical system, the half-width of a laser, the temperature change in a projection optical system due to exposure, etc. When the bias is out of a tolerance range, the line width calculator calculates a correction value for the diaphragm of the projection optical system or a correction value for the effective light source of the illumination optical system in accordance with the bias which is to be corrected. Then, the diaphragm controlling unit is driven in accordance with the calculation results.

Abstract: To reduce and prevent local field anomalies created localized thinning of the coating of optical elements in the apparatus. The projection system is flood exposed to an intense beam of radiation for a substantial period of time. As the rate of thinning of the coating decreases with time, a uniform coating results.

Abstract: Scanning synchronization error in a projection imaging system is controlled by obtaining one or more scanning synchronization error maps comprising a plurality of error components, obtaining one or more focal plane deviation (FPD) error maps comprising a plurality of error components, separating the one or more synchronization error maps and one or more FPD error map error components into one or more repeatable and non-repeatable parts, converting the repeatable parts into one or more mathematical models that express the repeatable parts in mode correctable and uncorrectable terms, inputting lens distortion map data, scanning synchronization error map data, FPD error map data, and the one or more mathematical models into a database linked to a process controller that executes process control algorithms, and correcting scanner motion of the projection imaging system based on output from the process controller.

Abstract: An exposure apparatus illuminates a pattern on an original form, introduces light from the pattern to a plate, and exposes the plate. The exposure apparatus includes at least one optical element, and forcing member that applies a force to the at least one optical element in a non-contact manner.

Abstract: An exposure apparatus includes a projection optical system of catadioptric type, and an optical element disposed on a reciprocating light path of the projection optical system, the optical element being movable to correct at least one of spherical aberration, astigmatism, and curvature of field of the projection optical system.

Abstract: A method for compensating for lens aberrations, which includes the steps of: (a) defining a cost metric which quantifies an imaging performance of an imaging system, where the cost metric reflects the effects of lens aberrations on the imaging performance; (b) defining a source illumination profile; (c) evaluating the cost metric based on the source illumination profile; (d) modifying the source illumination profile, and re-evaluating the cost metric based on the modified source illumination profile; and (e) repeating step (d) until the cost metric is minimized. The source illumination profile corresponding to the minimized cost metric represents the optimal illumination for the imaging device.

Abstract: An exposure apparatus according to this invention includes a projection optical system having a predetermined image forming characteristic; a reticle stage, arranged on one side of the projection optical system, and which holds a reticle having a transfer pattern and has a reference plate for positioning; and a wafer stage, arranged on the other side of the projection optical system, and which holds a wafer where the transfer pattern is transferred and has a reference mark. For transferring the transfer pattern to the wafer, a reticle protection pellicle and an optical device are arranged between the reticle and the projection optical system. For performing positioning using the reference plate and the reference mark, a correction optical device is arranged between the reference plate and the projection optical system. The correction optical device has a thickness equal to the total thickness of the optical device and pellicle.

Abstract: A projection optical system includes an optical element that includes and locally uses a reflective or refractive area that is substantially axially symmetrical around an optical axis, the optical element being rotatable around the optical axis.

Abstract: A method for purchasing items over a non-secure communication channel uses a secure communication device. The secure communication device includes a host processor, a secure memory that includes a laser-scribed encryption key, and a non-secure memory for storing encrypted data. A user's sensitive data is encrypted within the secure memory using the laser-scribed encryption key and stored as encrypted data in the non-secure memory. An encrypted credit card number and an encrypted secret key is retrieved from the non-secure memory, the encrypted credit card and secret key are decrypted with the laser-scribed encryption key, the credit card number is encrypted with a session key, and the encrypted credit card number is transferred over the network to a destination such as an internet vendor.

Abstract: A projection exposure apparatus includes a projection optical system for projecting a pattern on a substrate, a holding portion for holding an optical element which propagates light toward the projection optical system, a mask which is arranged on or near a plane of an image of the optical element formed by the projection optical system and has a transmission portion, an actuator for driving the optical element along one of focal planes of the projection optical system, and a measurement device for measuring an intensity of light which emerges from the optical element, and passes through the projection optical system and the transmission portion of the mask, while the optical element is driven. The measurement device is disposed at a point in a plane conjugate to a pupil plane of the projection optical system or a point in a plane spaced apart from the mask enough to separately detect respective rays emerging from plural points of the plane.

Abstract: A lithographic manufacturing process is disclosed in which first information of a lithographic transfer function of a first lithographic projection apparatus is obtained. The information is compared with second information of a reference lithographic transfer function (e.g. of a second lithographic projection apparatus). The difference between the first and second information is calculated. Then, the change of machine settings for the first lithographic projection apparatus, needed to minimize the difference, is calculated and applied to the first lithographic projection apparatus. In an exemplary application, a match between the first and second lithographic projection apparatus of any pitch-dependency of feature errors is improved.

Abstract: A reticle consisting of a 2-dimensional array of standard overlay targets is exposed several times onto a photoresist coated silicon wafer using a photolithographic scanner. Next, the overlay targets are measured for placement error using a conventional overlay metrology tool. The resulting overlay error data is then fed into a software program that generates the lens contribution to the intra-field error map for the photolithographic projection scanning system.

Abstract: A corrective filter for use in an optical system to correct a defect in a reticle and/or pellicle. The corrective filter may be positioned between a light source and the reticle, between the reticle and a wafer, or in combination with the reticle and/or pellicle. The invention provides a method of characterizing the optical properties of the corrective filter in a photolithography system.