Method for characterizing a diffractive optical element, and method for producing a diffractive optical element with implementation of the characterization method

Abstract

A diffractive optical element (DOE) has first and second structure portions for specifying a first and a second optical path length for used radiation incident on the DOE, with the path lengths differing from one another. The first and the second structure portions appear alternately on a used surface of the DOE. A raw DOE is initially provided (10) when characterizing the diffractive optical element. Subsequently, interrelated first and / or second structure portions on the raw DOE are determined and interrelated first isolation structure portions, which are completely isolated from other first structure portions by way of second structure portions, and / or interrelated second isolation structure portions, which are completely isolated from other second structure portions by way of first structure portions, are ascertained therefrom. During the production of a correspondingly characterized DOE, at least one contact component can be applied to the raw DOE for the purpose of eliminating unwanted isolations between the structure portions. As a result, an option is developed for the production of diffractive optical elements with more precise diffraction, which in turn can be used when characterizing a surface shape of an optical surface of an optical element.

Description

[0001] Method for characterizing a diffractive optical element and method for producing a diffractive optical element by carrying out the characterization method

[0002] This patent application claims priority from German patent application DE 10 2022 207 138.7, the contents of which are incorporated herein by reference.

[0003] The invention relates to a method for characterizing a diffractive optical element. Furthermore, the invention relates to a method for producing a diffractive optical element by performing such a characterization method. Furthermore, the invention relates to a diffractive optical element produced by such a method, as well as to a method for characterizing a surface shape of an optical surface of an optical element, performed using such a diffractive optical element.

[0004] A diffractive optical element which is used in the characterization of a surface shape of an optical surface of an optical element is known from the technical article “Quasi-absolute measurement of aspheres with a combined diffractive optical element as reference” by Simon et al., Applied Optics, Vol. 45, No. 34, 2006, pages 8606 to 8612, the technical article “Redistribution of output weighting coefficients for complex multiplexed phase-diffractive elements”, by Liu et al., Optics Express, Vol. 12, No. 19, 2004, pages 4347 to 4352 and DE 10 2019 215 707 A1 and the references cited therein.

[0005] It is an object of the present invention to provide the possibility of producing precise diffractive optical elements which in turn can be used in characterizing a surface shape of an optical surface of an optical element.

[0006] This object is achieved according to the invention by a characterization method having the features specified in claim 1.

[0007] The diffractive optical element (DOE) characterized in the process can be a phase mask.

[0008] According to the invention, it was recognized that, within the framework of a DOE manufacturing process, a degradation of a design and arrangement of first and second structural sections, i.e., two types of structural sections, specified for optimal diffraction of the DOE, occurs due to the occurrence of insulating structural sections that are surrounded by structural sections of the respective other structural type in such an insulating manner that they have no or insufficient contact with the structural sections of the same type. This can lead, particularly in cases where at least one structural section type is made of conductive material, to undesirable electrical potential differences between the structural sections of the same type and, consequently, in particular to undesirable structural depth variations with correspondingly undesirable variations in diffraction efficiency or phase / wavefront.

[0009] The characterization method enables the identification of corresponding insulation structure sections, in which harmful manufacturing inhomogeneities may occur, particularly due to potential differences, on a raw DOE, which represents an intermediate product for the DOE to be manufactured, which can be taken into account during the production of the DOE from the intermediate product by implementing appropriate compensation measures.

[0010] The provided DOE can be a raw DOE which, prior to the actual production of diffractive structure sections, is present, for example, in the form of a particularly binary computer bitmap representing the arrangement and design of the various structure sections. At least one type of structure section can be spatially predetermined, for example, by a mask material on a structure section type. At least one of the structure section types, or the mask material that predetermines it, can be made of electrically conductive material. The first structure sections can be predetermined by a hard mask structure in preparation for an etching production process for the DOE. The mask material can be a chromium hard mask. The first structure sections can be raised structure regions, for example when the DOE is designed as a reflection grating.When the DOE is designed as a phase grating, the first structural sections can be sections of a first, longer optical transmission path length, for example, thicker layer regions of an optical material. When the DOE is designed as a reflection grating, the second structural sections can be recessed structural regions. When the DOE is designed as a phase grating, the second structural sections can be sections of a second, smaller optical transmission path length, for example, less thick layer regions of the optical material. The DOE can be designed as a computer-generated hologram (CGH). The first isolation structural sections are exclusively of the structure type of the first structural sections. The second isolation structural sections are exclusively of the structure type of the second structural sections.

