CN116745702A - Method for adjusting an optical system, in particular for microlithography - Google Patents
Method for adjusting an optical system, in particular for microlithography Download PDFInfo
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- CN116745702A CN116745702A CN202180092081.0A CN202180092081A CN116745702A CN 116745702 A CN116745702 A CN 116745702A CN 202180092081 A CN202180092081 A CN 202180092081A CN 116745702 A CN116745702 A CN 116745702A
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- 230000003287 optical effect Effects 0.000 title claims abstract description 174
- 238000000034 method Methods 0.000 title claims abstract description 48
- 238000001393 microlithography Methods 0.000 title claims abstract description 17
- 230000009897 systematic effect Effects 0.000 claims abstract description 46
- 239000000463 material Substances 0.000 claims description 15
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 12
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- 230000008021 deposition Effects 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 6
- 238000003384 imaging method Methods 0.000 claims description 6
- 238000005468 ion implantation Methods 0.000 claims description 6
- 238000007689 inspection Methods 0.000 claims description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
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- ORUIBWPALBXDOA-UHFFFAOYSA-L magnesium fluoride Chemical compound [F-].[F-].[Mg+2] ORUIBWPALBXDOA-UHFFFAOYSA-L 0.000 description 9
- 229910001635 magnesium fluoride Inorganic materials 0.000 description 9
- 238000010586 diagram Methods 0.000 description 8
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- 229910021486 amorphous silicon dioxide Inorganic materials 0.000 description 1
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Classifications
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70216—Mask projection systems
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/62—Optical apparatus specially adapted for adjusting optical elements during the assembly of optical systems
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/08—Mirrors
- G02B5/0891—Ultraviolet [UV] mirrors
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70216—Mask projection systems
- G03F7/70258—Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system
- G03F7/70266—Adaptive optics, e.g. deformable optical elements for wavefront control, e.g. for aberration adjustment or correction
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70216—Mask projection systems
- G03F7/70308—Optical correction elements, filters or phase plates for manipulating imaging light, e.g. intensity, wavelength, polarisation, phase or image shift
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70216—Mask projection systems
- G03F7/70316—Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/7055—Exposure light control in all parts of the microlithographic apparatus, e.g. pulse length control or light interruption
- G03F7/70566—Polarisation control
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70591—Testing optical components
- G03F7/706—Aberration measurement
Abstract
The application relates to a method for adjusting an optical system, in particular for microlithography, comprising a plurality of optical elements, each of which is provided with an optically effective layer system, comprising the following steps: determining a system wavefront provided by the optical system in a predefined plane during operation; determining a systematic wavefront deviation between the determined systematic wavefront and a target systematic wavefront; and performing a layer operation on the at least one optical element such that the determined systematic wavefront deviation is reduced. In this case, according to one aspect, a predetermined look-up table is used to select a layer operation suitable for reducing systematic wavefront deviation, in which look-up table the respective wavefront contributions of the at least one optical element to the systematic wavefront are listed for different layer operations of the layer system of the optical element.
Description
Cross Reference to Related Applications
The present application claims priority from german patent application DE 10 2021 201 193.4 filed on 2 months 9 of 2021. The content of this DE application is incorporated by reference into the text of the present application.
Technical Field
The present application relates to a method for adjusting an optical system, in particular for microlithography.
Background
Microlithography is used for the production of microstructured components such as integrated circuits or liquid crystal displays. The microlithography process is carried out in a device known as a projection exposure apparatus, which comprises an illumination device and a projection lens. In this case, the image of the mask (=reticle) illuminated by the illumination device is projected by means of a projection lens onto a substrate (for example a silicon wafer) which is coated with a photosensitive layer (photoresist) and arranged in the image plane of the projection lens, so that the mask structure is transferred onto the photosensitive coating of the substrate.
The mask inspection device is used for inspecting a reticle of a microlithographic projection exposure apparatus.
In projection lenses or inspection lenses designed for the EUV range (i.e. at a wavelength of e.g. about 13.5nm or about 6.7 nm), reflective optical elements are used as optical components of the imaging process due to the lack of availability of suitable light-transmitting refractive materials.
In the development of projection lenses with even higher resolution and the accompanying increasing precision requirements, the use of available degrees of freedom or manipulators to perform the corresponding adjustment methods that "normalize" the individual optical systems also presents an increasingly demanding challenge. "conditioning" within the meaning of the present application is understood to mean an iterative reduction of optical effects of process defects (e.g. grinding defects on the lens element, spiral effects on the optical element or its mount, etc.) associated with the process of manufacturing the optical system or the associated optical element.
