DE102022210024A1 - Method and device for qualifying a computer-generated hologram, regularization method and lithography system - Google Patents

Abstract

The invention relates to a method for qualifying a computer-generated hologram (CGH) (2) which, when illuminated coherently with a test radiation (3), forms at least one test wavefront (4) of the test radiation (3) for testing a mirror (5) of an EUV - projection exposure system (100) is set up, wherein the test wave front (4) is measured over the entire surface by means of a measuring radiation (7) by means of an optical measuring device (6) that qualifies and/or simulates the CGH (2). According to the invention, the CGH (2) is only qualified with regard to an effect on the test radiation (3) in that the effect of the CGH (2) on the test wavefront (4) and/or a phase of the test radiation (2) is reconstructed , wherein an error propagation of a residue on the at least one test wavefront (4) is taken into account, the residue resulting from a deviation between a measurement and a simulation of an effect of the CGH (2) on the measurement radiation (7), in particular a measurement wavefront of the measurement radiation ( 7), results.

Description

The invention relates to a method for qualifying a computer-generated hologram (CGH) which, in the case of coherent illumination with a test radiation, is set up to form at least one test wavefront of the test radiation for testing a mirror of an EUV projection exposure system, the test wavefront being measured using a CGH-qualifying and/or or simulating optical measuring device is measured over the entire surface by a measuring beam.

The invention also relates to a regularization method for a method for reconstructing an effect of a CGH on a test wavefront.

The invention also relates to a device for qualifying a CGH, which is set up for coherent illumination with a test radiation to form at least one test wavefront of the test radiation for testing a mirror of an EUV projection exposure system, having an optical measuring device that qualifies and/or simulates the CGH for full-surface Measurement of the CGH by a measurement radiation.

The invention also relates to a lithography system, in particular a projection exposure system for semiconductor lithography, with an illumination system with a radiation source and an optical system, which has at least one optical element, wherein at least one of the optical elements has an optical surface, which is at least partially measured with a CGH is.

Optical elements for guiding and shaping radiation in projection exposure systems are known from the prior art. In the known optical elements, a surface of the optical element often guides and shapes the light waves incident on the optical element. Precise control of the shape of the surface is therefore of particular advantage in order to form an exact wavefront with the desired properties.

Lithography systems are known from the prior art which use ultraviolet radiation, in particular DUV (deep ultraviolet) and/or EUV (extreme ultraviolet) light, in order to produce microlithographic structures with the greatest precision. In this case, the light from a radiation source is directed via a number of mirrors to a wafer to be exposed. An exact formation of the surface shape of the mirror makes a decisive contribution to the quality of the exposure.

Since the accuracy requirements for the optical elements of a lithography system, in particular for mirror surfaces, can amount to fractions of nanometers, it is known from the prior art to use interferometric measuring methods and devices to check the quality of the optical elements of the lithography system.

It is known from the prior art to use computer-generated holograms (CGHs) for the high-precision measurement of mirror surfaces and/or lens surfaces. Test wavefronts adapted to the surfaces are generated by means of the CGHs, the reflection of which on the surfaces is measured interferometrically with a reference wave. Test wave errors, which are caused by an incorrect formation of the CGH, are therefore indistinguishable from errors in the mirror surface and/or lens surface to be measured.

It is also known from the prior art to first qualify the CGH using separate measurement techniques and to calibrate an error in the CGH determined in this way from the test wavefront and/or the entire surface measurement.

In the not previously published German patent application entitled "Method for the areal, spatially resolved determination of at least one structural parameter" with the filing date of January 8th, 2021 and official file number 102021200110.6 describes a method for the areal, spatially resolved determination of at least one structural parameter of a geometric and/or optical structural model of a computer-generated hologram, CGH, or wafer using at least one optical measuring method. The content of this patent application, which is not a prior publication, is hereby incorporated by reference into the present application.

A disadvantage of such indirect methods according to the prior art is that errors in a qualification of the CGH and/or a modeling of the CGH can lead to systematic errors in the test wave and thus in the surface measurement.

It is known from the prior art to use diffractive measurement structures, in particular computer-generated holograms (CGH), to check the optical surface of mirrors, with the measurement structure forming a test wave front which corresponds to the desired shape of the optical element to be checked. Deviations of the actual shape of the mirror from a target shape of the mirror, are determined according to the prior art using interferometric methods.

The accuracy with which the test wave front can be formed and thus also the accuracy with which the optical surface can be checked depends on the manufacturing quality of the CGH.

It is known from the prior art to qualify or calibrate the CGH.

The generic DE 10 2017 221 005 A1 discloses a method and a device for calibrating a diffractive measurement structure.

According to the general state of the art, diffractive optical masks and/or diffractive gratings or more generally diffractive measuring structures are often used in beam paths of optical measuring systems in order to enable a measuring technique. Test setups for mirror pass measurement technology using CGHs as measurement structures are known from the prior art. Furthermore, absorbing measuring gratings for system qualifications and/or masks for measuring imaging qualities are known.

What the aforementioned measurement techniques known from the prior art have in common is that optical properties of the measurement techniques or precise knowledge of the optical properties of the components of the measurement structures have a major influence on the measurement accuracy that can be achieved. Properties of the diffractive measurement structures that are not precisely known can lead to relevant error contributions, in particular for a required measurement accuracy in the nanometer range or below.

The present invention is based on the object of creating a method for qualifying a CGH which avoids the disadvantages of the prior art, in particular enabling rapid and reliable qualification of the CGH.

According to the invention, this object is achieved by a method having the features specified in claim 1.

The present invention is also based on the object of creating a regularization method which avoids the disadvantages of the prior art, in particular enabling a stable and reliable execution of a method for reconstructing an effect of a CGH.

According to the invention, this object is achieved by a regularization method having the features specified in claim 8 .

The present invention is also based on the object of creating a device for qualifying a CGH which avoids the disadvantages of the prior art, in particular enabling rapid and reliable qualification of the CGH.

According to the invention, this object is achieved by a device having the features specified in claim 10

Furthermore, the present invention is based on the object of creating a lithography system which avoids the disadvantages of the prior art, in particular having reliably tested mirrors.

According to the invention, this object is achieved by a lithography system having the features specified in claim 11.

In the method according to the invention for qualifying a computer-generated hologram (CGH), which is set up in the case of coherent illumination with a test radiation to form at least one test wavefront of the test radiation for testing a mirror of an EUV projection exposure system, the test wavefront is determined using a CGH-qualifying and/or simulating optical measuring device measured by a measuring radiation over the entire surface. According to the invention, it is provided that the CGH is only qualified with regard to an effect on the test radiation in that the effect of the CGH on the test wavefront and/or a phase of the test radiation is reconstructed, with an error propagation of a residue on the at least one test wavefront being taken into account, wherein the residue results from a deviation between a measurement and a simulation of an effect of the CGH on the measurement radiation, in particular a measurement wavefront of the measurement radiation.