[0011] The first and second structural sections occur alternately or alternately on the usable area of ​​the DOE. The period of alternation between the different structural sections is usually not constant, but can vary, in particular, over several orders of magnitude.

[0012] A method for determining and determining the insulation structural sections according to claim 2 is suitable if the arrangement and design of the structural sections can be examined over the entire usable area within a binary representation. This examination can be carried out pixel by pixel. Alternatively or additionally, the examination can be carried out over polygonally bordered regions. Alternatively or additionally, this examination can be carried out over regions defined by a few support points, which can be curvilinearly or curvilinearly bordered, in particular by spline functions between the support points. In general, information on regions of the structural sections to be examined can also be provided in vector form.

[0013] A determination method according to claim 3 enables a very significant data reduction when examining the first and second structural sections. Compared to the pixel-by-pixel examination of an entire binary representation of the structural sections, a data reduction of a factor of 10 4 up to 10 6 The scaling factors used in the scaled phase function representation can be a wavelength of a wave function representation and / or a spatial coordinate of the phase function representation of the structural sections. Scaling factors can be selected in the range between 100 and 500, resulting in corresponding data reductions, which can be quadratically influenced by the scaling factors.

[0014] In a determination and detection method according to claim 4, the recognized circumstance that the presence of potentially disturbing isolation structural sections results from beat effects of a wave function representation can be exploited. This can be achieved by using a merit function that incorporates the linear combinations of the basis vectors describing the structural sections. Regarding the regions of the binary representation to be examined, what has already been explained above with regard to claim 2 applies.

[0015] The advantages of a DOE manufacturing method according to claim 5 correspond to those already explained above with reference to the characterization method, which is part of the manufacturing method. With the help of the at least one applied contact component, the undesirable electrical potential differences between the mutually insulated structural sections of the same type, and thus undesirable insulation between the structural sections, can be eliminated. During the subsequent completion of the DOE, particularly during an etching process, no undesirable inhomogeneity, for example in an etching depth, arises due to the undesirable electrical potential differences.

[0016] At least one contact component according to claim 6 enables the cancellation of a potential difference for a corresponding plurality of previously insulated insulation structure sections. Contact components according to claim 7, which can be in the form of long needles and / or line segments, have proven successful in practice. Applying a single contact component is often sufficient to avoid undesirable electrical potential differences on the usable surface of the DOE.

[0017] This applies in particular to contact components with a length according to claim 7.

[0018] A plurality of contact components according to claim 8 has also proven successful in practice. In this case, locally isolated structural sections of the same type are connected to one another by one of the plurality of contact components.

[0019] Contact components according to claim 9, which may have the form of short needles, have proven suitable for applying a plurality of contact components.

[0020] The advantages of a DOE according to claim 10 correspond to those already explained above with reference to the characterization method and to the manufacturing method using this characterization method.

[0021] The same applies to the characterization method according to claim 11, which also leads to more precise results due to the more precisely diffracting DOE. Embodiments of the invention are explained in more detail below with reference to the drawings. In these:

[0022] Fig. 1 shows a section of a useful surface of a diffractive optical element (DOE) with first, hatched structural sections and second, white-colored structural sections shown pixel by pixel for specifying different optical path lengths for useful radiation incident on the DOE;

[0023] Fig. 2 shows a cross-section through the structural sections according to line II in a subsection of the DOE according to Fig. 1;

[0024] Fig. 3 schematically shows a plan view of an embodiment of the DOE, manufactured without applying contact components that connect insulation structure sections to one another, wherein a profile parameter “etch depth during the manufacture of the structure sections” is shown as a function of a location on the DOE in a contour line representation;

[0025] Fig. 4 shows a top view of the DOE according to Fig. 3, wherein a result of a characterization method including determining and ascertaining interconnected first and / or second structural sections in a local section or candidate region of the DOE is reproduced; Fig. 5 shows a result of a variant of the characterization method, comprising determining interconnected first and / or second structural sections and ascertaining isolation structural sections by examining a scaled phase function representation of the first and second structural sections using a first, low scaling factor s;

[0026] Fig. 6 to 8 in a representation similar to Fig. 5 further results of the characterization method when reproducing the structural sections via the scaled phase function representation with ever increasing scaling factor s;

[0027] Fig. 9 again shows a section of the DOE with ring structures, comprising isolation structure sections, i.e. first and second structure sections of the DOE, which are completely isolated from other first and second structure sections via first and second structure sections;