For the prior art, reference is made to US7,629,572B2, US 4,533,449, EP 3 286 595b1 and WO 2017/125362 A1 by way of example only.
Disclosure of Invention
The object of the present application is to provide a method for adjusting an optical system, in particular for microlithography, which method makes it possible to achieve a settable wavefront effect as precisely as possible.
This object is achieved by a method according to the features of independent patent claim 1.
According to one aspect, a method according to the application for adjusting an optical system, in particular for microlithography, the optical system comprising a plurality of optical elements, each optical element being provided with an optically effective layer system, comprises the steps of:
-determining a system wavefront provided by the optical system in a predefined plane during operation;
-determining a systematic wavefront deviation between the determined systematic wavefront and the target systematic wavefront; and
-performing a layer operation on at least one optical element such that the determined systematic wavefront deviation is reduced;
a predetermined look-up table is used to select a layer operation suitable for reducing systematic wavefront deviation, in which look-up table the respective wavefront contributions of at least one optical element to the systematic wavefront are listed for different layer operations of the layer system of said optical elements.
According to the above aspect, a layer operation suitable in a specific case for reducing the systematic wavefront deviation between the determined systematic wavefront and the target systematic wavefront is selected by referring to a predetermined lookup table and the sensitivity for the relevant layer operation stored in the lookup table and any other manipulator present in the optical system. The contribution of the corresponding wavefront to the system wavefront or the resulting wavefront change compared to the optical design can be listed in the look-up table for different layer operations of the relevant optical element or for different configurations of the layer system manipulated according to the application.
Within the meaning of the present application, the term "layer operation" is also understood to mean the deposition of a layer on an optical element which is not initially coated.
According to one embodiment, in the step of determining the system wavefront, the optical element is coated. In this case, the coating may be a coating of the relevant element, which does not yet correspond to the final layer design (in this sense a "partial" coating). Furthermore, the layer operations may also be performed iteratively on different layers of the layer system, in each case with systematic wavefront characterization being effected between the individual iteration steps.
The application is based on the following concepts, inter alia: the adjustment of the optical system consisting of a plurality of optical elements is performed, in particular with respect to the adjustment of the system wavefront provided by the optical system in a predefined plane during operation, such that the layer operation performed on at least one of the optical elements or the optical effect or wavefront contribution caused by the layer system located on the relevant optical element itself is used as a degree of freedom for the adjustment.
In other words, the present application includes the following principles: the actual system wavefront in the predefined plane is initially determined at the beginning of the system adjustment, and then a layer operation (considered as degrees of freedom during the system adjustment) of at least one optical element (which has been incorporated into the optical system during the determination of the actual system wavefront at the beginning of the system adjustment) is determined as to how to perform, thereby reducing the deviation between the determined actual system wavefront and the final striving target system wavefront.
The present application differs from conventional methods in particular in that the layer operation of the optical element which has been incorporated into the optical system during the actual system wavefront determination performed at the beginning of the system adjustment, and optionally has been provided with its optically effective coating (i.e. has contributed to the measured actual system wavefront), is used as a degree of freedom for the adjustment, thereby improving the wavefront properties of the overall system or reducing the wavefront aberration.
In particular, the concept according to the application differs first from conventional methods in which the wavefront correction is performed only by processing elements that have not been incorporated into the optical system at the beginning of the adjustment process. In this case, reference may be made to EP 3 286 595B1 as an example. Furthermore, the concept according to the application also differs from conventional methods in which individual optical elements are modified in each case only in order to optimize the wavefront properties or transmission properties of the relevant optical element (instead of the entire system). In this regard, as an example, reference may be made to US7,629,572B2.
According to one embodiment, the layer operation includes: a locally varying deposition of a layer material is performed on the at least one optical element.
According to another embodiment, the layer operation comprises: locally varying layer removal is performed on the at least one optical element.
According to another embodiment, the at least one optical element comprises a metal made of silicon dioxide (SiO 2 ) And a sealing layer is formed. This is advantageous in particular in the case of layer operations which are achieved by layer removal, such as ion beam polishing, as will be explained below.
According to another embodiment, the layer operation comprises: ion implantation of local variations is performed in at least one optical element.
