WO2015173397A1 - Ermittlung einer korrigierten grösse - Google Patents
Ermittlung einer korrigierten grösse Download PDFInfo
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- WO2015173397A1 WO2015173397A1 PCT/EP2015/060770 EP2015060770W WO2015173397A1 WO 2015173397 A1 WO2015173397 A1 WO 2015173397A1 EP 2015060770 W EP2015060770 W EP 2015060770W WO 2015173397 A1 WO2015173397 A1 WO 2015173397A1
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70591—Testing optical components
- G03F7/706—Aberration measurement
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
- G01N21/956—Inspecting patterns on the surface of objects
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
- G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
- G03F1/82—Auxiliary processes, e.g. cleaning or inspecting
- G03F1/84—Inspecting
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70591—Testing optical components
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
- G03F7/7085—Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
- G01N21/956—Inspecting patterns on the surface of objects
- G01N2021/95676—Masks, reticles, shadow masks
Definitions
- the invention relates to a method and a device for determining a corrected variable which is dependent on at least one parameter in a parameter range of the at least one parameter.
- the invention further relates to a method for adjusting an imaging optical system of an optical system, and to a method for determining a plurality of corrected wavefront errors in an image field.
- measured values in a parameter range of interest of the at least one parameter can be provided by means of a measurement.
- performing the measurement in the entire parameter range can be associated with a high outlay and at a high cost for a measuring device used for the measurement. This can be circumvented by obtaining measured values of the size only in subregions of the parameter range. These can be disjunctive, ie separate and non-overlapping subregions.
- Such a procedure is for example in a opti ⁇ rule inspection system into account, which is used for examination of an object, for example, a lithography mask or a reticle.
- the inspection system can have means for illuminating the object arranged in an object plane with radiation and imaging optics. With the help of imaging optics, an object field in a picture field of a Image plane. For radiation measurement, a sensor arranged in the image plane can be used.
- the wavefront error represents the above-mentioned size and the image field represents the parameter range, in the present case with two parameters in the form of location coordinates.
- the measurement can be divided into discrete subregions or image regions . Obtain subfields of the image field. This can be achieved, for example, by arranging a sensor used for the measurement successively at different measuring positions. In this case, a plurality of partial measurements are successively performed with the aid of the sensor, and the sensor is moved between them to the individual measuring positions. Also possible is a radiation measurement with the aid of a sensor, which has partial sensors with non-overlapping detection areas.
- the provision of measured values of a variable in a plurality or disjoint subregions of a parameter region can result in the measurement values of the variable in the individual subregions having measurement errors which only occur individually in the corresponding subregions. From subarea to subarea, there may be a varying measurement error. Such a falsification of the measured values of the size impairs their informative value.
- determining a wavefront error may be used to determine adjustment processes for adjusting the imaging optics to reduce their aberrations.
- the use of a sensor at different measuring positions may be accompanied by incorrect positioning of the sensor. This can lead to measured values of the wavefront error in individual subdivisions. Regions of the image field in each case with a constant measurement error (offset or offset) are afflicted.
- the offset errors can be significantly greater than other measurement errors and in particular as the field variation of the resulting from the imaging optics wavefront error. This complicates the Bestim ⁇ tion of suitable Justage methodologiesen.
- Such a disadvantage can occur in a corresponding manner when using a sensor with a plurality of non-overlapping part sensors. In this case, offset errors occurring in partial areas of the image field can be a consequence of positional errors of the partial sensors.
- An object of the present invention is to provide a method and a device by means of which a reliable correction of measured values of a quantity throughput is feasible, wherein the measurement values are obtained in portions of a Para ⁇ meter range. Another object is to provide an inexpensive and reliable method for adjusting an imaging optics of an optical system. Another object is to provide a reliable method for determining multiple corrected wavefront errors in an image field.
- a method for determining a corrected variable which is dependent on at least one parameter in a parameter range of the at least one parameter.
- the method includes
- the method further comprises performing a correction of measured values of the size using an approximation in which measured values of the variable with a smooth function and with the partial regions assigned to the partial regions of the parameter region. approximate functions.
- a smooth function a progression of the size can be displayed over the parameter range.
- a subrange functions an individual change of the size in the subregions of the parameter range can be brought about.
- measured values of the size which relate to associated values of the at least one parameter, are provided in a plurality of disjoint partial areas of the parameter area. This makes it possible to perform the underlying measurement with a low measurement cost and low cost. However, this procedure can be associated with a faulty measurement, so that the measured values of the variable in individual partial areas of the parameter area can each have their own measuring errors that are independent of other partial areas.
- the actual, ie OH ne measurement error based on the Parameterbe prone size ⁇ can rich have corresponding regularities and predictable properties, and accordingly be described by a smooth function over the parameter range leaves.
- regularities are not or substantially not available.
- the method takes this circumstance into account by approximating the measured values of the size both with a smooth function that maps the course of the variable over the parameter range and with the subrange functions assigned to the subregions.
- a smooth function that maps the course of the variable over the parameter range and with the subrange functions assigned to the subregions.
- an individual change of the size in the associated subareas that is to say independently of other subareas, can be brought about via the subarea functions.
- an accurate approximation to the measured values of the size can be achieved with a small or minimal deviation.
- the bewirkbare using the sub-region features individu ⁇ elle change in size in individual areas of the parameter area is not only used for the approximation, but also serves as a basis for correction.
- individual measurement errors in individual subregions can be suppressed, ie eliminated, or at least partially or to a considerable extent reduced. It is therefore possible to provide a corrected and reconstructed size in the para- meter area, which the actual size, optionally up to a difference in the form of a kon ⁇ constants global offset value may come close.
- the method can be carried out with a suitable evaluation device.
- the size may depend on one parameter, but also on several, for example two parameters.
- the parameter range includes the multiple parameters, and the measured values of the quantity refer to associated parameter values of the several parameters.
- the at least one parameter is a location coordinate.
- the parameter area can be used for
- Example include two parameters in the form of location coordinates.
- the two location coordinates may, for example, be coordinates of a two-dimensional orthogonal coordinate system.
- the parameter range can represent, for example, an image field.
- the measured values of the size can relate to field or picture elements of the image field with associated pixel coordinates.
- Other parameters may also be used for the method.
- the at least one parameter may be a time.
- Another example is a parameter area comprising a time and one or more location coordinates.
- the size can in each case be changed by the same value in the associated subareas with the aid of the subregion functions.
- This embodiment can be used when constant or substantially constant measurement errors (displacements or offsets) are present in some areas of the parameter area, are subject to which all the measured values of the size in the relevant part preparation ⁇ chen.
- the smooth function used in the method may include several basic functions.
- the smooth function may be, for example, a polynomial function. It is possible to use basic polynomial functions.
- the correction includes forming corrected values of the magnitude.
- faulty measured values of the size can be replaced by the corresponding corrected values of the size.
- the corrected values of the size which can be as reconstructed values be ⁇ records, can actual, ie without measurement error-prone values of size come close and this essentially correspond.
- the approximation comprises a determination of coefficients of the subregion functions.
- measurements of the magnitude are corrected using the coefficients of the subrange functions.
- corrected values of the size can be formed with which as described above faulty measured values of the size can be replaced.
- the coefficients of the subrange functions can be used to reproduce entries or weightings thereof, and thus a magnitude of measurement errors in the individual subareas. The use of the coefficients of the subrange functions therefore makes it possible to reliably correct or suppress measurement errors. In this case mean values of the size can be reliably reconstructed in the subregions of the parameter range.
- the approximation comprises a formation of a function matrix of subrange functions and basic functions of the smooth function, a formation the pseudo inverse of the function matrix, and multiplying the pseudo inverse of the function matrix by a vector of measured values of magnitude to form a coefficient vector.
- the coefficient vector comprises coefficients of the subrange functions and coefficients of the smooth function basis functions.