[0028] Fig. 10 to 12 are vector addition representations for understanding a merit function for determining candidate areas (hotspots) for insulation structural sections on the usable area of ​​the DOE according to Fig. 9, in which investigated linear combinations of wave vectors of a phase function representation of the structural sections occur, which have vector residuals with lengths below a specified value (Figs. 10 and 12) and above a specified value (Fig. 11); Fig. 13 is a representation similar to Figs. 3 and 4, showing a result of a characterization method using a candidate area determination by examining linear combinations based on Fig. 12, with only the candidate areas on the usable area of ​​the DOE being highlighted as hotspots in which investigated linear combinations occur that have vector residuals with lengths below a specified value;

[0029] Fig. 14 shows a schematic representation of an example of insulation structure sections determined by means of a variant of the characterization method, using the example of concentrically nested, alternating first and second structure sections;

[0030] Fig. 15 shows the insulation structure sections according to Fig. 14 with an applied contact component in the form of a long needle or a line segment for connecting a plurality of the previously insulated insulation structure sections of Fig. 14 to one another;

[0031] Fig. 16, in a representation similar to Fig. 15, shows a variant for connecting the previously insulated insulation structural sections according to Fig. 14 by means of a plurality of contact components in the form of shorter needles, each of these applied contact components connecting at least two previously insulated insulation structural sections to one another; and

[0032] Fig. 17 shows a flow chart for a method for manufacturing a diffractive optical element, in which one of three different characterization methods is used to determine isolation structure sections on the useful surface of the DOE.

[0033] Fig. 1 shows a section of a diffractive optical element (DOE) 1, which can be implemented as a computer-generated hologram (CGH). The DOE 1 can be used in the characterization and, in particular, in the measurement of a surface shape of an optical surface of an optical element (not shown). This optical element can be an optical component of a collector, an illumination optics system, or a projection optics system of a projection exposure system for lithography, in particular for EUV lithography.

[0034] Examples of DOEs and surface shape characterization methods are known from the technical article "Quasi-absolute measurement of aspheres with a combined diffractive optical element as reference" by Simon et al., Applied Optics, Vol. 45, No. 34, 2006, pages 8606 to 8612, the technical article "Redistribution of output weighting coefficients for complex multiplexed phase-diffractive elements" by Liu et al., Optics Express, Vol. 12, No. 19, 2004, pages 4347 to 4352, DE 10 2019 215 707 A1 and the references cited therein. The DOE 1 according to Fig. 1 has first structural sections 2, which are illustrated in Fig. 1 as hatched areas, and second structural sections 3, which are illustrated in Fig. 1 as unfilled, white areas. The first structural sections 2 serve to specify a first optical path length for useful radiation incident on the DOE, which is illustrated in Fig. 1 by an incident beam arrow 4.The second structural sections 3 serve to specify a second optical path length for the useful radiation 4 incident on the DOE 1. The second optical path length differs from the first optical path length specified by the first structural sections 2. This results in a corresponding diffractive effect for the useful radiation 5 emerging from the DOE 1, which is again illustrated by a ray arrow in Fig. 1.

[0035] The two structural sections 2, 3, i.e., the two structural section types, which differ in the specified optical path length, occur alternately or are arranged alternately on a usable area 6 of the DOE 1. The DOE 1 can, in particular, be designed as a binary DOE. The area of ​​the first structural sections 2 across the usable area 6 approximately corresponds to the area of ​​the second structural sections 3. An area ratio between the area of ​​the first structural sections 2 across the usable area 6 and the entire usable area 6 can, for example, be in the range between 0.3 and 0.7. This area ratio can vary in different usable regions of the DOE 1.

[0036] The structural sections 2, 3 have profile details in the range of a few nanometers, for example in the range between 2 nm and 2,000 nm, for example between 2 nm and 10 nm or even between 10 nm and 2,000 nm. Structural variations of the structural sections 2, 3, for example periods or filling levels, typically vary in DOE 1 on length scales in the range between 50 pm and 1 cm, for example between 50 pm and 200 pm or even between 400 pm and 1 cm.

[0037] The design, in particular the areal extent of the structural sections 2, 3, is specified by a mask material on one of the structural section types 2, 3. In the example shown in Fig. 1, this design specification is achieved by applying a mask material to the location of the first structural sections 2. The mask material is made of an electrically conductive material. This mask material is a chromium hard mask.

[0038] As part of an etching manufacturing process during the production of the DOE 1, the second structural sections 3 are etched between the first structural sections 2 predetermined via the hard mask arrangement, so that the optical effect of the second structural sections 3 differs in the desired manner from that of the first structural sections 2 with regard to the predetermined optical path length for the incident useful radiation 4.