The application further relates to a method for adjusting an optical system, in particular for microlithography, comprising a plurality of optical elements, each of which is provided with an optically effective layer system, comprising the following steps:
-a system wavefront provided by the optical system in a predefined plane during the determining operation;
-determining a systematic wavefront deviation between the determined systematic wavefront and the target systematic wavefront; and
-performing a layer operation on at least one optical element such that the determined systematic wavefront deviation is reduced;
the layer operation includes: a locally varying deposition of the layer material is performed on the at least one optical element and/or a locally varying ion implantation is performed in the at least one optical element.
The layer system present on the at least one optical element may be a single layer or a multi-layer system during the determination of the actual system wavefront. Furthermore, the application is not further limited to the specific local area of the optical element or layer system in which the layer operation is implemented. In particular, the layer operation may alternatively be performed on an inner layer within the multilayer system, or on a cover layer located at the very top of the multilayer system or monolayer.
The determination of the systematic wavefront deviation between the determined systematic wavefront and the target systematic wavefront and the reduction of this deviation can be achieved in particular in an iterative process.
According to one embodiment, performing layer operations on at least one optical element is implemented such that: for at least one further characteristic property of the optical system, the deviation between the actual value given before the layer operation and the target value is reduced. The at least one further characteristic property of the optical system may particularly comprise a reflection behavior and/or a transmission behavior of the optical system.
The application further relates to a method for adjusting an optical system, in particular for microlithography, comprising a plurality of optical elements, each of which is provided with an optically effective layer system, comprising the following steps:
-determining a system wavefront provided by the optical system in a predefined plane during operation;
-determining a systematic wavefront deviation between the determined systematic wavefront and the target systematic wavefront; and
-performing a layer operation on at least one optical element such that the determined systematic wavefront deviation is reduced;
performing layer operations on the at least one optical element is further implemented such that: for at least one further characteristic property of the optical system, the deviation between the actual value given before the layer operation and the target value is reduced.
According to one embodiment, performing layer operations on at least one optical element is further implemented such that: the polarization effect of the optical system is changed.
According to one embodiment, performing layer operations on at least one optical element is further implemented such that: for the reflection behaviour of the optical system, the transmission behaviour of the optical system and the polarization effect of the optical system, the respective deviations between the actual values given before the layer operation and the target values are reduced in each case.
According to one embodiment, the at least one optical element on which the layer operation is performed is a lens element.
According to one embodiment, the at least one optical element on which the layer operation is performed is a mirror.
In particular, the optical system may be an imaging system. In this case, the predefined plane may be an image plane of the imaging system.
According to one embodiment, the optical system is designed for an operating wavelength of less than 250nm, in particular less than 200 nm.
According to another embodiment, the optical system is designed for an operating wavelength of less than 30nm, in particular less than 15 nm.
The application also relates to a microlithography optical system formed by performing the method having the above-mentioned features. The optical system may in particular be a projection lens of a microlithographic projection exposure apparatus or a projection lens of a mask inspection apparatus.
Further configurations of the application are evident from the description and the dependent claims.
The application is explained in more detail below on the basis of exemplary embodiments shown in the drawings.
Drawings
In the drawings:
fig. 1 shows a flow chart for elucidating a possible sequence of the method according to the application;
fig. 2 shows a schematic diagram for elucidating a possible structure of an optical element subjected in an exemplary embodiment to a layer operation according to the application;
figures 3a-6b show schematic diagrams for elucidating a change of the optical properties of the optical element of figure 2, which has been manipulated, which change can be obtained by a layer operation according to the application;
fig. 7 shows a schematic diagram of a possible structure of a microlithographic projection exposure apparatus designed for operation under DUV; and is also provided with
Fig. 8 shows a schematic diagram of a possible structure of a microlithographic projection exposure apparatus designed for operation under EUV.
Detailed Description
Fig. 1 shows a flow chart for elucidating a possible sequence of the method for adjusting an optical system according to the application.
The adjustment according to the application is carried out after providing the relevant optical system with a plurality of optical elements which are arranged and mounted in the beam path and which have been provided with an optically effective coating, the geometry and spacing of the respective coating and optical elements being set according to a predefined optical design. The purpose of performing this adjustment procedure is to obtain specifications established in each case for the specific application, in particular with respect to the system wavefront provided by the system during operation, which in turn is achieved in an iterative procedure using the available degrees of freedom.