Within the scope of the invention, a qualification of the CGH is to be understood as a metrological examination of the CGH, on the basis of the result of which a judgment with regard to at least one functionality of the CGH is made possible. If sufficient functionality is determined, the CGH is thereby qualified for further use. Within the scope of the invention, the functionality examined can in particular include the ability to form the desired wavefront shape.

The above-described qualification of the CGH can also include a calibration of the same.

The method according to the invention is also based on the measurement methods known from the prior art, although the qualification of the CGH is based on a merely effective, i. H. qualification that is only aimed at an effect is replaced. The task of effective qualification is not the most exact reconstruction possible of the physical and spatial configuration of the CGH, but rather the most exact reconstruction possible of the effect of the CGH on the test wavefront and/or the phase of the test radiation. As a result, the computing effort and/or the time required for the qualification of the CGH can be reduced while at the same time having a high level of reliability. In particular, all measures can be omitted that are not only aimed at reconstructing the effect of the CGH on the test wave front and/or the phase of the test radiation.

Alternatively or additionally, it can be provided that an error propagation of a residue to the phase of the test radiation is taken into account.

According to the prior art, the probability of model parameters p of the CGH is maximized when a CGH is reconstructed.

Equivalently, for Gaussian distributions, the least squares of the vectorial merit function terms given in formula (1) are minimized. $$cO{v}_c^{-\frac{1}{2}}\left(c_k\left(x,p\left(x\right)\right)-c_{k,me}\left(x\right)-{\displaystyle {\sum }_l{\mathrm{e.g}}_{k,l}{Z}_l\left(x\right)}\right)$$

In formula (1), c is a simulation model of the CGH, which assigns a prediction C _k of a measured value C _k,m to the parameters p at a location x of the CGH. The last term in formula (1) represents an optional calibration of the residual by subtracting certain basis functions Z _I.

As an alternative or in addition to the residue given in formula (1), the vectorial merit function term given in formula (2) can be minimized. The merit function term given in formula (2) involves spatial a priori parameter correlations, which are designed as a Gaussian field. $$cO{v}^{-\frac{1}{2}}\left(p-E\left(p\right)\right)$$

In the term given in formula (2), the spatial correlations are contained in the variance matrix (cov). The E in bold describes the formation of an expectation value.

Alternatively or additionally, the vectorial merit function can also be given by the term shown in formula (3). The term shown in formula (3) is point-by-point a priori information (priors) or so-called “rubber bands”. The point-by-point a priori information can, for example, take into account specification limits and/or external measurements. In particular, scanning force microscopy measurements can be taken into account as external measurements. $$\frac{1}{{\sigma }_k\left(x\right)}\left(p_k\left(x\right)-{\mu }_k\left(x\right)\right)$$

In formula (3), σ _k indicates a standard deviation of the external measurement and µ _k indicates an average value of the external measurement.

In the formulas (1), (2), (3), the expressions p, p _k and z _k,I are fit parameters. The expressions cov _c ^-1/2 , cov ^-1/2 , σ _k and µ _k are statistical hyperparameters.

In the Bayesian statistics preferably used within the scope of the invention, a hyperparameter is to be understood as a parameter of a previous distribution or a prior distribution. In particular, the term can be used to distinguish hyperparameters from parameters of a mathematical model for the underlying system to be analyzed.

The full merit function is obtained from formulas (1), (2), (3) by taking the square sum over all detection points x on the CGH and all channels k of each term.

The method according to the invention can be used in particular to qualify a diffractive optical element, in particular a CGH. The qualification in turn serves in particular to ensure that when the CGH is used, correctly formed wavefronts emanate from the CGH. In the method according to the invention, the qualification takes place in that an effect of the CGH on the test wavefront and/or the phase of the test radiation is determined. According to the invention, this is done by minimizing a mathematical term, which describes residual portions causing qualification errors, using a mathematical formula approach. In particular, the minimization can also include the formation of a derivation.

It can be provided that the simulated phase is based on an intensity as a function an error propagation and preferably a regularization can be determined. In particular, the phase can be determined according to formula (9). $$\varphi \left(I_0+\mathrm{\Delta }I\right):=\frac{\partial \varphi }{\partial p}{\left(\frac{\partial I}{\partial p}\right)}^{-1}\mathrm{\Delta }I$$

In an advantageous development of the method according to the invention, it can be provided that the CGH is measured by the optical measuring device using a scatterometry method, an ellipsometry method, an interferometry method and/or a ptychography method.

The methods described above are particularly suitable for carrying out a separate measurement on the CGH to be qualified.

In an advantageous development of the method according to the invention, it can be provided that the error propagation of the residue is taken into account, in particular minimized, as part of a mathematical optimization.

Instead of using the residuals directly, it is advantageous to use the error propagation of the residuals to the phases φ and/or one or more other measurement channels. The error propagation of the residuals is given by formula (4). $$cO{v}_{\varphi \text{'},\varphi }^{-\frac{1}{2}}\left(\frac{\partial \varphi }{\partial m}\left(p\right)m\left(p,\mathrm{e.g}\right)\right)$$

In formula (4), the expression cov _φ,φ ' describes an estimated preconditioned phase covariance matrix. In particular, it can be provided that the estimated, preconditioned phase covariance matrix results from a weighted rescaling from the identity matrix. Furthermore, expressions Z _i for optional calibration functions can also be provided as additional summands in formula (4), as they have already been described above or are described in connection with formula (6).

Furthermore, in formula (4), the expression m represents the entire vectorial merit function described above. Here, the expressions according to formula (2) and formula (3) are an optional component of the vectorial merit function m. Furthermore, all covariance matrices can be considered trivial be formed covariance matrices.

In all of the aforementioned cases, the differential from formula (4) can be evaluated according to formula (5). $$\frac{\partial \varphi }{\partial m}:=\frac{\partial \varphi }{\partial p}\frac{\partial p}{\partial m}\text{and}\frac{\partial p}{\partial m}:={\left(\mathrm{i.e}{m}^t\cdot \mathrm{i.e}m\right)}^{-1}\mathrm{i.e}{m}^t$$

In formula (5), dm gives the Jacobian matrix of the merit function m after the parameters p.

führen können.If the terms according to formula (2) and formula (3) are omitted, degenerate differentials dm can occur in the expression according to formula (5), which result in unrestricted values of the expression $\frac{\partial \varphi }{\partial m}$

being able to lead.

Of course, such a phenomenon can also occur in the presence of the terms according to the formula (2) or (3). However, this is less likely due to the regularization terms contained in the merit function.

annuliert werden. Umgekehrt können große oder gar unbeschränkte Differentiale dm systematische Fehler verstärken. Diesem Effekt wirken jedoch die Regularisierungsterme entgegen. Zudem sind unbeschränkte Werte von dm zuvor bekannt und können so durch Abmaskierung aus der Messung entfernt werden. In einer Weiterbildung des erfindungsgemäßen Verfahrens kann vorteilhafterweise in Verallgemeinerung der Abmaskierung eine Gewichtung vorgenommen werden, welche einen Teil des durch die Fehlerpropagation eingeführten Bias kompensiert.An advantage of the method according to the invention is that the error propagation filters out part of the systematic error of the measurement method, namely error terms in the residual according to formula (1), which are expressed by the expression $\frac{\partial \varphi }{\partial m}$

be cancelled. Conversely, large or even unbounded differentials can increase dm systematic errors. However, the regularization terms counteract this effect. In addition, unconstrained values of dm are known beforehand and can thus be removed from the measurement by masking. In a further development of the method according to the invention, a weighting can advantageously be carried out in generalization of the masking, which weighting compensates part of the bias introduced by the error propagation.