- the correction comprises multiplying a matrix of subrange functions by a vector of coefficients (determined by the approximation) of the subrange functions to form a product, and subtracting the product to its mean value from the vector of magnitude measures. By doing so, corrected values of the size may be formed which may substantially correspond to the actual size.
- the product may be the entries or weights of all approximated subrange functions.
- the associated mean can also be called
- Gleichanteil be designated.
- the phrase "up to its average” can be met by the average value of the product is subtracted from the product, and the ⁇ ser term is subtracted from the vector of measured values of the size.
- mean-free subrange functions are used. These are subrange functions which have the mean value zero with respect to the parameter range. Such subrange functions can be formed by subtracting from each of the subvalued subrange functions the respective mean value.
- telwertectomy with ⁇ portion functions the subtraction of the average value of the product described above is included (mean of total entries of the partial region functions) implicitly in the approximation and correction.
- the average value of the product has the value zero when using mean-free subrange functions, so that a sub ⁇ tratechnisch of the same can be omitted.
- correction step therefore, if the other steps use mean-free partial area functions, only the product can be subtracted from the vector of measured values of the size.
- a polynomial function which can comprise simple polynomial basis functions can be used as a smooth function.
- a smooth function which comprises orthogonalized or orthonormal basis functions. It is also possible to use a polynomial function with normalized polynomial basis functions.
- the approximation and correction are performed in a common manner by forming a function matrix of subrange functions and basis functions of the smooth function, forming the pseudoinverse of the function matrix, forming a sub-matrix from the pseudo-inverse of the function matrix, via the sub-matrix Coefficients of the subarea functions are generated, a matrix of subarea functions is multiplied by the subarray to form a product, the product is subtracted from an identity matrix to form a correction matrix, and the correction matrix is multiplied by a vector of measured values of magnitude.
- This embodiment with the aid of which corrected values of the size can be formed in a simple manner, likewise satisfies the requirement of approximating the measured values of the variable with a minimum deviation.
- the approximation and correction are based on a simple multiplication of measured values of the size with the correction matrix.
- the method can be performed such that corrected values constituted the size of the ⁇ .
- the correction comprises formation of an approximated course of the variable.
- the approximated Ver ⁇ run the size of the actual, ie affected without measurement error size come close and this substantially. It is possible to replace the measured values of the size by the approximated course of the size. In this way For example, a plot of the size over the entire parameter range of interest may be reconstructed.
- the formation of the approximated shape of the size allows elimination of dot noise.
- the correction struts comprises a forming we ⁇ a complement value of the quantity, wherein the complement value of the variable to a value of at least one parameter is one for which a measured value of the size before ⁇ located.
- the providing of the at least one incremental value of the magnitude may be done based on an approximated history of the magnitude.
- an approximate curve of the magnitude can be carried out with the aid of the embodiment described below, in which the approximation and correction are likewise carried out in a common manner.
- it is provided to form a function matrix of subrange functions and basic functions of the smooth function, to form the pseudoinverse of the function matrix, to form a sub-matrix from the pseudo-inverse of the function matrix, whereby coefficients of the basic functions of the smooth function can be generated via the sub-matrix, a matrix from basic functions of the smooth function to multiply with the sub-matrix to form a history generation matrix, and to multiply the history generation matrix with a vector of measurements of magnitude.
- This embodiment with the help of an approximated course of the size can be easily formed of the claim shall also meet, to achieve a Ann ⁇ ⁇ approximation of the measured values of size with a minimum deviate ⁇ chung.
- the approximation and correction are based on a simple multiplication of measured values of the size with the progression generation matrix. It is possible to use the progression generation matrix that has once been formed in each case in order to obtain approximated progressions of the magnitude from measured values of the Size to be formed, which are obtained by means of various measurements.
- the processing performed in the method, measurement on a plurality of separate, non-overlapping partial areas, and in addition at least ei ⁇ NEN further partial region of the parameter area refers which overlaps with at least one of the separate, non-overlapping portions.
- different configurations may be considered.
- At least a portion of the disjoint portions considered in the method is a merged portion for which common measures of size are provided.
- Such foiled ⁇ nigter portion can be composed of overlapping portions.
- Common measurements of interest ⁇ the size may be provided on the basis of appropriate pre-processing or correction of first in the individual over- lapping portions obtained measurement values.
- a stitching method can be performed.
- the merged section ⁇ area and the associated common measuring values in the evaluation performed with the aid of the smooth function and the portion functions correction or approximation may be used.
- the associated partial area can be assigned a corresponding partial area function, and the correction sequence as described above or according to one of the embodiments described above (for example formation of corrected values of the size, determination and use of coefficients of the partial area functions for correction, use of the pseudo inverses of the function matrix , the correction matrix, the history generation matrix, etc.).
- Assigned to the combined portion partial area function is selected such that hereby an indi vidual ⁇ changing the size or the size summonrufbar JE because it can be changed by the same value in the subarea.
- the further section Subregion function carried out with the help of a indi ⁇ viduelle change in size in the other sub-range of the parameter range can be caused.
- Rich functional further Sectionbe- may be selected such that hereby which is variable in size ⁇ teressierende each by the same value in the ⁇ be encountered portion.
- a number of further subarea functions can be used in a corresponding manner.
- the correction process may be as described above or according to one of the embodiments described above (for example formation of corrected values of the size, determination and use of coefficients of the subrange functions for correction, use of the pseudo inverses of the function matrix, the correction matrix, the history generation matrix, etc.). be performed.
- a double, or in the case of more than two overlapping subareas a multiple approximation takes place.
- an optical size is considered.
- the parameter area may include two location coordinates, and represent a picture field.
- the optical size may be, for example, a
- Distortion act act with which an occurring in an image ⁇ field distortion, for example, a pillow-shaped or barrel distortion can be reproduced.
- erroneous measured values of the distortion variable which are obtained in several or discrete partial areas of the image field, can be corrected as indicated above. This may for example be considered to reconstruct the distortion across the entire image ⁇ field by, for example, an approximated course of Veronias devis over the image field and / or He ⁇ t tshong size for the purpose of interpolation and / or extrapolation are formed.
- the wavefront error may be in the form of a coefficient to a Zernike polynomial of a wavefront evolution.
- This may be, for example, a Zernike coefficient Z2 or Z3 representing a distortion or possibly local image offset, or Zernike coefficient Z4 representing a focus offset to Zernike polynomial Z4.
- the Zernike polynomials Z2, Z3, Z4 considered here are Zernike polynomials according to Noll's indexing.
- the method may be applied to erroneous measured values of the wavefront error, which are provided in the disjoint partial preparation ⁇ surfaces of an image field, to correct as above angege ⁇ ben.
- the measurement is a radiation measurement carried out with the aid of a spatially resolving sensor.
- the spatially resolving sensor can be, for example, an electronic sensor having a plurality of radiation-sensitive sensor elements or pixels.
- the sensor may, for example, be realized in the form of a CCD sensor (charge-coupled device) with radiation-sensitive photodiodes. Measuring signals of the sensor can, after a corresponding further processing or evaluation, be translated into location-dependent measured values of the optical variable which relate to picture elements of a picture field.
- the provision of measured values of the optical size at picture elements in a plurality or disjoint subregions of an image field using a spatially resolving sensor can be realized in different ways. For example, it can be considered to arrange the sensor for the measurement at different measuring positions.
- it can be considered to arrange the sensor for the measurement at different measuring positions.
- a spatially resolving sensor for the measurement, which has several partial sensors with non-adjacent and non-overlapping detection areas.
- measured values of the optical quantity at pixels in disjoint subregions of an image field can be provided.
- measuring errors can, by which measurement values of the optical size in single ⁇ NEN portions of the image field distorted differently be caused by misalignment of part sensors of the sensor.
- a sensor having a photosensitive layer such as a photographic plate or a film. After the radiation measurement or exposure of the light-sensitive layer, a development of the same can take place, and as part of an analysis of the layer, location-dependent measured values of the optical variable at image points of an image field can be provided.