The optical system to be adjusted may in particular be a microlithography optical system and more particularly a projection lens of a microlithography projection exposure apparatus or a mask inspection apparatus. Examples of microlithographic projection exposure apparatuses (designed for operation under DUV and EUV, respectively) will be described below with reference to fig. 7 and 8.
At the beginning of the adjustment method according to the application, first, step S110 comprises determining a (actual) system wavefront provided by the optical system in a predefined plane, e.g. an imaging plane forming a projection lens of the optical system. In step S120, the actual system wavefront is compared with the target system wavefront required according to the predefined specification, thereby determining a system wavefront deviation.
In step S130, at least one optical element of the optical system is layer-operated such that the system wavefront deviation is reduced. In this case, the layer operation may include, in particular: locally varying layer removal is performed on the relevant optical element, locally varying deposition of layer material is performed on the element, and/or locally varying ion implantation (e.g. plasma immersion ion implantation).
The layer operation is implemented such that the desired specification of the system wavefront provided by the optical system during operation is ultimately achieved. For this purpose, for determining a suitable layer operation, a predetermined look-up table can also be consulted, in which the respective wavefront contributions of the relevant optical elements to the system wavefront are listed for different configurations of the manipulated layer system of the optical elements and optionally of other manipulators present in the optical system. In a further embodiment, the currently set system wavefront in each case can also be determined in an iterative process in which the layer operation is repeatedly performed and compared with the target system wavefront.
It is important for the application that the layer operation itself performed is used as a degree of freedom for adjustment during adjustment of the optical system. In this case, the optical element subjected to the layer operation is already incorporated into the optical system during the initial determination of the actual system wavefront, so that the wavefront contribution of the optical element is also taken into account concomitantly during the adjustment from the beginning.
In the following, first of all, based on a specific exemplary embodiment, and with reference to the schematic diagrams in fig. 2 and the diagrams in fig. 3a-3b, fig. 4a-4b, fig. 5a-5b and fig. 6a-6b, a change of the optical properties of an optical element of which the layer system has been processed, which change can be obtained by a layer operation according to the application, is described. Although reference is made below by way of example to a specific layer design of an optical element that is manipulated in accordance with the application and the layer design will be described in more detail with reference to fig. 2, the application is not limited to the materials or layer thicknesses used in this exemplary embodiment. For other suitable layer materials, reference is made for example to US10,642,167B2 and US 5,963,365.
Further, the layer design selected in the exemplary embodiment corresponds to a layer design of a lens element configured for operation at a wavelength of DUV or approximately 193nm. However, the application is also not limited thereto, but in further applications can also be implemented in optical elements in the form of mirrors, in particular operating at EUV (i.e. at wavelengths of less than 30nm, in particular less than 15 nm).
In the exemplary embodiment of fig. 2, optical element 200 on substrate 201 includes a layer system of layers 202-206, the respective materials and layer thicknesses being specified in table 1.
Table 1
| Layer(s) | Material | Refractive index | Thickness [ nm ]] |
| 201 | CaF 2 | 1.50150 | |
| 202 | SiO 2 | 1.58854 | 28.22 |
| 203 | MgF 2 | 1.43758 | 34.56 |
| 204 | SiO 2 | 1.58854 | 30.28 |
| 205 | MgF 2 | 1.43758 | 18.20 |
| 206 | SiO 2 | 1.58854 | 12.00 |
| Medium (D) | Air-conditioner | 1 |
According to table 1 and fig. 2, the layer selected in the above layer design is made of amorphous silicon dioxide (SiO 2 ) The structure of the structured sealing layer 206 (arranged at the position furthest from the substrate 201) is advantageous, in particular in the case of layer operation by layer removal such as ion beam polishing, for example, in view of the directional dependency of the layer removal process which is avoided in this case (which occurs when sealing layers with an amorphous or at least partly crystalline phase, for example sealing layers with a columnar structure, are used), and isotropic layer removal can be achieved. However, in further embodiments (particularly in the case of additional layer operations by depositing layer materials), other materials, such as crystalline magnesium fluoride (MgF) 2 ) May also be used as a material for the sealing layer. In this regard, by way of example only, table 2 shows one possible layer design with a composition made of SiO 2 Substrate made of MgF 2 And a sealing layer is formed.
