Optical diffractive element for suppressing at least one target wavelength by destructive interference

Abstract

An optical diffractive element for suppressing at least one target wavelength by destructive interference. The optical diffractive element has at least three diffractive structure levels. The levels of diffractive structures (N1, N2, N3, N4) may be assigned to at least two groups of diffractive structures. A first of the group of diffractive structures is used to suppress a first target wavelength [lambda] 1. A second one of the group of diffractive structures is configured to suppress a second target wavelength [lambda] 2. For the two target wavelengths [lambda] 1 and [lambda] 2, the following conditions are satisfied: ([lambda] 1-[lambda] 2) 2 / ([lambda] 1 + [lambda] 2) 2lt; and 20%. The morphology of the level of diffraction structures may be described as a superposition of two binary groups of diffraction structures. A boundary region between adjacent surface sections of each of the binary diffractive structure groups has a linear path, and sections along the linear path at most overlap each other. The result is an optical diffractive element with an extended possibility of use, in particular for stray light suppression.

Description

[0001] This application is a divisional application of Chinese Patent Application (Application No.: 202080009374.3, Application Date: January 14, 2020, Invention Title: Optical Diffraction Element for Suppressing at Least One Target Wavelength by Destructive Interference).

[0002] This patent application claims priority to German Patent Applications DE 10 2018 220 629.5 and DE 10 2019 210 450.9, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to an optical diffraction element for suppressing at least one target wavelength by destructive interference. Furthermore, the present invention relates to an extreme ultraviolet light (EUV) collector of a projection exposure apparatus including such an optical diffraction element, an illumination system including such an EUV collector, an optical system including such an illumination system, a projection exposure apparatus including such an optical system, a method for manufacturing a structured element by means of such a projection exposure apparatus, and a structured element manufactured in this way. Background Art

[0004] An EUV collector comprising an optical diffractive element in the form of a grating is known from WO 2017 / 207401 A1 and from WO 2014 / 114405 A2. Embodiments of gratings for suppressing infrared (IR) wavelengths in EUV projection exposure apparatuses are known from the following publications: "Multilayer EUV optics with integrated IR-suppression gratings", T. Feigl et al., 2016 EUVL Workshop, Berkeley, June 13 - 16, 2016. EP 1 540 423 B1 describes a grating-based spectral filter for suppressing radiation outside the band used in EUV lithography systems. US 2014 / 0131586 A1 describes a phase grating for a mask inspection system. DE 10 2009 044 462 A1 describes an optical filter element comprising a grating structure for diffracting infrared radiation within an EUV illumination system. The technical articles "Multilevel blazed gratings in resonance domain: an alternative to the classical fabrication approach", M. Oliva et al., OPTICS EXPRESS, Vol. 19, No. 15, 2011, pp. 1473 - 1475, and "Highly efficient three-level blazed grating in the resonance domain", M. Oliva et al., OPTICS LETTERS, Vol. 35, No. 16, 2010, pp. 2774 - 2776 describe different variants of blazed gratings. The technical article "Diffractive elements designed to suppress unwanted zeroth order due to surface depth error", V. Kettunen et al., Journal of Modern Optics, Vol. 51, No. 14, 2004, pp. 2111 - 2123 discloses diffractive elements for suppressing unwanted zeroth order diffraction due to profile depth error.

[0005] DE 195 16 741 A1 discloses an optically effective diffractive structure arrangement. DE 100 54 503 A1 discloses an optical diffractive binary grating structure. WO 2007 / 031 992 A1 discloses a diffractive grating with a spatially varying duty cycle.

[0006] The grating can be used to suppress stray light whose wavelength deviates from the wavelength of the light used. Then, this stray light can be diffracted by the grating towards a light trap (beam dump), while the light used takes a different path. Summary of the Invention

[0007] The object of the present invention is to develop an optical diffractive element of the type mentioned above, such that its scope of use is extended, in particular, to the suppression of stray light.

[0008] This object is achieved according to a first aspect of the invention by means of an optical diffractive element which

[0009] - comprises a periodic grating structure profile having three diffractive structure levels, the periodic grating structure profile comprising diffractive structures,

[0010] - predefines different structural depths relative to a reference plane,

[0011] - wherein the diffractive structures are arranged such that the wavelength range near a first target wavelength λ1 in the infrared wavelength range (which is diffracted by the grating structure profile) has radiation components which have at least three different phases that cancel each other out in the zero and / or + / − first order diffraction at least at the first target wavelength λ1,

[0012] - wherein the diffractive structure levels predefine the topography of the grating period of the grating structure profile which regularly repeats along a periodic travel direction,

[0013] - wherein the diffractive structure levels comprise:

[0014] -- a neutral diffractive structure level which corresponds to a reference height of zero,

[0015] -- a positive diffractive structure level which is set to an optical path length that is λ1 / 4 + / - 20% higher than the neutral diffractive structure level, and

[0016] -- a negative diffractive structure level which is set to an optical path length that is λ1 / 4 + / - 20% lower than the neutral diffractive structure level.

[0017] A wavelength range to be suppressed near the target wavelength λ1 can be selected to cover multiple wavelengths to be suppressed, such as different wavelengths of pre-pulses and main pulses of an EUV plasma light source.

[0018] In the case of the optical diffraction element according to this first aspect, first, the positive diffraction structure layer and secondly, the negative diffraction structure layer are implemented to have a tolerance range of up to 20% near an optical path length difference of λ1 / 4 with respect to the neutral diffraction structure layer. This tolerance can also be less than + / - 20% compared to the path length difference λ1 / 4 and can be, for example, + / - 10%, + / - 5%, + / - 3%, + / - 2% or even + / - 1%.

[0019] In the case of the optical diffraction element according to this first aspect, the grating period of the grating structure profile can be subdivided into four period segments of the diffraction structure layer. Two of the four period segments can be implemented as neutral diffraction structure segments with a neutral diffraction structure layer. One of the four period segments can be implemented as a positive diffraction structure segment with a positive diffraction structure layer. One of the four period segments can be implemented as a negative diffraction structure segment with a negative diffraction structure layer. In the case of this embodiment of the optical diffraction element, the two neutral diffraction structure layers can be arranged in the grating period in such a way that they are separated from each other by the positive diffraction structure layer or by the negative diffraction structure layer. The separation of the two neutral diffraction structure layers from each other realizes the sequence of the diffraction structure layers, in which, in the period travel direction, there are an equal number of descending edges or sidewalls (structure depth increases, edge "towards the valley") and ascending edges or sidewalls (structure depth decreases again, edge "towards the peak") each having a comparable structure height difference with respect to each other. Then, first, the descending edge and secondly, the ascending edge compensate for each other with respect to possible phase errors, thereby reducing or completely avoiding the entire phase error that may originate from undesired edge structuring and / or undesired edge positions.

[0020] Optionally, the two neutral diffraction structure layers can also be directly arranged in sequence in the grating period as a neutral diffraction structure layer with twice the length.

[0021] The grating period of the grating structure profile can be subdivided such that the four period segments therein can have equal lengths along the period travel direction, where if the lengths differ from each other by less than + / - 20%, they are considered to have equal lengths. Such an optical diffraction element produces a particularly good destructive interference suppression effect for the target wavelength. The lengths of the four period segments can deviate from each other by less than 20%, for example, less than 15%, less than 10%, less than 5%, less than 2% or even less than 1%. The lengths of the four period segments can also be exactly equal.

[0022] The grating period of the grating structure profile can be subdivided such that the four period segments therein can have the following sequence: a positive diffraction structure level, a neutral diffraction structure level, a negative diffraction structure level, a neutral diffraction structure level. Such a sequence of period segments has been found to be particularly suitable. The corresponding sequence can be achieved by cyclically permuting the sequence indicated above, thus obtaining the following sequence, for example: a neutral diffraction structure level, a positive diffraction structure level, a neutral diffraction structure level, a negative diffraction structure level.

[0023] The following sequence of four period segments is also possible: a negative diffraction structure level, a neutral diffraction structure level, a positive diffraction structure level, a neutral diffraction structure level. Cyclic permutation is also possible in this variant.

[0024] The following additional variant can be used as the sequence of the four period segments: a neutral diffraction structure level, a neutral diffraction structure level; a positive diffraction structure level, a negative diffraction structure level. Here, therefore, two neutral diffraction structure levels exist directly adjacent to each other, being a common neutral diffraction structure level of particularly twice the length. For example, cyclic permutation is also possible in this variant.

[0025] In the case of an optical diffraction element according to this first aspect, the arrangement of the diffraction structures can be such that a target wavelength range of a target wavelength (which is diffracted by the grating structure profile) included in the infrared wavelength range has radiation components that have at least three different phases that cancel each other out in the zero and / or + / - first order diffraction of the first target wavelength, where the target wavelength range includes, in addition to the first target wavelength λ1, a second target wavelength λ2 different therefrom, where the arrangement of the diffraction structures is such that a wavelength range near the second target wavelength (which is diffracted by the grating structure profile) in the infrared wavelength range also has radiation components that have at least three different phases that cancel each other out in the zero and / or + / - first order diffraction of the first target wavelength, where the target wavelength range includes, in addition to the first target wavelength, a target wavelength different therefrom, where the arrangement of the diffraction structures is such that a wavelength range near the second target wavelength (which is diffracted by the grating structure profile) in the infrared wavelength range has radiation components that have at least three different phases that cancel each other out in the zero and / or + / - first order diffraction of the second target wavelength, where for the two target wavelengths λ1 and λ2 the following holds: (λ1 - λ2) 2 / (λ1 + λ2) 2 < 20%. The advantages of such an optical diffraction element correspond to those already explained above.

[0026] For the upper limit value characterizing the difference between the two target wavelengths, it can hold that: (λ1 - λ2) 2 / (λ1 +λ2) 2 < 10%, < 5%, < 2%, < 1%, < 0.5%, < 0.2%, < 0.1% or even < 0.05%. For example, the upper limit value can be 0.037%. The upper limit value can also be significantly smaller, such as 0.0002%. The two target wavelengths suppressed by at least two diffraction structure groups of the optical diffraction element can be exactly the same. The deviation (λ1 - λ2) characterizing the difference between the two target wavelengths 2 / (λ1 + λ2) 2 can be greater than 0.0001%, can be greater than 0.001%, can be greater than 0.01%, can be greater than 0.1%, can be greater than 0.2%, can be greater than 0.5%, can be greater than 0.7% and can even be even greater.

[0027] The target wavelength can be in the IR wavelength range, for example, in the range of the general emission wavelength of a carbon dioxide (CO2) laser at 10.6 μm. Alternatively or in addition, wavelengths in the near-infrared (NIR) wavelength range, in the visible wavelength range, in the ultraviolet (UV) wavelength range or in the deep ultraviolet (DUV) wavelength range can constitute the target wavelengths to be suppressed. One of the two target wavelengths can be 10.2 µm, and the other of the two target wavelengths can be 10.6 µm. The target wavelength can be adapted to the wavelengths of the pre-pulse and the main pulse of an EUV plasma light source.

[0028] The design of at least two diffraction structure groups for suppressing two different target wavelengths results in the suppression of wavelengths within a predefinable wavelength bandwidth, which can also be referred to as the suppression design bandwidth. The wavelengths located within this suppression design bandwidth (i.e., those that can be effectively suppressed by the optical diffraction element) can correspond to the target wavelengths, and / or can be between the target wavelengths, and / or can be outside the wavelength range between the target wavelengths. To suppress the wavelength of 10.2 μm, for example, the first target wavelength targeted by the design of the first diffraction structure group can be 10.25 μm, and the second target wavelength targeted by the design of the second diffraction structure group can be 10.55 µm. The target wavelengths are selected depending on the requirements of the optical diffraction element for suppressing multiple different wavelengths or wavelength bandwidths as needed. In this case, in addition to the target wavelengths, the positions of additional minima of destructive interference can also be taken into account, or which wavelengths are deliberately not to be suppressed can be considered.

[0029] Those discussed above in connection with the optical diffraction element can hold here for the selection of the target wavelengths λ1 and λ2.

[0030] The foregoing object is achieved according to a second aspect of the invention by an optical diffraction element that suppresses at least one target wavelength by destructive interference, said optical diffraction element

[0031] - comprises at least three diffraction structure levels, which define different structural depths relative to a reference plane,

[0032] - wherein said three diffraction structure levels can be assigned to at least two diffraction structure groups,

[0033] - wherein a first group of said diffraction structure groups is implemented to suppress a first target wavelength λ1 in the zero-order diffraction, and

[0034] - wherein a second group of said diffraction structure groups is implemented to suppress a second target wavelength λ2 in the zero-order diffraction,

[0035] - wherein for said two target wavelengths λ1 and λ2 the following holds:

[0036] - wherein the topography of said diffraction structure levels can be described as a superposition of two binary diffraction structure groups,

[0037] - wherein each of said binary diffraction structure groups has:

[0038] -- a first surface section having a first structural depth;

[0039] -- a second surface section having a second structural depth, which alternates with said first surface section along a traveling direction,

[0040] - wherein the boundary region between adjacent surface sections of each of said binary diffraction structure groups has a linear course, wherein

[0041] -- a first boundary region of the first of said two binary diffraction structure groups, and

[0042] -- a second boundary region of the second of said two binary diffraction structure groups

[0043] -- at most the sections along their linear courses are superposed on one another.

[0044] An optical diffraction element using at least three diffraction structure levels (which in turn can be assigned to at least two diffraction structure groups for suppressing corresponding target wavelengths not far from each other) surprisingly produces an improvement in the suppression of target wavelengths significantly beyond the suppression effects of individual diffraction structure groups. Compared with the optical diffraction elements of the prior art, this provides a design freedom that can be used to enhance the flexibility of the usage possibilities of the optical diffraction element. The different diffraction structure groups can occupy the same optically used area of the optical diffraction element, that is, they do not have to be arranged on mutually separated sections of the aforementioned optically used area. The optical diffraction element can in particular be designed such that the two diffraction structure groups are designed specifically for suppressing the same target wavelength or stray light wavelength. Alternatively or additionally, the optical diffraction element can be designed specifically for suppressing multiple target wavelengths by means of an appropriate design of the diffraction structure groups. In the case of such an optical diffraction element comprising multiple diffraction structure groups, it has been found that the diffraction effect is improved compared with an optical diffraction element comprising only one diffraction structure group. By using an optical diffraction element comprising multiple diffraction structure groups, the same suppression effect can thus be achieved with looser manufacturing tolerances compared with the prior art.

[0045] A diffraction structure group is an arrangement of at least two diffraction structure levels that are set up and fabricated for suppressing only one target wavelength. An example of a diffraction structure group is an optical grating. The assignment rule of the at least three diffraction structure levels to at least two diffraction structure groups is such that at least one diffraction structure level is assigned to multiple diffraction structure groups.

[0046] The optical diffraction element according to the first aspect initially discussed may also comprise at least one or at least two diffraction structure groups of this type.

[0047] The advantages in terms of the maximum difference between the two target wavelengths correspond to those already explained above. Those already discussed above in connection with the optical diffraction element according to the first aspect can be established here for the selection of the target wavelengths λ1 and λ2.

[0048] For the second target wavelength λ2, the latter also holds through destructive interference weakening or suppression due to an appropriate design of the diffraction structure of the optical diffraction element.

[0049] The optical diffraction element can comprise exactly three diffraction structure levels and can comprise exactly two diffraction structure groups. Alternatively, the optical diffraction element can also comprise more than three diffraction structure levels (such as four, five, six or even more diffraction structure levels) and correspondingly also comprise more than two diffraction structure groups.

[0050] A binary structure is a structure comprising positive structures ("peaks") and negative structures ("valleys"), wherein the total area of ​​the positive structures corresponds to the total area of ​​the negative structures within a predefined tolerance. The difference between the total area of ​​the first positive structure and the second negative structure may be less than 20%, less than 10%, less than 5%, less than 2% and also less than 1%. The total areas may also be completely identical.

[0051] Since the boundary region of the first binary structure and the second binary structure at most overlaps with each other along the linear path of the boundary region, it is possible to produce the optical diffraction element by means of a relatively simple to produce photolithographic mask structure. This provides the possibility of accurately producing the optical diffraction element, wherein firstly narrow tolerances are met for the area of ​​the diffraction structure levels and also for their structure depth. In particular, it is possible to produce diffraction structure groups with a desired large and desired precise sidewall steepness of the boundary region.

