EUV Optical Element Thermal Aberration Control
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Solution Overview
Problem
Microlithographic projection exposure apparatuses, particularly those using EUV radiation, face significant optical aberrations due to temperature gradients in optical elements like mirrors, which can lead to deteriorated imaging properties.
Innovation Solution
The method involves creating a targeted inhomogeneous temperature distribution on at least one portion of the optical element's surface during breaks in operation, using a heating device to irradiate the surface with heating radiation. This approach reduces aberrations compared to homogeneous temperature distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a homogeneous temperature distribution is applied to the optical element, then the heating process is simple, but optical aberrations increase due to temperature gradients
Solution Approach 1:
The patent applies local quality by creating different temperature zones at specific locations on the optical element surface. Instead of uniform heating, the heating device irradiates selected regions with different heating powers to generate tailored temperature distributions that compensate for optical aberrations while maintaining overall system simplicity.
2Stability of the object's composition
If the optical element is heated during operation, then temperature uniformity improves, but imaging quality deteriorates due to induced aberrations
Solution Approach 1:
The patent applies preliminary anti-action by pre-heating the optical element during breaks in operation to establish an optimized temperature distribution before exposure begins. This preliminary heating creates a stable thermal state that compensates for aberrations that would otherwise develop during actual imaging operations.
Solution Approach 2:
The heating process is performed in advance during operational breaks rather than during active imaging. This preliminary action allows the optical element to reach an optimal temperature distribution before the actual exposure operation begins, ensuring high imaging quality while maintaining temperature stability.
3Manufacturing precision
If heating radiation is applied during breaks in operation, then aberrations are reduced, but energy consumption increases
Solution Approach 1:
The heating process operates periodically during breaks in the projection exposure apparatus operation rather than continuously. The heating device is activated during operational pauses and deactivated during active imaging, reducing overall energy consumption while maintaining effective aberration control through repeated thermal optimization cycles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The inhomogeneous temperature distribution effectively minimizes optical aberrations, improving the imaging quality of the projection exposure apparatus by reducing wavefront aberrations and other deformation-related issues.
Implementation Method 1
heating at least one optical element, such as at least one mirror, of the projection exposure apparatus by irradiating a surface of the optical element with heating radiation
Implementation Method 2
irradiating a surface of the optical element with heating radiation... creating a targeted inhomogeneous temperature distribution on at least one portion of the surface of the optical element
Data Source
AI summary
A method of operating a projection exposure apparatus for microlithography, comprises: heating an optical element of the projection exposure apparatus by irradiating a surface of the optical element with heating radiation during a break in operation in which the surface of the optical element is not irradiated by exposure radiation. An inhomogeneous temperature distribution which reduces aberrations of the projection exposure apparatus is created on a portion of the surface of the optical element during the heating in the break in operation, with the inhomogeneous temperature distribution being created by irradiating the portion with heating radiation with at least one continuous heating radiation profile formed by a beam shaping element. A related projection exposure apparatus for microlithography is disclosed.