- Providing measured values of the optical quantity in disjoint partial regions of the image field can be effected, for example, by the analysis only relating to partial regions of the layer, the layer being irradiated only in partial regions, or a subdivided layer being used.
- the method can also be used with respect to other variables measured in several or disjoint subareas of a parameter range.
- a possible example is a height or vertical From ⁇ elongation of a test specimen. This may come in also Be ⁇ tracht to provide by means of a measurement corresponding location-dependent measurements in disjoint portions of a saudi ⁇ dimensional image field, and to correct measurement errors caused by performing the method described above.
- the measurement of the height can be carried out, for example, with the aid of a raster force microscope or with the aid of a surface interferometer.
- a method for adjusting an imaging optics of an optical system is proposed.
- the method described above or according to one of the above-described embodiments is used.
- men designed methods for determining a corrected optical size performed.
- the determination of the corrected optical quantity on the basis of which the adjustment is performed may include, for example, a formation of corrected values of the optical quantity. Additionally or alternatively, the formation of an approximate course of the optical variable and / or the formation of at least one additional value of the optical variable may be provided.
- the spatially resolving sensor may or may not be part of the optical system.
- the sensor can be used, for example, within the framework of a construction of the optical system.
- an object ⁇ example, a reticle may be used, which has the Teststruk- structure (s) and which is irradiated with the radiation used.
- the imaging optics the radiation coming from the object, ie a transmitted or reflected radiation component, can be guided to the spatially resolving sensor.
- a device for determining a corrected variable which is dependent on at least one parameter in a parameter range of the at least one parameter has a measuring device with the help of which measured values of the size can be provided in a plurality of separate and non-overlapping partial regions of the parameter range.
- the pre ⁇ device further comprises an evaluation device for the correction of measured values of the size.
- the evaluation device is designed to perform the correction using an approximation, in which measured values of the variable are approximated with a smooth function and with the sub-area-assigned subrange functions. With the aid of the smooth function, a progression of the size can be displayed over the parameter range. With the aid of the subrange functions, an individual change of the size in the subregions of the parameter range can be brought about.
- measured values of the size can be provided in a plurality of disjoint partial areas of the parameter area. Therefore, the measuring device can have a low-cost construction. A possible effect associated therewith, that the measured values of the size each have separate and independent from other part preparation ⁇ chen measurement errors in individual areas of the parameter area, can be suppressed by the correction by means of the evaluation device.
- a plurality corrected large ⁇ SEN in the same range of parameters.
- measured values of the plurality of sizes can be provided in several or disjunctive subareas of the parameter area, and a separate error correction (each with its own approximation), as described above, can be carried out for each of the variables.
- a separate error correction each with its own approximation
- an approximated course and / or at least one supplementary value can be provided. This may, for example, be considered for optical variables such as the wavefront errors or coefficients to Zernike polynomials of a wavefront development described above.
- an additional correction of the second size or of measured values of the second size is performed.
- the additional correction of the second variable may be based on coefficients of subrange functions that are determined in the error correction of the first quantity.
- the additional correction of the second quantity may be provided before or after a second size error correction performed according to the above approaches using an approximation.
- subrange functions where all subrange functions or a part or a subgroup of the subrange functions together describe a smooth progression over the parameter range.
- modified subrange functions whose sum is equal to zero for all subrange functions or for the subset of subrange functions. That's for
- Example is possible by the scaled sum of all these subrange functions of each of these subrange functions is subtracted, where the scaling factor is the reciprocal of the number of these subrange functions.
- the associated coefficients of the subrange functions may be modified accordingly prior to the formation of the product described above (product of the matrix of subrange functions with the vector of the coefficients of the subrange functions) for subtraction from the vector of measured values of the considered variable.
- a method for determining a plurality of corrected wavefront aberrations dependent on two location coordinates in one image field.
- the method comprises performing a radiation measurement with the aid of a spatially resolving sensor, wherein measured values of the plurality of wavefront errors are provided in a plurality of separate and non-overlapping partial regions of the image field.
- the method further comprises performing a joint correction of measured values of the plurality of wavefront errors using an approximation in which measured values of the wavefront errors are approximated with a plurality of smooth functions associated with the wavefront errors and with subregion functions assigned to the partial areas of the image field.
- Used to be ⁇ sought wavefront errors associated smooth features, about which courses of the wavefront error can be reproduced over the image field, and assigned to the portions of the image field portion functions.
- the subrange functions are chosen such that actual effects of erroneous positioning of the sensor on the measured wavefront errors are simulated or modeled. In this way, an accurate and reliable correction of the wavefront error is possible and can be provided, which agree well with the ⁇ did neuter wavefront errors thus corrected wavefront error.
- the effects of erroneous positioning of the spatially resolving sensor on the measured wavefront errors can be determined, for example, by means of a measurement or a simulation, for example by beam propagation.
- the subrange functions used in the method can be specified.
- faulty positioning with respect to translational degrees of freedom and rotational degrees of freedom can be described.
- dx, dy, dz-translations and DRX dry-, drz rotations are modeled.
- the wavefront aberration may be caused by a Abbil ⁇ dung optics of an optical system.
- the spatially resolving sensor can be irradiated with the radiation coming from the imaging optics.
- it is further executed to the possibility ⁇ instructed in carrying out the method for determining the plurality of corrected wavefront error, and thereafter to adjust the imaging optics based.
- the wavefront errors corrected by means of the method can be present, for example, in the form of coefficients for Zernike polynomials of a wavefront development.
- the Zernike coefficients can be corrected to the Zernike polynomials Z2, Z3 and Z4 in a common manner.
- the spatially resolving sensor is arranged at different measuring positions. Measuring errors can be caused by incorrect positioning of the sensor.
- the spatially resolving sensor has several partial sensors. In this case, erroneous positioning and thus measurement errors can be a consequence of positional errors of partial sensors of the sensor.
- the smooth functions used may each comprise several basic functions.
- the smooth functions may be, for example, polynomial functions.
- the correction includes forming corrected values of the plurality of wavefront errors. Faulty measured values of the wavefront errors can hereby be replaced by the corresponding corrected values, which can also be referred to as reconstructed values.
- the approximation comprises a determination of coefficients of the subregion functions. Furthermore, measurements of the multiple wavefront errors are corrected using the coefficients of the subrange functions. In this way, corrected values for ⁇ He set can be formed of faulty measurements of the wavefront error.
- the approximation includes forming a function matrix of subrange functions and basic functions of the smooth functions, forming the pseudo inverse of the function matrix, and multiplying the pseudo inverse of the function matrix by a vector of measurements of the plurality of wavefront errors to form a coefficient vector.
- the coefficient vector comprises Ko ⁇ efficient the portion functions and coefficients of the basis functions of the smooth functions.
- the correction comprises a multiplication of a matrix of partial area functions with a vector from (determined by means of the approximation) coefficients of the partial region functions to form a product, and a subtraction of the product up to its With ⁇ mean value of the vector of measured values of the several wavefront errors. In this way, corrected values of the Wavefront errors are formed, which may correspond to the actual wavefront errors substantially.
- the product may be the entries or weights of all approximated subrange functions.
- the phrase "to the mean” may be met by subtracting the mean of the product from the product and subtracting that term from the vector of measurements of the multiple wavefront errors partial region to partial region of the image field present and based on measurement errors differences in the measured values of wave front errors are corrected. A uniform or glo ⁇ bale correction over all the portions of the image field is therefore avoided.
- mean-free subrange functions are used. These are subrange functions which have the mean value zero with respect to the image field. Such subrange functions may be formed by subtracting from each of the subset of the averaged subrange functions the respective mean.
- mean-free subrange functions allows a unique approximation and makes it possible for the subtraction of the mean value of the product described above to be included implicitly in the approximation and correction.