[0039] Fig. 2 shows a cross section through adjacent structural sections 2, 3 along a section line II in Fig. 1.

[0040] Head regions of the first structural sections 2, i.e., positive structures, were protected by the mask material during the manufacturing process. A web width of the first structural sections 2 is marked CD (critical dimension) in Fig. 2. A typical etch depth of the second structural sections 3, i.e., the negative structures of the DOE 1, is marked ed (etch depth) in Fig. 2. Micro-trenching regions resulting from the etching process of the second structural sections 3 are marked mt in Fig. 2. Such micro-trenching regions mt can be viewed as a profile deviation from a desired structure, for example, with a rectangular profile. Corresponding desired values ​​can also be defined for the etch depth and the critical dimension. The deviations of the etch depth or the critical dimension from corresponding desired values ​​can be referred to as deltaED or deltaCD.Potential differences caused by unconnected components of structural sections 2 or 3 regularly lead to a deviation from the respective target value in the respective geometric parameters. The deviation may have a different amplitude depending on the parameter under consideration. The potential differences have been observed to lead to deviations in the etch depth (ed) and a profile flank angle (swa, sidewall angle).

[0041] A flank angle of structural flanks between the structural levels N1 and N2, which are defined by the first structural sections 2 and the second structural sections 3, is illustrated at a in Fig. 2. The following applies to the etching depth ed: ed = N1 - N2.

[0042] The desired diffractive effect of the DOE 1 requires a complex distribution of the first structural sections 2 and the second structural sections 3 over the usable area 6 of the DOE 1.

[0043] This distribution regularly results in larger areas of first structural sections 2 and / or second structural sections 3 being interconnected. In particular, this can result in interconnected first isolation structural sections, i.e., first structural sections 2 that are completely isolated from other first structural sections 2 via second structural sections 3. Alternatively or additionally, second isolation structural sections, i.e., areas of second structural sections 3 that are completely isolated from other second structural sections 3 via first structural sections 2, can occur.

[0044] Such first and / or second insulation structure sections may have an undesirable varying effect on the etching depth ed.

[0045] Fig. 3 illustrates the effect of a varying etching depth ed over the entire usable area 6 of a non-inventive embodiment of a DOE 1 in which the variation in the etching depth ed was not compensated. Shown within the usable area 6 are contour lines edi which illustrate the isolines of the etching depth ed. Over a large part of the usable area 6, the etching depth variation is very small and the etching depth remains practically constant across the usable area 6 in these areas. In an area 7 of high etching depth variation, the etching depth ed changes very significantly locally on the usable area 6, which in the contour line representation with the isolines edi has the effect, for example, of a mountain on a map. Such an area 7 of high etching depth variation is undesirable because it has an undesirable varying effect on the diffraction effect of the DOE 1.

[0046] Fig. 4 shows the DOE 1 according to Fig. 3, wherein, instead of a variation of the etching depth ed in the region 7 of high etching depth variation, a design of the first structural sections 2 and the second structural sections 3 is shown. In region 7 of Fig. 3, Fig. 4 shows a concentric arrangement of first structural sections 2i, 1i and an intermediate second structural section 3i. The annular outer first structural section 22 is in turn completely surrounded by a continuous second structural section 32. Beyond the region 7 of high etching depth variation, the structural sections 2, 3 are not shown in Fig. 3.

[0047] It has been shown that regions of high etch depth variation corresponding to region 7 in Figs. 3 and 4 are attributable to corresponding insulation structure sections of the type of structure sections 2i, 3i and 22, namely, on the one hand, interconnected first insulation structure sections 2i or 22, which are completely insulated from other first structure sections 2i via second structure sections 3i and / or 32, and also interconnected second insulation structure sections 3i, which are completely insulated from other second structure sections 32 via first structure sections 2i, 22. In particular, the conductive mask material on the first insulation structure sections 2i, 22 can be at a different electrical potential during the etching of the second structure sections 3 compared to the other first structure sections 2i, which leads to a changed etching behavior in region 7 of high etch depth variation.

[0048] As part of a DOE 1 characterization process, a raw DOE is first provided, which contains the structural data from which the desired DOE 1 is later fabricated. The raw DOE can be a pixelated, binary representation of the DOE, for example, a CGH layout (see the section in Fig. 1). The raw DOE does not necessarily have to be a physically fabricated DOE intermediate.

[0049] Now, interconnected first and / or second structural sections 2, 3 are determined on the raw DOE. From these determined interconnected first and / or structural sections 2, 3, interconnected first insulation structural sections, for example, 2i, 22 in Fig. 4, and / or interconnected second insulation structural sections, for example, 3i in Fig. 4, are determined.

