Glass Substrate Surface Profile for Photomask Flatness
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Solution Overview
Problem
Current methods for achieving high flatness in glass substrates for photomasks are insufficient to meet the increasing demands of miniaturization in semiconductor manufacturing, as traditional polishing techniques struggle to achieve the required level of surface flatness, especially when photomasks are chucked and placed on mask stages.
Innovation Solution
A glass substrate design with specific surface features, including defined regions and profiles, where the profile is characterized by average height differences and extrapolated curves, ensures a peak-to-valley value of 70 nm or less, allowing for improved flatness when combined with chucking deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional polishing techniques are used to improve surface flatness, then manufacturing process is simple, but the flatness level cannot meet the required 30 nm or less height variation
Solution Approach 1:
The patent applies preliminary action by pre-forming specific surface profiles (convex or concave) on the glass substrate before chucking. The surface is polished to create predetermined curvature patterns that will compensate for deformation during the chucking process, ensuring the final flatness meets the 30 nm requirement without requiring extreme polishing precision.
Solution Approach 2:
The patent changes the surface geometry parameters by introducing controlled convex or concave profiles with specific curvature radii. These parameter changes in surface shape allow the substrate to deform predictably during chucking, transforming the flatness problem into a controlled geometric compensation problem that is easier to manufacture.
2Manufacturing precision
If extreme flatness of 30 nm or less is pursued through polishing alone, then measurement precision requirement increases, but manufacturing becomes increasingly difficult and costly
Solution Approach 1:
The patent transforms the flatness parameter into a controlled surface profile parameter. Instead of追求 extreme flatness through complex multi-step polishing, the invention introduces convex or concave profiles with controllable curvature radii that simplify the manufacturing process while achieving the required final flatness through predictable deformation during chucking.
3Manufacturing precision
If the glass substrate surface is made extremely flat before chucking, then flatness is improved, but chucking deformation cannot be effectively compensated
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming surface profiles that counteract the expected chucking deformation. The convex or concave patterns are designed to deform in opposite directions to the chucking-induced deformation, effectively compensating for it and maintaining flatness stability during the chucking process.
4Manufacturing precision
If conventional polishing methods are used, then manufacturing cost is low, but the flatness cannot achieve the required level for next-generation semiconductor manufacturing
Solution Approach 1:
The patent changes the surface geometry from requiring extreme flatness to requiring controlled curvature patterns. This parameter change allows the use of conventional polishing equipment and methods while achieving the required final flatness, thereby maintaining manufacturing simplicity and low cost.
Data Source
AI summary
A glass substrate for a mask blank includes a first surface and a second surface. The first surface and second surface face each other. Each of the first surface and the second surface is approximately square having a vertical length and a horizontal length being equal to the vertical length. The first surface of the glass substrate has specific profile properties.