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DE-102025111510-A1 - Method for optimizing an imaging DUV/UV optic for a projection exposure system

DE102025111510A1DE 102025111510 A1DE102025111510 A1DE 102025111510A1DE-102025111510-A1

Abstract

To optimize an imaging DUV/UV optic (11) for a projection exposure system, an upper design limit (RMS G ) for an aberration is specified. The shapes of lens surfaces of a plurality of lenses (L i ) of the imaging optic (11), whose lens surfaces have highly transmissive layers (S) for useful light (4), are optimized, including their highly transmissive layers (S) of a lens design of the imaging optic (11), such that the upper design limit (RMS G ) is met. Using such an optimization procedure, the aberration correction of the imaging DUV/UV optic for the projection exposure system is improved.

Inventors

  • Hubertus Borsch
  • Sonja Schneider
  • Thilo Pollak

Assignees

  • CARL ZEISS SMT GMBH

Dates

Publication Date
20260513
Application Date
20250325

Claims (13)

  1. Method for optimizing an imaging DUV/UV optic (11) for a projection exposure system (1), - wherein the imaging optic (11) comprises a plurality of lenses (L1 to L17) whose lens surfaces have highly transmissive layers (S) for useful light (4), - comprising the following steps: -- specifying an upper design limit (RMS G ) to be complied with for an aberration, -- optimizing shapes of the lens surfaces including their highly transmissive layers (S) of a lens design of the imaging optic (11) such that the upper design limit (RMS G ) is complied with.
  2. Procedure according to Claim 1 , characterized in that during optimization the shapes of only some of the lens surfaces including their highly transmissive layers (S) are optimized as correction lens surfaces, while the shapes of the other lens surfaces are optimized without coating.
  3. Procedure according to Claim 1 or 2 , characterized in that , in order to optimize the shapes of the lens surfaces including their highly transmissive layers of the lens design of the imaging optics (11) so that the design limit (RMS G ) is complied with, a correction asphere is applied to the at least one correction lens surface.
  4. Imaging DUV/UV optics, optimized using a method according to one of the Claims 1 until 3 .
  5. Imaging optics according to Claim 4 , characterized by at least ten lenses.
  6. Imaging optics according to Claim 4 or 5 , characterized in that at least two lens surfaces including their highly transmissive layers (S) are optimized to achieve the design limit (RMS G ).
  7. Imaging optics according to one of the Claims 4 until 6 , characterized in that the highly transmissive layers (S) have several bilayers, each consisting of two alternating layers of materials with different refractive indices.
  8. Imaging optics according to Claim 7 , characterized in that several layer types are used which differ in at least one thickness of the respective individual layers.
  9. Imaging optics according to one of the Claims 4 until 8 , characterized in that the layers (S) have a layer thickness modulation.
  10. Optical system comprising an illumination optic (5) for illuminating an object field (14) in which an object (7) to be imaged can be arranged, with DUV/UV illumination light (4), and with a projection lens (11) for imaging the object field (14) into an image field (14a) in which a substrate (13) to be exposed can be arranged, wherein the illumination optic (5) and/or the projection lens (11) is an imaging optic according to one of the Claims 4 until 9 exhibits.
  11. Projection exposure system with an optical system according to Claim 10 .
  12. Method for producing structured components comprising the following steps: - providing a wafer (13) on which at least a layer of a photosensitive material is applied, - providing a reticulum (7) having structures to be imaged, - providing a projection exposure system (1) according to Claim 11 , - Projecting at least part of the reticulum (7) onto an area of the layer of the wafer (13) using the projection exposure system (1).
  13. Structured component, manufactured according to a process according Claim 12 .

Description

The invention relates to a method for optimizing an imaging DUV/UV optic for a projection exposure system. Furthermore, the invention relates to an imaging DUV/UV optic optimized by such a method, an optical system with such an imaging optic, a projection exposure system with such an optical system, a method for manufacturing a structured component with such a projection exposure system, and a structured component manufactured by such a method. An imaging optic of the type mentioned at the beginning is known from the EP 0 744 665 B1 and the DE 196 16 922 A1 . It is an object of the present invention to improve an imaging error correction of an imaging DUV/UV optic for a projection exposure system for projection lithography. This problem is solved according to the invention by an optimization method with the features specified in claim 1. According to the invention, it was recognized that even in the design of DUV/UV optics, i.e., optics for a useful light wavelength range between 100 nm and 400 nm, the influence of highly transmissive layers, i.e., lens coatings that advantageously maintain a high transmission of the optics, cannot be neglected. Accordingly, a method is proposed for DUV/UV optics in which the influence of the highly transmissive layers is modeled during the design process. This involves optimizing the shapes of the lens surfaces, including their highly transmissive layers, during the lens design phase to comply with a design limit for aberrations. This allows, in particular, layer-related, i.e., systematic, errors to be corrected. Interference resulting from the layers can be predicted, and a correction simulation of the lens surfaces best suited for correction, including their selection, can be performed. In principle, techniques can be used in the optimization process that are suitable for EUV optics, for example, from the... EP 1 282 011 B1 are known. The imaging DUV/UV optics can be a projection optic for imaging an object field of the projection exposure system, in which an object to be imaged can be arranged, onto an image field in which a substrate to be exposed can be arranged. Alternatively or additionally, the imaging DUV/UV optics optimized using this method can be an imaging optic as part of an illumination optic for illuminating the object field, for example, a REMA lens. In the method according to claim 2, certain lens surfaces are selected during the optimization step as surfaces to be adapted with respect to their surface shape, including their high-transmissive layers. The other lens surfaces then remain unchanged from the original lens design, calculated without the high-transmissive layers, during the optimization process. This reduces the complexity of the optimization process. For example, two, three, four, or five of the lens surfaces can be optimized as corrective lens surfaces. In the method according to claim 3, the correction lens surfaces to be modified within the optimization process are designed as correction aspheres, i.e., as surfaces whose shape is only modified to a comparatively small extent compared to the original shape. The difference between the resulting correction asphere and the original surface can be implemented with a small amplitude shape variation. This shape variation can have a peak-to-valley (PV) value of a maximum of 100 nm. For this purpose, the correction asphere is compared with the surface optimized without its high-transmissive layer. The advantages of an imaging DUV optic according to claim 4 correspond to those already explained in connection with the optimization method. An imaging optic according to claim 5 can be provided with very good correction of imaging errors. The imaging optic can have at least 15 lenses. The imaging optic can have 17 lenses. Typically, the imaging optic has fewer than 30 lenses. An embodiment of the imaging optics according to claim 6 allows for good optimization. In particular, exactly two, exactly three, exactly four, or exactly five of the lens surfaces, including their high-transmissive layers, can be optimized to achieve the design limit. A layer configuration according to claim 7 has proven successful in practice. The respective highly transmissive layer can comprise between two and ten, and for example three, bilayers , each consisting of two alternating material layers, thus resulting in a total of six material layers. The layer materials can be Al₂O₃ and/or MgF₂ . Different layer thicknesses of the layer types according to claim 8 have also proven effective in practice for optimizing the high-transmissive layers. Each layer type can therefore be a sequence of individual layers that differ in the thickness of at least one individual layer and, in particular, in the thickness of all individual layers. The layer types can differ in at least one of the materials. The layer types can differ in exactly one of the materials. Alternatively, the layer types can also differ in more than one of the materials.