Projection Lens for EUV Microlithography, Film Element and Method for Producing a Projection Lens Comprising a Film Element

摘要

A film element of an EUV-transmitting wavefront correction device is arranged in a beam path and includes a first layer of first layer material having a first complex refractive index n1=(1−δ1)+iβ1, with a first optical layer thickness, which varies locally over the used region in accordance with a first layer thickness profile, and a second layer of second layer material having a second complex refractive index n2=(1−δ2)+iβ2, with a second optical layer thickness, which varies locally over the used region in accordance with a second layer thickness profile. The first and second layer thickness profiles differ. The deviation δ1 of the real part of the first refractive index from 1 is large relative to the absorption coefficient β1 of the first layer material and the deviation δ2 of the real part of the second refractive index from 1 is small relative to the absorption coefficient β2 of the second layer material.

主权项

1. Projection lens (PO) for imaging a pattern arranged in an object plane (OS) of the projection lens into an image plane (IS) of the projection lens with electromagnetic radiation having a working wavelength λ from the extreme ultraviolet range (EUV) comprising:
a plurality of mirrors having mirror surfaces which are arranged in a projection beam path between the object plane and the image plane such that a pattern arranged in the object plane is imaged into the image plane by the mirrors, and
a wavefront correction device (WFC) comprising a film element having a film which is arranged in the projection beam path in an operating mode of the wavefront correction device and is configured to transmit at the working wavelength λ a predominant proportion of the EUV radiation impinging in an optical used region, wherein the film element comprises: a first layer (L1), which consists of a first layer material having a first complex refractive index n1=(1−δ1)+iβ1 and has a first optical layer thickness, which varies locally over the used region in accordance with a first layer thickness profile; and a second layer (L2), which consists of a second layer material having a second complex refractive index n2=(1−δ2)+iβ2 and has a second optical layer thickness, which varies locally over the used region in accordance with a second layer thickness profile, wherein the first layer thickness profile differs from the second layer thickness profile, and wherein the deviation δ1 of the real part of the first refractive index from 1 is large relative to the absorption coefficient β1 of the first layer material and the deviation δ2 of the real part of the second refractive index from 1 is small relative to the absorption coefficient β2 of the second layer material.