In an advantageous development of the method according to the invention, it can be provided that during the mathematical optimization within the scope of at least one smoothing method and/or a regularization method, a deviation of at least one parameter of the CGH between a measurement and a simulation is compensated by at least one linear combination of, preferably less than ten is described and/or controlled using smooth basis functions.

Alternatively or additionally, the regularization terms according to formula (2) and/or (3) can be present in the merit function, while at least the residual expression according to formula (1) is phase-propagated according to formula (6) below. $$cO{v}_{\varphi \text{'},\varphi }^{-\frac{1}{2}}\left(\frac{\partial \varphi }{\partial c}\left(c\left(p\right)-c_{meas\mathrm{and}\mathrm{right}e\mathrm{i.e}}-{\displaystyle \sum {\mathrm{e.g}}_i{Z}_i}\right)-{\displaystyle \sum {\mathrm{e.g}}_j^{\text{'}}{Z}_j}\right)$$

In formula (6), the basis functions Z _i and Z _j are described by Zernike polynomial terms. Both Zernike calibrations are optional.

In all of the aforementioned cases, it can be advantageous if direct propagation according to formula (7) is used instead of the propagated residual term shown in formula (6). $$cO{v}_{\varphi \text{'},\varphi }^{-\frac{1}{2}}\left(\varphi \left(c\left(p\right)\right)-\varphi \left(c_{meas}\right)-{\displaystyle \sum {\mathrm{e.g}}_i{Z}_i}\right)$$

In formula (7), the function ϕ(c) results from a specific fit of data (c(p), ϕ(p)) at measurement points p. This can in particular be recorded data from a database. The fit can be a polynomial fit and/or a local linear regression.

• - die Abweichungen wenigstens eines Parameters des CGHs über eine Phasensensitivität propagiert wird, und/oder
• - wenigstens eine Kalibrationsfunktion einen hohen Winkel zu der Fehlerpropagation des Residuums, insbesondere als eine Funktion eines Ortes, einschließt.

In an advantageous development of the method according to the invention, it can be provided that

• - the deviations of at least one parameter of the CGH is propagated via a phase sensitivity, and/or
• - at least one calibration function includes a high angle to the error propagation of the residual, in particular as a function of a location.

The solutions described above have the potential advantage that they can minimize error in the determination of the desired phase itself. In particular, the error can be minimized despite systematic model errors and without using a phase measurement.

In particular, there is no need for an adjustment calibration of the phase using the calibration functions Z _i . The term calibration does not refer to the calibration of the CHG, but to a calibration of the parameter deviation.

In the case of the method according to the invention, however, it should be noted that according to the design and the aim of carrying out the method, the phase propagation introduces a strong distortion into a parameter reconstruction. In particular, the distortion can occur despite resetting the phase covariance to a propagated c-covariance.

Under certain circumstances, the phenomenon described above can lead to significant noise or errors in critical CGH parameters. Critical parameters of the CGH are, for example, those parameters with a high phase sensitivity and at the same time a low sensitivity of the separate measurement or the c-measurement. The separate measurement can be carried out scatterometrically and/or interferometrically.

It is of particular advantage if strong a priori information and/or parameter correlations are provided for the aforementioned critical parameters in order to limit the distortion. These are described below.

In particular, a statistical interpretation of the merit function as a log likelihood of Bayesian updated Gaussian fields may no longer be expedient.

als spezielle Vorkonditionierung dient, sofern er regulär ist. Eine Regularität des Ausdrucks $\frac{\partial \varphi }{\partial m}$

erfordert hierbei eine gleiche Anzahl von Phasen und Messkanälen bzw. c-Kanälen.Furthermore, it can be provided that the expression $\frac{\partial \varphi }{\partial m}$

serves as a special preconditioning if it is regular. A regularity of expression $\frac{\partial \varphi }{\partial m}$

requires the same number of phases and measurement channels or c-channels.

In an advantageous development of the method according to the invention, it can be provided that during the mathematical optimization at least one fit parameter is selected in such a way that a full covariance matrix is error-propagated via a phase sensitivity.

Provision can be made for systematic errors to be detected using the method according to the invention. For this purpose, in particular deviations between a conventional and a phase-optimized merit function can be analyzed. In this case, the deviations characterize effective parameters p, which attempt to compensate for systematic errors that have not been recorded.

Provision can be made for the simulated phase φ _sim (l) to be determined on the basis of an interpolation or a fit data record (I(pi), φ(p _ί )). Here I designates an intensity and i an index of a measuring point.

In an advantageous development of the method according to the invention, it can be provided that the at least one fit parameter is optimized within a linearity range of the optimization, in particular after a previous rough optimization.

The fit parameters can be similar to those in the publication "Germer et al. Developing an uncertainty analysis for optical scatterometry, March 2009, SPIE Proceeding”. be elected. In this case, the full covariance matrix is again error-propagated via the phase sensitivity.

The optimization within the linearity range improves and simplifies the implementation of the optimization of the fit parameters.

The invention also relates to a regularization method having the features specified in claim 8.

In the inventive regularization method for a method for reconstructing an effect of a CGH on a test wavefront and/or a phase of a test radiation, a deviation of at least one parameter of the CGH between a measurement and a simulation of an effect of the CGH on a measurement radiation, in particular a measurement wavefront of the measurement radiation , described and/or controlled by at least one smooth basis function and/or a linear combination of several, preferably less than ten, smooth basis functions.

A regularization or a regularization method is to be understood within the scope of the invention as a mathematical measure or a mathematical method through which solutions for so-called "mathematically poorly set tasks" can be found and/or through which an overfitting of measurement data can be avoided by a mathematical model.

In the regularization method according to the invention, the expected value is described by linear combinations of a few basic functions Z _i which, among other things, contain correlations according to formula (8). $$p\mathrm{right}iO\mathrm{right}:=\frac{1}{{\sigma }_k}\left(p_k\left(x\right)-{\mu }_k-{\displaystyle \sum _i\mathrm{e.g}{\text{'}}_{k,i}{Z}_i\left(x\right)}\right)$$

In the regularization method according to the invention, it can be provided that the at least one basis function is modified in such a way that a regularization kernel is at least approximately decorrelated to a phase sensitivity of the test radiation, and/or at least two basis functions are provided which have correlations between at least two different locations on the CGH .

The procedure according to formula (8) is initially equivalent to the so-called Tykhonov regularization, in which the difference p−μ is projected onto a subspace which is spanned by the basis functions Z _k . A norm of the projection is then minimized.