[0052] The optical diffraction element can be manufactured so that a rising boundary region (ie, a rising level side wall) is assigned a falling boundary region with the same structural depth (ie, the same structural height difference).

[0053] Furthermore, the optical diffractive element according to the second aspect may have the features which have been discussed above with reference to the optical diffractive element according to the preceding claims.

[0054] In the case of the optical diffraction element, the first boundary region of the first of the two binary diffraction structure groups and the second boundary region of the second of the two binary diffraction structure groups can run completely separated from each other. Such a completely separated path of the boundary regions further simplifies the photolithographic production of the optical diffraction element, in particular.

[0055] The first group in the group of diffraction structures can be implemented as a first diffraction grating provided on the grating surface. The aforementioned first diffraction grating can have a first grating period and a first structure depth, which is the optical path difference between the first diffraction positive structure and the first diffraction negative structure, measured perpendicular to the surface section of the grating surface respectively surrounding these first structures. The second group in the group of diffraction structures can be implemented as a second diffraction grating provided on the grating surface. Such a second diffraction grating can have a second grating period and a second structure depth, which is the optical path difference between the second diffraction positive structure and the second diffraction negative structure, measured perpendicular to the surface section of the grating surface respectively surrounding these second structures. Regarding such an embodiment, compared with the gratings of the prior art, a grating using at least two diffraction gratings having substantially independent grating periods from each other and substantially independent structure depths (where the structure depth is small compared to the grating period, at least in the case of one of the diffraction gratings) provides a design freedom that can be used to enhance the flexibility of the usage possibilities of the grating. The two diffraction gratings can occupy the same grating surface, in other words, they are not provided on separated sections of the grating surface. Therefore, the two diffraction gratings exist in a superposed manner on the grating surface. The grating can be designed such that its stray light suppression is improved by the two diffraction gratings designed to suppress equivalent stray light wavelengths. Optionally or additionally, the grating can be designed such that multiple stray light wavelengths can be suppressed. Moreover, it has been unexpectedly found that by using such a grating including multiple diffraction gratings, compared with a grating including only one diffraction grating, the diffraction effect (especially the suppression effect due to the destructive interference in the zero-order diffraction) is improved. The same suppression effect can thus be achieved with a loose manufacturing tolerance by using a grating including multiple diffraction gratings.

[0056] The grating can be implemented as a reflective grating, but alternatively can also be implemented as a transmissive grating and, for example, as a phase grating.

[0057] The grating surface can be implemented as a plane or a curved surface, such as a convex surface or a concave surface. The grating surface can be, for example, part of an optical surface of an optical element having some other optical functions in addition to a beam collector or a mirror. The first diffraction grating and / or the second diffraction grating can be implemented as a binary grating, where the surface area of the positive structure is equal to the surface area of the negative structure. In the simplest case, the structure depth can be the height difference between the corresponding diffraction positive structure and the associated diffraction negative structure.

[0058] The grating can be additionally provided with a highly reflective layer, and especially an optional auxiliary layer for protecting the grating and / or the highly reflective layer. The highly reflective layer can be implemented as a multilayer. The highly reflective layer can be implemented for EUV light, especially in the wavelength range between 5 nm and 30 nm.

[0059] The optical diffraction element can be implemented as a multi-level diffraction grating with corresponding levels of the set diffraction structure.

[0060] In this case, the structural depth can be one-sixth of the target wavelength. With the multi-level grating fabricated accordingly, the structural depth can also be one-fourth of the target wavelength.

[0061] Depending on the number m of different levels of the diffraction structure, depending on the target wavelength λ N the structural depth can be: b = λ N / (2m).

[0062] The grating period can be in the millimeter range and can be, for example, 1 mm or 2 mm.

[0063] The levels of the diffraction structure can be implemented as flat surfaces.

[0064] The grating periods of different diffraction gratings can be in integer ratios to each other. The grating periods can have a defined phase shift with respect to each other.

[0065] The ratio of the grating periods can be 1:2. By using three diffraction gratings, the ratio of the grating periods can be 1:2:4 or 1:2:2.

[0066] The surface area ratio of the surface area of the first diffraction positive structure to the surface area of the first diffraction negative structure can be in the range between 0.9 and 1.1. The surface area ratio of the surface area of the second diffraction positive structure to the surface area of the second diffraction negative structure can be in the range between 0.9 and 1.1. Correspondingly, an accurate binary diffraction structure group is obtained.

[0067] The ratio between the first grating period and the first structural depth can be greater than 10. The ratio between the second grating period and the second structural depth can be greater than 10.

[0068] Correspondingly, different target wavelengths can be suppressed. In addition to the two target wavelengths λ1 and λ2, further target wavelengths that deviate more significantly can thus also be suppressed. For example, different target wavelengths in the infrared wavelength range and additional target wavelengths in the ultraviolet wavelength range can possibly be suppressed simultaneously.

[0069] The period ratio of the first grating period to the second grating period can be in the range between 0.9 and 1.1.

[0070] An optical diffraction element with such a period ratio can be well fabricated. The grating periods of the first and second diffraction gratings can be exactly equal, but can also be different.

[0071] Such an advantageous combination of the optical diffraction element, especially for good reflection conditions at EUV wavelengths, enables good suppression of stray light including higher wavelengths in the case of the second diffraction grating.

[0072] The structural depth ratio of the structural depth of the first diffraction grating to the structural depth of the second diffraction grating can be in the range between 0.9 and 1.1. The structural depths of the first and second diffraction gratings can be different from each other, but can also be equal. In the range between 1.1 and 20, a significantly larger structural depth ratio between the two diffraction gratings is also possible, such as a structural depth ratio near 10.

[0073] In the case of an optical diffraction element comprising two diffraction gratings arranged on the grating surface, the first grating period can travel along the first period traveling direction of the first diffraction grating, and the second grating period can travel along the second period traveling direction of the second diffraction grating, where the two period traveling directions can travel non-parallel to each other. Such an optical diffraction element in which the period traveling directions of the first and second diffraction gratings do not travel parallel to each other has been proven to be worthy of adoption. The minimum angle between the period traveling directions can be 90°, such that the two period traveling directions are perpendicular to each other. Smaller minimum angles (e.g., in the range of 60°, 55°, 45°, or 30°) are also possible.

[0074] Alternatively, embodiments of optical diffraction elements in which the two period traveling directions of at least two diffraction structure groups travel parallel to each other are also possible.

[0075] An optical diffraction element comprising two diffraction gratings arranged on the grating surface can comprise at least one additional diffraction grating arranged on the grating surface. The aforementioned additional diffraction grating can comprise an additional diffraction positive structure and an additional diffraction negative structure, where the surface area ratio of the surface area of the additional diffraction positive structure to the surface area of the additional diffraction negative structure is in the range between 0.9 and 1.1. The aforementioned additional diffraction grating has an additional grating period and an additional structural depth, which is the optical path difference measured between the additional diffraction positive structure and the additional diffraction negative structure, perpendicular to the surface section of the grating surface respectively surrounding these additional structures. Such an optical diffraction element comprising at least one additional diffraction grating is correspondingly further improved in terms of available design freedom. At least two of the period traveling directions of at least three diffraction gratings can have mutually different directions. Alternatively, all of the period traveling directions of the at least three diffraction gratings can also be possible to travel parallel to each other.

[0076] In the case of an optical diffraction element including a first diffraction grating, a second diffraction grating and additional diffraction gratings are both provided on the grating surface, and the ratio between the additional grating period and the additional structure depth can be greater than 10. The period ratio between the first grating period and the additional grating period can be in the range between 0.9 and 1.1. The first grating period can travel along a first period traveling direction of the first diffraction grating, and the additional grating period can travel along an additional period traveling direction of the additional diffraction grating, where the two period traveling directions do not travel parallel to each other.

[0077] The advantages of such an optical diffraction element correspond to those already explained above. The grating periods of the first diffraction grating and the additional diffraction gratings can be equal, but can also be different. A corresponding period ratio within the range between 0.9 and 1.1 or equal grating periods can also exist between the second diffraction grating and at least one additional diffraction grating.

[0078] The ratio of the structural depth of the first diffraction grating to that of the additional diffraction grating can be in the range between 0.9 and 1.1; the structural depths of the first and additional diffraction gratings can be different from each other, but can also be equal. A corresponding structural depth ratio within the range between 0.9 and 1.1 or equal structural depths can also exist between the second diffraction grating and at least one additional diffraction grating. A significantly larger structural depth ratio between the additional diffraction grating and the structural depth of the first and / or second diffraction grating within the range between 1.1 and 20 (for example, around 10) is also possible.

[0079] The minimum angle between the period traveling directions of the first diffraction grating and the additional diffraction grating can be in the range between 20° and 25°. Some other minimum angles (for example, within the range between 10° and 80°) are also possible. A corresponding traveling direction angle can also exist between the period traveling direction of the second diffraction grating and the period traveling direction of at least one additional diffraction grating.

[0080] The surface areas of the diffraction positive structures and diffraction negative structures of the various diffraction structure groups can have an equal contribution to the entire grating surface. Such an equal surface area contribution in particular results in a binary grating for different diffraction structure groups of the optical diffraction element. This ensures high stray light suppression in the region of zero-order diffraction in the case of a proper design of the optical diffraction element.

[0081] The characteristics of the optical diffraction element in the two aspects discussed above can also be combined with each other.

[0082] An optical diffraction element of the type of at least one of the two aspects discussed above can be manufactured by a mask etching method in which at least one mask structure is used. A plurality of mask structures different in terms of the positions of their mask regions and / or mask gaps can also be used. Then, the substrate can be etched by sequentially using these different masks or by shifting the same mask structure in at least two sequential etching steps. Three or more different mask structures can also be used in such a mask etching method for manufacturing an optical diffraction element.

[0083] The advantages of a collector or collector mirror of an optical diffraction element that can be used in a projection exposure apparatus, in particular in an EUV projection exposure apparatus, and has the properties described above correspond to those already explained above with reference to the optical diffraction element. These advantages are particularly evident in the case of use associated with an EUV light source (wherein a plasma is initiated by a laser-induced discharge). The collector or the collector mirror can be an EUV collector / collector mirror for a wavelength range of particularly between 5 nm and 30 nm, and / or a deep ultraviolet (DUV) collector / collector mirror, i.e., a collector mirror for a wavelength range of particularly between 150 nm and 250 nm.

[0084] This applies in particular to an EUV collector mirror, wherein the collector mirror is implemented in such a way as to direct EUV radiation towards a focus region, and wherein the optical diffraction element is implemented in such a way as to direct radiation of at least one target wavelength away from the focus region. The radiation of the at least one target wavelength is also referred to as stray light.

[0085] The illumination system can include such a collector, in particular an EUV collector, and an illumination optical unit for illuminating an object field in which an object to be imaged can be disposed. Light used in DUV or EUV can be used as illumination light. The advantages of such an illumination system correspond to those already explained above with reference to the collector according to the invention. The light used is not precisely suppressed by the optical diffraction element, i.e., has a wavelength different from the stray light to be suppressed.

[0086] The illumination system can be fabricated with an optical diffraction element implemented as described above in order to obtain a uniform distribution of the stray light in the region of the stray light removal position and, for example, in the region of a light beam stack provided for this purpose. Alternatively or additionally, it is possible to ensure a predefined distribution function of the light used, particularly in a specified section of the illumination beam path of the illumination system (e.g., in the region of the pupil plane).

[0087] The optical system may include such an illumination system, as well as a projection optical unit for imaging an object field into an image field, where the substrate may be disposed in the image field, and where a section of the object to be imaged can be imaged onto the substrate. The projection exposure apparatus may include such an optical system and a light source, in particular an EUV light source. To manufacture a structured element, a mask blank and a wafer may be provided. The structures on the mask blank may be projected onto the photosensitive layer of the wafer by means of such a projection exposure apparatus. Thus, microstructures and / or nanostructures may be manufactured on the wafer. The advantages of such an optical system, such an projection exposure apparatus, such a manufacturing method and such a microstructured and / or nanostructured element correspond to those already explained above with reference to the collector according to the invention.

[0088] As long as an EUV light source is used, it may include a pump light source for producing a plasma that generates EUV wavelengths. The pump light source may be implemented to produce a pre-pulse with a pre-pulse light wavelength and to produce a main pulse with a main pulse light source. The pre-pulse light wavelength may be different from the main pulse wavelength. In the case of the pump light source of the EUV light source of the projection exposure apparatus, the corresponding difference between the wavelengths of the pre-pulse light first and the main pulse light second may have the upper limit value and / or the lower limit value already explained above in connection with the target wavelengths λ1 and λ2.

[0089] In particular, semiconductor elements (such as memory wafers) may be manufactured using the projection exposure apparatus.

[0090] In particular, during the manufacture of the structured element, light in a wavelength range may be irradiated onto the collector such that light with a first wavelength λ1 diffracts away from the focal region of the collector. The first wavelength λ1 may be within the wavelength range and may be within the infrared wavelength range. Such a wavelength range may include radiation components that include at least three different phases that interfere destructively with each other at at least one diffraction order. Such at least one diffraction order may be the zero-order diffraction of the first wavelength λ1, the positive first-order diffraction of the first wavelength λ1, or the negative first-order diffraction of the first wavelength λ1. The wavelength range may also include a second wavelength λ2, and the method may also include diffracted light with such a second wavelength λ2 that is away from the collector focal region. The second wavelength λ2 may be different from the first wavelength λ2 and may be within the infrared wavelength range. The wavelength range may include a radiation component that includes at least three additional different phases that interfere destructively with each other at at least one diffraction order, and such at least one diffraction order may be the zero-order diffraction of the second wavelength λ2, the positive first-order diffraction of the second wavelength λ2, and the negative first-order diffraction of the second wavelength λ2. Description of the Drawings

[0091] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. In the said drawings:

[0092] Figure 1 Schematically shows a projection exposure apparatus for EUV microlithography technology;

[0093] Figure 2 Shows details of the light source of the projection exposure apparatus in the environment of an EUV collector of a field splitter mirror of an illumination optical unit for guiding the light used for EUV from a plasma source region to the projection exposure apparatus, where the EUV collector is illustrated in a meridional cross section;

[0094] Figure 3 In comparison with Figure 2 A more abstract illustrative drawing shows the guiding of the light used for EUV and its secondary stray light components of different wavelengths in the case of reflection / diffraction at the EUV collector;

[0095] Figure 4 Shows a plan view of a section of a grating surface of a grating that includes two diffraction gratings as a group of diffraction structures having mutually perpendicular periodic traveling directions and equal grating periods, where the structural depths of three diffraction structure levels of a diffraction structure predefined as a square in Figure 4 are illustrated by different thin line types, where the grating constitutes an embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference;

[0096] Figure 5 Shows in a graph the wavelength-dependent reflectivity R of a grating according to Figure 4 for the calculated ideal case, for another calculated more practical case, and for a reference grating not according to the present invention, where two diffraction gratings of the grating are implemented to suppress two different wavelengths;

[0097] Figure 6 In comparison with Figure 5 A similar graph shows the relationship in the case of a grating according to Figure 4 where two diffraction gratings have equal structural depths such that the grating is implemented to suppress only one wavelength;

[0098] Figure 7 In comparison with Figure 4 A similar illustrative drawing shows another embodiment of a grating that includes two diffraction gratings as a group of diffraction structures having periodic traveling directions that are at an angle of 45° with respect to each other, where the grating constitutes an embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference;

[0099] Figure 8 In comparison with Figure 4 and Figure 7Similar exemplary diagrams showing additional embodiments of a grating comprising three diffraction gratings as a group of diffraction structures (wherein two of them have periodic traveling directions perpendicular to each other, and wherein the third diffraction grating has a diagonal periodic traveling direction relative thereto), wherein the grating constitutes an embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference;

[0100] Figure 9 In a manner similar to Figure 5 and Figure 6 Similar curves showing the reflection relationship in the case of a grating according to Figure 8 , wherein all three diffraction gratings are implemented to suppress the same wavelength;

