EUV Multilayer Mirror Interlayer Design for Diffusion Control
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Solution Overview
Problem
Current lithographic apparatuses using extreme ultraviolet (EUV) radiation face challenges in reflecting wavelengths around 6.9 nm due to chemical interaction between layers in multilayer mirrors, leading to interlayer diffusion and reduced reflectivity.
Innovation Solution
A multilayer mirror design with alternating layers of materials like La, U, Th, and B compounds, separated by interlayers such as Sn, Mo, or Cr, and optionally capped with Ru, Rh, or Ta, to enhance reflectivity and prevent diffusion within the 6.4 nm to 7.2 nm wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multilayer mirrors with alternating layers of metal (La, U, Th) and B compounds are used to reflect EUV radiation, then reflectivity is improved, but interlayer diffusion occurs leading to reduced performance
Solution Approach 1:
An interlayer of intermediate material is inserted between the metal layer and B compound layer to prevent direct chemical interaction. This intermediary layer acts as a diffusion barrier, blocking the interlayer diffusion that would otherwise occur between La/U/Th and B4C/B9C, thereby maintaining the structural integrity and reflectivity of the multilayer mirror over time
Solution Approach 2:
The patent employs composite material structures combining metal layers (La, U, or Th) with B compound layers (B4C or B9C) in alternating sequences. This composite approach creates a multilayer mirror that leverages the high reflectivity of metal-B compound interfaces for EUV radiation while managing the chemical interaction issues through the interlayer separation
2Ease of manufacture
If no interlayer separation is used between metal and B compound layers, then manufacturing is simpler, but chemical interaction causes interlayer diffusion and reduced reflectivity
Solution Approach 1:
The interlayer serves as a protective intermediary that prevents direct contact between the metal layer and B compound layer. Although it adds a step to manufacturing, it prevents the chemical interaction that would lead to interlayer diffusion and reflectivity degradation, thereby ensuring long-term reliability of the multilayer mirror structure
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
The solution provides improved reflectivity and reduced interlayer diffusion, enabling more efficient EUV radiation reflection and maintaining mirror performance across the critical wavelength range, thus supporting advanced lithographic processes.
Implementation Method 1
Such a multilayer mirror reflects the EUV radiation according to Bragg's Law
Data Source
AI summary
A multilayer mirror to reflect radiation having a wavelength in the range of 2-8 nm has alternating layers. The alternating layers include a first layer and a second layer. The first and second layers are selected from the group consisting of: U and B4C layers, Th and B4C layers, La and B9C layers, La and B4C layers, U and B9C layers, Th and B9C layers, La and B layers, U and B layers, C and B layers, Th and B layers, U compound and B4C layers, Th compound and B4C layers, La compound and B9C layers, La compound and B4C layers, U compound and a B9C layers, Th compound and a B9C layers, La compound and a B layers, U compound and B layers, and Th compound and a B layers. An interlayer is disposed between at least one of the first layers and the second layer.