However, the additional fit parameters z _k,i offer the advantage that on the one hand the basis functions Z _i do not have to be orthogonal and on the other hand the fit coefficients Z _i can be controlled directly.

• Erfindungsgemäß wird statt der a-priori-Information (prior) gemäß Formel (8) eine Fehlerpropagation $\frac{\partial \varphi }{\partial p},prior$
  
  über die Phasensensitivitäten verwendet.

Furthermore, in the expression given in formula (8) for the a priori information, the expression µ _k also covers the pointwise prior according to formula (3), so that the solution described below covers both a priori terms:

• According to the invention, instead of the a priori information (prior) according to formula (8), error propagation is used $\frac{\partial \varphi }{\partial p},p\mathrm{right}iO\mathrm{right}$
  
  used over the phase sensitivities.

einschließen.Furthermore, it is advantageous if the basis functions are chosen in such a way that they have a high angle to the phase sensitivity and/or to components and/or to high singular values of the error propagation mapping $\frac{\partial \varphi }{\partial I}$

lock in.

The regularization method according to the invention serves in particular to smooth critical parameters of the phase sensitivities.

Within the scope of the invention, a phase sensitivity can be understood to mean a phase position of the test wave front and/or the wave front of the measurement radiation.

It can be provided that a regulation core of the regularization method is modified in such a way that it is as complementary as possible or decorrelated or orthogonal to the phase sensitivity to be measured.

According to formula (2), spatial correlations are mapped using a correlation matrix.

Alternatively, the correlation matrix can be selected trivially to take spatial correlations into account, while the expected value is described by linear combinations of fewer basic functions Z _i .

The invention also relates to a device for qualifying a CGH having the features mentioned in claim 10 .

The device according to the invention for qualifying a CGH, which is set up in the case of coherent illumination with a test radiation to form at least one test wavefront of the test radiation for testing a mirror of an EUV projection exposure system, has an optical measuring device that qualifies and/or simulates the CGH for the full-surface measurement of the CGHs by a measurement radiation. According to the invention, the measuring device is set up to qualify the CGH with regard to an effect on the test radiation only in that the effect of the CGH on the test wavefront and/or a phase of the test radiation is reconstructed, with error propagation of a residue on the at least one test wavefront being taken into account is, the residue resulting from a deviation between a measurement and a simulation of an effect of the CGH on the measurement radiation, in particular a measurement wave front of the measurement radiation.

The device according to the invention is therefore used for the full-surface measurement of at least one test wavefront emanating from a CGH coherently illuminated with a test radiation and preferably has an optical measuring device that qualifies and simulates the CGH by means of a test radiation, which is set up to assign the CGH only with regard to an effect on the test radiation qualify and to take into account an error propagation of a residual to the at least one test wavefront.

The invention also relates to a lithography system having the features specified in claim 11.

The lithography system according to the invention, in particular a projection exposure system for semiconductor lithography, comprises an illumination system with a radiation source and an optical system which has at least one optical element, wherein at least one of the optical elements has an optical surface which is at least partially measured with a CGH. According to the invention, the CGH is qualified at least partially by means of the method according to the invention or one of its advantageous configurations and/or at least partially by means of the device according to the invention or one of its advantageous configurations. Alternatively or additionally, the CGH is at least partially qualified by means of a method which is or is regularized by means of the regularization method according to the invention or one of its advantageous configurations.

It can also be provided that the CGH is at least partially qualified by means of a method which is or is at least partially regularized by means of the regularization method according to the invention or one of its advantageous configurations.

The optical element is preferably a mirror of the lithography system designed as an EUV projection exposure system.

Features that have been described in connection with one of the objects of the invention, namely given by the method according to the invention, the regularization method according to the invention, the device according to the invention or the lithography system according to the invention, can also be advantageously implemented for the other objects of the invention. Likewise, advantages that were mentioned in connection with one of the objects of the invention can also be understood in relation to the other objects of the invention.

In addition, it should be noted that terms such as "comprising", "having" or "with" do not exclude any other features or steps. Furthermore, terms such as "a" or "that" which indicate a singular number of steps or features do not exclude a plurality of features or steps - and vice versa.

In a puristic embodiment of the invention, however, it can also be provided that the features introduced in the invention with the terms “comprising”, “having” or “with” are listed exhaustively. Accordingly, one or more listings of features may be considered complete within the scope of the invention, e.g. considered for each claim. The invention can consist exclusively of the features mentioned in claim 1, for example.

It should be mentioned that designations such as “first” or “second” etc. are primarily used for reasons of distinguishability of the respective device or method features and are not necessarily intended to indicate that features are mutually dependent or related to one another.

Exemplary embodiments of the invention are described in more detail below with reference to the drawing.

The figures each show preferred exemplary embodiments in which individual features of the present invention are shown in combination with one another. Features of an exemplary embodiment can also be implemented separately from the other features of the same exemplary embodiment and can accordingly easily be combined with features of other exemplary embodiments by a person skilled in the art to form further meaningful combinations and sub-combinations.

Elements with the same function are provided with the same reference symbols in the figures.

• 1 eine EUV-Projektionsbelichtungsanlage im Meridionalschnitt;
• 2 eine DUV-Projektionsbelichtungsanlage;
• 3 eine schematische Darstellung einer möglichen Ausführungsform der erfindungsgemäßen Vorrichtung;
• 4 eine blockdiagrammartige Darstellung einer möglichen Ausführungsform des erfindungsgemäßen Verfahrens;
• 5 eine blockdiagrammartige Darstellung einer möglichen Ausführungsform des erfindungsgemäßen Regularisierungsverfahrens;
• 6 eine flussdiagrammartige Darstellung eines Verfahrens zur Qualifizierung nach dem Stand der Technik; und
• 7 eine flussdiagrammartige Darstellung des erfindungsgemäßen Verfahrens zur Qualifizierung.

Show it:

• 1 an EUV projection exposure system in the meridional section;
• 2 a DUV projection exposure system;
• 3 a schematic representation of a possible embodiment of the device according to the invention;
• 4 a block diagram representation of a possible embodiment of the method according to the invention;
• 5 a block diagram representation of a possible embodiment of the regularization method according to the invention;
• 6 a flow chart representation of a method for qualification according to the prior art; and
• 7 a flowchart-like representation of the method for qualification according to the invention.

The following are first with reference to 1 the essential components of an EUV projection exposure system 100 for microlithography are described as an example of a lithography system. The description of the basic structure of the EUV projection exposure system 100 and its components should not be understood as limiting here.

In addition to a radiation source 102 , an illumination system 101 of the EUV projection exposure system 100 has illumination optics 103 for illuminating an object field 104 in an object plane 105 . In this case, a reticle 106 arranged in the object field 104 is exposed. The reticle 106 is held by a reticle holder 107 . The reticle holder 107 can be displaced in particular in a scanning direction via a reticle displacement drive 108 .

In 1 a Cartesian xyz coordinate system is drawn in for explanation. The x-direction runs perpendicularly into the plane of the drawing. The y-direction is horizontal and the z-direction is vertical. The scanning direction is in 1 along the y-direction. The z-direction runs perpendicular to the object plane 105.