[0101] Figure 10 In a manner similar to Figure 9 Similar curves showing the reflection relationship in the case of a grating of the type shown in Figure 8 , wherein the three diffraction gratings have different structural depths such that the grating is implemented to suppress different wavelengths;

[0102] Figure 11 In a manner similar to Figure 8 Similar exemplary diagrams showing additional embodiments of a grating comprising three diffraction gratings as a group of diffraction structures having respective periodic traveling directions that pair-wise present non-zero angles, wherein the grating constitutes an embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference;

[0103] Figure 12 and Figure 13 In a manner similar to Figure 11 Similar exemplary diagrams showing further embodiments of gratings each comprising three diffraction gratings as a group of diffraction structures having periodic traveling directions corresponding to those of the embodiments according to Figure 11 , wherein the diffraction structures of the embodiments according to Figure 12 and Figure 13 are arranged to be offset from each other in the respective periodic traveling directions and in a manner related to the embodiment according to Figure 11 , wherein the grating constitutes a further embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference;

[0104] Figure 14 A side view showing a first group of diffraction structures belonging to an additional embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference, implemented as a binary grating having a first grating period and a first structural depth;

[0105] Figure 15 In a manner similar to Figure 14Similar illustrative diagrams showing additional diffraction structure groups as part of the optical diffraction element, where the additional diffraction structure groups are further implemented as binary gratings having a grating period and a structure depth, and where possible overlay errors during the fabrication of this diffraction structure group are additionally indicated in dashed lines;

[0106] Figure 16 Showing the optical diffraction element that appears with the superposition of the two diffraction structure groups according to Figure 14 and Figure 15 ;

[0107] Figures 17 to 19 In a similar illustrative diagram to Figures 14 to 16 showing two diffraction structure groups, and an additional optical diffraction element that appears therefrom as a result of the superposition;

[0108] Figures 20 to 22 In a similar illustrative diagram to Figures 14 to 16 showing two diffraction structure groups, and an additional optical diffraction element that appears therefrom as a result of the superposition;

[0109] Figure 23 Showing in a graph Figure 16 , Figure 19 or Figure 22 the reflectivity of an optical diffraction element of the type shown, where the structure height of the corresponding first diffraction structure group is fixed at a value for suppressing the target wavelength, and the reflectivity is plotted as a function of the structure height of the other diffraction structure group;

[0110] Figure 24 Showing again in a graph the reflectivity of the optical diffraction element, again where the structure depth of the first diffraction structure group is fixed, and it is plotted as a function of the difference between the structure depths of the two diffraction structure groups and normalized to the structure depth of the first diffraction structure group;

[0111] Figure 25 Showing in a similar illustrative diagram to Figure 14 a diffraction structure group, which is implemented as a binary grating having a grating period and a structure depth, as part of an additional embodiment of an optical diffraction element for suppressing at least one target wavelength by destructive interference, where the aforementioned additional embodiment appears as a result of the superposition of three diffraction structure groups;

[0112] Figure 26 Showing an additional diffraction structure group, which is again implemented as a binary grating for an embodiment of this variant of the optical diffraction element;

[0113] Figure 27 Showing an additional diffraction structure group, which is again implemented as a binary grating for an embodiment of this variant of the optical diffraction element;

[0114] Figure 28 A display optical diffraction element is formed as a superposition of the three diffraction structure groups according to Figures 25 to 27 ;

[0115] Figures 29 to 32 with Figures 25 to 28 similar illustrative diagrams showing three diffraction structure groups, which are again each implemented as a binary grating with a grating period and a structure depth in each case, and a further embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference, the aforementioned further embodiment emerging therefrom due to the superposition;

[0116] Figure 33 with Figure 9 and Figure 10 similar graphs showing the wavelength-dependent reflection relationship in the case of an optical diffraction element of any one of the types according to Figure 8 , Figures 11 to 13 , Figure 28 or Figure 32 , where the diffraction structure groups have different structure depths such that the grating is implemented to suppress different wavelengths, yet they are closer to each other compared to the variant according to Figure 10 ;

[0117] Figure 34 with Figure 4 similar illustrative diagrams showing a section of the grating surface of a grating comprising three diffraction gratings as diffraction structure groups, where two of the gratings have parallel period traveling directions and the third grating has a period traveling direction perpendicular thereto, and where the diffraction structure groups with the same period traveling direction are superposed in the manner of the embodiment according to Figure 16 , Figure 19 or Figure 22 , where the structure depth of the diffraction structure that is rectangular in Figure 34 is illustrated by different line types as a further embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference.

[0118] Figure 35 Again, a further embodiment of a light diffraction element that suppresses at least one target wavelength by destructive interference is shown in a schematic side view, which is implemented as a three-level grating and is implemented to suppress only one target wavelength;

[0119] Figure 36 with Figure 35 similar illustrative diagrams showing a further embodiment of a light diffraction element that suppresses at least one target wavelength by destructive interference, which is again fabricated by three diffraction structure levels that can be assigned to two diffraction structure groups and the depicted variables (which are depicted for the theoretical explanation of the calculation of the suppression efficiency for the at least one target wavelength);

[0120] Figure 37 with an exemplary diagram similar to Figure 35 and Figure 36 showing a further embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference, implemented to have four diffraction structure levels that can be assigned to corresponding multiple diffraction structure groups;

[0121] Figure 38 and Figure 39 with an exemplary diagram similar to Figure 37 showing two further embodiments of an optical diffraction element that suppresses at least one target wavelength by destructive interference, again implemented to have four diffraction structure levels;

[0122] Figure 40 Showing a wavelength-dependent reflectivity of an optical diffraction element of two diffraction structure groups of a type including embodiments such as according to Figure 4 , Figure 7 , Figure 16 , Figure 19 , Figure 22 , Figure 35 , Figure 36 , where the two diffraction structure groups are implemented to have a structural depth for suppressing two DUV wavelengths;

[0123] Figure 41 with an exemplary diagram similar to Figure 40 showing the wavelength-dependent reflectivity of an optical diffraction element for a total of five diffraction structure levels to which four diffraction structure groups (to which different structural depths can be assigned) are assigned, where two target wavelengths in the IR range above 10 μm and two target wavelengths in the DUV range equivalent to the target wavelengths according to Figure 40 are suppressed;

[0124] Figure 42 Showing the magnified details shown in Figure 41 in the DUV range between 0.1 μm and 0.4 μm;

[0125] Figure 43 Again showing, in a graph, the wavelength-dependent reflectivity between 10.0 μm and 11.0 μm for various optical diffraction elements having different sidewall steepness tolerances of the diffraction structure groups;

[0126] Figure 44 Showing an optical diffraction element according to Figure 16 and two photolithography mask structures that can be used in the manufacture of an optical diffraction element for the boundary region between adjacent surface sections of a binary structure for predefining the binary structure of the optical diffraction element, the aforementioned binary structures being superimposed on each other;

[0127] Figure 45 With an exemplary diagram similar to Figure 44 showing an optical diffraction element and two lithography mask structures according to Figure 19 which can be used in the manufacture of an optical diffraction element for re - defining the boundary regions between surface sections of said diffraction structure groups;

[0128] Figure 46 Showing a further embodiment of an optical diffraction element that suppresses at least one target wavelength by destructive interference, which comprises a periodic grating structure profile containing a diffraction structure having three diffraction structure levels arranged in such a way that they are suppressed by destructive interference at said target wavelength;

[0129] Figure 47 Showing an optical diffraction element according to Figure 46 wherein said three diffraction structure levels have a height or level difference with respect to each other which results in perfect destructive interference of said target wavelength in terms of zero - order diffraction;

[0130] Figure 48 With an exemplary diagram similar to Figure 47 showing a variant of an optical diffraction element according to Figure 46 wherein, in order to illustrate the diffraction compensation effect occurring in the case of such a height error, first the positive diffraction structure level and then the negative diffraction structure level are implemented with a height difference that is somewhat too large with respect to the neutral diffraction structure level;

[0131] Figure 49 With an exemplary diagram similar to Figure 46 showing a further embodiment of an optical diffraction element comprising three diffraction structure levels with a different sequence compared to the embodiment according to Figure 46 ;

[0132] Figure 50 Showing a further embodiment of an optical diffraction element, wherein substantially one grating period is illustrated and wherein the periodic grating structure profile of said optical diffraction element contains a diffraction structure having four diffraction structure levels;

[0133] Figure 51 With an exemplary diagram similar to Figure 50 showing a further embodiment of an optical diffraction element containing five diffraction structure levels within one grating period;

[0134] Figure 52 With a curve diagram similar to Figure 5 showing, by means of three diffraction structure levels that can be assigned to two diffraction structure groups, Figure 19 , Figure 36 , Figure 45 and Figure 46The wavelength-dependent reflectance R of a grating-form optical diffraction element produced in such a way that in each case there is a structural depth difference λ / 4 between the diffraction structure levels, where λ is in each case the target wavelength to be suppressed;

[0135] Figure 53 In a manner similar to Figure 44 and Figure 45 the illustrative diagrams show Figure 19 、 Figure 36 、 Figure 45 and Figure 46 optical diffraction elements of the type shown, and further embodiments of two lithography mask structures which can be used in the manufacture of an optical diffraction element for redefining the surface section of the diffraction structure group or the boundary region between the diffraction structure levels;

[0136] Figure 54 In a manner similar to Figure 44 and Figure 45 the illustrative diagrams show Figure 19 、 Figure 36 、 Figure 45 and Figure 46 optical diffraction elements of the type shown, and further embodiments of two lithography mask structures which can be used in the manufacture of an optical diffraction element for redefining the surface section of the diffraction structure group or the boundary region between the diffraction structure levels;

[0137] Figure 55 In a manner similar to Figure 44 and Figure 45 the illustrative diagrams show Figure 19 、 Figure 36 、 Figure 45 and Figure 46 further embodiments of optical diffraction elements of the type shown, and further embodiments of two lithography mask structures which can be used in the manufacture of an optical diffraction element for redefining the surface section of the diffraction structure group or the boundary region between the diffraction structure levels; and

[0138] Figure 56 In a manner similar to Figure 44 and Figure 45 the illustrative diagrams show Figure 19 、 Figure 36 、 Figure 45 and Figure 46 further embodiments of optical diffraction elements of the type shown, and further embodiments of two lithography mask structures which can be used in the manufacture of an optical diffraction element for redefining the surface section of the diffraction structure group or the boundary region between the diffraction structure levels. Detailed Description

[0139] The projection exposure apparatus 1 for microlithography technology includes a light source 2, which is used for illumination light or imaging light 3, and this will be explained in more detail below. The light source 2 is an EUV light source that generates light in a wavelength range between, for example, 5 nm and 30 nm, especially between 5 nm and 15 nm. The illumination light or imaging light 3 is also referred to as the light used in EUV below.

[0140] In particular, the light source 2 can be a light source with a wavelength of 13.5 nm or a light source with a wavelength of 6.9 nm. Other EUV wavelengths or wavelengths in the DUV range between 150 nm and 250 nm, for example 193 nm, are also possible. The beam path of the illumination light 3 is very schematically illustrated in Figure 1 below.

[0141] The illumination optical unit 6 is used to guide the illumination light 3 from the light source 2 to the object field 4 in the object plane 5. The aforementioned illumination optical unit includes: a field facet mirror FF, which is very schematically illustrated in Figure 1 below; and a pupil facet mirror PF, which is arranged downstream in the beam path of the illumination light 3 and is also very schematically illustrated. A field-forming mirror 6b for grazing incidence (GI mirror; grazing incidence mirror) is arranged in the beam path of the illumination light 3 between the pupil facet mirror PF (pupil facet mirror) arranged in the pupil plane 6a of the illumination optical unit and the object field 4. Such a GI mirror 6b is not essential.

[0142] The pupil facet (not illustrated in more detail) of the pupil facet mirror PF is part of the transmission optical unit, which transmits, especially images, the field facet (also not illustrated) of the field facet mirror FF into the object field 4 in a superimposed manner. Embodiments known from the prior art can be used for the field facet mirror FF on the one hand and the pupil facet mirror PF on the other hand. For example, such an illumination optical unit is known from DE 10 2009 045 096 A1.

[0143] Using a projection optical unit or an imaging optical unit 7, the object field 4 is imaged onto the image field 8 in the image plane 9 with a predetermined reduction ratio. Projection optical units that can be used for this purpose are known from, for example, DE 10 2012 202 675 A1.

[0144] To facilitate the description of various embodiments of the projection exposure apparatus 1 and the projection optical unit 7, a Cartesian xyz coordinate system is indicated in this figure, from which the positional relationships of the respective elements illustrated in the said figure are obvious. In Figure 1 below, the x direction travels perpendicular to the plane of this figure into it. The y direction is in Figure 1extends towards the left in the middle, and the z-direction travels upwards in Figure 1 the middle. The object plane 5 travels parallel to the xy-plane.

[0145] The object field 4 and the image field 8 are rectangular. Alternatively, for the object field 4 and the image field 8, a curved or curved surface embodiment may also be possible, i.e., in particular, partially annular. The object field 4 and the image field 8 have an x / y aspect ratio greater than 1. Therefore, the object field 4 has a longer object field size in the x-direction and a shorter object field size in the y-direction. These object field sizes extend along the field coordinates x and y.

[0146] One of the exemplary embodiments known from the prior art can be used for the projection optical unit 7. In this case, what is imaged is a part of the reflection mask 10 (also called mask master) that coincides with the object field 4. The mask master 10 is carried by the mask master holder 10a. The mask master holder 10a is shifted by the mask master shift driver 10b.

[0147] Through the imaging of the projection optical unit 7, it is achieved on the surface of the substrate 11 in the form of a wafer carried by the substrate holder 12. The substrate holder 12 is shifted by the wafer or substrate shift driver 12a.

[0148] Figure 1 Schematically illustrate the beam 13 of the illumination light 3 entering the aforementioned projection optical unit between the mask master 10 and the projection optical unit 7, and the beam 14 of the illumination light 3 exiting the projection optical unit 7 between the projection optical unit 7 and the substrate 11. In Figure 1 it, the numerical aperture (NA) on the image field side of the projection optical unit 7 is not reproduced to scale.

[0149] The projection exposure device 1 is of the scanner type. Both the mask master 10 and the substrate 11 are scanned in the y-direction during the operation of the projection exposure device 1. A stepper type of the projection exposure device 1 is also possible, in which the stepwise shifting of the mask master 10 and the substrate 11 in the y-direction is achieved between individual exposures of the substrate 11. These shifts are synchronized with each other by appropriate actuation of the shift drivers 10b and 12a.

[0150] Figure 2 Show the details of the display light source 2.

[0151] The light source 2 is a Laser Produced Plasma (LPP) source. For the purpose of generating plasma, tin microdroplets 15 are produced as a continuous sequence of microdroplets by a tin microdroplet generator 16. The trajectory of the tin microdroplets 15 extends transversely to the principal ray direction 17 of the light 3 used for EUV. Here, the tin microdroplets 15 freely fall between the tin microdroplet generator 16 and the tin extraction device 18, and the aforementioned microdroplets pass through the plasma source region 19. The light 3 used for EUV is emitted through the plasma source region 19. When the tin microdroplets 15 reach the plasma source region 19, they are struck there by the pump light 20 from the pump light source 21. The pump light source 21 can be, for example, an infrared laser source in the form of a CO2 laser. Some other IR laser sources are also possible, especially solid-state lasers such as Nd:YAG lasers. The pump light source 21 can include a light source unit for generating an optical pre-pulse; and a light source unit for generating a main optical pulse. On the one hand, the optical pre-pulse and on the other hand, the main optical pulse can have different optical wavelengths.

[0152] The pump light 20 is transmitted into the plasma source region 19 through a mirror 22 (which can be a mirror that can be tilted in a controlled manner) and through a focusing lens assembly 23. The plasma that emits the light 3 used for EUV is generated by being struck by the pump light from the tin microdroplets 15 that reach the plasma source region 19. The beam path of the light 3 used for EUV is illustrated in Figure 2 the middle between the plasma source region 19 and the field splitter mirror FF to the extent that the light used for EUV is reflected by a collector mirror 24 (which is also referred to hereinafter as the EUV collector 24). The EUV collector 24 includes a central channel opening 25 for the pump light 20 focused towards the plasma source region 19 through the focusing lens assembly 23. The collector 24 is implemented as an elliptical mirror and transmits the light 3 used for EUV emitted through the plasma source region 19 (which is arranged at one elliptical focus) to the intermediate focus 26 of the light 3 used for EUV (which is arranged at the other elliptical focus of the collector 24).