Table 2
| Layer(s) | Material | Refractive index | Thickness [ nm ]] |
| 1 (substrate) | SiO 2 | 1.56 | |
| 2 | MgF 2 | 1.42 | 19.86 |
| 3 | LaF 3 | 1.69 | 80.91 |
| 4 | MgF 2 | 1.42 | 36.64 |
| Medium (D) | Air-conditioner | 1 |
By way of example only, table 3 shows one possible layer design with a composition made of SiO 2 Substrate made of SiO 2 And a sealing layer is formed.
TABLE 3
| Layer(s) | Material | Refractive index | Thickness [ nm ]] |
| 1 (substrate) | SiO 2 | 1.56312 | |
| 2 | MgF 2 | 1.44551 | 21.81 |
| 3 | LaF 3 | 1.72862 | 29.31 |
| 4 | MgF 2 | 1.44551 | 19.01 |
| 5 | SiO 2 | 1.58854 | 12.00 |
| Medium (D) | Air-conditioner | 1 |
The application is not limited to adjusting only the wavefront characteristics of the optical system. Instead, an additional adjustment is possible, so that the properties of the optical system (in particular the reflection behavior and/or the transmission behavior) are further improved. In this case, studies carried out by the inventors have revealed that the further (e.g. reflection or transmission) properties can be concomitantly improved or optimized in the same conditioning method by the layer operation according to the application.
In the diagrams discussed below for elucidating the changes in the optical properties of the optical element 200 of which the layer system has been manipulated, which changes can be obtained by the layer operation according to the application, for each of the figures 3a-3b and 4a-4b the behavior of the unpolarized light incident on the optical element 200 is taken into account, whereas in figures 5a-5b and 6a-6b the dependence on the polarization state is taken into account.
In fig. 3a-3b, the changes in phase (fig. 3 a) and reflectivity (fig. 3 b) resulting in a thickness change in the range of-2 nm to +2nm are plotted for the above-described exemplary embodiments from fig. 2 and table 1. In this case, the negative sign of the thickness variation corresponds to the reduction of the layer thickness achieved by the layer operation. Further, in this and hereinafter, it is assumed that the incident angle is 15 °.
As is evident from fig. 3a, a phase change of about 1.5nm can be achieved by varying the layer thickness by 2 nm. Meanwhile, according to fig. 3b, with such a thickness variation of 2nm, the variation value of the reflectance is about 0.15 percentage points, which is within an acceptable range. Furthermore, by appropriate modification or optimization of the layer design, it can be achieved that the change in reflectivity is less sensitive to the reaction of thickness variations.
According to fig. 4a-4b, the dependence of the phase and the reflectivity changes on the angle of incidence, respectively, is plotted, said changes being achieved by the layer operation according to the application, wherein as an example, in each case a thickness change of 1.5nm is taken as a basis. As is evident from the proportions selected for the phase values in fig. 4a, the phase change achieved in the case of the layer operation is practically independent of the angle of incidence. With respect to the variation of the reflectivity achieved according to fig. 4b, it should be noted that the sign varies with the angle of incidence.
As is evident from fig. 5a-5b, the dependence of the phase change on the thickness change achieved in the case of layer operation according to the application is substantially independent of the polarization state of the electromagnetic radiation incident on the relevant optical element. In contrast, for the changes in reflectivity achieved in each case, specific differences in the distribution dependent on the thickness variation are confirmed, depending on whether the electromagnetic radiation is s-polarized or p-polarized.
According to fig. 6a-6b, the difference between s-polarization and p-polarization achieved in terms of phase change (fig. 6 a) and reflectivity change (fig. 6 b) is more pronounced as the angle of incidence increases. It follows that the application to optical elements having relatively large angles of incidence in the beam path is also advantageous for achieving layer operation according to the application in case a change in the polarization state is sought.
Fig. 7 shows a schematic diagram of a possible structure of a microlithographic projection exposure apparatus 700 which is designed for operation at wavelengths in the DUV range (i.e. for operating wavelengths of less than 250nm, in particular less than 200nm, for example about 193 nm), and which comprises an illumination device 702 and a projection lens 708.