The EUV projection exposure system 100 includes projection optics 109. The projection optics 109 are used to image the object field 104 in an image field 110 in an image plane 111. The image plane 111 runs parallel to the object plane 105. Alternatively, there is also an angle other than 0° between the object plane 105 and the image plane 111 is possible.

A structure on the reticle 106 is imaged on a light-sensitive layer of a wafer 112 arranged in the region of the image field 110 in the image plane 111. The wafer 112 is held by a wafer holder 113. The wafer holder 113 can be displaced via a wafer displacement drive 114, in particular along the y-direction. The displacement of the reticle 106 on the one hand via the reticle displacement drive 108 and on the other hand the wafer 112 via the wafer displacement drive 114 can be synchronized with one another.

The radiation source 102 is an EUV radiation source. The radiation source 102 emits in particular EUV radiation 115, which is also referred to below as useful radiation, illumination radiation or projection radiation. The useful radiation 115 has in particular a wavelength in the range between 5 nm and 30 nm. The radiation source 102 can be a plasma source, for example an LPP source (“laser produced plasma”, plasma generated using a laser radiation source) or a DPP (Gas Discharged Produced Plasma) source. It can also be a synchrotron-based radiation source. The radiation source 102 can be a free-electron laser (FEL).

The illumination radiation 115 emanating from the radiation source 102 is bundled by a collector 116 . The collector 116 can be a collector with one or more ellipsoidal and/or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 116 can be used in grazing incidence ("Grazing Incidence", GI), i.e. with angles of incidence greater than 45°, or in normal incidence ("Normal Incidence", NI), i.e. with angles of incidence smaller than 45° of the illumination radiation 115 are applied. The collector 116 can be structured and/or coated on the one hand to optimize its reflectivity for the useful radiation 115 and on the other hand to suppress stray light.

After the collector 116, the illumination radiation 115 propagates through an intermediate focus in an intermediate focal plane 117. The intermediate focal plane 117 can represent a separation between a radiation source module, comprising the radiation source 102 and the collector 116, and the illumination optics 103.

The illumination optics 103 comprises a deflection mirror 118 and a first facet mirror 119 arranged downstream of this in the beam path. The deflection mirror 118 can be a planar deflection mirror or alternatively a mirror with a purely deflection effect act beyond bundle-influencing effect. Alternatively or additionally, the deflection mirror 118 can be designed as a spectral filter, which separates a useful light wavelength of the illumination radiation 115 from stray light of a different wavelength. If the first facet mirror 119 is arranged in a plane of the illumination optics 103 which is optically conjugate to the object plane 105 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 119 includes a multiplicity of individual first facets 120, which are also referred to below as field facets. Of these facets 120 are in the 1 only a few shown as examples.

The first facets 120 can be embodied as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or part-circular edge contour. The first facets 120 can be embodied as planar facets or alternatively as convexly or concavely curved facets.

Like for example from the DE 10 2008 009 600 A1 is known, the first facets 120 themselves can each also be composed of a multiplicity of individual mirrors, in particular a multiplicity of micromirrors. The first facet mirror 119 can be embodied in particular as a microelectromechanical system (MEMS system). For details refer to the DE 10 2008 009 600 A1 referred.

The illumination radiation 115 runs horizontally between the collector 116 and the deflection mirror 118, ie along the y-direction.

A second facet mirror 121 is arranged downstream of the first facet mirror 119 in the beam path of the illumination optics 103. If the second facet mirror 121 is arranged in a pupil plane of the illumination optics 103, it is also referred to as a pupil facet mirror. The second facet mirror 121 can also be arranged at a distance from a pupil plane of the illumination optics 103 . In this case, the combination of the first facet mirror 119 and the second facet mirror 121 is also referred to as a specular reflector. Specular reflectors are known from US 2006/0132747 A1 , the EP 1 614 008 B1 and the U.S. 6,573,978 .

The second facet mirror 121 comprises a plurality of second facets 122. In the case of a pupil facet mirror, the second facets 122 are also referred to as pupil facets.

The second facets 122 can also be macroscopic facets, which can have round, rectangular or hexagonal borders, for example, or alternatively facets composed of micromirrors. In this regard, also on the DE 10 2008 009 600 A1 referred.

The second facets 122 can have plane or alternatively convexly or concavely curved reflection surfaces.

The illumination optics 103 thus forms a double-faceted system. This basic principle is also known as the "Fly's Eye Integrator".

It can be advantageous not to arrange the second facet mirror 121 exactly in a plane which is optically conjugate to a pupil plane of the projection optics 109 .

The individual first facets 120 are imaged in the object field 104 with the aid of the second facet mirror 121 . The second facet mirror 121 is the last beam-forming mirror or actually the last mirror for the illumination radiation 115 in the beam path in front of the object field 104.

In a further embodiment of the illumination optics 103 that is not shown, transmission optics can be arranged in the beam path between the second facet mirror 121 and the object field 104 , which particularly contribute to the imaging of the first facets 120 in the object field 104 . The transmission optics can have exactly one mirror, but alternatively also have two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 103 . The transmission optics can in particular comprise one or two mirrors for normal incidence (NI mirror, "normal incidence" mirror) and/or one or two mirrors for grazing incidence (GI mirror, "gracing incidence" mirror).

The illumination optics 103 has the version in which 1 shown, exactly three mirrors after the collector 116, namely the deflection mirror 118, the field facet mirror 119 and the pupil facet mirror 121.

In a further embodiment of the illumination optics 103, the deflection mirror 118 can also be omitted, so that the illumination optics 103 can then have exactly two mirrors downstream of the collector 116, namely the first facet mirror 119 and the second facet mirror 121.

The imaging of the first facets 120 by means of the second facets 122 or with the second facets 122 and a transmission optics in the object plane 105 is regularly only an approximate mapping.

The projection optics 109 includes a plurality of mirrors Mi, which are numbered consecutively according to their arrangement in the beam path of the EUV projection exposure system 100 .

At the in the 1 example shown, the projection optics 109 includes six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or another number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 115. The projection optics 109 are doubly obscured optics. The projection optics 109 has an image-side numerical aperture which is greater than 0.5 and which can also be greater than 0.6 and which can be 0.7 or 0.75, for example.

Reflection surfaces of the mirrors Mi can be designed as free-form surfaces without an axis of rotational symmetry. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflection surface shape. Just like the mirrors of the illumination optics 103, the mirrors Mi can have highly reflective coatings for the illumination radiation 115. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optics 109 has a large object-image offset in the y-direction between a y-coordinate of a center of the object field 104 and a y-coordinate of the center of the image field 110. This object-image offset in the y-direction can be something like this be as large as a z-distance between the object plane 105 and the image plane 111.

The projection optics 109 can in particular be anamorphic. In particular, it has different image scales βx, βy in the x and y directions. The two image scales βx, βy of the projection optics 109 are preferably at (βx, βy)=(+/−0.25, +/-0.125). A positive image scale β means an image without image reversal. A negative sign for the imaging scale β means imaging with image inversion.

