Optical Element Surface Shape Correction via Electron Irradiation
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Solution Overview
Problem
Existing methods for changing the shape of optical elements via electron irradiation often result in deviations from the desired shape due to material stresses, particularly in narrow tolerance definitions for EUV lithography, leading to inaccuracies in surface correction.
Innovation Solution
A device and method that utilize an electron irradiation unit to apply a locally resolved energy dose distribution, controlled by a unit that optimizes the energy dose distribution using a merit function to minimize the difference between desired and actual surface shape changes, accounting for both local compaction and deformation caused by stresses acting parallel to the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electron irradiation is applied to change the surface shape of an optical element, then material densification occurs and surface correction is achieved, but deviations from the desired shape occur due to material stresses
Solution Approach 1:
The patent implements a feedback mechanism where the actual surface shape change is measured and compared with the desired shape change, and the electron irradiation parameters are adjusted based on this comparison to minimize deviations caused by material stresses
Solution Approach 2:
The patent changes the parameters of electron irradiation (energy dose distribution, irradiation patterns) to optimize the surface shape correction process and compensate for stress-induced deviations
2Ease of manufacture
If a simple linear relationship is assumed between local compaction and surface recess, then the processing is simple, but the actual shape correction deviates from the desired correction
Solution Approach 1:
The patent performs preliminary calculations and simulations to determine the optimal energy dose distribution before actual electron irradiation, taking into account the complex relationship between compaction and surface deformation to achieve accurate shape correction
Solution Approach 2:
The patent introduces an intermediary computational model that accounts for stress effects and converts desired shape changes into appropriate energy dose distributions, bridging the gap between simple irradiation and complex deformation behavior
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
This approach enables a highly accurate realization of the desired surface shape change by considering both surface depression and deformation, improving the precision of shape correction in optical elements, especially for EUV microlithography applications.
Implementation Method 1
a method exists in which electron bonds in the vicinity of the surface are redistributed as a result of the energy input of the electron beam, as a result of which a compaction of the material occurs
Implementation Method 2
a local compaction, which describes a material densification in the region of an area element of the surface
Data Source
AI summary
The disclosure relates to a device for changing a shape of a surface of an optical element via electron irradiation. The device includes an electron irradiation unit for radiating electrons onto the surface with a locally resolved energy dose distribution for the purpose of producing local material densifications in the optical element. Furthermore, the device includes a control unit for determining a locally resolved energy dose distribution from a predefined desired change of a surface shape of the optical element by optimization via a minimization of a merit function, in such a way that a difference between the desired change and an actual change of the surface shape of the optical element, the actual change being brought about on account of the predefinition determined, is minimized.