- the product in this case has to with ⁇ average value zero, thus the subtraction can be omitted. Therefore, with respect to the above-described correction step, if mean-free subrange functions are used, only the product may be subtracted from the vector of measurements of the multiple wavefront errors.
- this can be achieved by correspondingly modifying the associated coefficients before forming the product described above (product of the matrix of subrange functions with the vector of the coefficients of the subrange functions) for subtraction from the vector of measured values of the multiple wavefront errors become.
- the approximation and correction are performed together by forming a function matrix of subrange functions and basic functions of the smooth functions, forming the pseudoinverse of the function matrix, forming a sub-matrix from the pseudoinverse of the function matrix, via the sub-matrix Coefficients of the subarea functions are generated, a matrix of subarea functions is multiplied by the subarray to form a product, the product is subtracted from an identity matrix to form a correction matrix, and the correction matrix is multiplied by a vector of measurements of the plurality of wavefront errors.
- This embodiment in which corrected values of the multiple wavefront errors can be easily formed, also satisfies the requirement of approximating the measured values of the wavefront errors to achieve the smooth functions and subrange functions with a minimum deviation.
- a further embodiment can be carried out in which the correction comprises formation of approximated profiles of the plurality of wavefront errors. This allows elimination of dot noise. It may be considered to replace the measured values of the multiple wavefront errors by the approximated ones.
- interpolation and / or extrapolation can be performed by forming at least one supplementary value of at least one of the wavefront errors, wherein the supplemental value belongs to spatial coordinates for which there is no measured value of the wavefront error.
- This embodiment can be carried out on the basis of an approximated curve of the Subject Author ⁇ fenden wavefront error.
- the formation of approximated progressions of the multiple wavefront errors can be realized by the following embodiment. In this case, a function matrix of subrange functions and basic functions of the smooth functions is formed; if the pseudo inverse of the function matrix is formed, a subarray of the pseudoinverse of the
- Function matrix is formed, wherein coefficients of the basic functions of the smooth functions can be generated via the sub-matrix, a matrix of basic functions of the smooth functions is multiplied by the sub-matrix to form a history generator matrix, and the history generator ⁇ matrix with a vector of measured values of the multiple wave front error multiplied.
- the radiation measurement relates to a plurality of separate, non-overlapping partial regions and additionally at least one further partial region of the image field which overlaps with at least one of the separate, non-overlapping partial regions.
- at least one subarea of the disjoint subregions considered in the method is a unified subarea for which common measured values of the plurality of wavefront errors are provided, and for which an assigned subrange function is used to reproduce the influence of erroneous sensor positions becomes.
- a more unified subarea can be composed of overlapping subareas.
- Common measurements of meh ⁇ reren wavefront error of the united portion may be provided based on an appropriate pre-processing (such as stitching) of first in each overlapping sub-areas measured values obtained. Subsequently, the combined subarea and the associated measured values can be used for the common correction or approximation carried out with the help of the smooth functions and the subarea functions. It can also be formed and considered several unified subsections.
- measured values of the plurality of wave front errors are provided in at least one further partial region of the parameter area, wherein the white ⁇ tere portion with at least one of the separate and non-overlapping portions overlapped and Approxima ⁇ tion is performed with another, the further partial region zugeordne- th subregion function , with the help of which incorrect positioning of the spatially resolving sensor can be reproduced.
- the white ⁇ tere portion with at least one of the separate and non-overlapping portions overlapped and Approxima ⁇ tion is performed with another, the further partial region zugeordne- th subregion function , with the help of which incorrect positioning of the spatially resolving sensor can be reproduced.
- a corresponding device can be used for determining a plurality of corrected wavefront errors that depend on two location coordinates in one image field.
- the device has a spatially resolving sensor for carrying out a radiation measurement, with the aid of which measured values of the plurality of wavefront errors can be provided in a plurality of separate and non-overlapping partial regions of the image field.
- the device further has an evaluation device for the common correction of measured values of the plurality of wavefront errors.
- the evaluation device is configured to perform the correction using an approximative tion, in which measured values of the wavefront aberration with a plurality of the wavefront errors associated with smooth functions with the partial areas of the image field supplied arrange ⁇ th subregion functions are approximated.
- Figure 1 shows an optical system comprising an imaging optics, by means of which the radiation reflected at an object to egg ⁇ nem sensor can be performed;
- FIG. 2 shows a representation of measuring positions of a sensor including lateral mispositioning and its effect on a measurement of a wavefront error
- FIG. 3 shows a representation of an image field with a distortion grid and with partial regions which illustrate desired measurement positions and deviating actual measurement positions of a sensor
- 4 shows another representation of the image field of Figure 3, wherein belonging to the actual measurement positions partial areas of the image field are integrally ⁇ assigns to the target measurement positions
- FIG. 5 shows a further illustration of measurement positions of a sensor including vertical mispositioning and its effect on a measurement of a wavefront error
- FIG. 6 shows a further optical system comprising imaging optics with the aid of which radiation transmitted through an object can be guided to a sensor;
- FIG. 7 shows a representation of values of a wavefront error at picture elements in subareas of a picture field, comprising actual, measured and reconstructed values of the wavefront error
- FIG. 8 to 10 representations of an image field with different arrangements of subregions.
- the following is a concept for determining a corrected and dependent on at least one parameter size in a parameter range of the at least one parameter be ⁇ written .
- measured values of the size are provided on the basis of a measurement in a plurality or disjoint, ie separate and non-overlapping, subregions of the parameter range. This can cause the measured values of size are afflicted in individual areas of the parameter area with measurement errors that occur individu ⁇ ell in the partial regions. From subarea to subarea, there may be a variation of the measurement errors. Such a falsification of the measured values of the size diminishes their informative value.
- error contributions can be adjusted using the method described here or at least partially or substantially reduced.
- the size to be corrected is a location-dependent optical quantity, namely an imaging or wavefront error caused by the imaging optics 130.
- Zernike coefficients are considered among the Zernike polynomials Z2 and Z3, through which an image defect in the form of a lateral directories voltage or an image offset is reproduced, and to ei ⁇ NEN a focus offset reproducing Zernike coefficients for the Zernike polynomial Z4.
- These are the Zernike polynomials according to Noll's indexing.
- the coefficients to the corresponding Zernike polynomials are also designated below by Z2, Z3, Z4.
- the associated parameter range of the wavefront aberrations comprises two lateral orthogonal spatial coordinates, denoted by x and y below, and represents a two-dimensional image field 150.
- image field 150 For the purpose of simplification of the following description, such and relating to the image field 150 are Location coordinates x, y, possibly supplemented by a further vertical orthogonal location coordinate z, indicated in the figures by axes of an orthogonal xy or xyz coordinate system.
- the object 121 can be a lithography mask or a reticle, which can be examined with the inspection system 100 with regard to defects.
- the object 121 is located in an object plane 120.
- the system 100 includes means for irradiating the object 121 with radiation 115. Such means are summarized in FIG. 1 in the form of an illumination system 110.
- a further component of the system 100 is a projection or imaging optical system 130, which serves to guide a portion of the radiation 115 reflected by the object 121 in the direction of an image plane 140.
- an object field of the object plane 120 can be imaged with the aid of the imaging optics 130 in an image field 150 of the image plane 140.
- the image ⁇ field 150 may comprise, for example lateral dimensions in two stel ⁇ then centimeter range, for example, of about 21cm x 28cm.
- a spatially resolving and radiation-measuring sensor 141 is arranged, which can be irradiated with the radiation 115 coming from the imaging optics 130.
- the sensor 141 may be an electronic sensor with an array of radiation-sensitive sensor elements or pixels.
- the sensor 141 is realized in the form of a CCD sensor (charge-coupled device) with radiation-sensitive photodiodes.
- the sensor 141 as a time-delay integrating CCD sensor (TDI-CCD, Time Delay and Integration
- Charge-Coupled Device be formed.