Light from the light source 701 enters the illumination device 702, which illumination device 702 is symbolically represented in a highly simplified manner by lens elements 703, 704 and a diaphragm 705. When an ArF excimer laser is used as the light source 701, the operating wavelength of the projection exposure apparatus 700 in the illustrated example is 193nm. However, whenThe operating wavelength can also be 248nm, for example, when a KrF excimer laser is used, or when F is used 2 The operating wavelength of the laser as light source 701 may be 157nm. Between the illumination device 702 and the projection lens 708, a mask 707 is arranged in the object plane OP of the projection lens 708, which mask is held in the light path by a mask holder 706. Mask 707 has structures in the micrometer to nanometer range that are imaged by projection lens 708 onto image plane IP of projection lens 708 and reduced by, for example, a factor of 4 or 5. Projection lens 708 comprises a lens element arrangement by means of which an optical axis OA is defined, which is likewise represented in a highly simplified manner only by lens elements 709, 710, 711, 712, 720.
A substrate 716 or wafer, which has been provided with a photosensitive layer 715 and positioned by a substrate holder 718, is held in the image plane IP of the projection lens 708. An immersion medium 750 (which may be deionized water, for example) is located between the optical element 720 of the projection lens 708 and the photosensitive layer 715, the optical element 720 being the last optical element located on the image plane side.
Fig. 8 shows schematically a meridional cross-section of a possible structure of a microlithographic projection exposure apparatus designed for operation under EUV.
According to fig. 8, the projection exposure apparatus 1 comprises an illumination device 2 and a projection lens 10. The illumination device 2 is used for illuminating an object field 5 in an object plane 6 with radiation from a radiation source 3 via an illumination optical unit 4. The reticle 7 arranged in the object field 5 is exposed here. The reticle 7 is held by a reticle holder 8. The reticle carrier 8 can be displaced, in particular in the scanning direction, by a reticle displacement drive 9. For purposes of illustration, a Cartesian xyz coordinate system is depicted in FIG. 8. The x-direction extends towards the plane of the drawing. The y-direction extends horizontally and the z-direction extends vertically. The scanning direction extends along the y-direction in fig. 8. The z-direction extends perpendicular to the object plane 6.
The projection lens 10 is used to image the object field 5 into an image field 11 in an image plane 12. The structures on the reticle 7 are imaged onto a photosensitive layer of a wafer 13, which wafer 13 is arranged in the region of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer carrier 14 is displaceable, in particular in the y-direction, by a wafer displacement drive 15. The displacement of the reticle 7 by the reticle displacement drive 9 and the displacement of the wafer 13 by the wafer displacement drive 15 can be realized to be synchronized with one another.
The radiation source 3 is an EUV radiation source. The radiation source 3 emits in particular EUV radiation, which is also referred to as usage radiation or illumination radiation in the following. In particular, the radiation used has a wavelength in the range of 5nm to 30 nm. The radiation source 3 may be, for example, a plasma source, a synchrotron-based radiation source or a Free Electron Laser (FEL). Illumination radiation 16 emitted from the radiation source 3 is focused by a collector 17 and propagates into the illumination optical unit 4 through an intermediate focus in an intermediate focus plane 18. The illumination optical unit 4 includes a deflection mirror 19, a first (field) facet mirror 20 (with a schematically shown facet 21) and a second (pupil) facet mirror 22 (with a schematically shown facet 23) arranged downstream of the deflection mirror in the optical path.
The projection lens 10 comprises a plurality of mirrors Mi (i=1, 2, …), which are numbered sequentially according to their arrangement in the light path of the projection exposure apparatus 1. In the example shown in fig. 8, the projection lens 10 includes six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or any other number of mirrors Mi are equally possible. The penultimate mirror M5 and the last mirror M6 each have a through-opening for the illumination radiation 16. The projection lens 10 is a doubly-blocked optical unit. For example only, the image-side numerical aperture of the projection lens 10 may be greater than 0.5, in particular greater than 0.6, and may be, for example, 0.7 or 0.75.
The optical element subjected to the layer operation according to the present application may be, for example, one of the lens elements 709-712 and 720 of the projection lens 708 in fig. 7, or one of the mirrors M1 to M6 of the projection lens 10 in fig. 8.
While the application has been described in terms of specific embodiments, many variations and alternative embodiments will be apparent to those skilled in the art, such as by combinations and/or permutations of the features of the various embodiments. It will thus be apparent to those skilled in the art that such variations and alternative embodiments are encompassed by the present application, and that the scope of the application is limited only by the meaning of the appended patent claims and their equivalents.
