Protective Optical Measuring Scale for EUV Radiation Resistance
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Solution Overview
Problem
Existing optical position measuring devices in EUV lithography systems are vulnerable to damage from high-energy electromagnetic radiation and hydrogen radicals, leading to material removal and contamination of mirror optics.
Innovation Solution
A scale for optical position measuring devices is designed with a carrier substrate, reflector layers, and a protection layer made of titanium oxide, applied using sputtering, ensuring a thinner thickness on side surfaces compared to the top side to protect against radiation and radicals while maintaining high diffraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection layer is applied to protect the scale from EUV radiation and hydrogen radicals, then the resistance to radiation and radicals is improved, but the diffraction efficiency deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the protection layer to a specific range (5-50 nm) and selecting materials with appropriate optical properties (refractive index 1.4-2.5). This allows the protection layer to provide sufficient radiation resistance while maintaining acceptable diffraction efficiency for the optical position measuring device
Solution Approach 2:
The patent uses composite materials by combining the protection layer with the existing scale structure (carrier substrate, reflector layers, and spacer layer). The protection layer is made from specific materials such as silicon oxide, silicon nitride, or titanium oxide that provide both protective functionality and compatible optical properties
2Reliability
If the protection layer thickness is increased to improve protection against hydrogen radicals, then the resistance to material removal is improved, but the manufacturing precision deteriorates due to process fluctuations
Solution Approach 1:
The patent specifies a controlled thickness range of 5-50 nm for the protection layer, which is thin enough to minimize the impact of manufacturing process fluctuations (such as spin coating variations) while still providing adequate protection against hydrogen radical-induced material removal
Solution Approach 2:
The patent employs a thin protection layer that can be applied as a disposable protective barrier, accepting that the layer itself may be damaged or removed, but this thin layer prevents damage to the much more valuable and critical underlying scale structure
3Object-affected harmful factors
If a protection layer is applied to prevent contamination of mirror optics, then the cleanliness of mirror optics is improved, but the device complexity increases
Solution Approach 1:
The protection layer serves as an intermediary barrier between the EUV radiation environment and the scale structure. It prevents direct interaction between hydrogen radicals and the scale materials, thereby preventing contamination of downstream components like mirror optics without requiring complex active protection systems
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 scale provides reliable protection against EUV radiation and hydrogen radicals, preventing material removal and ensuring high-precision optical scanning without impairing diffraction efficiency.
Implementation Method 1
the protection layer is made of a material that prevents removal of material in the carrier substrate and/or in the reflector layers and/or in the spacer layer caused by hydrogen radicals
Implementation Method 2
applied using sputtering
Implementation Method 3
maintaining high diffraction efficiency
Data Source
AI summary
A scale for an optical position measuring device includes a carrier substrate, a first reflector layer arranged on the carrier substrate, a transparent spacer layer arranged on the reflector layer, a structured second reflector layer arranged on the spacer layer, and a protection layer with a defined thickness arranged on the top side of the scale over the second reflector layer. The protection layer is further arranged on the side surfaces of the scale.