- the sensor 141 coupled evaluation 160 is used.
- measured values of an optical variable of interest can be provided at picture elements of the image field 150.
- radiation 115 having the same wavelength as used in a lithography process may be used. Therefore, this process can be called an acute examination.
- the sensor 141 does not have a full surface and the entire frame 150 covering Er chargedsbe ⁇ rich but has a configuration with a plurality of spaced apart spatially resolving part sensors.
- Each sub-sensor has a corresponding sub-array of sensor elements or photodiodes and thus a corresponding sub-array
- the object 121 can be correspondingly positioned or moved in the object plane 120 during the examination.
- Each partial sensor of the sensor 141 may, for example, have a megapixel CCD chip with a number of sensor elements in the range of 10 6 .
- An example is an arrangement with approx. 3000 x 3000 pixels.
- an exemplary structure of the sensor 141 is indicated with four sub-sensors, wherein the partial sensors entspre ⁇ accordingly the part regions 151 of Figure 3 arranged to be Kgs ⁇ NEN. It is possible that the sensor 141 another or Has a larger number of sub-sensors, so that a corresponding number of detectable sub-fields 151 may be present.
- Picture ⁇ or wavefront errors that can be caused by the imaging optical system 130 to determine.
- a combination of distortion and phase retrieval measurement technology can be used.
- the aberrations are determined can be used to Justageprozes- se for adjusting the imaging optics 130 to develop so that the aberrations in terms of a reliable and accurate operation of the system are minimized 100 Kings ⁇ nen.
- Such a determination of aberrations for the purpose of adjusting the imaging optics 130 may already be provided within the scope of a construction of the system 100.
- a single spatially resolving sensor 143 for radiation detection can be used instead of the sensor 141 with partial sensors used in the constructed system 100.
- the positions of the partial sensors of the sensor 141 can be approached with the sensor 143, and in each case a partial measurement of the radiation 115 can be carried out at these measuring positions. In this way, radiation detection can again take place only in disjoint partial regions 151 of the image field 150.
- FIG. 1 (and corresponding to FIG.
- the sensor 143 has a Er chargedsbe ⁇ rich with other and larger lateral dimensions than the part of the sensors of the sensor 141, so that correspondingly different or larger portions 151 of the image field 150 he ⁇ are tangible.
- the sensor 143 Auswer ⁇ te worn 160 used.
- This evaluation device 160 may be other than that in the constructed system 100 used and assigned to the sensor 141 evaluation device 160.
- the sensor 143 can be realized in a manner comparable to the sensor 141 in the form of an electronic sensor, for example in the form of a CCD or TDI-CCD sensor, with an arrangement of radiation-sensitive sensor elements or photodiodes. In a corresponding manner, the sensor can have a megapixel CCD chip.
- measured values of one or more wave front-end errors of interest can be provided in pixels in disjoint partial regions 151 of the image field 150. These may be, for example, the Zernike coefficients Z2, Z3 and / or Z4.
- the sensor 143 may be, for example, a distortion measuring head. It should be noted that within the scope of a measurement of aberrations an object or reticle 121 with suitable test structures (not shown) can also be used, which can be imaged into the image field 150 by means of the imaging optics 130. By evaluating associated measurement signals, the desired measurement values of the wavefront error or frequencies of interest can be made available. For example, with respect to detecting a distortion error, a raster of markers may be used. Distortion of the imaging optics 130 causes a shift of the markings imaged in the image field 150. From the position of the imaged markers relative to their desired positions, the distortion can be determined.
- the positioning or positioning of the sensor 143 at different measuring positions can be carried out with the aid of a suitable positioning device, for example with the aid of a positioning table (not shown).
- the positioning accuracy of the sensor 143 is limited by the accuracy of the positioning device.
- the measurement may be affected due to mispositioning of the sensor 143.
- These may in particular be incorrect positioning in the degrees of translational freedom, ie in the x, y and z directions.
- This results in that the measured values provided an imaging or wavefront error 150 may have a constant measurement error or offset in each sub preparation ⁇ surfaces 151 of the image field.
- the incorrect positioning can be different, so that the offset errors which occur individually in subregions 151 of the image field 150 also vary, and may differ from each other with regard to the magnitude and / or the sign.
- this relationship figure shows 2 different lateral measurement positions of the sensor 143 with respect to the image or the image sensor plane 140 and the off ⁇ effect on the provision of measured values of a distortion reproducing wavefront error Z2, Z3. Furthermore, a target measuring position 145 provided for the sensor 143 or its detection range is indicated in the image plane 140. If the sensor 143, as shown in the middle illustration of Figure 2, is at its desired position 145, this leads to no deviation in the measurement the wavefront error Z2, Z3.
- a lateral Bloodpositionie ⁇ tion in the form of a deviation dx or dy of the sensor 143 with respect to the target measuring position 145, as illustrated in the left and right view of Figure 2, has the consequence that in the measurement of the wavefront error Z2 , Z3 in each case a deviation in the form of an offset error occurs.
- FIGS. 3 and 4 illustrate the relationship between lateral positioning errors of the sensor 143 and the measurement of falsifying offset errors in a further illustration. Shown here are an image field 150 and an exemplary aberration in the form of a pincushion distortion 165 present in the image field 150, which is indicated by a grating. Also shown are four partial regions 151 of the image field 150, in which a radiation measurement is carried out with the aid of the sensor 143 arranged at different measuring positions.
- Figure 3 shows both present in the measurement actual actual measurement positions of the sensor 143 with the corresponding scanned portions 151 and the target measurement positions of the sensor 143 with the corresponding portions 151 ⁇ (hatched lines).
- FIG. 4 This is illustrated in FIG. 4 in that the partial regions 151 of FIG. 3 including the solid grid lines of the distortion 165 are shifted relative to the desired measurement positions of the sensor 143.
- the present in the image field 150 distortion 165 is indicated by dashed grid lines.
- the discernible in the sub-areas 151 in Figures 4 dislocations between the solid and the Dashed grid lines make the offset errors that occur during the measurement clear.
- FIG. 5 shows different vertical measurement positions of the sensor 143 with Be ⁇ train on the image sensor plane 140 and its effect on providing measurements of the wavefront error Z4.
- the sensor 143 or its detection area is located at its nominal measuring position 145, this does not lead to any deviation in the measurement of the wavefront error Z4.
- Abnormal positioning dx, dy, dz of the sensor 143 are expressed in the disjoint measured wavefront errors by offset errors, ie apparent aberrations.
- the offset errors are within the detected with the sensor 143 sub-regions 151 of the image field 150 constant or substantially constant, and be ⁇ act in this manner a displacement of the measured wavefront error, including the mean values of the wavefront error, in the relevant part areas 151 From subarea 151 to subarea 151, and as non-systematic measurement errors also from measurement to measurement, there may be a variation of the offset errors.
- the offset errors can be significantly greater than other measurement errors and in particular as the field variation of the actual or true wavefront errors. This may apply in particular to the low-order wavefront errors or Zernike coefficients, in particular Z2, Z3 and Z4. This makes the determination of suitable The adjustment process may result in system 100 ultimately failing to meet the specification.
- the system 100 which is equipped with the sensor 141 with a plurality of non-overlapping partial sensors, it may be comparable to readings of one or more imaging aberrations of interest, for example the wavefront errors Z2, Z3 and / or Z4, to image ⁇ points in disjoint sections 151 of the image field 150 provide.
- a measurement is carried out with the aid of the sensor 141, and measuring signals of the sensor 141 are evaluated with the aid of the associated evaluation device 160 for providing the measured values. Based on this, a further adjustment or fine adjustment of the imaging optical system 130 can be carried out.
- the arrangement of the sensors of the sensor portion 141 is erroneous, so that the part having sensors capable ⁇ error, particularly with respect to the degrees of freedom x, y, z.
