Mask Blank Substrate Mark Geometry for Flatness
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Solution Overview
Problem
Conventional mask blank substrates with oblique section substrate marks experience edge roll-off and rising issues during polishing, affecting the flatness of the substrate surface, which existing techniques fail to adequately address.
Innovation Solution
A mask blank substrate with a substrate mark of an oblique section shape, where the distance from the boundary between the mark and the main surface to the R-surface is less than 1.5 mm, and an inclination angle greater than 45° and less than 90°, is used, along with a polishing process employing colloidal silica abrasive particles to minimize edge roll-off and improve flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a substrate mark of oblique section shape is formed on the mask blank substrate, then the substrate identification function is improved, but edge roll-off and rising occur during polishing causing flatness degradation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the distance from the boundary between the substrate mark and main surface to the R-surface (less than 1.5 mm) and setting the inclination angle within 45° to 90°. These parameter optimizations eliminate edge roll-off and rising during polishing while maintaining substrate identification functionality.
2Manufacturing precision
If conventional polishing processes are used on substrates with substrate marks, then polishing can be completed, but excessive processing time is required to achieve high flatness
Solution Approach 1:
The patent implements preliminary action by pre-optimizing the substrate mark geometry (distance < 1.5 mm, inclination angle 45°-90°) before polishing. This preliminary configuration prevents edge roll-off and rising from occurring, eliminating the need for time-consuming post-polishing flatness correction processes.
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 configuration effectively eliminates adverse effects on flatness due to the substrate mark, resulting in improved surface flatness and reduced processing time for achieving high flatness requirements in mask blank substrates.
Implementation Method 1
a polishing process of polishing a surface of a mask blank glass substrate using a polishing liquid containing polishing abrasive particles
Data Source
AI summary
A mask blank substrate is provided with a substrate mark comprising an oblique section. The inclination angle of the substrate mark with respect to a main surface is greater than 45° and less than 90° and the distance from the boundary between the main surface and the substrate mark to the outer periphery of the mask blank substrate is less than 1.5 mm.