[0153] In the far-field region of the light 3 used for EUV, the field splitter mirror FF is arranged downstream of the intermediate focus 26 in the beam path of the light 3 used for EUV.

[0154] The EUV collector 24 and other elements of the light source 2 (which may be the tin microdroplet generator 16, the tin extraction device 18, and the focusing lens assembly 23) are arranged in a vacuum housing 27. The vacuum housing 27 has a channel opening 28 in the region of the intermediate focus 26. In the region where the pump light 20 is incident on the vacuum housing 27, the vacuum housing includes a pump light incident window 29 for the optical pre-pulse and for the main optical pulse.

[0155] Figure 3 Very abstract display, first of all, the guiding of the light used by EUV (i.e., the illumination light 3) and secondly the stray light 30, in particular the radiation of longer wavelengths (e.g., IR radiation having the wavelength of the light pre-pulse and / or the main light pulse), between the plasma source region 19 of the light source 2 and the intermediate focal plane 26a (where the intermediate focus 26 is provided). At the same time, Figure 3 A variant of the lateral guiding of the pump light 20 to the plasma source region 19 is shown, i.e., the guiding of a channel opening of the type without a channel opening 25 in the EUV collector 24. Both the light 3 used and the stray light 30 emanate from the plasma source region 19. Both the light 3 used and the stray light 30 are incident on the surface sections 31, 32 of the entire impact surface 33 of the EUV collector 24. The surface sections 31, 32 are sections of the grating surface (also designated by 33 in this figure) of the EUV collector 24, and a grating for diffracting and collecting the stray light radiation 30 is provided on the aforementioned grating surface. Embodiments of this grating are described below. The grating surface may be provided only at the positions of the surface sections 31, 32 where the stray light 30 impinges thereon, or may also cover a larger section of the impact surface 33 and, in another variant, cover the entire impact surface 33.

[0156] Figure 4 A section of the grating surface 33 employing an embodiment of the grating 34 is shown. The grating 34 constitutes an optical diffraction element that suppresses at least one target wavelength by destructive interference.

[0157] The grating surface of the grating 34 can be implemented as a plane or a curved surface, such as, for example, the concave or convex surface of the impact surface 33 in the case of the collector mirror 24 according to Figure 2 and Figure 3

[0158] The grating 34 has (as a group of diffraction structures) two diffraction gratings 35, 36 provided on the grating surface 33. The diffraction grating 35 is also referred to as the first diffraction grating hereinafter. The diffraction grating 36 is also referred to as the second diffraction grating hereinafter.

[0159] In the case of the diffraction grating 35, the diffraction positive structure 37 and the diffraction negative structure 38 both travel horizontally alternately in Figure 4 . The periodic travel direction 39 of this first diffraction grating 35 travels vertically. For this horizontal path of the diffraction structures 37, 38, the periodic travel direction 39 thus travels vertically in Figure 4 .

[0160] In Figure 4In [the figure], the second diffraction grating 36 has a diffraction positive structure 40 traveling vertically, and diffraction negative structures 41 alternating therewith respectively. The periodic traveling direction 42 of the second diffraction grating 36 travels perpendicular to the diffraction structures 40 and 41 again, that is, horizontally in Figure 4 [the figure].

[0161] The diffraction structures 37, 38 and 40, 41 of the two diffraction gratings 35, 36 of the grating 34 are realized by four diffraction structure types or diffraction structure levels, which have different structure depths and are illustrated in Figure 4 [the figure] by different thin line types and by the numbers 1, 2, 3, 4 applied to the corresponding diffraction structures. The diffraction structure type "1" has a structure depth of "0". The diffraction structure type "2" has a structure depth of "dv". The surface section of the grating surface occupied by the corresponding diffraction structure type "2" is thus located at a position deeper by the structure depth dv perpendicular to the Figure 4 plane illustrated in [the figure] than the diffraction structure type "1".

[0162] The corresponding structure depth may refer to a depth value assigned with respect to a reference plane, where as a general rule, the reference plane selected is the one from which no material has been removed (structure depth = 0).

[0163] The respective areas of the diffraction structure types "1" to "4" are square in each case. Other boundary shapes that completely cover the diffraction structure types of the grating surface are also possible.

[0164] The diffraction structure type "3" has a structure depth dh, which is again measured perpendicular to the Figure 4 plane illustrated in [the figure] with respect to the diffraction structure type "1". The diffraction structure type "4" has a structure depth of dv + dh measured correspondingly.

[0165] In the case of the grating 34, the four diffraction structure types "1" to "4" are respectively arranged in a 2 × 2 array, where the diffraction structure type "1" is arranged in the upper left, the diffraction structure type "2" is arranged in the upper right, the diffraction structure type "3" is arranged in the lower left, and the diffraction structure type "4" is arranged in the lower right. Such 2 × 2 arrays of such groups of the four diffraction structure types are in turn arranged in a superstructure in the form of a 3 × 3 array in the embodiment according to Figure 4 [the figure]. Generally speaking, the grating 34 on the grating surface 33 can of course be horizontally and vertically extended in any desired manner by attaching further corresponding 2 × 2 arrays of the four diffraction structure types "1" to "4".

[0166] The diffractive positive structure 37 and the diffractive negative structure 38 located at a position with a deeper structure depth dh compared thereto are thus successively arranged in the periodic traveling direction 39 of the first diffractive grating 35. In the case of the second diffractive grating 36, one of the diffractive positive structures 40 is respectively followed by the diffractive negative structure 41 located at a position with a deeper structure depth dv in the periodic traveling direction 42. Two diffractive gratings 35, 36 that are superposed on each other and have corresponding structure depths dh and dv are thus realized in the grating 34.

[0167] In the case of an embodiment according to Figure 4 the structure depth is the height difference between the corresponding diffractive positive structure and the associated diffractive negative structure. More generally, the structure depth can be understood as the optical path difference between the diffractive positive structure and the associated diffractive negative structure.

[0168] On the diffractive positive structures 37, 40 and the diffractive negative structures 38, 41, a highly reflective coating may be applied over the entire area, possibly on the grating 34, and an auxiliary layer may also be applied as required.

[0169] The auxiliary layer provided below the highly reflective coating may be a layer for increasing the service life of the grating 34. Alternatively or additionally, the auxiliary layer may also be applied on the highly reflective coating to protect the latter from damage.

[0170] The highly reflective coating may be multilayered and is known, for example, for highly efficient reflection of radiation especially having an EUV wavelength.

[0171] The diffractive gratings 35, 36 of the grating 34 are each implemented as a binary grating. Here, the surface area of the diffractive positive structure is equal to the surface area of the diffractive negative structure.

[0172] The grating period of the diffractive grating 35 may be in the range between 0.5 mm and 5 mm, for example 2 mm. The grating period of the diffractive grating 36 may be in the range between 0.5 mm and 5 mm, for example 2 mm. Such a grating period is calibrated by P for Figure 4 the second diffractive grating 36 in Figure 4 The structure sidewalls of the corresponding diffractive structures 37, 38, 40, 41 may have a degree in the range between 1 μm and 10 μm, for example in the region of 5 μm, perpendicular to the extension of the corresponding diffractive structure, that is, measured in the corresponding periodic traveling direction 39 to 42. Such a sidewall degree or sidewall extension is indicated at F, where the size for

[0173] Figure 5Shown in a graph are the calculated results of the wavelength-dependent reflectivity of grating 34 for the design parameters dv = 2.65 μm and dh = 2.55 μm. The reflectivity of grating 34 is plotted at 43, and the foregoing reflectivity results from the calculation with the additional assumption that the sidewall extension F is 0, i.e., the result in the case of grating 34 with ideally steep sidewalls between the diffraction structures. In the case of suppressing the design wavelengths 10.2 μm and 10.6 μm for the corresponding stray light wavelengths (which are referred to as the target wavelengths), the result is a better suppression of the reflectivity of grating 34 in the ideal case of the reflectivity curve 43. These two wavelengths correspond to the wavelengths of the prepulse and the main pulse of the pump light source 21. -8 Better suppression of the reflectivity of grating 34 in the ideal case of the reflectivity curve 43.

[0174] For the two target wavelengths 10.2 μm (λ1) and 10.6 μm (λ2), the following holds:

[0175] (λ1 - λ2) 2 / (λ1 + λ2) 2 = 3.77∙10 -4

[0176] For this normalized target wavelength ratio, the following thus holds:

[0177] (λ1 - λ2) 2 / (λ1 + λ2) 2 < 10%

[0178] This normalized target wavelength ratio can also be less than 20%.

[0179] Regarding first the manufacturing accuracy of the structure depths dv and dh and the sidewall steepness, the reflectivity curve R(λ) taking into account the specified tolerances is plotted at 44 in Figure 5 . In the case of the target wavelengths 10.2 μm and 10.6 μm, the result is a better suppression of the reflectivity than 10 -6 .

[0180] The reference reflectivity curve 45 is also entered in Figure 5 for comparison purposes. The foregoing reference reflectivity curve represents the suppression result for an optical reference grating comprising only one diffraction grating, i.e., for example, diffraction grating 35 with horizontal diffraction structures or diffraction grating 36 with vertical diffraction structures. The same tolerances for the structure depth generation and for the sidewall steepness as in the case of the reflectivity curve 44 are taken into account here. It is evident that, although the tolerances are the same, the reference reflectivity curve 45 exhibits a better reflectivity suppression at 10 -4Since the reference grating for which the reference reflectivity curve 45 is calculated contains only one diffraction grating, only one wavelength (ie 10.6 μm) is suppressed here as well.

[0181] The two diffraction gratings 35 , 36 have a ratio between grating period (2 mm) and structure depth (in the region of 2.6 μm) which is significantly greater than 10 and in fact greater than 500 and in the region of 1000.

[0182] Since the two diffraction gratings 35, 36 are implemented as binary gratings, the surface area ratio of the surface area of ​​the diffractive positive structures 37, 40 to the surface area of ​​the diffractive negative structures 38, 41 is 1. Depending on the embodiment of the grating 34, the aforementioned surface area ratio may also deviate from 1 and may be in the range between 0.9 and 1.1.

[0183] The two diffraction gratings 35, 36 have the same grating period p, so that the period ratio of the two grating periods is 1. Depending on the embodiment of the grating 34, this period ratio may be in the range between 0.9 and 1.1. The difference between the two grating periods may also be significantly larger, so that a period ratio of 1:2 or 1:5 is obtained, for example.

[0184] The grating 34 constitutes an optical diffraction element that suppresses at least one target wavelength λ1, λ2 by destructive interference, and comprises at least three diffraction structure levels, which correspond to diffraction structure types 1 to 4. The aforementioned diffraction structure levels N1 to N4 predefine different structure depths d relative to the reference plane. i The diffraction structure levels N1 to N4 can be assigned to two diffraction gratings (i.e., two diffraction structure groups 35, 36), which in turn are used to suppress one of the two target wavelengths λ1, λ2, respectively. The first group of the aforementioned diffraction structure groups (i.e., the diffraction grating 35) is used to suppress the first target wavelength λ1 in the zero-order diffraction, and the second group of the diffraction structure groups (i.e., the diffraction grating 36) is used to suppress the second target wavelength λ2 in the zero-order diffraction.

[0185] The morphology of the diffractive structure levels N1 to N4 can be described as a superposition of two binary diffractive structure groups 35 and 36. Each of the two binary diffractive structure groups has a first surface segment (with a first structure depth) and a second surface segment (with a second structure depth) alternating with the first surface segment along the direction of travel of the respective diffractive structure group 35, 36. The boundary region between these adjacent surface segments of each of the binary diffractive structure groups has a linear path. Depending on the embodiment of the grating 34, the aforementioned linear path corresponds to Figure 4 The first boundary region of the first group of the two binary diffractive structure groups 35 (i.e.Figure 4 the line lines in Figure 4 the column lines in Figure 4 are superimposed on each other at most along the respective sections of their linear paths, i.e., in the region of the intersection points between the column lines and the line lines in the exemplary diagram according to

[0186] The diffraction grating 35 has a first grating period (with a first structural depth), which is the optical path difference between the first diffraction positive structure 37 and the first diffraction negative structure 38, measured perpendicular to the surface section of the grating surface 33 respectively surrounding these first structures. The second diffraction grating 36 has a second grating period and a second structural depth, which is in turn implemented as the optical path difference between the second diffraction positive structure 40 and the second diffraction negative structure 41, perpendicular to the surface section of the grating surface 33 respectively surrounding these second structures. The two period travel directions along which the two grating periods of these gratings 35, 36 travel are perpendicular to each other, i.e., they do not travel parallel to each other.

[0187] Due to the grating 34, the collector mirror of the EUV collector 24 is implemented such that it guides the EUV radiation 3 through towards the focal region 26, where the grating 34 is implemented as an optical diffraction element such that this optical diffraction element guides the radiation 30 (i.e., stray light) of at least one target wavelength away from the focal region 26.

[0188] Figure 6 in a similar exemplary diagram to Figure 5 shows the reflectivity relationship in a variant of the grating 34, where the magnitudes of the structural depths dv, dh are equal and have an absolute value of 2.65 μm. Then, both of the two diffraction gratings 35, 36 contribute to suppressing the stray light wavelength of 10.6 μm. Accordingly, a better suppression relationship appears again in the case of the ideal reflectivity curve 43 and in the case of the reflectivity curve 44 calculated using the design tolerance.

[0189] Figure 7 in a similar exemplary diagram to Figure 4 shows a variant of the grating that can be used instead of the grating 34 according to Figure 4 as an optical diffraction element for suppressing at least one target wavelength by destructive interference. The elements and functions corresponding to those already explained above with reference to Figure 4 are provided with the same reference signs and will not be discussed in detail again.

[0190] According to Figure 7 the grating 46 differs preliminarily from that shown in Figure 4 in that the period travel direction 39 of the first diffraction grating 35 does not travel perpendicularly, but at an angle of 45° with respect to the horizontal line. Accordingly, rhombic areas appear for the diffraction structure types "1" to "4".

[0191] Figure 8 Shows additional embodiments of grating 47 that can be used as alternative examples or as optical diffraction elements for suppressing at least one target wavelength by destructive interference in addition to the gratings described above. Corresponding to those already described above with reference to Figures 1 to 7 and particularly with reference to Figures 4 to 7 The elements and functions are provided with the same reference numerals and will not be discussed in detail.

[0192] Grating 47 has a total of three diffraction gratings as a diffraction structure group, two of which correspond to diffraction gratings 35 and 36 according to the embodiment of Figure 4 In Figure 8 the grating period of diffraction grating 35 is illustrated at ph, and the grating period of diffraction grating 36 is at pv.

[0193] The third diffraction grating 48 of grating 47 has a diffraction positive structure 49 and a diffraction negative structure 50 that travel diagonally with respect to the diffraction structures 37, 38 and 40, 41 of the first two diffraction gratings 35, 36. Compared with the diffraction positive structure 49, the diffraction negative structure 50 has a structure depth illustrated by dd in Figure 8 .

[0194] The overall height profile above the entire illustrated section of the grating surface of grating 47 can be understood as the juxtaposition of basic sections in the form of a 2 × 4 array, which is predefined by the boundaries of the horizontally traveling diffraction structures 37, 38 of diffraction grating 35 and the vertically traveling diffraction structures 40, 41 of diffraction grating 36. The type or level of diffraction structure on this 2 × 4 array is calibrated in Figure 8 by "000", "001", "010", "011", "100", "101", "110" and "111" set on the 2 × 4 array in the upper left corner.

[0195] The following table indicates the structure depth of these diffraction structure types in units of grating periods ph, pv, and their surface area ratios:

[0196]

[0197] Table 1

[0198] All diffraction structure types from "000" to "111" have the same surface area ratio (ph + pv) / 4 of the total surface area of grating 47. This ensures that all three diffraction gratings 35, 36 and 48 of grating 47 form a binary grating, and the surface area ratio of their diffraction positive structures 37, 40, 49 to their diffraction negative structures 38, 41, 50 is 1 in each case.