The projection optics 109 thus leads to a reduction in the ratio 4:1 in the x-direction, ie in the direction perpendicular to the scanning direction.

The projection optics 109 lead to a reduction of 8:1 in the y-direction, ie in the scanning direction.

Other imaging scales are also possible. Image scales with the same sign and absolutely the same in the x and y directions, for example with absolute values of 0.125 or 0.25, are also possible.

The number of intermediate image planes in the x-direction and in the y-direction in the beam path between the object field 104 and the image field 110 can be the same or, depending on the design of the projection optics 109, can be different. Examples of projection optics with different numbers of such intermediate images in the x and y directions are known from U.S. 2018/0074303 A1 .

In each case one of the pupil facets 122 is assigned to precisely one of the field facets 120 in order to form a respective illumination channel for illuminating the object field 104 . In this way, in particular, lighting can result according to Köhler's principle. The far field is broken down into a large number of object fields 104 with the aid of the field facets 120 . The field facets 120 generate a plurality of images of the intermediate focus on the pupil facets 122 respectively assigned to them.

The field facets 120 are each imaged onto the reticle 106 by an associated pupil facet 122 in a superimposed manner in order to illuminate the object field 104 . In particular, the illumination of the object field 104 is as homogeneous as possible. It preferably has a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

The illumination of the entrance pupil of the projection optics 109 can be geometrically defined by an arrangement of the pupil facets. The intensity distribution in the entrance pupil of the projection optics 109 can be set by selecting the illumination channels, in particular the subset of the pupil facets that guide light. This intensity distribution is also referred to as an illumination setting.

A likewise preferred pupil uniformity in the area of defined illuminated sections of an illumination pupil of the illumination optics 103 can be achieved by redistributing the illumination channels.

Further aspects and details of the illumination of the object field 104 and in particular the entrance pupil of the projection optics 109 are described below.

The projection optics 109 can in particular have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

The entrance pupil of the projection optics 109 cannot regularly be illuminated exactly with the pupil facet mirror 121 . When imaging the projection optics 109, which telecentrically images the center of the pupil facet mirror 121 onto the wafer 112, the aperture rays often do not intersect at a single point. However, a surface can be found in which the distance between the aperture rays, which is determined in pairs, is minimal. This surface represents the entrance pupil or a surface conjugate to it in position space. In particular, this surface shows a finite curvature.

The projection optics 109 may have different positions of the entrance pupil for the tangential and for the sagittal beam path. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second facet mirror 121 and the reticle 106 . With the help of this optical component, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

At the in the 1 In the arrangement of the components of the illumination optics 103 shown, the pupil facet mirror 121 is arranged in a surface conjugate to the entrance pupil of the projection optics 109 . The first field facet mirror 119 is arranged tilted to the object plane 105 . The first facet mirror 119 is tilted relative to an arrangement plane that is defined by the deflection mirror 118 .

The first facet mirror 119 is tilted relative to an arrangement plane that is defined by the second facet mirror 121 .

In 2 an exemplary DUV projection exposure system 200 is shown, in which the principle of the present invention for cleaning foreign particles from the lenses can basically also be used. The EUV-specific components, such as a collector mirror 116, are then not required for this or can be substituted accordingly. The DUV projection exposure system 200 has an illumination system 201, a device known as a reticle stage 202 for receiving and precisely positioning a reticle 203, by means of which the later structures on a wafer 204 are determined, a wafer holder 205 for holding, moving and precisely positioning the wafer 204 and an imaging device, namely projection optics 206, with a plurality of optical elements, in particular lenses 207, which are held in an objective housing 209 of the projection optics 206 via mounts 208.

As an alternative or in addition to the lenses 207 shown, various refractive, diffractive and/or reflective optical elements, including mirrors, prisms, end plates and the like, can be provided.

The basic functional principle of the DUV projection exposure system 200 provides that the structures introduced into the reticle 203 are imaged onto the wafer 204 .

The illumination system 201 provides a projection beam 210 required for imaging the reticle 203 onto the wafer 204 or a projection radiation in the form of electromagnetic radiation. A laser, a plasma source or the like can be used as the source for this radiation. The radiation is shaped in the illumination system 201 via optical elements in such a way that the projection beam 210 has the desired properties in terms of diameter, polarization, shape of the wave front and the like when it strikes the reticle 203 .

An image of the reticle 203 is generated by means of the projection beam 210 and transmitted to the wafer 204 in a correspondingly reduced size by the projection optics 206 . The reticle 203 and the wafer 204 can be moved synchronously, so that areas of the reticle 203 are imaged onto corresponding areas of the wafer 204 practically continuously during a so-called scanning process.

Optionally, an air gap between the last lens 207 and the wafer 204 can be replaced by a liquid medium that has a refractive index greater than 1.0. The liquid medium can be, for example, ultrapure water. Such a structure is also referred to as immersion lithography and has an increased photolithographic resolution.

The use of the invention is not limited to use in projection exposure systems 100, 200, in particular not with the structure described. The invention is suitable for any lithography system, but in particular for projection exposure systems with the structure described. The invention is also suitable for EUV projection exposure systems, which have a lower image-side numerical aperture than those associated with 1 is described. In particular, the invention is also suitable for EUV projection exposure systems, which have an image-side numerical aperture of 0.25 to 0.5, preferably 0.3 to 0.4, most preferably 0.33. Furthermore, the invention and the following exemplary embodiments are not to be understood as being restricted to a specific design. The following figures represent the invention only by way of example and in a highly schematic manner.

It should be pointed out that the device according to the invention described below and the method according to the invention for qualification can be used in particular in lithography systems and here in particular in projection exposure systems for semiconductor lithography, but can also be used in other areas in which precise measurement is important or where a test object, in particular an optical element, e.g. a mirror, is to be measured or processed with high precision.

3 shows a highly schematic representation of a possible embodiment of a device 1 for the qualification of a CGH 2.

The device 1 for qualifying the CGH 2, which when illuminated with a test radiation 3 (see 7 ) to form at least one test wavefront 4 (see 7 ) of the test radiation 3 for testing a mirror 5, in particular one of the mirrors 116, 118, 119, 120, 121, 122, Mi of the projection exposure system 100, has an optical measuring device 6 that qualifies and/or simulates the CGH 2 for the full-surface measurement of the CGHs by a measurement radiation 7 on.

The measuring device 6 is set up to qualify the CGH 2 with regard to an effect on the test radiation 3 simply by reconstructing the effect of the CGH 2 on the test wavefront 4 and/or a phase of the test radiation 3, with error propagation of a residual on the at least one test wavefront 4 is taken into account, with the residue resulting from a deviation between a measurement and a simulation of an effect of the CGH 2 on the measurement radiation 7, in particular a measurement wavefront of the measurement radiation 7.

For this purpose, the measuring device 6 has a computing device 6a for carrying out the corresponding numerical calculations and a camera 6b for detecting an intensity distribution of the measuring radiation 7 .