- Such positional errors similar to the above-described positioning errors of the sensor 143, can lead to constant or substantially constant offset errors in the subregions 151 of the image field 150 in the measurement of the wavefront errors Z2, Z3, Z4 (possibly also crosstalk to image errors higher order).
- ⁇ For further details, reference is made to the above description ⁇ .
- the positional errors of the image sensors of the sensor 141 may be a result of installation errors, but also during operation and / or over the life of drift such as temperature-induced dimensional changes of components are ⁇ call fixturege. Therefore, systematic, that is, the same for each measurement, as well as non-systematic, ie from measurement to measurement different measurement errors can be present. This likewise leads to an impairment of the adjustment of the imaging optics 130.
- the problem identified in the reflective system 100 can also occur in an inspection system operated in transmission, in which a transmitted radiation component is detected.
- Such a system 101 which has substantially the same construction and operation as the system 100, is shown schematically in FIG. It should be noted that correspond ⁇ provoking aspects and the same and equivalent com- ponents not be described again in detail here, but that instead, reference is made to the above description.
- the optical system 101 also includes system 110 for illuminating a ⁇ is arranged in an object plane 120 object 122 to radiation 115 to ariesssys-.
- the object 122 which can be partially irradiated, may be a reticle.
- a transmit ⁇ -oriented by the object 122 portion of the radiation 115 is by means of a Abbil- dung optics 130 guided toward an image plane 140th
- the imaging optics 130 can be used to image an object field of the object plane 120 into an image field 150 of the image plane 140.
- a position-resolving sensor is arranged 141 with multiple sensors, whose measurement signals can be further processed with an evaluation device 160, counted from ⁇ . In this way a Strah ⁇ lung gathering is carried out in the disjoint partial regions 151 of the image field 150 (see FIG. 3).
- system 101 it is also of interest
- a single spatially resolving sensor 143 can be used, which is moved to the positions of the partial sensors of the sensor 141 for radiation detection. Malpositioning of the sensor 143 in the Translational degrees of freedom x, y, z can lead to offset errors being provided by measured wavefront errors of interest, for example Z2, Z3 and / or Z4. Such offset errors can occur individually in partial areas 151 of the image field 150 and differ from offset errors of other partial areas 151.
- the correction can in the form of a permanent calibration on the basis of one or more measurements gen, for example, once or in rotation, provided ⁇ the.
- a tat ⁇ neuter that is not afflicted with measurement errors aberrations 150 may have regularities and predictable properties with respect to the entire image field, and extending through a smooth function across the image field 150 can be described. This is not or substantially not the case for the offset errors that occur indivi ⁇ duell in the subregions 151 of the image field.
- the correction is performed using an approximation, be in which provided readings of interest aberration approximated by a smooth function with the sub-regions 151 of the image field 150 associated Colourbe ⁇ rich functions.
- a profile of the imaging error can be displayed via the image field 150.
- the USAGE ⁇ finished smooth function or the basis functions can be assigned fixed ⁇ on the knowledge of the operation of the imaging optics 130th
- the subrange functions are chosen such that, within the framework of the approximation, the considered aberration can be changed by the same value in the individual subregions 151 of the image field 150 in each case. In this way, the effect of a faulty measurement or the individual occurrence of the offset error which falsifies the actual aberration can be reproduced in the subregions 151 of the image field 150. This can be achieved an accurate approximation of the measured values with a minimum deviate ⁇ chung, which in turn allows reliable reset or suppressing the measurement error.
- the object or image field 150 will be described on N diskre ⁇ th field points (xi, yi).
- x and y ⁇ ⁇ entspre the constituent local coordinates of the image points, and it is i 1, 2, ...,.
- the coordinates xi and y of all pixels of the image field 150 are preferably chosen such that the average of all coordinates xi and the average of all coordinates yi are zero. Such a determination of the Koordinatenur ⁇ jump proves to be numerically favorable.
- the frame 150 comprises n sections 151, which are referred to in Fol ⁇ constricting with Fi.
- 1 1, 2, n.
- ni of the N pixels (xi, yi) belong to the
- each pixel belongs to exactly one subfield Fi.
- the component power is defined as follows
- ⁇ 0, 1, 2, Wv and v 0, 1, 2, w.
- the characteristic subrange functions used in the approximation or their corresponding vectors, with the aid of which the aberration in the individual subregions Fi of the image field 150 can each be changed by the same value, can be defined with the identity matrix I as follows: ti (Xi> yi) and t ti (11)
- the function set of smooth function and subrange functions is compared to the measured aberrations or the corresponding measured values, hereinafter referred to as the vectors. tor a 'marked, approximated.
- the following procedure can be considered, in which initially matrices, ie a matrix of the subrange functions
- ßw x , w y J comprises the coefficients associated with the basis functions of the smooth function.
- the coefficients allow weightings of the individual functions to be defined or reproduced.
- the weighting coefficients a of the subrange functions are included. These are linked to the offset errors occurring during the measurement, and can therefore be used for error suppression, as described below.
- the feasible with the aid of the evaluation device 160 Def ⁇ lerkorrektur may refer to provide corrected values of the image defect, characterized corr hereinafter with the vector a.
- the measured values U 'of the aberration can be corrected by the corrected values a corr. be set.
- the corrected values a corr, which did the aberrations can correspond primarily Ü ⁇ extraneous, 130 may be used in the adjustment of the imaging optics.
- the vector c is formed according to formula (22) to obtain the coefficient vector a in accordance with formula (19), and the matrix T of the subrange functions is multiplied by the corresponding coefficient vector a to form a product.
- the product is the entries or weights of all approximated subrange functions.
- the product except for its mean value, is subtracted from the vector u 'of the measured values as follows:
- the mean value of the product can be subtracted from the product, and this term can be subtracted from the vector Ü '.
- this term can be subtracted from the vector Ü '.
- exemplary results of a Si ⁇ mulation in reference are shown on a wavefront error Z2 in FIG. 7
- This relates to values of the wavefront error Z2 at picture elements in four partial areas 151 of a picture field 150, wherein the partial areas 151 can be arranged corresponding to FIG.
- simulated actual values Z s of the wavefront error Z2 in the subregions 151 present at image points of the image field 150 are illustrated (true state).
- the values Z s were simulated based on rigid body tilting or movements of objective mirrors of imaging optics 130.
- FIG. 7 also shows reconstructed values Z r of the wavefront error Z2 formed on the pixels in the subregions 151 on the basis of larger solid points using the above-explained correction procedure.
- the smooth function used here was a third order polynomial in x and fifth Okay in y. It can be seen that in each of the sections the same Ver ⁇ reduction between the corrected values Z r and the actual values of Z s loan of the wavefront error is present Z2 151st This is the above-mentioned small global offset between the values Z r and Z s . It is clear from this illustration that the correction method makes it possible to reliably suppress offset errors which are the result of the measurement in disjoint subfields 151 of the image field 150.
- mean value-free subrange functions t t are used which, based on the image field 150, have the mean value zero.
- the approximation can be unique.
- the mean value of the entries of the subrange functions can be contained twice in the set of used functions, namely as Constant in the function and smooth as the sum of Operabe ⁇ rich functions in accordance with:
- Coefficients ä of the subrange functions, and the remaining coefficients ß can be generated via the other sub-matrix M p :
- I is the identity matrix.
- the matrix S formed by subtracting the product from the matrix T of the mean-free subrange functions and the sub-matrix M T from the identity matrix I, ie is referred to below as a correction matrix.
- Another variant of using the evaluation 160 feasible error correction is, in addition or as an alternative to corrected error-corrected values of the aberration under consideration, to form an approximated profile of the aberration.
- the approximated curve can essentially correspond to the actual imaging error, ie, without measurement error. It is also possible here to replace erroneous measured values of the aberration by the approximated curve, and to perform an adjustment of the imaging optical system 130 based on the approximated curve.
- the formation of the approximated course can also be carried out within the framework of a joint approximation and correction.