[0199] The periodic traveling direction 51 of the third diffraction grating 48 travels along a grating period pd at an angle of approximately 23° with respect to the periodic traveling direction 39 of the diffraction grating 35. This periodic traveling direction 51 is selected together with the offset of the arrangement of the diffraction structures 49, 50 of the third diffraction grating 48 such that the boundary between the diffraction structures 49, 50 of the third diffraction grating 48 travels along the diagonal of two structurally adjacent blocks (which are formed by the diffraction structures 37, 38 first and 40, 41 second that intersect each other). This offset variation of the arrangement of the diffraction structures 49, 50 along the periodic traveling direction 51 of the third diffraction grating 48 is possible, as indicated by the double-headed arrow 52 in Figure 8 .

[0200] The grating period pd of the third diffraction grating 48 is of the order of the grating periods ph, pv and is approximately 1.7 mm in the case of the grating 47.

[0201] Figure 9 In a similar illustration as Figure 5 and Figure 6 , data on the wavelength-dependent reflectivity R are shown for the case where the values for each of the structural depths dh, dv and dd are equal and have a numerical value of 2.65 μm in the illustrated example.

[0202] The reflectivity for the ideal case of preferably steep sidewalls (sidewall extension is 0) for the diffraction gratings 35, 36 and 48 is illustrated at 53 in Figure 9 . The reflectivity suppression for the target wavelength of 10.6 μm is better by several orders of magnitude than 10 -10 .

[0203] 54 illustrates the calculated results of the wavelength-dependent reflectivity, where again actual tolerances are assumed for the structural depths of the diffraction structures 37, 38, 40, 41, 49, 50 and for the sidewall extension. The result for the grating 47 comprising three diffraction gratings 35, 36, 48 is a reflectivity suppression which, although lower than in the ideal case, is still significantly better than 10 -10 .

[0204] As a reference value, Figure 9 the reflectivity curves 44 and 45 are also plotted first for the grating 34 comprising two diffraction gratings 35, 36 and for a conventional grating comprising only one diffraction grating, according to Figure 6 .

[0205] Figure 10 Again in a wavelength-dependent graph, the reflectivity relationships of embodiments of the grating 47 with the following structural depths are shown:

[0206] dh = 2.55 μm, dv = 2.65 μm and dd = 0.26 μm.

[0207] Therefore, the structural depth dd of the diffractive structures 49, 50 that travel diagonally is approximately ten times smaller than the structural depth of the diffractive structures 37, 38, 40, 41 of the diffraction gratings 35, 36 of the grating 47.

[0208] Again, the reflectivity of the ideal design of such a grating 47 with a sidewall extension of 0 is illustrated at Figure 10 55 in. For two suppression wavelengths at approximately 10.2 μm (λ1) and approximately 10.59 μm (λ2) and additional wavelengths in the region of 1.05 μm, the reflectivity suppression of the grating is in the range of 10 -8 or better in each case.

[0209] For the two IR wavelengths λ1, λ2 that are suppressed by the grating 47 as the target wavelengths, the explanations given above in connection with the grating 34 according to Figure 4 also hold for the normalized difference in the target wavelengths.

[0210] For the reflectivity curve with a predefined tolerance for the structural depth and then the sidewall extension first, it is further calculated at Figure 10 56 in.

[0211] In the case of the grating 47, there is thus a diffraction grating 48 with an additional grating period pd and an additional structural depth dd, where the aforementioned structural depth is the optical path difference between the diffractive positive structure 49 and the diffractive negative structure 50, measured perpendicular to the surface section of the grating surface 33 surrounding these two structures 49, 50 respectively. The ratio pd / dd between the grating period pd and the structural depth dd of the diffraction grating 48 is greater than 10. Optionally or additionally, the period ratio ph / pd can be in the range between 0.9 and 1.1. Optionally or additionally, the first grating period ph can travel along the first period traveling direction 39 of the first diffraction grating 35, and the additional grating period pd can travel along the additional period traveling direction 51 of the additional diffraction grating 48, and the two period traveling directions 39, 51 travel parallel to each other.

[0212] The surface areas of the diffractive positive structures 37, 40, 49 and the diffractive negative structures 38, 41, 50 of the various diffractive structure groups 35, 46, 48 contribute equally to the entire grating surface 33.

[0213] Another embodiment of the grating 57 that also includes three diffraction gratings 35, 36, 48 will be described below with reference to Figure 11 as follows. Corresponding to what has been described above with reference to Figures 1 to 10, and with particular reference to Figure 8 Those components and functions described are provided with the same reference numerals and will not be discussed in detail again.

[0214] The grating 57 differs from the grating 47 mainly in the orientation of the three periodic traveling directions 39, 42, and 51 of the three diffraction gratings 35, 36, and 48 stacked on one another. The periodic traveling direction 39 of the first diffraction grating 35 travels at an angle of approximately 23° with respect to the Figure 11 vertical line in. The periodic traveling direction 42 of the second diffraction grating 36 travels horizontally.

[0215] The periodic traveling direction 51 of the third diffraction grating 48 further travels at an angle of approximately 23° with respect to the vertical line, wherein the two periodic traveling directions 39 and 51 of the first diffraction grating 35 and the third diffraction grating 48 respectively exhibit an angle of approximately 46° with respect to each other.

[0216] Figure 11 The diamond-shaped basic section of the grating 57 corresponding to the 2 × 4 array of the grating 47 is emphasized again with diffraction structure types "000" to "111". In the case of these diffraction structure types "000" to "111" of the grating 57, the assignment of the structure depth and the surface area ratio is as indicated in Table 1 above regarding Figure 8 .

[0217] In the case of the grating 57, the offset of the structural boundary of the third diffraction grating 48 along the periodic traveling direction 51 causes the structural boundaries between the diffraction structures 37, 38 of the first diffraction grating 35, between the diffraction structures 40, 41 of the second diffraction grating 36, and between the diffraction structures 49, 50 of the third diffraction grating 48 to all intersect at Figure 11 the point P at the center of the basic section illustrated in.

[0218] In the case of the grating 57, the grating period ph is approximately 3.25 mm, the grating period pv is 2 mm, and the magnitude of the grating period pd is exactly the same as the grating period ph.

[0219] Figure 12 and Figure 13 show further embodiments of the gratings 58, 59, which differ from the grating 57 only in terms of the magnitude of the offset of the setting of the structural boundary between the diffraction structures 49, 50 along the periodic traveling direction 51. In the case of the grating 58 according to Figure 12 , the aforementioned offset causes the structural boundaries of the various diffraction gratings 35, 36, 48 not to intersect at a point in the corresponding basic section. In the case of the grating 59 according to Figure 13 , the offset causes the structural boundaries of the three diffraction gratings 35, 36, 48 to be the same as those according to Figure 11The embodiments intersect at different positions within the respective basic sections, and thus different distributions of diffraction structure types "000" to "111" are obtained accordingly.

[0220] In Figure 12 and Figure 13 the assignment of the structural depth and surface area ratio of the diffraction structure types "000" to "111" indicated within the emphasized unit cells is again as indicated in Table 1 regarding Figure 8 .

[0221] As a further embodiment of the grating 60 which is an optical diffraction element for suppressing at least one target wavelength by destructive interference, the following is explained with reference to Figures 14 to 16 . The elements and functions corresponding to those already explained above with reference to Figures 1 to 13 are denoted by the same reference numerals and will not be discussed in detail again.

[0222] The grating 60 is implemented as a superposition of two diffraction gratings 61 and 62 exemplified separately in Figure 14 (diffraction grating 61) and Figure 15 (diffraction grating 62). The diffraction gratings 61 and 62 constitute a diffraction structure group for suppressing the respective target wavelengths.

[0223] The diffraction grating 61 has a structural depth d1 and a grating period p1. The diffraction grating 62 has a structural depth d2 and a grating period p2. The two diffraction gratings 61 and 62 are both implemented as binary gratings.

[0224] The grating 60 obtained by the superposition of the two diffraction gratings 61 and 62 has a total of three diffraction structure levels or diffraction structure types, which have a structural depth of 0 (diffraction structure level N1), a structural depth of d2 (diffraction structure level N2), a structural depth of d1 (diffraction structure level N3), and a structural depth of d1 + d2 (diffraction structure level N4).

[0225] The grating periods p1 and p2 are equal in the case of the grating 60. The structural depths d1 and d2 are different in the case of the grating 60. In relation to the common period traveling direction x of the diffraction gratings 61 and 62, the two diffraction gratings 61 and 62 are displaced relative to each other by a quarter of the common period, i.e., p1 / 4 = p2 / 4 relative to each other.

[0226] In Figure 15 and Figure 16In [the figure], the coverage error 63 along the periodic traveling direction x is illustrated by a dashed line. Such a coverage error 63 can be understood as the superimposed phase error of two diffraction gratings 61, 62 along the periodic traveling direction, and causes changes in the extension of the various diffraction structure levels N1, N2, N3, N4 along the periodic traveling direction pixel x.

[0227] For the case where the two structural depths d1 and d2 are equivalent in an alternative embodiment of the grating 60, the two diffraction structure levels N2, N3 degenerate into a common structure level. As a result, such a grating containing two diffraction gratings with equivalent structural depths has only three diffraction structure levels.

[0228] In the case of the grating 60, the surface section of the diffraction structure group is demarcated by 61 P and 61 N The boundary region of the first group 61 of the two binary diffraction structure groups 61, 62 of the grating 60 (i.e., the side wall between the levels N of the diffraction structure group 61 i and the boundary region of the second group 62 of the two diffraction structure groups 61, 62 (i.e., Figure 15 the level side wall N in i / N j ) travel completely separated from each other.

[0229] As another embodiment of the grating 60 as an optical diffraction element for suppressing at least one target wavelength by destructive interference, the following is explained with reference to Figures 17 to 19 Elements and functions corresponding to those already explained above with reference to Figures 1 to 16 , and particularly with reference to Figures 14 to 16 are given the same reference numerals and will not be discussed in detail.

[0230] Figure 19 Shows a grating 64 that results from the superposition of two diffraction structure groups in the form of diffraction gratings 65 ( Figure 17 ) and 66 ( Figure 18 ). The grating 64 is an example of an optical diffraction element.

[0231] In the case of the diffraction gratings 65, 66, the following holds:

[0232] p1 = p2 and d1 = d2.

[0233] The phase shift of the two diffraction gratings 65, 66 relative to each other along the periodic traveling direction x is p1 / 4 = p2 / 4.

[0234] First, the extension ratios between the diffraction positive structures 67, 68 of the diffraction gratings 65, 66 and their associated diffraction negative structures 69, 70 are exactly inverted relative to each other, resulting in the diffraction positive structure 67 having the same extension along the periodic traveling direction x as the diffraction negative structure 70 of the diffraction grating 66, and the diffraction negative structure 69 of the diffraction grating 65 having the same extension along the periodic traveling direction x as the diffraction positive structure 68 of the diffraction grating 66. Therefore, the extensions of the first diffraction positive structures 67, 68 and their secondary diffraction negative structures 69, 70 are not equivalent in their respective diffraction gratings 65, 66, and in this sense, the two diffraction gratings 65, 66 are not binary gratings. In the case of the diffraction gratings 65, 66, this extension ratio can deviate significantly from 1:1 and be approximately 1:3. Different extension ratios between the first diffraction positive structures 67, 68 and their secondary diffraction negative structures 69, 70 in the respective diffraction gratings 65, 66 in the range between 10:1 and 1:10 are also possible.

[0235] The overlay error 63 is again indicated in Figure 18 and Figure 19 . Different from the case of the grating 60, the overlay error 63 in the case of the grating 64 does not cause a change in the surface area ratio between the three diffraction structure levels N1 (structural depth 0), N2 (structural depth d1 = d2), and N3 (structural depth d1 + d2) along the periodic traveling direction x.

[0236] Therefore, the grating 64 constitutes an optical diffraction element that includes a periodic grating structure profile containing diffraction structures and has three diffraction structure levels (N1 to N3) that are predefined with different structural depths d relative to a reference plane i .

[0237] In the case of the grating 64, the diffraction structures are arranged such that the wavelength range near the first target wavelength λ1 in the infrared wavelength range (which is diffracted by the grating structure profile) has radiation components that have at least three different phases that cancel each other out in the zero and / or + / - first order diffraction at least at the first target wavelength λ1.

[0238] The diffraction structure levels N1 to N3 define the topography of the grating period of the grating structure profile that is predefined to repeat regularly along the periodic traveling direction x. The diffraction structure levels N1 to N3 include: a neutral diffraction structure level N2 having a reference height of 0; a positive diffraction structure level N1 that is set to have an optical path length that is λ1 / 4 higher than the neutral diffraction structure level N2, where a tolerance of + / - 20% is possible for the aforementioned optical path length; and a negative diffraction structure level N3 that is set to have an optical path length that is λ1 / 4 + / - 20% lower than the neutral diffraction structure level N2.

[0239] The grating period of the grating structure profile of grating 64 is subdivided into four periodic segments of diffraction structure levels N1 to N3, where two of the four periodic segments (i.e., the two segments having the diffraction structure level N2) are implemented as neutral diffraction structure segments, one of the four periodic segments (i.e., the periodic segment having the diffraction structure level N1) is implemented as a positive diffraction structure segment, and one of the four periodic segments (i.e., the periodic segment having the diffraction structure level N3) is implemented as a negative diffraction structure segment.

[0240] Each of these four periodic segments (for example, the sequence N2, N1, N2, N3) has the same length along the periodic traveling direction x, and a tolerance range of + / - 20% is also possible here.

[0241] As a further embodiment of grating 60 as an optical diffraction element for suppressing at least one target wavelength by destructive interference, the following is explained with reference to Figures 20 to 22 Elements and functions corresponding to those already explained above with reference to Figures 1 to 19 and especially with reference to Figures 14 to 19 carry the same reference numerals and are not discussed in detail again.

[0242] Figure 22 Shows grating 71 produced as the superposition of two diffraction gratings 72 ( Figure 20 ) and 73 ( Figure 21 ).

[0243] Diffraction grating 72 has a structure depth d1 and a grating period p1. Diffraction grating 73 has a structure depth d2 and a grating period p2.

[0244] p2 = 2p1. The following holds: d1 ≠ d2.

[0245] Both diffraction gratings 72 and 73 are implemented as binary gratings having equal extensions of the diffraction positive structure and the diffraction negative structure along the periodic traveling direction x.

[0246] The grating 71 has four diffraction structure levels, namely N1 (structure depth 0), N2 (structure depth d2), N3 (structure depth d1), and N4 (structure depth d1 + d2).

[0247] Figure 21 and Figure 22 is also illustrated by a dashed line, an overlay error 63 caused by a phase shift of two diffraction gratings 72, 73 along the periodic traveling direction x. Due to the size ratio of the two diffraction gratings 72, 73, with respect to the relative extension of the diffraction structure levels N and N2, the overlay error 63 is indeed obvious, such that as seen during the period p2 of the grating 71, the ratio of the extensions of the diffraction structure levels N1 and N2 does not change regardless of the magnitude of the overlay error 63.

[0248] Due to the size ratio of the two diffraction gratings 72, 73, a level change occurs, which is caused by the diffraction grating 73 for a diffraction structure type of the diffraction grating 72 (in this case for its diffraction positive structure). The phase relationship between the two diffraction gratings 72, 73 along the periodic traveling direction x causes the sidewalls F of the diffraction gratings 72, 73 not to be superimposed at the same position along the periodic traveling direction x.

[0249] Figure 23 For a grating of the type of the gratings 60, 64 or 71 described above with reference to Figures 14 to 22 shows the correlation of the reflectivity R of the grating with the structure depth d2 of the corresponding second diffraction grating that constitutes this grating, and the corresponding first diffraction grating with the structure depth d1 is designed to suppress the target wavelength of 10.6 μm by destructive interference. For a structure depth d2 of 2.65 μm, that is, at approximately a quarter of the target wavelength, the maximum suppression of the target wavelength is obtained (the reflectivity is less than 10 -8 ).

[0250] The tolerance of the structure depth and / or the sidewall steepness is taken into account in the associated reflectivity curve 74.