[0050] In the following, different variants for this determination and identification of the insulation structure sections 2i, 3i are explained.

[0051] In one variant, this determination and ascertainment can be performed by pixel-by-pixel examination of an entire binary representation of the first and second structural sections 2i, 3i of the raw DOE. Thus, the binary representation of the structural layout of the raw DOE is examined to determine which structural sections meet the requirements of first insulation structural sections and second insulation structural sections, and these insulation structural sections are then marked on the usable area of ​​the raw DOE. Following this determination, measures can then be taken to prevent undesirable potential differences between the insulation structural sections 2i and 3i, respectively.

[0052] In a further variant of the determination and identification method for the insulation structure sections 2i, 3i, a scaled phase function representation of the first and second structure sections 2i, 3i can be examined. This allows for an approximate scaling of the DOE design. The amount of data to be analyzed can be reduced by a factor of, for example, 10,000 to 250,000 compared to the first variant explained above, without resulting in relevant limitations in the determination of the regions 7 with high etch depth variation. The DOE design is described by the following location-dependent phase function (cp (x, y)): r is the position vector with the coordinates x and y; gj and Wj carry the design information for the structuring of the first and second structural sections 2, 3. W are wave functions and g are the corresponding weight coefficients.

[0053] When scaling the phase function cp, the following scaling approach is chosen: s is the scaling factor. The scale transformation can be performed as simultaneous wavelength and pixel size scaling or as scaling of the wave design of the DOE (s Vk, « v(rs -1 )r), where v represents the wave vector of a respective basis wave function.

[0054] Figures 5 to 8 show the effect of this scale transformation for different scaling factors s for a fixed coordinate xo, yo, which is located in the center of the section of the following figure.

[0055] The section of DOE 1 shown in Figures 5 to 8 is again a section with concentrically arranged first and second structural sections 2i, 3i. The sequence from the center of this concentric structure is exactly the inverse of the sequence explained above in connection with Figure 4. Thus, a second structural section 3i is located at the center of the concentric structure according to Figure 5.

[0056] The first concentric circles starting from this center are, as already explained above in connection with Fig. 4, insulation structure sections 3i and 2i.

[0057] Fig. 5 shows the representation with a scaling factor s of approximately 10. The information about the arrangement and shape of the structural sections 2, 3 has practically not changed compared to the unscaled DOE design at this scaling factor.

[0058] Fig. 6 shows the scaled representation with the phase function cp and a scaling factor s of 21. Here, too, the essential information of Fig. 5 is still preserved.

[0059] Fig. 7 shows the information with a scaling factor s = 84. Here, too, it is still clear that in the center of Fig. 7, an area of ​​high etching depth variation is to be expected.

[0060] Only at a very large scaling factor in the range of 350, which was chosen in Fig. 8, the structure resolution is so weak that the isolation structure sections 2i, 3i, which can still be seen in Figures 5 to 7, are no longer recognizable.

[0061] Up to a scaling factor s in the range between 100 and, depending on the structuring of the raw DOE, 500, scaled phase function representations have proven useful, with which the areas 7 of high etching depth variation over the useful area 6 of the DOE 1 can be determined and identified with high accuracy.

[0062] The scaling factor s is chosen such that a resulting spatial variation of the waves W and the weights g remains smaller than a typical, expected size of an iteration structure section 2i, 3i.

[0063] Within the areas 7 of high etching depth variation found using the scaled phase function cp, an unscaled assignment can then be made, as explained above in connection with the first variant of the determination and assessment procedure.

[0064] With reference to Figures 9 to 12, a further variant of a determination and ascertainment method for interconnected first structural sections 2 and / or second structural sections 3 and the ascertainment of corresponding insulation structural sections 2i, 3i is explained below.

[0065] Fig. 9 again shows a variant of the DOE 1 with first structural sections 2i and second structural sections 3i arranged annularly one inside the other in a section of the usable area 6, as already explained above, for example, with reference to Fig. 5.

[0066] To enable a probability prediction as to whether, for example, an isolation structure section 2i is present on the usable area 6 of the DOE 1 at a location coordinate x, y of the usable area 6, the following merit function S is used: fce[-5,5] s f is the position vector of the considered location x, y; v crepresents a local wave vector corresponding to the wave vector W of the wave representation of the structures of DOE 1 explained above in connection with the phase function cp; k is a vector of integers, which in turn are tuned in the above formula from -5 to 5 for each of the 5 waves. This means that linear combinations up to the 5th order are investigated. Linear combinations of the five different local wave vectors c (c = 1, . . .5) are summed and their lengths are then evaluated. These local wave vectors are also called basis functions.

