EUV Lithography Pellicle Asymmetric Scattering Orientation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pellicle designs in extreme ultraviolet lithography (EUVL) scanners cause significant light scattering, leading to imaging errors and reduced pattern fidelity due to the collection of scattered light by the imaging system.
Innovation Solution
An EUVL scanner is designed with a pellicle comprising an EUV transmissive membrane of carbon nanotube bundles, oriented at an angle relative to the anamorphic high-numerical aperture imaging system's acceptance cone, minimizing light scattering by projecting scattered light outside the acceptance cone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pellicle is used in EUVL scanners, then the reticle is protected from contamination, but light scattering occurs causing imaging errors and reduced pattern fidelity
Solution Approach 1:
The patent applies asymmetry by using an anamorphic imaging system with non-circular acceptance cone cross-section. The pellicle scattering pattern (elliptical) is deliberately oriented at an angle relative to the imaging system's acceptance cone major axis. This asymmetric configuration ensures that scattered light falls outside the acceptance cone, preventing it from reaching the detector while maintaining reticle protection functionality.
Solution Approach 2:
The patent converts the harmful light scattering effect into a beneficial outcome by strategically orienting the scattering pattern. Instead of trying to eliminate scattering, the design accepts that scattering occurs but directs it away from the imaging system's acceptance cone through angular orientation, thereby transforming the harmful scattered light into harmless light that simply passes through the pellicle without being detected.
2Use of energy by moving object
If the pellicle is made more transmissive to EUV radiation, then EUV transmission is improved, but light scattering into the acceptance cone increases causing optical issues
Solution Approach 1:
The patent applies local quality by using carbon nanotube bundles with specific structural properties. The nanotube bundles provide localized high transmissivity for EUV radiation while maintaining the scattering characteristics needed to direct light away from the acceptance cone. The unique structure of carbon nanotubes creates localized optical properties that simultaneously achieve high EUV transmission and controlled scattering 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 configuration reduces optical issues related to pellicle light scattering, minimizing flare and enhancing pattern fidelity on the target wafer by maximizing the amount of scattered light not accepted by the imaging system.
Implementation Method 1
the pellicle comprising an EUV transmissive membrane which, in use, scatters transmitted light into an elliptical scattering pattern having a major axis
Data Source
AI summary
The present disclosure relates to a lithography scanner including: a light source configured to emit extreme ultra-violet (EUV) light; a pellicle including an EUV transmissive membrane that is configured to scatter the EUV light into an elliptical scattering pattern having a first major axis; a reticle configured to reflect the scattered EUV light through the pellicle; and an imaging system configured to project a portion of the reflected light that enters an acceptance cone of the imaging system onto a target wafer, wherein a cross section of the acceptance cone has a second major axis, and wherein the pellicle is arranged such that the first major axis is oriented at an angle relative to the second major axis.