[0251] The closer the second structure depth d2 is to the first structure depth d1 of a fixed 2.65 μm, the better the suppression of the target wavelength. When the structure depth d2 is in the range between 0 and approximately twice the structure depth d1, that is Figure 23In the range of approximately 0.2 μm to 5 μm, improvements in the suppression effect achieved by the first diffraction grating with a structural depth d1 have become apparent. For the design of the two structural depths d1 and d2, it is obvious that starting from a certain distance between the two structural depths, the suppression effects of the two diffraction gratings with structural depths d1 and d2 reinforce each other. Due to the condition of the separation between the two target wavelengths λ1 (for the first diffraction grating) and λ2 (for the second diffraction grating) for the suppression effects to reinforce each other, the following relationship is known:

[0252] |λ2 - λ1| / λ1 < 0.5

[0253] Assuming that the two target wavelengths do not differ much from each other, this condition can be written as follows, regardless of whether it is related to the first wavelength λ1 or the second wavelength λ2 and without absolute values:

[0254] (λ1 - λ2) 2 / (λ1 + λ2) 2 < 0.1

[0255] As long as this condition is satisfied for the two target wavelengths λ1, λ2 to be suppressed by the two diffraction gratings (i.e., the two diffraction structure groups of the optical diffraction element), the suppression reinforces each other in the case of the two target wavelengths λ1, λ2.

[0256] This is plotted in Figure 24 as the correlation of the reflectance with the structural depth difference of the first structural depth (d2 - d1) / (d1) normalized to a value range between -1.0 and 1.0. Between the values of -0.5 and 0.5 for this normalized structural depth difference, the corresponding reflectance curve 75 is significantly lower than the asymptotic reflectance value for larger structural depth differences.

[0257] As a further embodiment of the grating 60 of the optical diffraction element for suppressing at least one target wavelength by destructive interference, the following is explained with reference to Figures 25 to 28 Elements and functions corresponding to those already explained above with reference to Figures 1 to 24 , and in particular with reference to Figures 14 to 22 are provided with the same reference numerals and will not be discussed in detail.

[0258] Figure 28 Shows a grating 76 produced as the superposition of three diffraction gratings 77 ( Figure 25 ), 78 ( Figure 26 ) and 79 ( Figure 27 ). For the structural depths d1, d2, d3 of these three diffraction gratings 77 to 79, the following holds:

[0259] d1 > d2 > d3.

[0260] The three diffraction gratings 77 to 79 are each implemented as binary gratings in each case.

[0261] For the ratios of the grating periods p1, p2, and p3 of the three diffraction gratings 77 to 79, the following holds:

[0262] p1:p2:p3 = 1:2:4.

[0263] As a result, an optical diffraction element is obtained by which in principle three different target wavelengths can be suppressed by destructive interference, and which comprises three diffraction structure groups employing the three diffraction gratings 77 to 79. Due to this period ratio, the grating 76 is insensitive to covering errors (i.e., related to possible phase shifts of the diffraction structures of the three diffraction gratings 77 to 79 along the period travel direction x).

[0264] The grating 76 has the following eight diffraction structure levels: N1 (structure depth 0), N2 (structure depth d3), N3 (structure depth d2), N4 (structure depth d1), N5 (structure depth d2 + d3), N6 (structure depth d3 + d1), N7 (structure depth d1 + d2), and N8 (structure depth d1 + d2 + d3). These diffraction structure levels can be assigned to the three diffraction structure groups of the three diffraction gratings 77 to 79.

[0265] As a further embodiment of the grating 60 as an optical diffraction element for suppressing at least one target wavelength by destructive interference, the following is explained with reference to Figures 29 to 32 which. Corresponding to those already explained above with reference to Figures 1 to 28 and in particular with reference to Figures 25 to 28 which, the elements and functions carry the same reference signs and are not discussed in detail again.

[0266] Figure 32 Shows the grating 80 obtained by the superposition of three binary diffraction gratings 81 ( Figure 29 ), 82 ( Figure 30 ), and 83 ( Figure 31 ). For the structure depths d1, d2, d3 of the three diffraction gratings 81 to 83, the following holds: d1 > d2 > d3. For the grating periods p1, p2, and p3 of the diffraction gratings 81 to 83, the following holds:

[0267] p1:p2:p3 = 2:2:1.

[0268] Between the diffraction structures of the three diffraction gratings 81 to 83, the covering error of the phase relationship along the periodic traveling direction x (consistent with what has been explained above with respect to the embodiment according to Figures 14 to 22 and Figures 25 to 28 ) is, in terms of the ratio between the diffraction gratings 81 and 82, only a part because the latter have the same grating period.

[0269] The grating 80 also correspondingly has eight different diffraction structure levels that can be assigned to the three diffraction structure groups of the three diffraction gratings 81 to 83.

[0270] Figure 33 With an illustrative diagram similar to Figure 5 and Figure 10 , it shows the suppression effect of a grating of the type of the embodiment according to Figure 28 and Figure 32 (including three diffraction structure groups for suppressing three different target wavelengths).

[0271] The reflectivity curve 84 shows the wavelength-dependent suppression for structure depths d1 = 2.65 μm, d2 = 2.55 μm, and d3 = 2.60 μm, which is implemented to suppress the target wavelengths 10.2 μm, 10.40 μm, and 10.6 μm, assuming a sidewall extension F of 0 along the periodic traveling direction x, i.e., the ideal steep path of the diffraction structure of the associated diffraction grating. Better suppression is obtained for the three target wavelengths than 10 -11 .

[0272] Furthermore, the reflectivity curves taking into account the structure depth and / or sidewall steepness tolerance are plotted at 85 in Figure 33 . In the case of the reflectivity curve 85, better suppression is obtained for the edge target wavelengths 10.2 μm and 10.6 μm than 10 -9 , and better suppression is obtained for the central target wavelength 10.40 μm than 10 -10 .

[0273] In Figure 33 as a reference, the reflectivity curves 44 and 45 for a grating including only two diffraction gratings and for a grating including only one diffraction grating are depicted (see also Figure 5 ).

[0274] Figure 34 Another embodiment of the grating 86, which is an optical diffraction element that suppresses at least one target wavelength by destructive interference, is shown. The elements and functions corresponding to those already explained above with reference to Figures 1 to 33 , and particularly with reference to Figures 4 to 8 , carry the same reference numerals and will not be discussed in detail.

[0275] The grating 86 is produced as the superposition of a total of three diffraction gratings 87, 88, and 89. Two of these diffraction gratings (i.e., diffraction gratings 87 and 88) have a periodic traveling direction x that travels horizontally in Figure 34 . The third diffraction grating 89 has a periodic traveling direction y that travels vertically in Figure 34 . In a manner similar to that in Figure 4 and Figure 7 , in the case of the grating 86, the diffraction structure types (i.e., different diffraction structure levels) are emphasized by different thin lines. If the three diffraction gratings 87 to 89 have three different structural depths d1, d2, and d3, the result is again eight different diffraction structure levels corresponding to eight different thin line types. If two or all three of the three structural depths d1, d2, and d3 of the diffraction gratings 87 to 89 are equal, the result is a corresponding smaller number of different diffraction structure levels.

[0276] In the case of the embodiment based on the grating 86, the suppression of the corresponding target wavelength is independent of the overlay error.

[0277] Regarding the consideration of the number of diffraction structure levels, refer to the above explanation of the embodiment of the grating 76 based on Figure 28 and the 80 based on Figure 32 .

[0278] Based on the example of the optical diffraction element 91 including three diffraction structure levels illustrated in Figure 35 , the basic properties of such a diffraction element will also be explained below. The elements and functions corresponding to those already explained above with reference to Figures 1 to 34 carry the same reference numerals and will not be discussed in detail. The diffraction structure levels are labeled N1, N2, and N3 in Figure 35[[END .

[0279] The target wavelength to be suppressed has a wavelength of λ N .

[0280] The diffraction structure level N1 has a structural depth of 0. The diffraction structure level N2 has a structural depth d of λ N / 6. The deepest diffraction structure level N3 has a structural depth of 2d (= λ N / 3).

[0281] The superposition of a total of n diffraction gratings having structural depths d1, d2,... d n is suitable for suppressing a total of n target wavelengths λ1, λ2,... λ n . In this case, the number of possible diffraction structure levels is 2 nThus, as explained above, given three structural depths d1, d2, d3, eight diffractive structural levels N1 to N8 are obtained. Preferably, the various diffractive structural levels N i are arranged such that all diffractive structural levels N i occupy an equal surface area proportion of the total surface area of the diffractive element 91.

[0282] The optical diffractive element 91 is configured to be a variant of a so-called m-level grating having three levels in this case. Such an m-level grating includes m different diffractive structural levels, each of which occupies an equal surface area and has a structural height difference of d = λ N / (2m) with respect to each other. Again, good suppression of the target wavelength λ N is obtained, where the wavelength sensitivity is low.

[0283] According to ​ the three-level grating refers to a grating period p based on a sequence of three diffractive structural levels N1, N2, N3 with equal repetition.

[0284] ​ Another embodiment of an optical diffractive element 92 that suppresses at least one target wavelength by destructive interference is shown. This illustrative figure shows the diffractive structural levels N n in the region near the deepest diffractive structural level N i , that is, the diffractive structural levels N n-2 , N n-1 , N n , N n+1 , N n+2 .

[0285] The intensity of the reflected light in the zero-order diffraction can be written as follows, starting from the Fraunhofer approximation for the diffractive far field in a simplified manner for an N-level periodic phase grating:

[0286]

[0287] In this case, I(0) is the intensity of the zero-order diffraction, that is, the absolute value square of the field amplitude in the diffractive far field.

[0288] N is the number of levels of the phase grating. L n is the phase term assigned to the corresponding grating level. This phase term L i corresponding to the extension along the periodic traveling direction x of the corresponding diffractive structural level N n is illustrated in ​ . h n is a measure of the structural depth of the corresponding diffractive structural level (see ​ ). Λ is the wavelength of the diffracted light.

[0289] For a further embodiment of the optical diffraction element 93 that suppresses at least one target wavelength by destructive interference, the following is described with reference to ​ Those corresponding to those already described above with reference to ​ and, in particular, with reference to ​ are provided with the same reference signs and are not discussed in detail again.

[0290] ​ Shows a further embodiment of a stepped grating with an equivalent structural depth (designated here as h0) for various grating levels, and equivalent lengths of the diffraction structure levels N1, N2, N3 and N4 along the periodic travel direction (designated here by R). The periodic travel direction R can also be the radius of a concentric diffraction structure, the center of which can coincide with the center of the collector mirror 24.

[0291] Thus, the diffraction element 93 has a total of four diffraction structure levels N1 to N4, the structural depths of which differ by h0 in each case. Here, h0 = λ N / 4 holds, where λ N is the target wavelength to be suppressed.

[0292] In the periodic travel direction R, a complete period p of the diffraction element includes first the four descending diffraction structure levels N1 to N4, and then two successive ascending diffraction structure levels N5, N6, where the structural depth of the diffraction structure level N5 corresponds to the structural depth of the diffraction structure level N3, and the structural depth of the diffraction structure level N6 corresponds to the structural depth of the diffraction structure level N2.

[0293] For further embodiments of the optical diffraction elements 94, 95 that suppress at least one target wavelength by destructive interference, the following is described with reference to ​ and ​ Those corresponding to those already described above with reference to ​ and, in particular, with reference to ​ are provided with the same reference signs and are not discussed in detail again.

[0294] According to ​ the diffraction element 94 has, in succession along the periodic travel direction R within one grating period p, diffraction structure levels N1 (with structural depth 0), N2 (with structural depth h1), N3 (with structural depth h1 + h2) and N4 (with structural depth h2). The following holds: h1 < h2.

[0295] According to ​In the case of the diffractive element 95, along the period traveling direction R within one period p, the following are consecutive to each other: a diffractive structure layer N1 having a structural depth of 0, a diffractive structure layer N2 having a structural depth of h1, a diffractive structure layer N3 having a structural depth of h2, and a diffractive structure layer N4 having a structural depth of h1 + h2. Here, the following also holds: h1 < h2.

[0296] Starting from the equations described above in association with ​ the intensity in the zero-order diffraction can be specified as:

[0297]

[0298] In this case, λ1 and λ2 are the two target wavelengths to be suppressed by destructive interference using the diffractive elements 94 and 95, respectively. The following holds: h1 = λ1 / 4 and h2 = λ2 / 4.

[0299] For λ = λ1 and for λ = λ2, the following holds: I(0) = 0. Thus, these two wavelengths are optimally suppressed.

[0300] In ​ such a multi-layer grating of the type of the grating in the above-described embodiment, it can be generalized to suppress n target wavelengths by destructive interference. To suppress n wavelengths, 2n different diffractive structure layers N with the following heights are required i : h1, h2,... h n , 0, h1 + h2, h1 + h3,..., h1 + h n , where in addition, the different structural depths h1 to h n satisfy the following relationship:

[0301] h1 < h i < h i+1 < 2h1

[0302] With the optical diffractive element described above, as an alternative or in addition to the target wavelengths suppressed in the infrared wavelength range, wavelengths in other wavelength ranges, for example in the DUV wavelength range, can also be suppressed.

[0303] ​ Shown in a graph, for example, the wavelength-dependent reflectivity R of a variant of an optical diffractive element having two structural depths d1 and d2 of the type of the gratings 60, 64 or 71 according to ​ , ​ and ​ In this case, the existing structural depths are as follows: d1 = 45 nm and d2 = 52 nm. As a result, at​ The reflectivity curve 96 shown as a solid line in []. In addition, the reflectivity curves 97 and 98 for the corresponding gratings each containing only one diffraction grating (designed with structural depths d1 (reflectivity curve 97) and d2 (reflectivity curve 98)) are depicted by dashed lines.

[0304] The reflectivity curve 96 shows suppression for the two target wavelengths λ1 ≈ 180 nm and λ2 ≈ 210 nm.

[0305] For the difference measure of these two target wavelengths λ1, λ2, the following holds:

[0306] (λ1 - λ2) 2 / (λ1 + λ2) 2 = 0.006

[0307] Here, the suppression at these two DUV wavelengths is better than 10 -5 better.

[0308] ​ shows ​ or ​ the reflectivity R of an embodiment of an optical diffraction element of the type shown, which in this case is fabricated as a superposition of a total of four diffraction gratings with different structural depths d1 to d4. The following holds here: d1 = 45 nm, d2 = 2 nm, d3 = 2.55 μm, and d4 = 2.65 μm.

[0309] ​ The wavelength - dependent reflectivity curve 97 corresponding to the structural depths d3 and d4 shows two reflectivity minima, where the suppression better than 10 -6 is better at λ3 = 10.2 μm and at λ4 = 10.6 μm.

[0310] In addition, corresponding to the two structural depths d1 and d2, the grating with the reflectivity curve 97 also suppresses the two DUV wavelengths λ1 ≈ equal to 180 nm and λ2 ≈ equal to 210 nm, where, as shown by the magnified detail in the DUV range in [] ​ the suppression is better than 10 -6 better.

[0311] ​The curve illustrates how the requirements regarding the structure depth and / or the sidewall steepness tolerance are relaxed as the number of diffraction structure groups increases, by virtue of using an optical diffraction element composed of a plurality of diffraction structure groups. This illustrative figure again shows the reflectivity as a function of the wavelength in the range between 10.0 and 11.0 μm. In this case, the target wavelength in the region of 10.6 μm is to be suppressed better than 10 -4 is.

[0312] The reflectivity curve for an optical diffraction element comprising only one diffraction structure group (i.e., comprising only one diffraction grating) is illustrated at ​ 98 in, assuming that the structure depth d has a value of 2.65 μm and is allowed to vary within a tolerance bandwidth of 0.5%.

[0313] 99 indicates the reflectivity curve for an optical diffraction element comprising two diffraction gratings as diffraction structure groups, each having an identical structure depth d1 = d2 of 2.65 μm and allowing a tenfold tolerance bandwidth of 5%. In the region of this target wavelength, in the case of the reflectivity curve 99, a better suppression is obtained than in the case of the reflectivity curve 98, although this tolerance bandwidth is ten times higher.