[0067] A basic idea here is that interconnected first and / or second structural sections 2i, 3i experience additional modulation through beats caused by a slow structural variation. Analogous to the moiré effect, these modulations can be achieved by generating resonances from the linear combinations of the individual waves k.c v c , which define the DOE structures, i.e., the course of the structural sections 2, 3. In the above equation, integer multiples of the local wave vectors v are summed, and their resulting length (Euclidean norm), i.e., the vector residue, is evaluated.

[0068] Figures 10 to 12 show examples of such linear combinations.

[0069] For certain linear combinations, which are shown in Figures 10 and 12, one obtains sum lengths or residuals which are equal to 0 or close to the value 0. The size S of the above merit function increases strongly at these positions xi, yi according to Fig. 10 and X2, y2, according to Fig. 12, because the vector sum £ c k c v c in the denominator of the merit function S.

[0070] The additional sum over k censures that linear combinations with larger integers are weighted less than linear combinations with smaller integer values. This results in a location-dependent hotspot map S(r) over the usable area 6 of DOE 1.

[0071] Fig. 13 shows an example of such a location-dependent hotspot map S(r). At the locations Si, S2, and S3, the merit function S assumes larger values, as illustrated by isolines of the merit function in Fig. 13. The locations Si represent smaller, circular hotspots or candidate regions in which insulation structure sections 2i or 3i may be present. The hotspots S2 are examples of elliptically bordered candidate regions in which insulation structure sections 2i, 3i may occur. The hotspot S3 is an example of a longer-wavelength variation of the parameter F, i.e., a more extensive candidate region in which insulation structure sections 2i, 3i are to be expected. The candidate or hotspot regions Si correspond to the regions 7 of higher etch depth variation explained above in connection with Figures 5 to 8.The hotspot areas Si are also referred to as candidate areas with respect to the occurrence of isolation structure sections 2i, 3i.

[0072] A typical length scale of the hotspot regions Si and the regions 7 with high etch depth variation is in the range of 1 mm to 1 cm. The same applies to the size range of the insulation components 2i, 3i.

[0073] In the determination procedures based on the merit function S according to Figures 9 to 13, linear combinations of basis functions are examined for describing the DOE structural sections assigned to the basis vectors i, which describe the structural sections 2, 3 within the framework of a phase function representation. By evaluating the merit function S, candidate regions Si are determined on the useful area 6 of the DOE 1, in which examined linear combinations of the basis vectors Vi occur, which have vector residuals with lengths below a specified value. Such a default value can, for example, be a vector length less than — a typical basis vector length Vi. By simply thresholding S, a representation with discrete hotspots can be created from the continuous, CGH-location-dependent variation of S.

[0074] In the hotspot areas Si determined in this way, a pixel-by-pixel examination of a binary representation of the first structural sections 2 and the second structural sections 3 of the DOE 1 can then be carried out, i.e. within the determined candidate areas Si.

[0075] In the production of a DOE corresponding to DOE 1 with the first structural sections 2 and the second structural sections 3, which alternate on the usable area 6 of DOE 1, a raw DOE 1R is first produced. This method is also explained below with reference to the flow chart in Fig. 17. Fig. 14 shows an example of such a raw DOE 1R with a usable area 6.

[0076] The raw DOE 1R is provided in a provisioning step 10 (see Fig. 17). Within the scope of this provisioning step 10, design information for the design of the structural sections 2, 3 of the DOE 1 can be input into a DOE design computer, particularly pixel-by-pixel in a bitmap. A bitmap of a corresponding pixel-by-pixel representation can have E 000,000 x E 000,000 pixels. The number of pixels can also be considerably larger.

[0077] The raw DOE 1R is then characterized according to one of the methods described above.

[0078] At the beginning of the characterization process, a test step 11 first decides whether sufficient computing capacity is available for a pixel-by-pixel examination of an entire, in particular binary, representation of the first and second structural sections 2, 3 of the DOE 1. If this is the case, a complete and, in particular, pixel-by-pixel examination of the representation of the first and second structural sections 2, 3 is carried out in an examination step 12, and this involves determining interconnected first and / or second structural sections 2, 3 and, in this way, determining the insulating structural sections 2i, 3i. Insulating structural sections 2i, 3i determined in this way are again reproduced in a region of the usable area 6 of the raw DOE 1R according to Fig. 14 as concentrically nested structural sections 31, 2i, 32, 22, and 3s.After characterization and, in particular, determination of the insulation structure sections 2i, 3i, the manufacturing process involves applying at least one contact component to the raw DOE 1R in an application step 13 (see Fig. 17). Such contact components are explained in more detail below using exemplary embodiments. Following the application 13 of the at least one contact component, the DOE 1 is then completed from the raw DOE 1R with the at least one applied contact component in a completion step 14.

