Lens Heating Mitigation via Illumination Design
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Solution Overview
Problem
Lens heating during lithographic projection leads to non-uniform temperature distribution and wavefront aberrations, affecting imaging quality, as certain areas of the lens absorb more heat than others, and existing methods are inadequate for fully correcting these aberrations without inducing additional issues.
Innovation Solution
Generating a lens heating sensitivity map using heat load locations and Zernike polynomials to strategically place extra poles or modify the illumination source, ensuring diffraction patterns reduce lens heating effects without compromising imaging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional illumination modes are used in lithographic projection, then imaging can be performed, but lens heating causes non-uniform temperature distribution and wavefront aberrations that deteriorate imaging quality
Solution Approach 1:
The patent applies local quality by creating a lens heating sensitivity map that identifies specific sensitive areas within the lens. Instead of treating the entire lens uniformly, the solution places extra poles or modifies illumination source shapes to specifically target and mitigate heating in the identified sensitive areas, allowing differential treatment of different lens regions based on their individual heating susceptibility.
Solution Approach 2:
The patent implements preliminary anti-action by proactively counteracting lens heating effects before they significantly degrade imaging quality. The method involves determining heat load locations, generating a sensitivity map, and placing extra poles or modifying illumination sources in advance to generate diffraction patterns that preemptively reduce heating effects in sensitive areas, rather than attempting to correct aberrations after they occur.
2Object-affected harmful factors
If extra poles are placed to reduce lens heating effects, then heating mitigation is achieved, but device complexity increases
Solution Approach 1:
The patent applies partial action by placing only the necessary extra poles or making minimal modifications to the illumination source shape, rather than redesigning the entire optical system. The sensitivity map guides the placement of a limited number of extra poles only in the specific locations needed to mitigate heating effects, avoiding unnecessary complexity while achieving the desired mitigation.
3Object-affected harmful factors
If illumination source shape is modified to reduce lens heating, then heating mitigation is achieved, but imaging performance may be affected
Solution Approach 1:
The patent applies local quality by making targeted, localized modifications to the illumination source shape rather than uniformly altering the entire illumination profile. The sensitivity map identifies specific angular regions that contribute to heating, and the illumination source is modified only in those specific regions, preserving imaging performance in unaffected areas while mitigating heating locally.
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
Effectively mitigates lens heating effects by identifying sensitive areas and adjusting optical elements, maintaining imaging quality while reducing wavefront aberrations and distortion.
Implementation Method 1
the extra pole generates a diffraction pattern configured to reduce the lens heating effect
Implementation Method 2
alter the shape of the illumination source so that diffraction patterns generated by the illumination source fall outside sensitive areas of the pupil
Data Source
AI summary
A method for reducing the effects of lens heating of a lens in an imaging process includes determining heat load locations on the lens according to an illumination source and a reticle design, obtaining a lens response characterization according to the heat load locations, and utilizing the heat load locations and the lens response characterization to generate a lens heating sensitivity map.