[0314] In ​ 100 indicates the reflectivity curve for an optical diffraction element comprising two diffraction gratings as diffraction structure groups, having different structure depths (d1 = 2.65 μm, d2 = 2.55 μm), each allowing a tolerance bandwidth of 3.5%. A suppression corresponding to that of the reflectivity curve 99 is obtained at the target wavelength of 10.6 μm.

[0315] In ​ 101 indicates the reflectivity curve for an optical diffraction element comprising three diffraction structure groups in the form of three diffraction gratings (having an identical structure depth d1 = d2 = d3 of 2.65 μm and a tolerance bandwidth of 12% for this structure depth).

[0316] Due to the mutually reinforcing suppression effect of the three diffraction gratings in the region of this target wavelength, this very high tolerance bandwidth in turn results in a very good suppression corresponding to the requirement "better suppression than 10 -4 is".

[0317] ​ The grating 60 comprising diffraction structure levels N1 to N4 is again shown, as has been explained above especially with reference to ​ . Furthermore, ​ two lithography mask structures 105, 106 that can be used during the lithographic fabrication of the grating 60 are illustrated.

[0318] In ​ it is illustrated that the lithography mask structure 105 closest to the grating 60 has a mask region 107 that is impermeable to the etching medium and an intervening mask gap 108 that is permeable to the etching medium. The periodicity of the mask structure 105 corresponds to the periodicity of the diffraction grating 62 according to ​ . The mask structure 105 defines, firstly, the layer sidewall N4 / N3 between the diffraction structure levels N4 and N3, and, secondly, the N1 / N2 between the diffraction structure levels N1 and N2.

[0319] The setting offset concerned here along the periodic travel direction x is the second lithography mask structure 106 having a mask region 109 and a mask gap 110. The periodicity of this second lithography mask structure 106 corresponds to the periodicity of the diffraction grating 61 according to ​ . The second lithography mask structure 106 defines the positions of the layer sidewall N3 / N1 between the diffraction structure levels N3 and N1 and, secondly, the N2 / N4 between the diffraction structure levels N2 and N4.

[0320] The topography of the diffraction structure levels N1 to N4 of the grating 60 can be described as (i.e., can be manufactured by means of the lithography mask structures 105, 106) the superposition of two binary structures of the diffraction structure groups 61, 62 (see also ​ and ​ ). Each of these binary structures 61, 62 has a first surface section (with a first structure depth), i.e., the positive structures 61 P , 62 P of the structure groups 61, 62, and a second surface section (with a second structure depth), i.e., the negative structures 61 N , 62 N , which alternate with the first surface section 61 P , 62 P along the periodic travel direction x. The boundary regions between these adjacent surface sections, firstly 61 P / 61 N and, secondly, 62 P / 62 N , i.e., the layer sidewalls N i / N j explained above of each of the binary structures 61, 62, all have a linear path perpendicular to the periodic travel direction and perpendicular to the Figures 14 to 16 and Figure 44 illustrated plane in . The boundary regions N3 / N1, N2 / N4 of the first binary structure 61 and the boundary regions N4 / N3, N1 / N2 of the second binary structure 62 travel completely separated from each other, i.e., do not superimpose on each other in their paths perpendicular to the periodic travel direction x.

[0321] When observed along the traveling direction x of the period, another characteristic of the grating 60 is that each rising hierarchical sidewall (i.e., first N3 / N1 and then N4 / N3) is respectively assigned a falling hierarchical sidewall with the same structural depth. In this case, the rising hierarchical sidewall N3 / N1 is assigned to the falling hierarchical sidewall N2 / N4. The rising hierarchical sidewall N4 / N3 is assigned to the falling hierarchical sidewall N1 / N2. The first assigned hierarchical sidewalls N3 / N1 and N2 / N4 have the structural depth d1 in this case. The hierarchical sidewalls N4 / N3 and N1 / N2 assigned to each other also have the structural depth d2.

[0322] During the manufacture of the grating 60, first one of the two mask structures 105, 106 (for example, the mask structure 105) is used, and in the region of the mask gap 108, in a first etching step using the etching region provided by the corresponding source, a negative structure having the width of the mask gap 108 (with a predefined first etching depth d2) is manufactured in the substrate. After that, the mask structure 105 is removed and the mask structure 106 is used, and in a further etching step, the substrate is etched further to a depth d1 until the diffraction structure levels N1 to N4 corresponding to Figure 44 the bottom illustrative diagram have appeared. Therefore, the mask manufacture of the grating 60 involves using a first mask structure first for photolithographically etching the substrate, and then a second mask structure with different positions regarding the mask region and the mask gap. This difference in the position of the mask region / mask gap can be achieved by replacing the first mask structure with another mask structure and / or by shifting the mask structure along the traveling direction x.

[0323] The manufacturing method may also include more than two etching steps, and it may also use more than two different mask structures and / or more than two etching steps.

[0324] Figure 45 Shows the relationship during the photolithographic manufacture of the grating 64 (see also Figures 17 to 19 ). The elements and functions corresponding to those already described above with reference to Figures 1 to 44 , and particularly with reference to Figures 14 to 19 and Figure 44 are provided with the same reference numerals and will not be discussed in detail.

[0325] In Figure 45 , two photolithographic mask structures 111, 112 are illustrated for the grating 64. The aforementioned mask structures also have periodically successive mask regions and mask gaps. In this case, the photolithographic mask structure 111 has a mask region 113 and a mask gap 114, and the photolithographic mask structure 112 has a mask region 115 and a mask gap 116.

[0326] During the lithographic fabrication of the grating 64, the lithographic mask structure 111 defines the layer sidewalls first N3 / N2 and second N2 / N3, and the additional lithographic mask structure 112 defines the layer sidewalls first N2 / N1 and second N1 / N2. Here, the grating 64 is also produced as a superposition of two binary structures 65, 66 (see Figure 17 and Figure 18 ), the aforementioned two binary structures being perpendicular to the periodic travel direction x and perpendicular to the boundary region of the plane of the illustration in Figures 17 to 19 and Figure 45 (i.e., the layer sidewalls N i / N j ) are completely separated in travel, i.e., not superimposed on each other.

[0327] Here, as viewed along the periodic travel direction x, it also holds again that each ascending layer sidewall (i.e., the sidewalls N2 / N1 and N3 / N2) is again assigned a descending layer sidewall of the same structural depth, i.e., the ascending layer sidewall N2 / N1 is assigned the descending layer sidewall N1 / N2, and the ascending layer sidewall N3 / N2 is assigned the descending layer sidewall N2 / N3.

[0328] The above is especially described with reference to Figures 20 to 22 , Figures 25 to 28 and Figures 29 to 32 The gratings 71, 76, 80 can also be described as the corresponding superposition of binary structures whose boundary regions between their surface segments (i.e., their layer sidewalls N i / N j ) are not superimposed on each other, as already explained above with reference to the aforementioned gratings 60 and 64. In the case of the gratings 76 and 80, these can be described as the superposition of three binary structures whose boundary regions (i.e., layer sidewalls N i , N j ) are not superimposed on each other. For these gratings 71, 76, 80, as viewed along the periodic travel direction x, it also holds that each ascending layer sidewall is assigned a descending layer sidewall of the same structural depth.

[0329] In the case of the optical diffraction element described above with a periodic travel direction of diffraction structure groups that are not parallel to each other, this results in the intersection of the layer sidewalls (i.e., the boundary regions between different surface segments of the diffraction structures). In this case, the aforementioned boundary regions also only overlap with each other at points, i.e., at most along the segments of the linear path of the layer sidewalls, i.e., where the layer sidewalls intersect.

[0330] For a further embodiment of the optical diffraction element 117 in the form of a grating that suppresses at least one target wavelength by destructive interference, the following is with reference toFigure 46 be described. Elements and functions corresponding to those already described above Figures 1 to 45 are denoted by the same reference signs and will not be discussed in detail.

[0331] The grating 117 is embodied as a grating structure profile that is periodic along the periodic travel direction x and includes a diffraction structure having three diffraction structure levels N1, N2, and N3.

[0332] The intermediate diffraction structure level N2 predefines a reference height of 0 (d = 0) and is thus also referred to as the neutral diffraction structure level. The additional diffraction structure level N1 has a structure depth of d = +λ / 4 measured relative to this reference height and is thus also referred to as the positive diffraction structure level. The third diffraction structure level N3 has a structure depth of d = -λ / 4 measured relative to this reference height and is thus also referred to as the negative diffraction structure level.

[0333] Thus, the three diffraction structure levels N1 to N3 predefine different structure depths relative to the reference plane d = 0.

[0334] The grating period p of the grating structure profile of the grating 117 is subdivided into a total of four period segments of the diffraction structure levels N1 to N3. Two of these four period segments are embodied as the neutral diffraction structure level N2, one of the four period segments is embodied as the positive diffraction structure level N1, and the fourth segment of the four period segments is embodied as the negative diffraction structure level N3. In the periodic travel direction x, along Figure 46 the sequence of the selected unit monomers (the aforementioned unit monomers are enclosed by a dashed line) is: N2, N1, N2, N3.

[0335] Along the periodic travel direction x, the four period segments within one grating period p have the same structure length x N .

[0336] Alternatively, the lengths of the period segments (i.e., the x extensions of the respective diffraction structure levels N1 to N3) may also be different from each other in pairs. Then, the following should be satisfied as a limitation for the lengths x Ni of the period segments of the diffraction structure levels N1 to N3:

[0337] x N1 + x N3 = 2x N2

[0338] Thus, the sum of the extensions of the levels deviating from the neutral diffraction structure level should (to a good approximation) be equal to twice the extension of the neutral diffraction structure level.

[0339] The arrangement of the diffraction structure levels N1 to N3 described (i.e., the structure depth and length along the periodic travel direction x) is such that the first target wavelength λ1 in the infrared wavelength range (which is diffracted by the grating structure profile) has radiation components that have three different phases that cancel each other out in the zero-order diffraction of this first target wavelength λ1. Thus, an inhibition effect is obtained, as has been explained above especially in connection with Figures 1 to 45 other optical diffraction elements. As revealed by theoretical considerations, this inhibition effect is squared compared to the inhibition of a single binary grating (not shown). As a result, if a binary grating in which the positive diffraction structure level N1 is further provided instead of the negative diffraction structure level N3 has an inhibition of 10 -2 , the grating 117 has an inhibition effect of, for example, 10 -4 .

[0340] The target wavelength can be in the range between 10 µm and 11 µm.

[0341] The influence of the structure depth error on the diffraction efficiency is explained below with reference to Figure 47 and Figure 48 . It is assumed here that light with the wavelength λ to be inhibited is incident on the grating 117 from above at normal incidence in Figure 47 and Figure 48 . This assumption of "normal incidence" is only used as a model assumption for the following considerations. In reality, the angle of incidence of the light often deviates from normal incidence. Thus, the structure depth of the optical diffraction element described here is then adapted to the corresponding angle of incidence. The method for performing this design adaptation is known to those skilled in the art. In reality, the angle of incidence of the light varies with the wavelength to be inhibited, and the structure depth of the optical diffraction element thus also varies above the EUV collector. In the case of an EUV collector 24 with a rotationally symmetric design, the structure depth of the diffraction structure group can vary continuously from the center of the EUV collector 24 towards the edge of the EUV collector 24.

[0342] Regions of equal phase P0 of the reflected light waves are illustrated by solid dots in Figure 47 and Figure 48 . Since the diffraction structure levels N1 first and N3 second are each offset by an optical path length of λ / 4 relative to the neutral diffraction structure level N2 in each case, it is obvious that for each of the total four period segments of the grating period of the grating 117 illustrated in Figure 47 , two regions of the reflected light are obtained in each case, the phase P0 of which is reflected relative to two further regions with an offset of only half a wavelength (i.e., λ / 2), which, in the case of exactly λ / 4 structure depth in Figure 47 , results in exactly the inhibition of the incident light, i.e., results in destructive interference of the reflected light.

[0343] Figure 47 Show a case where the positive diffraction structure level N1 has a structural depth greater than λ / 4 and the negative diffraction structure level N3 has a structural depth with the same absolute value as the structural depth of the positive diffraction structure level N1 (i.e., the absolute terms correspondingly are also greater than λ / 4). Thus, height errors exist in the case of the grating according to Figure 47 of the grating.

[0344] The region of the equal phase P of the light that is first reflected by the positive diffraction structure level N1 and secondarily reflected by the negative diffraction structure level N3 is illustrated by hollow circles in 0, d the Figure 48 is illustrated by hollow circles.

[0345] As shown by comparing the positions in the beam directions of the reflected light of these two phases P that are respectively reflected by the levels N1 and N3 with the corresponding phase position P0 in the case of the perfect suppression scenario according to 0, d In the case of the scenario according to Figure 47 In the case of the scenario according to Figure 48 In the case of the scenario according to 0, d These two phases P exist near the correct phase positions in such a way that they are respectively shifted upward and downward by the same distance, and as a result, the average value of the two shifted phases P 0, d becomes again located at the position of the exact phase position according to Figure 47 Compared with a binary grating having only two diffraction structure levels corresponding to the diffraction structure levels N1 and N2 and the corresponding height errors, this averaging results in an improvement in suppression in the case of the grating having the three diffraction structure levels N1 to N3.

[0346] Figure 49 Show another variant of an optical diffraction element that suppresses at least one target wavelength in the form of a grating 118 that includes diffraction structures and also has three diffraction structure levels N1, N2, and N3. The elements and functions corresponding to those that have been described above with reference to Figures 1 to 48 and in particular with reference to Figures 46 to 48 are given the same reference numerals and will not be discussed in detail again.

[0347] Figure 49 Again, the unit cell that extends along the periodic travel direction x during one period p is illustrated by a dashed line. First, there is a neutral diffraction structure level N2 in this unit cell in the periodic travel direction x, which has twice the length 2x compared with the other two diffraction structure levels N . Thus, within the illustrated unit cell, the sequence of the diffraction structure levels in the periodic travel direction is: a neutral diffraction structure level N2 with a twice length 2x N , a positive diffraction structure level N1 with a single length x N , a positive diffraction structure level N1 with a single length xN The negative diffraction structure level N3. Thus, in the case of the grating 118, within the unit cell, the positive diffraction structure level N1 is immediately followed by the negative diffraction structure level N3, such that the sidewalls of the intermediate level have a structural depth of λ / 2.

[0348] Figure 50 Shows a further embodiment of an optical diffraction element that suppresses at least one target wavelength, the aforementioned optical diffraction element being fabricated as a grating 120 and again including a diffraction structure having four diffraction structure levels N1 to N4. Corresponding elements and functions to those already explained above with reference to Figures 1 to 49 and in particular with reference to Figures 46 to 49 are provided with the same reference numerals and will not be discussed in detail. Along the periodic propagation direction, the grating 120 has the following sequence of diffraction structure levels: a positive diffraction structure level N1 with a structural depth of +λ / 4, a neutral diffraction structure level N2, a negative diffraction structure level N3 with a structural depth of -λ / 4, a double negative diffraction structure level N4 with a structural depth of -λ / 2, a negative diffraction structure level N3, and a neutral diffraction structure level N2. Thus, the unit cell of the grating 120 includes the sequence of diffraction structure levels N1, N2, N3, N4, N3, N2 or a corresponding cyclic permutation.

[0349] Figure 51 Shows a further embodiment of an optical diffraction element that suppresses at least one target wavelength, the aforementioned optical diffraction element being fabricated as a grating 121 and again including a diffraction structure having five diffraction structure levels N1 to N5. Corresponding elements and functions to those already explained above with reference to Figures 1 to 50 and in particular with reference to Figures 46 to 50 are provided with the same reference numerals and will not be discussed in detail. Along the periodic propagation direction, the grating 121 has the following sequence of diffraction structure levels: a positive diffraction structure level N1 with a structural depth of +λ / 4, a neutral diffraction structure level N2, a negative diffraction structure level N3 with a structural depth of -λ / 4, a double negative diffraction structure level N4 with a structural depth of -λ / 2, a triple negative diffraction structure level N5 with a structural depth of -3λ / 4, a double negative diffraction structure level N4 with a structural depth of -λ / 2, a negative diffraction structure level N3 with a structural depth of -λ / 4, and a neutral diffraction structure level N2. Thus, the unit cell of the grating 121 includes the sequence of diffraction structure levels N1, N2, N3, N4, N5, N4, N3, N2 or a corresponding cyclic permutation.