[0079] Fig. 15 shows an example of a correspondingly completed DOE 1 based on the raw DOE 1R according to Fig. 14.

[0080] During application step 13, a contact component 15 in the form of a short-circuit line was applied to the insulating structural sections 2i, 3i in such a way that, in particular, the first, conductive structural sections 2i, 22 connect to a structural section 2 of the DOE 1 that externally surrounds the structural section 3s. Electrical potential differences between the otherwise insulated structural sections 2i, 22 and the surrounding structural section 2 are eliminated via the electrical contacting by the contact component 15.

[0081] In the embodiment according to Fig. 15, the contact component 15 extends to the edge of the usable area 6. This length of the contact component 15 is not mandatory. It is sufficient if the length of the contact component 15 is so long that the first structural sections 2i and 22 are bridged all the way to the surrounding first structural section 2. The contact component 15 therefore connects the interconnected first insulating structural sections 2i and 22, which were completely insulated from the surrounding first structural section 2 via second structural sections 3i, 32 and 3s, to one another and also to the surrounding first structural sections 2. The contact component increasingly also connects the second structural sections 3i, 32 and 3s to one another, which in turn were completely insulated from other second structural sections 3i via the first structural sections 2i and 22.

[0082] The contact component 15 has a length L on the useful surface 6 which is greater than ten times a typical extension S of one of the structural sections 2i, 3i along the contact component 15. The typical extension F of the structural sections 2i, 3i in the example of Figures 14 and 15 is a radial extension of the structural sections 2i, 3i.

[0083] 16 which is an alternative to the application method 13 according to Fig. 15, instead of a long contact component 15, a plurality of shorter contact components 16i are applied to the insulating structural components 2i, 3i in order to remove their insulation and connect them to the surrounding structural sections 2 and 3 respectively. For example, the short contact component 16i connects the conductive first structural section 22 to the surrounding structural section 2. The short contact component 162 ensures the same connection and also connects the two second structural sections 32 and 3s to one another. The short contact component 163 ensures a corresponding connection. The short contact component 164 connects the second structural sections 3i and 32 as well as 3s and also connects the two first structural sections 2i and 22 to one another.The short contact component I65 connects the outermost second structural section 3s with a surrounding second structural section 3. The short contact component I6e connects the first structural component li- with the first surrounding structural component 2. The short contact component I67 connects all structural components 2i, 3i with at least the outer first structural section 2.

[0084] Each of the applied contact components 16i thus connects at least two previously insulated insulation structure sections 2i, 2i+i, 2 or 3i, 3i+i, 3 with each other.

[0085] The short contact components 16i have a length on the useful surface 6 of the DOE 1 that is less than ten times a typical extension of one of the structural sections 2i, 3i along the short contact component 16i.

[0086] As practice has shown, the application of the contact components 15, 16i does not have any significant effect on the diffractive behavior of the DOE 1.

[0087] The produced DOE 1 can then be used to characterize a surface shape of an optical surface of an optical element, as described, for example, in DE 10 2019 215 707 AL

[0088] If the test step 11 shows that an existing computing capacity available for the characterization method would be exceeded in a pixel-by-pixel examination of the structure sections 2, 3 on the entire usable area 6, a further selection step 18 takes place in the characterization method. Here, a selection is made as to whether the determination of the insulation structure sections 2i, 3i or the identification of hotspots 7 or Si, in which such insulation structure sections 2i, 3i can occur, is carried out by examining a scaled phase function representation, which was explained above with reference to Figures 5 to 8, or by examining linear combinations of basis vectors of the phase function representation assigned to basis functions, as described above in connection with Figures 9 to 13.

[0089] In the first case, a scaling step 19 of the phase function cp is performed first, followed by a cluster analysis, i.e., an examination of the correspondingly scaled phase function representation for the presence of existing insulation structure sections. This occurs in an examination step 20. Following this, the contact components 15 and 16 are applied in application step 13, respectively, and the DOE 1 is completed 14, as already explained above.