- the procedure can be similar to the above described simplification, said mean value-free partial region functions t t of the formula (24) are used and the pseudoinverse M "of the function matrix M is decomposed according to formula (27).
- R: PM ⁇ , (33) is referred to below as the history generation matrix.
- a further variant of the procedure which can be carried out with the aid of the evaluation device 160 comprises an interpolation
- a supplementary value belongs to a pixel for which no measured value of the aberration is present.
- Forming the tendonss we ⁇ a supplementary value which can also be considered in the context of adjustment of the imaging optics 130, is performed on the basis of the approximated curve.
- crosstalk may also occur.
- causes of errors for offset errors of a first measured aberration can also have an effect on at least one second measured aberration, so that it can be subject to corresponding offset errors.
- verti ⁇ kale incorrect positioning of a sensor by which offset errors in the measurement of the wavefront error Z4 departmentgeru ⁇ be called (see FIG. 4), also in an occurrence of offset errors in the measurement of the wavefront error Z2 and / or Z3 lead.
- Such a crosstalk to the second aberration can be suppressed by performing an approximation on the basis of an error correction of the first aberration (for example Z4), which is done in the manner described above, using an approximation.
- an additional correction of the second error Abbil ⁇ dung is performed.
- the additional correction can be made based on the coefficient ä ⁇ Operabe rich functions which are determined on the basis of the error correction of the first aberration, for example.
- an error correction of the second aberration may be performed according to the above approaches using an approximation.
- a further correction method can furthermore be used, which will be discussed in more detail below.
- erroneous measurement values are Droppings of several Abbil- or wavefront errors which can be caused by the Abticiansop ⁇ tik 130, corrected in a common manner. Much the same or comparable features may be used as described above with respect to the correction of a single measured wavefront error. With regard to matching details and aspects, reference is therefore made to the above description.
- measured values of the wavefront errors of interest are provided on the basis of a radiation measurement at pixels in a plurality of disjoint partial regions 151 of the image field 150. This is done with the help of several Sectionsenso ⁇ ren having sensor 141 or by means of the disposed at different measuring positions of the sensor 143.
- the measurement signals from the sensor 141 or 143 are evaluated using the da ⁇ associated evaluation device 160, whereby the measuring values of the plurality of interest wavefront errors are provided can. Due to faulty sensor positions, which are 141 position errors of the sensors in the sensor part, the measurements can include corresponding measurement ⁇ error.
- faulty positioning can tion degrees of freedom with respect to translational degrees of freedom and rotavirus, that dx, dy, dz-translations and rotations or tilts Ver ⁇ with respect to the x, y, z axes are considered.
- the method is carried out using an approximation in which measured values of the wavefront errors of interest are jointly approximated with a plurality of smooth functions assigned to the wavefront errors and subrange functions assigned to the subregions of the image field become.
- the smooth functions which include several Basisfunktio ⁇ nen and in which it may be polynomial are determined such that hereby profiles of the corresponding wavefront error can be reproduced over the image field 150th
- the smooth functions or their basic functions can be determined on the knowledge of the operation of the Ab ⁇ education optics 130.
- the subrange functions are chosen such that hereby the influence of erroneous positioning of the sensor
- the 141 or 143 are reproducible to the measured values of the plurality of wavefront errors.
- the actual effects of incorrect positioning can be simulated or modeled on the measurement of the wavefront errors.
- Such effects can be determined, for example, by means of a measurement or a simulation, for example by beam propagation.
- the subrange functions are defined. With the help of such subrange functions can be in the
- Steps for suppressing the measurement errors can also be used here with the aid of the evaluation device connected to the sensor 141 or 143
- the sensor 141 or 143 and the associated evaluation device as ⁇ 160 may form an apparatus for determining a plurality of corrected wavefront errors in this sense. Furthermore, the adjustment of the imaging optics 130 may be based on the corrected wavefront errors.
- corrected values a may be formed of several corr ⁇ ren wavefront error, with which measured values are a 'of the wavefront error replaced. This can be done as follows.
- a function matrix M consisting of a matrix T of subrange functions and a matrix P of basic functions of the smooth functions, as well as the pseudoinverse M "of the radio functions formation matrix M formed.
- a coefficient vector c belonging to the function matrix M is formed by multiplication of the matrix M " with the vector Ü 'of the measured values of the several wavefront errors according to formula (22) This represents a solution of the fit problem indicated under formula (18)
- Coefficient vector c comprises coefficients a belonging to the subarea functions and coefficients b associated with the basis functions
- Mean value of the vector Ü 'of the measured values according to formula (23) is subtracted to form the corrected values a corr of the multiple wave front errors.
- This procedure makes it mög ⁇ Lich, primarily relative, that is, from partial region to Operabe ⁇ area of the image field 150 present differences in the measurement values to correct ⁇ and a uniform or global Cor ⁇ rection over all the portions to be avoided.
- a correction matrix S is formed by the product of the matrix T of the central value-free portion functions and the sub-matrix M T from the identity matrix I in accordance with formula (30) is subtracted.
- the formation of the corrected values a korr of the plurality of wave front error (by multiplying the matrix S with the measured values Ü 'according to formula This procedure also leads to the solution of the fit problem according to formula (18).
- a formation of approximated progressions a flt of the plurality of wavefront errors takes place. This allows elimination of dot noise. It is possible to replace measured values of the wavefront errors by the approximated characteristics.
- a sub-matrix M p is formed from the provided pseudoinverse M "of the matrix M, via which coefficients ⁇ the
- Basic functions P of the smooth functions can be generated. Furthermore, a course generation matrix R is formed by multiplying the matrix P of the basic functions of the smooth functions by the sub-matrix M p according to formula (33). The formation of the approximated curves a flt of the multiple wavefront errors is performed by multiplying the matrix R by the measured values U 'according to formula (34). This pre ⁇ hens, likewise leads to the solution of the Fitproblems of mel For ⁇ (18).
- Another variation includes an interpolation and / or extrapolation, by a complement value of we ⁇ iquess one of the plurality of wavefront error is formed at least, wherein the complement value is one of location coordinates, is present for wel ⁇ che no measured value of the wavefront error.
- This embodiment can take place on the basis of an approximated course of the relevant wavefront error.
- the measurement relates to at least one further subarea 152 of the image field 150 which coincides with at least one of the separate non-overlapping subareas 151 overlaps (see, for example, Figure 9, which will be discussed in more detail below).
- a formation of a combined partial area with common measured values may be considered, which comprises the further partial area 152 and the at least one partial area 151 overlapping therewith.
- Common measured values of the wavefront error or errors may be provided on the basis of a suitable preprocessing or correction of measured values initially obtained in the individual overlapping partial regions 151, 152. This can be done for example by means of a stitching method.
- the combined portion and its ⁇ corresponding measured values can then come in accordance with the arrival and the disjoint partial regions thereof in the correction and Approximation used.
- the associated subarea is assigned a corresponding subarea function.
- a plurality of merged section ⁇ areas can be formed, this common measurement values soirge ⁇ represents, and these used for less of the correction approximation and be.
- This case can be considered when several other parts of present 152, which overlap with other sub-areas ⁇ 151 (see FIG. 9). In this case, it is also possible that only unified and discrete subregions are formed.
- the further subarea 152 overlapping with at least one of the separate and non-overlapping subregions 151
- the following sequence may also be considered.
- the approximation is performed with a further partial area function assigned to the further partial area 152.
- the further partial range function may be selected such that a change of the considered wavefront error can be produced by the same value within the context of the approximation in the respective partial region 152, or erroneous sensor positioning can be reproduced.
- the further overlapping partial area 152 is treated like the remaining partial areas 151. Therefore, in an overlap region of overlapping partial regions 151, 152, a double approximation, or in the case of more than two overlapping partial regions, a multiple approximation can take place. In the case of a plurality of further subareas 152, a plurality of further subarea functions can be used in a corresponding manner. In the following, with reference to FIGS. 8 to 10, he will explain with which configurations or arrangements of subregions 151, 152 of an image field 150 intended for measurement the methods described above can be used.
