Low-Expansion Glass Substrate Mirror-Finished Lateral Wall
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Solution Overview
Problem
In EUV lithography, foreign particles and scratches on reflective masks can lead to defective circuit patterns due to the generation of fine glass fragments from the lateral end walls of glass substrates, which are difficult to remove and cause defects in integrated circuit fabrication.
Innovation Solution
The solution involves forming a low-expansion glass substrate with a mirror-finished surface on the lateral end wall, applying a protective film, or subjecting the lateral end wall to etching to prevent glass fragment generation and adherence, thereby reducing the number of foreign particles and improving surface non-defectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the lateral end wall of the glass substrate is left with a normal polished surface, then the manufacturing process is simple, but fine glass fragments are generated from the lateral end wall causing foreign particles on the substrate surface
Solution Approach 1:
The lateral end wall is subjected to preliminary treatments (chamfering, notching, or mirror finishing) before the main substrate fabrication steps. This preliminary action prevents glass fragment generation during subsequent handling and processing, thereby reducing foreign particles on the substrate surface without significantly complicating the overall manufacturing process
Solution Approach 2:
Instead of treating the entire substrate surface uniformly, the invention applies specific surface treatments only to the lateral end wall regions where glass fragments are most likely to generate. This localized approach (chamfering, notching, or mirror finishing) improves surface non-defectiveness where needed while keeping the rest of the manufacturing process simple
2Reliability
If a mirror-finished surface is provided on the lateral end wall, then glass fragment generation is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The mirror-finished surface treatment is applied only to the lateral end wall rather than the entire substrate. This localized high-precision treatment reduces glass fragment generation at the critical region while keeping the overall manufacturing complexity manageable by leaving other areas with standard polishing
Solution Approach 2:
The invention provides several levels of surface treatment options for the lateral end wall (chamfering, notching, or mirror finishing). The manufacturer can select the appropriate level based on the specific application requirements, allowing partial application of complex treatments only when necessary to achieve the desired foreign particle reduction
3Manufacturing precision
If the glass substrate is highly polished to reduce surface defects, then manufacturing precision improves, but the lateral end wall becomes a source of glass fragments
Solution Approach 1:
The invention differentiates the treatment of different regions: the main substrate surface is highly polished for manufacturing precision, while the lateral end wall is given special treatments (chamfering, notching, or mirror finishing) to prevent glass fragment generation. This localized differentiation resolves the contradiction by addressing each region's specific requirements
Solution Approach 2:
The substrate is segmented into different functional regions (main surface and lateral end wall) with different surface treatment requirements. The lateral end wall is separated and treated differently through chamfering, notching, or mirror finishing, preventing it from becoming a source of glass fragments while maintaining high polish quality on the main substrate surface
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
This approach effectively decreases the number of foreign particles adhering to the substrate surface, enhancing the precision of integrated circuit fabrication by preventing glass fragment generation and adherence, ensuring high-quality circuit pattern transfer in EUV lithography.
Implementation Method 1
at least one of the lateral surface, the chamfered portion and the notched portion being provided with a mirror-finished surface
Implementation Method 2
the lateral end wall being covered with a protective film for prevention of dust generation
Implementation Method 3
the lateral end wall being subjected to etching
Implementation Method 4
The substrate needs to comprise a material that has a low coefficient of thermal expansion in order to avoid distortion even under illumination of an EUV ray
Data Source
AI summary
A low-expansion glass substrate for a reflective mask, wherein the glass substrate is suited for a base material of a reflective mask employed in a lithographic process in semiconductor fabrication, comprises a lateral surface, a chamfered portion and a notched portion formed along an outer periphery thereof, at least one of the lateral surface, the chamfered portion and the notched portion being provided with a mirror-finished surface.