EUVL Pellicle Membrane Scattering Axis Orientation
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Solution Overview
Problem
In extreme ultraviolet lithography (EUVL) devices, typical pellicle designs cause directionally-preferential scattering of light, leading to decreased fidelity of patterns transferred to the target wafer due to imaging errors from scattered light.
Innovation Solution
An EUVL device with a light-transmissive pellicle membrane that scatters transmitted light along a preferential scattering axis, oriented to minimize the ratio of captured scattered light to non-scattered light, using an asymmetric illumination distribution and a carbon nanotube-based pellicle membrane to deflect scattered light outside the imaging system's acceptance cone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light-transmissive pellicle membrane is used to protect the reticle, then the reticle is protected from contamination, but light scattering occurs that decreases pattern fidelity
Solution Approach 1:
The patent changes the physical parameters of the pellicle membrane by using carbon nanotube bundles with specific diameter (100 nm or shorter) and controlled alignment in a planar direction. This parameter optimization reduces light scattering while maintaining protection function
Solution Approach 2:
The patent uses composite carbon nanotube bundle structures as the pellicle membrane material. The bundles are formed by assembling multiple carbon nanotubes in a controlled arrangement, creating a composite material that provides both mechanical protection and optimized optical properties with reduced scattering
2Manufacturing precision
If an asymmetric illumination distribution is used, then the ratio of captured scattered light to non-scattered light is minimized, but the illumination system becomes more complex
Solution Approach 1:
The patent applies asymmetric illumination distribution in the source-pupil plane, where the illumination is intentionally made non-uniform with specific angular distributions. This asymmetric approach allows scattered light to be directed outside the acceptance cone while maintaining useful illumination for pattern transfer
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 significantly reduces the amount of scattered light imaged onto the target wafer, improving the fidelity of the transferred pattern without requiring complex re-designs of the imaging system, with the non-scattered fraction being 90% - 95% of the light transmitted through the pellicle membrane.
Implementation Method 1
the pellicle membrane scatters transmitted light along a preferential scattering axis
Data Source
Figure 1A~1C
Figure 2A~2B
AI summary
The present invention relates to an extreme ultraviolet lithography, EUVL, device (20) comprising: a reticle (220) comprising a lithographic pattern to be imaged on a target wafer (250); a light-transmissive pellicle membrane (232) mounted in front of, and parallel to, the reticle (220), wherein the pellicle membrane (232) scatters transmitted light along a preferential scattering axis (214); and an extreme ultraviolet, EUV, illumination system (210) configured to illuminate the reticle (220) through the pellicle membrane (232), wherein an illumination distribution (212) provided by the EUV illumination system (210) is asymmetric as seen in a source-pupil plane of the EUV illumination system (210); wherein light reflected by the reticle (220) and then transmitted through the pellicle membrane (232) comprises a non-scattered fraction and a scattered fraction formed by light scattered by the pellicle membrane (232); the EUVL device (20) further comprising: an imaging system (240) having an acceptance cone (260) configured to capture a portion of said light reflected by the reticle (220) and then transmitted through the pellicle membrane (232), wherein the imaging system (240) is configured to project the captured portion onto the target wafer (250); wherein the preferential scattering axis (214) is oriented with respect to the illumination distribution (212) such that a scattered fraction of the captured portion is reduced compared to at least one other orientation of the preferential scattering axis (214).