EUV Reflecting Element Sputter-Resistant Layer
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Solution Overview
Problem
Extreme UV radiation generating devices face challenges with the mobilization of undesirable materials such as heat, high-energy ions, and debris from plasma generation, which damage optical components like reflectors, leading to reduced reflectivity and shortened lifetimes.
Innovation Solution
An extreme UV radiation reflecting element comprising a highly reflective first layer and a second layer with sputter resistance, typically 5 nm thick, made of materials like highly covalent metal oxides or carbon composites, which enhances reflectivity and extends the device's lifetime while being less susceptible to oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a highly reflective first layer is used to maintain high reflectivity, then reflectivity is improved, but the layer is susceptible to damage from sputtering by high-energy ions and debris
Solution Approach 1:
A second layer made of sputter-resistant material (such as carbon, silicon dioxide, or silicon nitride) with thickness of 1-10 nm is deposited on the highly reflective first layer. This intermediary layer protects the reflective material from direct exposure to high-energy ions and debris from the plasma, significantly reducing sputtering damage while maintaining high reflectivity through the protective layer's transparency to EUV radiation.
Solution Approach 2:
The reflecting element combines two distinct materials with complementary properties: a highly reflective material (such as platinum, iridium, or ruthenium) for high reflectivity and a sputter-resistant material (such as carbon, silicon dioxide, or silicon nitride) for protection against plasma debris. This composite structure leverages the strengths of both materials to achieve both high reflectivity and durability.
2Reliability
If the second protective layer is made thicker to increase sputter resistance, then resistance to sputtering is improved, but reflectivity is reduced due to increased absorption
Solution Approach 1:
The thickness of the second protective layer is precisely controlled within the range of 1-10 nm, with optimal values between 3-7 nm. This parameter optimization balances two competing requirements: sufficient thickness to provide adequate sputter protection and thin enough to maintain high transparency to EUV radiation, ensuring both durability and high reflectivity are achieved simultaneously.
3Ease of manufacture
If conventional materials are used for the reflecting element, then manufacturing is simpler, but the lifetime is shortened due to damage from heat, ions, and debris
Solution Approach 1:
The sputter-resistant second layer is deposited on the reflective first layer before the component is exposed to the plasma environment. This preliminary protective coating prevents direct interaction between the plasma debris and the reflective material, significantly extending the component's lifetime in the harsh EUV generation environment while maintaining manufacturing feasibility through standard deposition techniques.
Solution Approach 2:
The invention specifies precise thickness parameters for both layers: the first reflective layer is optimized for maximum reflectivity (typically 50-200 nm) and the second protective layer is optimized for sputter resistance while maintaining transparency (1-10 nm). These parameter specifications enable reproducible manufacturing with controlled quality while achieving extended lifetime performance.
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 maintains high reflectivity and extends the lifetime of the reflecting element, facilitates easier cleaning, and allows for refurbishment by repeated deposition of the second layer, significantly reducing sputter resistance and oxidation effects.
Implementation Method 1
a second layer having a thickness of 5 nm and essentially made out of a material with a sputter resistance of ≤10 nm per 108 shots
Implementation Method 2
either grazing angle of incidence or so called normal angle of incidence reflectors will be necessary for the collection and focusing of the light emitted from the plasma
Implementation Method 3
a laser produced plasma (LPP) produced by a focused laser beam irradiating a target material to produce the plasma
Implementation Method 4
a electric discharge produced plasma (DPP) produced by an electrical discharge between a pair of electrodes
Data Source
AI summary
The invention relates to an improved EUV reflecting element comprising a) a first layer essentially made out of a highly reflective material b) a second layer having a thickness of ≦5 nm and essentially made out of a material with a sputter resistance of ≦10 nm per 108 shots and whereby the second layer is provided in the path of the incident and/or reflected EUV light.