Claims (23)
1. A method for adjusting an optical system, in particular for microlithography, the optical system comprising a plurality of optical elements, each of the plurality of optical elements being provided with an optically active layer system, the method comprising the steps of:
a) Determining a system wavefront provided by the optical system in a predefined plane during operation;
b) Determining a systematic wavefront deviation between the determined systematic wavefront and a target systematic wavefront; and
c) Performing a layer operation on at least one optical element such that the determined systematic wavefront deviation is reduced,
layer operations suitable for reducing the systematic wavefront deviation are selected using a predetermined look-up table in which the respective wavefront contributions of the at least one optical element to the systematic wavefront are listed for different layer operations of the layer system of the at least one optical element.
2. The method of claim 1, wherein the optical element is coated during the determining of the system wavefront in step a).
3. The method according to claim 1 or 2, wherein the layer operation comprises performing a locally varying deposition of layer material on the at least one optical element.
4. A method according to any one of claims 1 to 3, wherein the layer operation comprises performing locally varying layer removal on the at least one optical element.
5. Any of the preceding claimsThe method of claim, wherein the at least one optical element comprises a metal oxide composed of silicon dioxide (SiO 2 ) And a sealing layer is formed.
6. The method of any preceding claim, wherein the layer operation comprises performing locally varying ion implantation in the at least one optical element.
7. A method for adjusting an optical system, in particular for microlithography, the optical system comprising a plurality of optical elements, each of the plurality of optical elements being provided with an optically active layer system, the method comprising the steps of:
a) Determining a system wavefront provided by the optical system in a predefined plane during operation;
b) Determining a systematic wavefront deviation between the determined systematic wavefront and a target systematic wavefront; and
c) Performing a layer operation on at least one optical element such that the determined systematic wavefront deviation is reduced;
the layer operation includes performing a locally varied deposition of layer material on the at least one optical element and/or performing a locally varied ion implantation in the at least one optical element.
8. A method according to any one of the preceding claims, characterized in that a predetermined look-up table is used for selecting a layer operation suitable for reducing the systematic wavefront deviation, in which look-up table the respective wavefront contributions of the at least one optical element to the systematic wavefront are listed for different layer operations of the layer system of the at least one optical element.
9. A method according to any of the preceding claims, characterized in that the determination of the systematic wavefront deviation between the determined systematic wavefront and the target systematic wavefront is effected in an iterative process.
10. The method according to any of the preceding claims, wherein performing layer operations on the at least one optical element is further implemented such that: for at least one further characteristic property of the optical system, the deviation between the actual value given before the layer operation and the target value is reduced.
11. A method for adjusting an optical system, in particular for microlithography, the optical system comprising a plurality of optical elements, each of the plurality of optical elements being provided with an optically active layer system, the method comprising the steps of:
a) Determining a system wavefront provided by the optical system in a predefined plane during operation;
b) Determining a systematic wavefront deviation between the determined systematic wavefront and a target systematic wavefront; and
c) Performing a layer operation on at least one optical element such that the determined systematic wavefront deviation is reduced;
performing layer operations on the at least one optical element is further implemented such that: for at least one further characteristic property of the optical system, the deviation between the actual value given before the layer operation and the target value is reduced.
12. Method according to claim 10 or 11, characterized in that the at least one further characteristic property of the optical system comprises a reflection behavior and/or a transmission behavior of the optical system.
13. The method according to any of the preceding claims, wherein performing layer operations on the at least one optical element is further implemented such that: the polarization effect of the optical system is changed.
14. The method according to any of the preceding claims, wherein performing layer operations on the at least one optical element is further implemented such that: for the reflection behaviour of the optical system, the transmission behaviour of the optical system and the polarization effect of the optical system, the respective deviations between the actual values given before the layer operation and the target values are reduced in each case.
15. The method according to any one of claims 1 to 14, wherein the at least one optical element on which the layer operation is performed is a lens element.
16. The method according to any one of claims 1 to 14, wherein the at least one optical element on which the layer operation is performed is a mirror.
17. The method according to any of the preceding claims, wherein the optical system is an imaging system.
18. The method of claim 17, wherein the predefined plane is an image plane of the imaging system.
19. The method according to any of the preceding claims, characterized in that the optical system is designed for an operating wavelength of less than 250nm, in particular less than 200 nm.
20. Method according to any one of the preceding claims, characterized in that the optical system is designed for an operating wavelength of less than 30nm, in particular less than 15 nm.