4 shows a block diagram representation of a possible embodiment of a method for qualifying a CGH.

The computer-generated hologram to be qualified is here in a coherent illumination with the test radiation 3 to form the at least one test wave front 4 of the test radiation 3 for testing the mirror 5, in particular one of the mirrors 116, 118, 119, 120, 121, 122, Mi of the projection exposure system 100 furnished. In the method, the test wavefront 4 is measured over the entire area by the measuring radiation 7 by means of the optical measuring device 6 that qualifies and/or simulates the CGH 2 .

In this case, the CGH 2 is only qualified with regard to an effect on the test radiation 3 in that the effect of the CGH 2 on the test wavefront 4 and/or a phase of the test radiation 3 is reconstructed in a reconstruction block 10 . In an error propagation block 11, an error propagation of a residual to the at least one test wavefront 4 is taken into account.

As part of the error propagation block 11, it can preferably be provided that the error propagation of the residual is taken into account, in particular reduced, preferably minimized, as part of a mathematical optimization.

In a determination block 12, the residue is determined from a deviation between a measurement and a simulation of an effect of the CGH 2 on the measurement radiation 7, in particular a measurement wavefront of the measurement radiation 7.

As part of the determination block 12 it can be provided that the CGH 2 is measured by the optical measuring device 6 using a scatterometry method, an ellipsometry method, an interferometry method and/or a ptychography method in a measuring block 13 .

A smoothing block 14 can preferably be provided as part of the reconstruction block 10, in which, during the mathematical optimization within the scope of at least one smoothing method and/or a regularization method, a deviation of at least one parameter of the CGH 2 between a measurement and a simulation is determined by at least one linear combination, preferably less than ten smooth basis functions is described and/or controlled.

As part of the error propagation block 11, provision can preferably be made for the deviation of at least one parameter of the CGH 2 to be propagated via one or more phase sensitivities.

As part of the smoothing block 14 can be provided that at least one calibration function, preferably at a high angle to the error propagation of the residual, in particular as a function as location.

As part of the error propagation block 11, provision can preferably be made for the basis functions smoothing the parameters to be selected in that the full covariance matrix propagated via the phase sensitivities is as small as possible in a suitable norm.

Alternatively or additionally, it can be provided that during the mathematical optimization at least one fit parameter is selected in such a way that a full covariance matrix is error-propagated via a phase sensitivity.

Within the framework of the error propagation block 11, provision can preferably also be made for the at least one fit parameter to be optimized within a linearity range of the optimization, in particular after a previous rough optimization.

5 shows a block diagram representation of a possible embodiment of a regularization method. The regularization method is used for a method for reconstructing an effect of the CGH 2 on the test wavefront 4 and/or a phase of the test radiation 3. Such a method for reconstruction is, for example, in connection with 4 explained. In the regularization method, a deviation of at least one parameter of the CGH 2 between a measurement and a simulation of an effect of the CGH 2 on the measurement radiation 7 , in particular a measurement wave front of the measurement radiation 7 , is determined in a deviation block 20 .

In a control block 21, which preferably represents Bayesian advance information or a priori information, the deviation is described and/or controlled by at least one smooth basis function and/or a linear combination of several, preferably fewer than ten, smooth basis functions. The control block 21 and the deviation block 20 together preferably represent the Bayesian a posteriori distribution of the measurement parameters.

Alternatively or additionally, it can be provided that within the framework of the control block 21 at least one basis function is modified in such a way that a regularization core is at least approximately decorrelated to a phase sensitivity of the test radiation 4 .

As an alternative or in addition, at least two basic functions can be provided within the framework of the control block 21, which have correlations between at least two different locations on the CGH.

6 shows a flowchart-like representation of a method for qualifying the CGH 2 according to the prior art

In this respect, this shows in 6 The flowchart shown not only shows a procedure for qualifying the CGH 2, but also the further use of the CGH 2.

The related to 6 The steps and measures described can also be found as part of the method according to the invention.

In particular, the method according to the prior art involves a rigorous wavefront calculation. in the in 6 In the exemplary embodiment illustrated, after the illustrated qualification of the CGH 2 , rigorous wave fronts emanate from the CGH 2 in the direction of the mirror 5 .

In a first step, intensities I _mess of the zeroth order of diffraction are measured on a diffraction measuring station. In this case, a wavelength of the measurement radiation 7 and/or a polarization of the measurement radiation 7 can be varied. The diffraction measurement stand can in particular be an optical measurement device 6 .

In a minimization step 30, which is carried out in 6 is represented by an arrow, a difference I _sim (p) - I _mess is minimized.

This leads to a spatial-physical model of the CGH 2, which contains one or more model parameters p. For example, the model parameters p can be a web height 31 or etching depth , a web width 32 , a web flank inclination 33 or flank angle and/or a web incision depth 34 and/or an edge position error .

Alternatively or additionally, the error parameters edge position error, flank angle and web incision depth 34 can be modeled over the entire surface, simulated via RCWA-Maxwell solver and scatterometrically, in particular by means of the measuring device 6 and/or a diffraction measuring stand with the conventional and/or the phase-optimized merit function according to formula (4 ) and the regularization method according to the invention, i.e. according to formula (5).

A "noise" in the determination of the web flank inclination 33 or the flank angle can be caused by its weak scatterometric Sensitivity conditional and suggest the use of a site-correlating prior.

In a simulation step 35, the phases φ _sim (p) of the test radiation 3 emanating from the CGH 2 and/or the test wave front 4 are calculated or simulated from the set of model parameters p.

The mirror 5 is then measured using the CGH 2, with the test wavefront 4 emanating from the CGH 2 being sufficiently known from the previous steps, so that interferometrically measurable deviations between the test wavefront 4 and the shape of the mirror 5 can be differentiated with regard to their origin. In particular, it is possible to decide through the rigorous calculation of the test wavefront 4 whether a deviation from the shape of the mirror 5 is due to an incorrect manufacture of the shape of the mirror 5 or to an incorrect design of the test wavefront 4 that deviates from the shape of the mirror 5 .

Provision can be made for further measurements, such as AFM measurements (atomic force microscopy measurements), to be included in the creation of the model of the CGH 2 or the determination of the model parameters p. In an AFM measurement, the web heights 31 are measured directly, for example. However, under certain circumstances, taking into account the directly measured web height 31 can 6 illustrated rigorous calibration of the CGHs 2 worsen.

7 shows a flowchart-like representation of the embodiment of the method according to the invention. With regard to the allocation of reference numbers, see 6 referred.

Here, as a starting point, the intensities I _mess of the zeroth order of diffraction of the measuring radiation 7 are again measured by means of the optical measuring device 6 with varying wavelength and/or varying polarization.

At the in 7 The procedure shown is based on a determination of the model parameters P, as described in 6 have been described. In particular, no web height 31, no web width 32, no web flank inclination 33 and no web incision depth 34 is determined. Instead, an effective model, ie one that describes the effect, of the CGH 2 is determined, for which purpose a set of model parameters p′ is used.