- the sub-regions 151, 152 may have different geometric shapes, so that different from the fi gures ⁇ 3, 4, other than rectangular shapes even round nikför- such case ⁇ game triangular, hexagonal or or Mige contours may be present, as shown by way of example in Figures 8 to 10.
- Such forms depend on the design of a sensor used for the measurement or on its detection range. If only one sensor, for example the sensor 143 moved to different measuring positions, is used, all partial regions 151, 152, deviating from FIGS. 8 to 10, can have the same contours.
- FIG. 8 illustrates a measurement in which all partial regions 151 of the image field 150 are disjoint. ⁇ thereof from yielding to a measurement and thus the provision of measured values can relate to at least one further partial area 152 of the image field 150 in addition that overlaps with Wenig ⁇ least one of the separate, non-overlapping portions of the 151st This can be realized for example by means of arranged on ⁇ under different measurement positions union sensor 143rd
- Figure 9 illustrates an example ⁇ exemplary measurement with six pairs of overlapping portions 151, 152.
- the Darge ⁇ presented with solid lines portions 151 mutually disjoint, and are indicated by dashed lines further subregions 152 to each other disjoint.
- the above-described approaches may be considered. It is possible, for example, to form three composite or combined subregions from the six pairs overlapping subregions 151, 152, to provide common measured values for each of the unified subregions with the aid of preprocessing, and to base these on the correction and approximation.
- subareas assigned to the merged subareas are used.
- FIG. 10 illustrates another exemplary measurement with overlapping partial regions 151, 152. Together, these cover a coherent region of the image field 150.
- the partial regions 151 are disjoint with each other, and the further partial regions 152 indicated by dashed lines are disjoint to one another.
- the method sequence for carrying out the approximation with the subarea functions assigned to the individual subregions 151, 152 comes into consideration.
- the sub-area functions are selected such that an individual change of the size in the sub-areas of the parameter area can be brought about in the context of the approximation.
- the correction can refer to it, corrected values of the quantity, an ap ⁇ proxim believing course of the size and / or form at least a supplementary value of the quantity.
- Ver ⁇ a drawing size by which an image field in a passing on ⁇ distortion can be reproduced.
- erroneous measured values of the distortion variable which can be obtained in several or disjoint partial areas of the image field can be corrected. This includes, for example, forming corrected values of the distortion quantity to replace measured values. It is also possible to reconstruct the distortion over the entire image field. This can be done, for example, by forming an approximated curve and / or by forming supplementary values for interpolation and extrapolation.
- a different size in subregions of a parameter range can also be measured and corrected according to the approaches described above.
- the measurement can be carried out, for example, with the aid of an atomic force microscope or with the aid of a surface interferometer.
- the associated parameter range may additionally or alternatively also have one or more other parameters than location coordinates.
- the at least one parameter on which the variable is dependent can also be a time.
- Another case ⁇ play a parameter area comprising a time and we ⁇ ilias a spatial coordinate.
- a further possible modification with regard to the method for determining a single corrected variable is to correct, instead of offset errors, other measurement errors that occur individually in partial regions of a parameter range.
- suitable subrange functions are used with the aid of which a falsification of the measured quantity can be simulated by such measurement errors in the subregions of the parameter range.
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JP2017512438A JP6751079B2 (ja) | 2014-05-16 | 2015-05-15 | 補正光学変数を求める方法及び装置 |
US15/353,406 US9841685B2 (en) | 2014-05-16 | 2016-11-16 | Determination of a corrected variable |
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DE102014209348.1A DE102014209348A1 (de) | 2014-05-16 | 2014-05-16 | Ermittlung einer korrigierten Größe |
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EP3570110A1 (de) * | 2018-05-16 | 2019-11-20 | ASML Netherlands B.V. | Schätzung eines parameters eines substrats |
EP3696605A1 (de) | 2019-02-13 | 2020-08-19 | ASML Netherlands B.V. | Verfahren und lithographievorrichtung zur messung eines strahlungsbündels |
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DE102009038558A1 (de) * | 2009-08-24 | 2011-03-10 | Carl Zeiss Sms Gmbh | Verfahren zur Emulation eines fotolithographischen Prozesses und Maskeninspektionsmikroskop zur Durchführung des Verfahrens |
DE102010062763A1 (de) * | 2010-12-09 | 2012-06-14 | Carl Zeiss Smt Gmbh | Verfahren zum Vermessen eines optischen Systems |
DE102012111008A1 (de) * | 2012-11-15 | 2014-05-15 | Precitec Optronik Gmbh | Optisches Messverfahren und optische Messvorrichtung zum Erfassen einer Oberflächentopographie |
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TW550377B (en) * | 2000-02-23 | 2003-09-01 | Zeiss Stiftung | Apparatus for wave-front detection |
US7088458B1 (en) * | 2002-12-23 | 2006-08-08 | Carl Zeiss Smt Ag | Apparatus and method for measuring an optical imaging system, and detector unit |
JP4753009B2 (ja) * | 2005-05-24 | 2011-08-17 | 株式会社ニコン | 計測方法、露光方法、及び露光装置 |
US7580113B2 (en) * | 2006-06-23 | 2009-08-25 | Asml Netherlands B.V. | Method of reducing a wave front aberration, and computer program product |
JP2008186912A (ja) * | 2007-01-29 | 2008-08-14 | Nikon Corp | 収差評価方法、調整方法、露光装置、露光方法、およびデバイス製造方法 |
JP5503193B2 (ja) * | 2009-06-08 | 2014-05-28 | キヤノン株式会社 | 波面収差の測定装置、露光装置及びデバイス製造方法 |
KR101336399B1 (ko) * | 2009-11-19 | 2013-12-04 | 캐논 가부시끼가이샤 | 계측 장치, 가공 방법 및 컴퓨터 판독가능한 저장 매체 |
KR101529807B1 (ko) * | 2011-01-20 | 2015-06-17 | 칼 짜이스 에스엠티 게엠베하 | 투영 노광 도구를 조작하는 방법 |
US9046791B2 (en) * | 2011-11-30 | 2015-06-02 | Changchun Institute Of Optics, Fine Mechanics And Physics, Chinese Academy Of Sciences | Apparatuses and methods for detecting wave front abberation of projection objective system in photolithography machine |
DE102012202057B4 (de) * | 2012-02-10 | 2021-07-08 | Carl Zeiss Smt Gmbh | Projektionsobjektiv für EUV-Mikrolithographie, Folienelement und Verfahren zur Herstellung eines Projektionsobjektivs mit Folienelement |
DE102013218991A1 (de) * | 2013-09-20 | 2015-03-26 | Carl Zeiss Smt Gmbh | Vorrichtung zum Bestimmen einer optischen Eigenschaft eines optischen Abbildungssystems |
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DE102009038558A1 (de) * | 2009-08-24 | 2011-03-10 | Carl Zeiss Sms Gmbh | Verfahren zur Emulation eines fotolithographischen Prozesses und Maskeninspektionsmikroskop zur Durchführung des Verfahrens |
DE102010062763A1 (de) * | 2010-12-09 | 2012-06-14 | Carl Zeiss Smt Gmbh | Verfahren zum Vermessen eines optischen Systems |
DE102012111008A1 (de) * | 2012-11-15 | 2014-05-15 | Precitec Optronik Gmbh | Optisches Messverfahren und optische Messvorrichtung zum Erfassen einer Oberflächentopographie |
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US20170068166A1 (en) | 2017-03-09 |
JP6751079B2 (ja) | 2020-09-02 |
JP2017524946A (ja) | 2017-08-31 |
US9841685B2 (en) | 2017-12-12 |
DE102014209348A1 (de) | 2015-11-19 |
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