Yttrium Carbide EUV Pellicle for High Irradiation Stability
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Solution Overview
Problem
Current EUV lithography pellicles face challenges in achieving high extreme ultraviolet transmittance, thermal stability, mechanical stability, and chemical durability, especially in environments with high irradiation intensity beyond 250 W, where materials like polycrystalline silicon and SiN-based materials fall short.
Innovation Solution
A pellicle layer incorporating yttrium carbide (YCx) with an atomic percentage of carbon between 25% to 45%, combined with capping and intermediate layers, provides high extreme ultraviolet transmittance of 90% or more, along with thermal and mechanical stability, and chemical durability, using materials like Y2C, Y, Si, Ru, C, B, N, and O to enhance stability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If polycrystalline silicon or SiN-based materials are used for EUV lithography pellicles, then the pellicle structure is established, but the extreme ultraviolet transmittance is insufficient and thermal stability deteriorates in high irradiation environments beyond 250 W
Solution Approach 1:
The patent employs a composite material structure consisting of a core layer made of yttrium carbide (YCx) with specific carbon content (25-45 atomic%), combined with capping layers and intermediate layers. This composite structure achieves both high extreme ultraviolet transmittance (90% or more) and thermal stability, resolving the contradiction between transmittance and thermal reliability that plagues conventional polycrystalline silicon or SiN-based pellicles.
Solution Approach 2:
The patent optimizes the carbon content parameter in yttrium carbide to within 25-45 atomic% to achieve the desired balance between transmittance and stability. Additionally, the thickness parameters of each layer (core layer, capping layers, intermediate layers) are precisely controlled to optimize both optical performance and thermal resistance, directly addressing the transmittance-stability contradiction.
2Illumination intensity
If the pellicle material is optimized for high extreme ultraviolet transmittance, then transmittance improves to 90% or more, but maintaining thermal and mechanical stability becomes challenging
Solution Approach 1:
The multi-layer composite structure with yttrium carbide core provides both high transmittance and stability. The specific composition of yttrium carbide (YCx with 25-45 atomic% carbon) offers inherent thermal and mechanical stability while maintaining optical performance, thus achieving both high transmittance and composition stability simultaneously.
Solution Approach 2:
Different layers of the pellicle are assigned different functions: the core layer (yttrium carbide) provides thermal stability and mechanical strength, while the capping and intermediate layers are optimized for chemical durability and interface stability. This local differentiation of material properties allows each layer to contribute to overall stability without compromising transmittance.
3Illumination intensity
If the pellicle is designed for high extreme ultraviolet transmittance of 90% or more, then optical performance improves, but chemical durability in intense irradiation environments becomes insufficient
Solution Approach 1:
The composite structure includes capping layers and intermediate layers that provide chemical durability protection to the yttrium carbide core layer. These additional layers form a protective system that enhances chemical resistance while maintaining the high transmittance property of the core material, thus resolving the contradiction between optical performance and chemical durability.
Solution Approach 2:
The capping and intermediate layers serve as protective barriers that shield the core layer from chemical degradation in the harsh EUV irradiation environment. This beforehand protection allows the core layer to maintain its optical performance without suffering from chemical damage, thus achieving both high transmittance and chemical durability.
4Ease of manufacture
If conventional materials are used for EUV pellicles, then manufacturing is simpler, but the pellicle cannot withstand high irradiation intensity beyond 250 W
Solution Approach 1:
While the composite structure is more complex than conventional single-material pellicles, each layer can be deposited using standard thin-film deposition techniques. The manufacturing process, though multi-step, remains within conventional semiconductor fabrication capabilities, achieving a reasonable balance between manufacturing complexity and irradiation resistance reliability.
Data Source
AI summary
A pellicle for extreme ultraviolet (EUV) lithography is based on yttrium carbide and used in a EUV lithography process. The pellicle for EUV lithography includes a pellicle layer that has a core layer containing yttrium carbide. The yttrium carbide is YCx in which the atomic percentage of carbon is within a range of 25% to 45%.