21. A microlithography optical system formed by performing the method according to any of claims 1 to 20.
22. The optical system according to claim 21, characterized in that the optical system is a projection lens of a microlithographic projection exposure apparatus.
23. The optical system of claim 22, wherein the optical system is a projection lens of a mask inspection apparatus.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102021201193.4 | 2021-02-09 | ||
| DE102021201193.4A DE102021201193A1 (en) | 2021-02-09 | 2021-02-09 | Method for adjusting an optical system, in particular for microlithography |
| PCT/EP2021/086614 WO2022171339A1 (en) | 2021-02-09 | 2021-12-17 | Method for the adjustment of an optical system, more particularly for microlithography |
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| CN116745702A true CN116745702A (en) | 2023-09-12 |
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| CN202180092081.0A Pending CN116745702A (en) | 2021-02-09 | 2021-12-17 | Method for adjusting an optical system, in particular for microlithography |
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| JP (1) | JP2024506056A (en) |
| CN (1) | CN116745702A (en) |
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| US4533449A (en) | 1984-04-16 | 1985-08-06 | The Perkin-Elmer Corporation | Rapid surface figuring by selective deposition |
| EP0824721B1 (en) * | 1996-03-07 | 2000-07-26 | Koninklijke Philips Electronics N.V. | Imaging system and apparatus for ultraviolet lithography |
| JP3924806B2 (en) | 1996-06-10 | 2007-06-06 | 株式会社ニコン | Anti-reflection coating |
| US7261957B2 (en) | 2000-03-31 | 2007-08-28 | Carl Zeiss Smt Ag | Multilayer system with protecting layer system and production method |
| US7629572B2 (en) | 2005-10-28 | 2009-12-08 | Carl Zeiss Laser Optics Gmbh | Optical devices and related systems and methods |
| EP3159912A1 (en) | 2007-01-25 | 2017-04-26 | Nikon Corporation | Optical element, exposure apparatus using this, and device manufacturing method |
| DE102008041144A1 (en) * | 2007-08-21 | 2009-03-05 | Carl Zeiss Smt Ag | Optical arrangement for e.g. projection lens, has structure for optimizing arrangement with respect to angle of incident angle-dependent polarization division in phase and amplitude, and another structure compensating change of wave front |
| DE102011083461A1 (en) | 2011-09-27 | 2013-03-28 | Carl Zeiss Smt Gmbh | A method of forming a top layer of silicon oxide on an EUV mirror |
| DE102011054837A1 (en) | 2011-10-26 | 2013-05-02 | Carl Zeiss Laser Optics Gmbh | Optical element |
| DE102012212194B4 (en) | 2012-07-12 | 2017-11-09 | Carl Zeiss Smt Gmbh | Microlithographic projection exposure apparatus and method for modifying an optical wavefront in a catoptric objective of such a system |
| DE102012223669A1 (en) | 2012-12-19 | 2013-11-21 | Carl Zeiss Smt Gmbh | Method for correcting wavefront reflected from mirror for microlithography projection exposure system having projection optics, involves correcting wavefront by removing layer of multi-layer coating in one selected portion |
| DE102013212462A1 (en) * | 2013-06-27 | 2015-01-15 | Carl Zeiss Smt Gmbh | Surface correction of mirrors with decoupling coating |
| DE102014225197A1 (en) | 2014-12-09 | 2015-11-26 | Carl Zeiss Smt Gmbh | Method for changing a surface shape, reflective optical element, projection objective and EUV lithography system |
| DE102015207153A1 (en) * | 2015-04-20 | 2016-10-20 | Carl Zeiss Smt Gmbh | Wavefront correction element for use in an optical system |
| DE102016200814A1 (en) | 2016-01-21 | 2017-07-27 | Carl Zeiss Smt Gmbh | Reflective optical element and optical system for EUV lithography |
| NL2020103A (en) * | 2017-01-17 | 2018-07-23 | Asml Netherlands Bv | Lithographic Apparatus and Method |
| DE102018203241A1 (en) * | 2018-03-05 | 2019-09-05 | Carl Zeiss Smt Gmbh | Optical element, and method for correcting the wavefront effect of an optical element |
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- 2021-02-09 DE DE102021201193.4A patent/DE102021201193A1/en active Pending
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| DE102021201193A1 (en) | 2022-08-11 |
| JP2024506056A (en) | 2024-02-08 |
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