[0090] In the other case, after the selection step 18, a hotspot detection is performed based on examined linear combinations using the merit function S, as explained above with reference to Figures 9 to 13. This occurs in a linear combination detection step 21 for determining the hotspot areas Si, as explained above in connection with Figures 9 to 13.

[0091] After the linear combination detection step 21, an examination step 22 is carried out again on the basis of a cluster analysis of the hotspot areas Si and, on the basis of the insulation structure sections 2i, 3i thus determined, the application step 13 and the completion step 14 for the DOE 1, as already explained above.

Claims

Patent claims 1. Method for characterizing a diffractive optical element (DOE) (1, 1R), comprising - first structural sections (2) for specifying a first optical path length for useful radiation (4) incident on the DOE (1), - second structural sections (3) for specifying a second optical Path length for useful radiation (4) incident on the DOE (1), which differs from the first optical path length, - wherein the first and second structural sections (2, 3) are arranged on a Usable area (6) of the DOE (1) occur alternately, with the following steps: - Providing (10) a raw DOE (1R), - Determining first structural sections (2) and / or second structural sections (3) connected to one another on the raw DOE (1R), - Determining from these specific interconnected first structural sections (2) and / or second structural sections (3): — interconnected first insulation structural sections (20) which are completely isolated from other first structural sections (2i, 2) via second structural sections (30), and / or — interconnected second insulation structural sections (30) which are completely insulated from other second structural sections (3i, 3) via first structural sections (20).

2. Method according to claim 1, characterized in that the determination of the interconnected first structural sections (2) and / or second structural sections (3) and the determination of the insulating structural sections (2i, 30) are carried out by examining (12) a binary representation of the first structural sections (2) and the second structural sections (3).

3. Method according to claim 1 or 2, characterized in that the determination of the interconnected first structural sections (2) and / or second structural sections (3) and the determination of the isolation structural sections (2i, 30) are carried out by examining (19, 20) a scaled phase function representation (cp) of the first structural sections (2) and the second structural sections (3).

4. Method according to claim 1 or 2, characterized in that the determination of the interconnected first structural sections (2) and / or second structural sections (3) and the determination of the insulation structural sections (2i, 30 by - examining (21) linear combinations of basis vectors assigned to basis functions, which describe the structural sections (2, 3) in the context of a phase function representation, - Determination of candidate areas (S0 on the usable area (6) of the Raw DOE (1R), in which investigated linear combinations occur that have vector residuals with lengths below a specified value, - Examining (22) a binary representation of the first structural sections (2) and the second structural sections (3) within the candidate areas (S0). Method for producing a diffractive optical element (DOE) (1), comprising - first structural sections (2) for specifying a first optical path length for useful radiation (4) incident on the DOE (1), - second structural sections (3) for specifying a second optical Path length for useful radiation (4) incident on the DOE (1), which differs from the first optical path length, - wherein the first and second structural sections (2, 3) are arranged on a Usable area (6) of the DOE (1) occur alternately, with the following steps: - Providing (10) and producing a raw DOE (1R); - carrying out the characterization method according to one of claims 1 to 4 for the raw DOE (1R); - applying (13) at least one contact component (15; 160) to the raw DOE (1R), which — at least two interconnected first insulation structural sections (20) determined by means of the characterization method, which were completely isolated from other first structural sections (2i, 2) via second structural sections (3i, 3), and / or — connecting at least two interconnected second insulation structural sections (30) determined by means of the characterization method, which were completely isolated from other second structural sections (3i, 3) via first structural sections (2i, 2); - Completing (14) the DOE (1) from the raw DOE (1R) with the at least one applied contact component (15; 160. Method according to claim 5, characterized in that at least one of the contact components (15; 16?) is applied such that it connects more than two previously insulated insulation structural sections (2i, 22, 3i, 32, 3s) to one another. Method according to claim 5 or 6, characterized in that the contact component (15) has a length on the useful surface (6) that is greater than ten times a typical extension (S) of one of the structural sections (2, 3) along the contact component (15). Method according to one of claims 5 to 7, characterized in that a plurality of the contact components (16i) are applied such that in each case one of the applied contact components (160) connects at least two previously insulated insulation structural sections (2i, 22; 3i, 32; 32, 3s) to one another.Method according to one of claims 5 to 8, characterized in that the contact components (160) have a length on the useful surface (6) that is less than ten times a typical extension of one of the structural sections (2, 3) along the contact component (160). Diffractive optical element (DOE) (1) produced by a method according to one of claims 5 to 9. Method for characterizing a surface shape of an optical surface of an optical element, carried out by means of a DOE (1) according to claim 10.

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