[0350] The additional diffraction structure level N4 in the case of the grating 120, and N4, N5 in the case of the grating 121 result in an additional enhancement of the diffraction effect, i.e., in terms of an additional enhancement of the destructive interference at the target wavelength λ.

[0351] Figure 52 Showing a sequence having diffraction structure levels N1, N2, and N3 Figure 46 The reflectivity curve 125 of a grating of the type shown, wherein the diffraction structure levels have a structure depth d (d ≈ 2.6 μm) of λ / 4 in each case, and a periodic propagation direction x (x N1 = x N2 = x N3 ) and the equivalent structural lengths x of the diffraction structure levels N1 to N3 in the periodic propagation direction x N . As a result, the reflectivity curve 125 has a broad reflectivity minimum at around the wavelength λ = 10.4 μm. Between 10.2 μm and 10.6 μm, the reflectivity is less than 2∙10 -6 . Between 10.1 μm and 10.7 μm, the reflectivity is less than 3∙10 -6 . Between 10.0 μm and 10.8 μm, the reflectivity is less than 5∙10 -6 . This results in a very good suppression of interfering wavelengths within the indicated wavelength range. -6 .

[0352] Figure 53 In the form of Figure 44 and Figure 45 it is shown the relationship during the lithographic fabrication of a grating 64 with a period p = 4x N (see also Figures 17 to 19 ).

[0353] Elements and functions corresponding to those already explained above with reference to Figures 1 to 52 , and in particular with reference to Figures 14 to 19 , Figure 44 and Figure 45 carry the same reference signs and will not be discussed in detail again.

[0354] For the grating 64, Figure 53 a further embodiment of a lithographic mask structure 126, 127 is illustrated which is used during the lithographic fabrication of the grating 64 and again has periodically successive mask regions and mask gaps. In this case, the lithographic mask structure 126 has successive mask regions 128 and 129 and mask gaps 130 and 131 therebetween, and the mask structure 127 has successive mask regions 132 and 133 and mask gaps 134 and 135 therebetween.

[0355] During the lithographic production of the grating 64, the mask region 128 of the mask structure 126 defines the level side walls first N3 / N2 and secondly N1 / N2. A further mask region 129 of the mask structure 126 defines the level side walls N2 / N1 and N2 / N3 for the next sequence of diffractive structure levels of the grating 64 that follows in the periodic running direction x. The further lithographic mask structure 127 defines the diffractive structure level N2 beginning in the periodic running direction x with the mask region 132. i The periodic level sidewalls N2 / N1 and N2 / N3, and the mask region 133 of the mask structure 127 defines the diffraction structure level N i The next period of the layer sidewall N3 / N2 and N1 / N2. The grating 64 is generated as a superposition of two binary structures, the two binary structures are perpendicular to the periodic travel direction x (perpendicular to Figure 53 The boundary areas of the diagram plane in the figure are completely separated from each other, that is, they do not overlap with each other.

[0356] The mask structures 128, 129 and 132, 133 all have the same x extension, ie 2x N The mask gaps 131 and 134 have the same x extension, ie, both are x N The mask structures 130 and 135 also have the same x extension, namely 3x N .

[0357] Therefore, the mask structures 126, 127 alternately predefine different levels of sidewalls for respectively successive periods p of the grating 64. By means of a shift in the period length p, most of the mask structures 126 and 127 can be converted into one another.

[0358] Figure 54 An alternative embodiment of two mask structures 136, 137 is shown during the lithographic production of the grating 64. Figures 1 to 53 , and with particular reference to Figures 14 to 19 , Figure 44 and Figure 53 Elements and functions of those explained carry the same reference numerals and are not discussed again in detail.

[0359] The mask structure 136 has mask regions 138, 139 and mask gaps 140, 141 therebetween. The mask structure 137 has mask regions 142, 143 and mask gaps 144 and 145 therebetween. The x extension of the mask regions 138 and 143 is firstly 3x N , so x N The mask regions 139 and 142 have an x ​​extension of three times the magnitude. The mask gaps 140, 141, 144 and 145 all have a 2xN extension

[0360] During the lithographic manufacture of the grating 64, the lithographic mask structure 136 defines, by means of the mask regions 138, the layer sidewalls N3 / N2 and N2 / N3 of the first period p of the diffraction structure levels N1 to N3 of the grating 64, and the mask region 139 defines the layer sidewalls first N2 / N1 and second N1 / N2 of the second period p of the diffraction structure levels N1 to N3. The further lithographic mask structure 137 defines, by means of the mask region 142, the layer sidewalls N2 / N1 and N1 / N2 of this first period, and, by means of the mask region 143, the layer sidewalls N3 / N2 and N2 / N3 of the subsequent period p of the diffraction structure levels N1 to N3.

[0361] Here, in a manner similar to that which also holds in the case of the embodiment according to Figure 54 , the mask structures 136 and 137 alternately predefine different layer sidewalls of the subsequent periods of the diffraction structure levels N1 to N3. The mask structures 136 and 137 can also be converted into one another by means of a shift by the period length p = 4x N .

[0362] The relationship during a further embodiment of manufacturing the grating 146 by means of two mask structures 147, 148 will be explained with reference to Figure 55 . In contrast to Figure 53 and Figure 54 (each of which shows two grating periods of the grating 64), one grating period p is shown in Figure 55 . Within this grating period p, the grating 146 has, in the travel direction x, the following sequence of diffraction structure levels N i : N1, N2, N1, N2, N3 and N2. This grating period p has an extension of 6x N . All diffraction levels N1 each have an extension of x N .

[0363] The mask structure 147 has, according to the period p, mask regions 149, 150 and intervening mask gaps 151, 152, and the mask structure 148 has, according to the period p, only one assigned mask region 153 and one mask gap 154. The mask regions 149 and 150 have an extension of 2x N . The mask gaps 151, 152 have an extension of x N . The mask region 153 has an extension of 3x N . The mask gap 154 likewise has an extension of 3x N .

[0364] Within the sequence of hierarchical sidewalls during a period p along the period travel direction x, the following assignments hold with respect to predefining the respective hierarchical sidewalls through the mask regions of the respective mask structures:

[0365]

[0366] Regarding the relationship during a further embodiment of manufacturing the grating 155 by means of two mask structures 156, 157, reference will be made to Figure 56 for explanation. In contrast to Figure 53 and Figure 54 (each of which shows two grating periods of the grating 64), one grating period p is shown in Figure 56 . Within this grating period p, the grating 155 has the following sequence of diffractive structure levels N i : N2, N1, N2, N3, N2, and N3. Thus, in the case of the grating 155, there is also a period p with an extension of 6x N . Each of the diffractive structure levels N i has an extension of x N along the period travel direction x.

[0367] For the manufacture of the grating 155, again two lithographic mask structures 156 and 157 are illustrated in Figure 56 . In this case, the mask structure 156 has mask regions 158 and 159 and mask gaps 160, 161 therebetween, and the mask structure 157 has only one mask region 162 and one mask gap 163 according to the period. Each of the mask regions 158 and 159 has an extension of x N . Each of the mask gaps 160, 161 also has an extension of 2x N . First, the mask region 162 and then the mask gap 163 each have an extension of 3x N .

[0368] During the lithographic manufacture of the grating 155, the following assignments of mask regions hold for the hierarchical sidewalls:

[0369]

[0370] The structure of the grating explained above can have the following effect: Stray light radiation having, for example, an infrared wavelength reflected by the EUV collector 24 undergoes destructive interference in the zero order, and the stray light intensity is thus suppressed in the zero order. In this case, the optical diffractive element explained above generally serves as a reflective element.

[0371] The body of the EUV collector 24 can be made of aluminum. Alternative materials for this body are copper, alloys containing the components copper and / or aluminum, or alloys of copper and aluminum oxide or silicon produced by powder metallurgy.

[0372] To manufacture a microstructured or nanostructured element, the projection exposure apparatus 1 is used as follows: First, a reflective mask 10 or a mask master and a substrate or a wafer 11 are provided. Thereafter, the structures on the mask master 10 are projected onto the photosensitive layer of the wafer 11 by means of the projection exposure apparatus 1. Then, the microstructures or nanostructures on the wafer 11, and thus the microstructured element, are manufactured by developing the photosensitive layer.

Claims

1. An element, comprising: A periodic grating structure profile having a grating period including first, second, third, and fourth structural segments, wherein: The first structural segment has a neutral structural level; The second structural segment has a neutral structural level; The third structural segment has a positive structural level higher than the neutral structural level; The fourth structural segment has a negative structural level lower than the neutral structural level; The neutral structural level, the positive structural level, and the negative structural level define the topography of the grating period that repeats regularly along one direction; and Along the said direction, the structural segments have the same length within + / - 20%.

2. The element according to claim 1, wherein Along the said direction, the structural segments have the following sequence: the third structural segment; the first structural segment; the fourth structural segment; and the second structural segment.

3. The element according to claim 1, wherein, Along the said direction, the third structural segment is located between the first structural segment and the second structural segment.

4. The element according to claim 1, wherein, Along the said direction, the fourth structural segment is located between the first structural segment and the second structural segment.

5. The element according to claim 1, wherein Along the said direction, the first structural segment, the second structural segment, the third structural segment, and the fourth structural segment have the same length within + / - 15%.

6. The element according to claim 1, wherein: The first structural segment, the second structural segment, the third structural segment, and the fourth structural segment are configured such that a wavelength range including a first infrared wavelength λ1 is diffracted by the periodic grating structure profile, The positive structural level is higher than the neutral structural level by an optical path length of λ1 / 4 + / - 20%.

7. The element according to claim 6, wherein The negative structural level is lower than the neutral structural level by an optical path length of λ1 / 4 + / - 20%.

8. The element according to claim 1, wherein: The first structural segment, the second structural segment, the third structural segment, and the fourth structural segment are configured such that a wavelength range including a first infrared wavelength λ1 is diffracted by the periodic grating structure profile, The negative structural level is lower than the neutral structural level by an optical path length of λ1 / 4 + / - 20%.

9. The element according to claim 1, wherein: The first structural segment, the second structural segment, the third structural segment, and the fourth structural segment are configured such that a wavelength range including a first infrared wavelength λ1 is diffracted by the periodic grating structure profile, The wavelength range includes radiation components that cancel each other out in interference in at least one diffraction order, and the at least one diffraction order is selected from the group consisting of: the zero-order diffraction of the first infrared wavelength λ1; The positive first-order diffraction of the first infrared wavelength λ1; and the negative first-order diffraction of the first infrared wavelength λ1.

10. The element according to claim 9, wherein: The wavelength range further includes a second infrared wavelength λ2 different from the first infrared wavelength λ1, The wavelength range includes radiation components that cancel each other out in interference in at least one diffraction order, and the at least one diffraction order is selected from the group consisting of: the zero-order diffraction of the second infrared wavelength λ2; The positive first-order diffraction of the second infrared wavelength λ2; and the negative first-order diffraction of the second infrared wavelength λ2.

11. The element according to claim 10, wherein, (λ1 - λ2) 2 / (λ1 + λ2) 2 < 20%.

12. The element according to claim 9, wherein (λ1 - λ2) 2 / (λ1 + λ2) 2 < 20%.

13. The element according to claim 1, wherein: The first structural section, the second structural section, the third structural section, and the fourth structural section are configured such that a first wavelength range including a first wavelength λ1 is diffracted by the periodic grating structure profile; The first wavelength λ1 is an infrared wavelength; The first wavelength range includes radiation components that destructively interfere with each other in at least one diffraction order selected from the group consisting of: the zero-order diffraction of the first wavelength λ1; the positive first-order diffraction of the first wavelength λ1; and the negative first-order diffraction of the first wavelength λ1; The first structural section, the second structural section, the third structural section, and the fourth structural section are configured such that a second wavelength range including a second wavelength λ2 is diffracted by the periodic grating structure profile; The second wavelength range includes radiation components that destructively interfere with each other in at least one diffraction order selected from the group consisting of: the zero-order diffraction of the second wavelength λ2; the positive first-order diffraction of the second wavelength λ2; and the negative first-order diffraction of the second wavelength λ2; and The second wavelength λ2 is selected from the group consisting of: a near-infrared wavelength, an ultraviolet wavelength, and a deep-ultraviolet wavelength.

14. A collector, comprising: The element according to claim 1, wherein the collector is a lithography collector.

15. An illumination system, comprising: A lithography collector including the element according to claim 1; and An illumination optical unit configured to illuminate an object field.

16. An optical system, comprising: A lithography collector including the element according to claim 1; An illumination optical unit configured to illuminate an object field; and A projection optical element configured to image the object field onto an image field.

17. A device, comprising: A light source; A lithography collector including the element according to claim 1; An illumination optical unit configured to illuminate an object field; A projection optical unit configured to image the object field onto an image field, wherein the device is a projection exposure device.

18. An element, comprising: A periodic grating structure profile having a grating period, wherein: The periodic grating structure profile includes a diffraction structure configured such that a first wavelength range including a first infrared wavelength λ1 is diffracted by the periodic grating structure profile; The first wavelength range includes radiation components that destructively interfere with each other in at least one diffraction order selected from the group consisting of: the zero-order diffraction of the first infrared wavelength λ1; the positive first-order diffraction of the first infrared wavelength λ1; and the negative first-order diffraction of the first infrared wavelength λ1; The first wavelength range includes a second infrared wavelength λ2 different from the first infrared wavelength λ1; The diffraction structure is configured such that a second wavelength range including the second infrared wavelength λ2 is diffracted by the periodic grating structure profile; The second wavelength range includes radiation components that destructively interfere with each other in at least one diffraction order selected from the group consisting of: the zero-order diffraction of the second infrared wavelength λ2; the positive first-order diffraction of the second infrared wavelength λ2; and the negative first-order diffraction of the second infrared wavelength λ2; (λ1 - λ2) 2 / (λ1 + λ2) 2 < 20%; and The periodic grating structure profile includes exactly three different structural levels such that each diffraction structure has a structural level selected from one of the three different structural levels.

19. An element, comprising: Periodic grating structure profile with a grating period, wherein: The periodic grating structure profile includes a diffraction structure configured such that a first wavelength range including a first wavelength λ1 is diffracted by the periodic grating structure profile; The first wavelength λ1 is an infrared wavelength; The first wavelength range includes radiation components that destructively interfere with each other in at least one diffraction order selected from the group consisting of: the zero-order diffraction of the first wavelength λ1; the positive first-order diffraction of the first wavelength λ1; and the negative first-order diffraction of the first wavelength λ1; The diffraction structure is configured such that a second wavelength range including a second wavelength λ2 is diffracted by the periodic grating structure profile; The second wavelength range includes radiation components that destructively interfere with each other in at least one diffraction order selected from the group consisting of: the zero-order diffraction of the second wavelength λ2; the positive first-order diffraction of the second wavelength λ2; and the negative first-order diffraction of the second wavelength λ2; The second wavelength λ2 is selected from the group consisting of: near-infrared wavelength, ultraviolet wavelength, and deep-ultraviolet wavelength; and The periodic grating structure profile includes exactly three different structural levels such that each diffraction structure has a structural level selected from one of the three different structural levels.

20. An element, comprising: Periodic grating structure profile with a grating period, wherein: The periodic grating structure profile includes a diffraction structure configured such that a first wavelength range including a first wavelength λ1 is diffracted by the periodic grating structure profile; The first wavelength λ1 is an infrared wavelength; The first wavelength range includes radiation components that destructively interfere with each other in at least one diffraction order selected from the group consisting of: the zero-order diffraction of the first wavelength λ1; the positive first-order diffraction of the first wavelength λ1; and the negative first-order diffraction of the first wavelength λ1; The diffraction structure is configured such that a second wavelength range including a second wavelength λ2 is diffracted by the periodic grating structure profile; The second wavelength range includes radiation components that destructively interfere with each other in at least one diffraction order selected from the group consisting of: the zero-order diffraction of the second wavelength λ2; the positive first-order diffraction of the second wavelength λ2; and the negative first-order diffraction of the second wavelength λ2; The second wavelength λ2 is selected from the group consisting of: ultraviolet wavelength and deep-ultraviolet wavelength.

Images