Based on the effective model of the CGH 2 , a simulated phase position φ _sim (I) of the measurement radiation 7 is precalculated in a first calculation step 40 as a function of the intensity of the measurement radiation 7 .

In a second calculation step 41, a phase position of the test radiation 3 is simulated as a function of the effective model parameter set p′, a phase position φ _sim (p′). In a third calculation step 42, a difference between the simulated phase position as a function of the effective model parameter set p' and the simulated phase position as a function of the measured intensity distribution of the measuring radiation 7 at the optical measuring device 6 is minimized.

Forgoing an exact determination of the spatial-physical model parameters p for the CGH 2 is in 7 symbolized by a dashed representation of the CGH 2.

In the 7 The procedure shown in turn enables the determination of a rigorously determined test wavefront 4, that is rigorous wavefronts, when measuring the mirror 5. This goal is in the in 7 However, the procedure explained above is achieved without a complete reconstruction of the CGH 2 .

The 1 and 2 each show a lithography system, in particular a projection exposure system 100, 200 for semiconductor lithography, with an illumination system 101, 201 with a radiation source 102 and optics 103, 109, 206, which have at least one optical element 116, 118, 119, 120, 121, 122 , Mi, 207 exhibits. At the in the 1 and 2 In the projection exposure systems 100, 200 shown, at least one of the optical elements 116, 118, 119, 120, 121, 122, Mi, 207 has an optical surface which is at least partially measured with the CGH 2, which is at least partially measured using the method described above and/or at least is partially qualified by means of the device 1 described above.

The invention is particularly suitable for mirrors 5, which are mirrors 116, 118, 119, 120, 121, 122, Mi of EUV lithography systems 100. However, the invention can also be used in connection with optical elements or lenses 207 of DUV projection exposure systems 200 .

Reference list:

1

contraption

2

CGH

3

test radiation

4

test wavefront

5

Mirror

6

optical measuring device

6a

computing device

6b

camera

7

measuring radiation

10

reconstruction block

11

error propagation block

12

investigation block

13

survey block

14

smoothing block

20

deviation block

21

control block

30

minimization step

31

web height

32

bridge width

33

web slope

34

Web incision depth

35

simulation step

40

first calculation step

41

second calculation step

42

third calculation step

100

EUV projection exposure system

101

lighting system

102

radiation source

103

lighting optics

104

object field

105

object level

106

reticle

107

reticle holder

108

reticle displacement drive

109

projection optics

110

image field

111

picture plane

112

wafers

113

wafer holder

114

Wafer displacement drive

115

EUV / useful / illumination radiation

116

collector

117

intermediate focal plane

118

deflection mirror

119

first facet mirror / field facet mirror

120

first facets / field facets

121

second facet mirror / pupil facet mirror

122

second facets / pupil facets

200

DUV projection exposure system

201

lighting system

202

reticle stage

203

reticle

204

wafers

205

wafer holder

206

projection optics

207

lens

208

version

209

lens body

210

projection beam

wed

Mirror

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EN 102021200110 [0010]
• DE 102017221005 A1 [0015]
• DE 102008009600 A1 [0112, 0116]
• US 2006/0132747 A1 [0114]
• EP 1614008 B1 [0114]
• US6573978 [0114]
• US 2018/0074303 A1 [0133]

Claims (10)

Method for qualifying a computer-generated hologram (CGH) (2), which, when illuminated coherently with a test radiation (3), forms at least one test wavefront (4) of the test radiation (3) for testing a mirror (5) of an EUV projection exposure system (100 ) is set up, wherein the test wavefront (4) is measured over the entire surface by means of an optical measuring device (6) that qualifies and/or simulates the CGH (2) by means of a measuring radiation (7), characterized in that the CGH (2) with regard to an effect on the test radiation (3) is only qualified in that the effect of the CGH (2) on the test wavefront (4) and/or a phase of the test radiation (2) is reconstructed, with an error propagation of a residue on the at least one test wavefront (4) is taken into account, the residue resulting from a deviation between a measurement and a simulation of an effect of the CGH (2) on the measurement radiation (7), in particular a measurement wavefront of the measurement radiation (7). procedure after claim 1 , characterized in that the CGH (2) is measured by the optical measuring device (6) using a scatterometry method, an ellipsometry method, an interferometry method and/or a ptychography method. procedure after claim 1 or 2 , characterized in that the error propagation of the residual is taken into account, in particular minimized, as part of a mathematical optimization. procedure after claim 3 , characterized in that during the mathematical optimization as part of at least one smoothing method and/or a regularization method, a deviation of at least one parameter of the CGH (2) between a measurement and a simulation is described by at least one linear combination of, preferably fewer than ten, smooth basis functions and /or controlled. procedure after claim 4 , characterized in that - the deviations of at least one parameter of the CGH (2) are propagated via a phase sensitivity, and/or - at least one calibration function includes a large angle to the error propagation of the residue, in particular as a function of a location. procedure after claim 4 or 5 , characterized in that the basis functions are selected on the basis of properties of a full covariance matrix propagated over one or more phase sensitivities. procedure after claim 6 , characterized in that the at least one fit parameter is optimized within a linearity range of the optimization, in particular after a previous rough optimization. Regularization method for a method for reconstructing an effect of a CGH (2) on a test wavefront (4) and/or a phase of a test radiation (3), according to which a deviation of at least one parameter of the CGH (2) between a measurement and a simulation of an effect of the CGHs (2) on a measurement radiation (7), in particular a measurement wave front of the measurement radiation (7), is described and/or controlled by at least one smooth basis function and/or a linear combination of several, preferably fewer than ten, smooth basis functions. Device (1) for qualifying a CGH (2) which, when illuminated coherently with a test radiation (3), forms at least one test wave front (4) of the test radiation (3) for testing a mirror (5) of an EUV projection exposure system (100) is set up, having an optical measuring device (6) that qualifies and/or simulates the CGH (2) for the full-area measurement of the CGH (2) by a measuring beam (4), characterized in that the measuring device (6) is set up to measure the CGH (2) with regard to an effect on the test radiation (3) only to be qualified in that the effect of the CGH (2) on the test wavefront (4) and/or a phase of the test radiation (3) is reconstructed, with error propagation of a residue the at least one test wavefront (4) is taken into account, with the residue resulting from a deviation between a measurement and a simulation of an effect of the CGH (2) on the measurement radiation (7), in particular a measurement wavefront of the measurement radiation (7). Lithography system, in particular projection exposure system (100, 200) for semiconductor lithography, with an illumination system (101, 201) with a radiation source (102) and an optical system (103, 109, 206) which has at least one optical element (116, 118, 119, 120, 121, 122, Mi, 207), wherein at least one of the optical elements (116, 118, 119, 120, 121, 122, Mi, 207) has an optical surface which is at least partially measured with a CGH (2). is, characterized in that the CGH (2) - at least partially by means of a method according to any one of Claims 1 until 7 and/or - at least partially by means of a device (1) according to claim 10 is qualified, and/or - is at least partially qualified by means of a method which is at least partially qualified by means of a regularization method according to claim 8 is regularized.

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