Metal Silicate Membranes for EUV Lithography
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Solution Overview
Problem
Designing a membrane that is stable in the environment within a lithographic apparatus is challenging due to alternating reducing and oxidizing conditions, high temperatures, free radicals, ions, and electrons, which cause degradation of materials such as nitrides, oxides, and metals, especially at small thicknesses required to minimize EUV radiation absorption.
Innovation Solution
A membrane comprising a core substrate and a metal silicate layer, where the metal silicate layer acts as an outermost protective layer, is proposed. This metal silicate layer, such as yttrium silicate or ruthenium silicate, is stable even at thicknesses less than 5 nm, resisting oxidation, thermal de-wetting, and plasma etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thin capping layer is provided to minimize EUV radiation absorption, then EUV transmissivity is improved, but the layer becomes subject to significant degradation from oxidation, reduction, and thermal effects
Solution Approach 1:
The invention uses a composite material structure consisting of a metal silicate layer (such as yttrium silicate, ruthenium silicate, or hafnium silicate) combined with a core substrate. This composite structure provides both the required thin thickness for high EUV transmissivity and the chemical/thermal stability to resist degradation in the harsh lithographic environment. The metal silicate layer specifically resists oxidation, reduction, and thermal de-wetting that plague conventional thin metal or oxide layers.
Solution Approach 2:
The invention changes the material parameters by selecting specific metal silicates with appropriate thicknesses (5-50 nm) that optimize both EUV transmissivity and environmental stability. By controlling the thickness parameter within this specific range and selecting metals with appropriate atomic numbers and silicate formation tendencies, the layer maintains sufficient transparency to EUV radiation while being thick enough to resist degradation from plasma exposure, temperature cycling, and chemical reactions.
2Object-affected harmful factors
If the pellicle is made sufficiently thick to stop particles, then particle protection is improved, but EUV radiation absorption increases
Solution Approach 1:
The invention employs an ultra-thin metal silicate film (5-50 nm) that acts as a flexible protective barrier. This thin film is sufficient to stop particles from reaching the reticle while maintaining high EUV transmissivity. The film's flexibility and thinness allow it to provide particle protection without significantly absorbing EUV radiation, resolving the contradiction between protection and transmissivity.
3Loss of energy
If conventional materials (nitrides, oxides, metals) are used at small thicknesses, then EUV transmissivity is improved, but stability in the lithographic environment deteriorates
Solution Approach 1:
The invention replaces conventional single-material layers (nitrides, oxides, or metals) with a composite metal silicate structure. This composite material inherently provides both the thinness required for high EUV transmissivity and the chemical/thermal stability needed to resist oxidation, reduction, and thermal de-wetting. The metal silicate composition creates a material that is stable in the alternating reducing and oxidizing environment of the lithographic apparatus.
Solution Approach 2:
The invention avoids using conventional thin layers of metals, oxides, or nitrides that would degrade quickly in the lithographic environment. Instead, it uses metal silicates that are specifically selected for their long-term stability, effectively replacing short-lived conventional materials with long-lasting silicate-based materials that can withstand the harsh environment throughout the pellicle's operational lifetime.
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 metal silicate layer provides stability and protection to the membrane, maintaining EUV transmissivity of 96% or more even at thin thicknesses, thus effectively reducing EUV radiation absorption and extending the membrane's lifespan within the harsh lithographic apparatus environment.
Implementation Method 1
resisting oxidation, thermal de-wetting, and plasma etching
Implementation Method 2
resisting oxidation, thermal de-wetting, and plasma etching
Implementation Method 3
resisting oxidation, thermal de-wetting, and plasma etching
Implementation Method 4
maintaining EUV transmissivity of 96% or more even at thin thicknesses, thus effectively reducing EUV radiation absorption
Data Source
AI summary
Novel membranes for use in a lithographic apparatus are disclosed. A first membrane includes a core substrate and a metal silicate layer. The metal silicate layer is an outermost layer of the first membrane. A second membrane includes a core substrate and an yttrium silicate layer. The yttrium silicate layer may be an outermost layer of the membrane or, alternatively, the yttrium silicate layer may be disposed between the core substrate and a layer of yttrium or yttrium oxide. The first and second membranes may be provided within an EUV lithographic apparatus. For example, the membranes may form part of a pellicle. The pellicle may be suitable for use adjacent to a reticle within an EUV lithographic apparatus. The membranes may form part of a dynamic gas lock. The membranes may form part of a spectral filter.