Polishing Layered Optical Element for Low-Roughness EUV Mirrors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The production of EUV lithography mirrors with low roughness in specific frequency ranges is challenging due to materials like titanium-doped quartz glass and glass ceramic, which can form stratification streaks or crystallite defects, leading to imaging fluctuations.
Innovation Solution
An optical element with a substrate structure containing a primary layer of glass or silicon dioxide and a polished layer of titanium-doped quartz glass, up to 500 μm thick, is formed along a concave or convex figure, with optional interlayers and a reflection layer stack, to achieve thermal expansion matching and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polished layer of titanium-doped quartz glass is formed along the figure to compensate for roughness, then imaging accuracy is improved, but the complexity of the production process increases
Solution Approach 1:
The patent applies preliminary action by forming the polished layer before the figure is formed. The substrate structure is first created with the polished layer already in place, and then the figure is formed on top of it. This sequence allows the polished layer to compensate for roughness defects that may arise during subsequent figure formation and polishing operations, thereby improving imaging accuracy while managing production complexity through optimized process sequencing.
2Manufacturing precision
If the thickness of the polished layer is increased to compensate for roughness, then imaging accuracy is improved, but the thermal stress in the optical element increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thickness of the polished layer to be within the range of 1 μm to 100 μm. This optimized thickness range is sufficient to compensate for roughness and improve imaging accuracy while remaining thin enough to minimize thermal stress. The patent also adjusts the titanium content in the polished layer to match the substrate structure, further reducing thermal expansion differences and associated stresses.
Solution Approach 2:
The patent applies local quality by creating a polished layer with specific local properties (titanium doping, controlled thickness) that are optimized for the specific function of compensating roughness. The polished layer has a different composition and structure than the substrate structure, with a titanium content tailored to match the substrate's thermal expansion characteristics, thereby achieving local optimization that balances imaging accuracy with thermal stress minimization.
3Stress or pressure
If the titanium content in the polished layer is increased to match thermal expansion, then thermal stress is reduced, but the difficulty of producing a uniform layer increases
Solution Approach 1:
The patent applies parameter changes by optimizing the titanium content in the polished layer to fall within a specific range (5-20 wt% TiO2) that balances thermal expansion matching with manufacturability. This optimized range provides sufficient thermal expansion matching to reduce thermal stress while avoiding the production difficulties associated with very high titanium contents. The patent also specifies a controlled thickness range (1-100 μm) that facilitates uniform layer formation.
4Manufacturing precision
If the figure is formed in a complex manner to compensate for roughness, then imaging accuracy is improved, but the production time increases
Solution Approach 1:
The patent applies preliminary action by forming the polished layer before the figure is formed. This sequence allows the polished layer to compensate for roughness defects that may arise during subsequent figure formation and polishing operations. By preparing the polished layer in advance, the patent avoids the need for complex corrective measures later in the process, thereby improving imaging accuracy while reducing overall production time.
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 imaging accuracy and reduced thermal stress, avoiding defects like striae and crystallite formation, while maintaining high thermal expansion matching and enabling efficient production processes.
Implementation Method 1
The solution provides improved imaging accuracy and reduced thermal stress, avoiding defects like striae and crystallite formation, while maintaining high thermal expansion matching
Implementation Method 2
a lateral face of the substrate structure has a convex or concave figure, and an up to 500 μm-thick polished layer containing titanium-doped quartz glass or TiO2—SiO2, formed along the figure
Data Source
AI summary
An optical element (100, 200, 300, 400, 500, 600, 700), includes: a substrate structure (102, 202, 302, 402, 502, 602, 702) containing at least one primary layer (110, 210, 310, 410, 510, 610, 710) containing SiO2, with a lateral face (104, 204, 304, 404, 504, 604, 704) of the substrate structure (102, 202, 302, 402, 502, 602, 702) having a convex or concave FIG. 112, 212, 312, 412, 512, 612, 712), and a polishing layer (114, 214, 314, 414, 514, 614, 714) up to 500 μm-thick, which contains TiO2·SiO2 and is formed along the FIG. 112, 212, 312, 412, 512, 612, 712).