Mask Blank Side Surface Shielding for Charge-Up Prevention
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Solution Overview
Problem
The miniaturization of semiconductor devices requires high-NA exposure for fine pattern formation, but immersion exposure with NA>1 faces challenges in achieving expected CD accuracy due to mask blank charge-up during electron beam writing, particularly for DRAM half-pitch 45 nm and beyond, where the etching mask film's surface resistance causes charge-up issues affecting resist resolution and alignment mark formation.
Innovation Solution
A mask blank manufacturing method where the etching mask film is not formed at the side surfaces or chamfered surfaces of the substrate, allowing the light-shielding film to be exposed for grounding and preventing charge-up, while extending the film forming region of the etching mask film to prevent alignment mark lacks, using a shielding plate made of an elastic material to shield the substrate surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the etching mask film is formed on the side surfaces of the substrate to extend the film forming region, then alignment mark formation is improved, but charge-up occurs during electron beam writing affecting resist resolution
Solution Approach 1:
The patent applies local quality by creating different surface properties in different regions of the substrate. The side surfaces are made conductive through light-shielding film formation to prevent charge-up, while the main surface maintains the etching mask film for proper alignment mark formation. This localized differentiation resolves the contradiction between preventing charge-up and ensuring alignment mark quality.
Solution Approach 2:
The substrate surface is segmented into distinct functional regions: the main surface for pattern formation with etching mask film, and the side surfaces for charge-up prevention with light-shielding film. This segmentation allows each region to optimize its function without interfering with the other, solving the contradiction between alignment mark formation and charge-up prevention.
2Measurement precision
If the etching mask film is not formed at the side surfaces to prevent charge-up, then resist resolution is maintained, but the film forming region is reduced affecting alignment mark formation
Solution Approach 1:
Different regions of the substrate are assigned different film configurations: the main surface has the etching mask film for proper alignment marks, while the side surfaces exclude the etching mask film to prevent charge-up. This local differentiation simultaneously achieves both resist resolution and alignment mark formation.
Solution Approach 2:
The light-shielding film acts as an intermediary element on the side surfaces, providing the conductive path for charge dissipation without interfering with the alignment mark formation on the main surface. This intermediary structure resolves the contradiction by mediating between charge-up prevention and alignment mark requirements.
3Measurement precision
If immersion exposure with NA>1 is used for fine pattern formation, then resolution is improved, but mask blank charge-up affects CD accuracy
Solution Approach 1:
The patent implements preliminary action by forming the conductive light-shielding film on the side surfaces before the electron beam writing process. This pre-established conductive path prevents charge-up during subsequent high-NA exposure and electron beam processing, thereby maintaining both resolution and CD accuracy without interference from charge-up effects.
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 prevents charge-up during electron beam writing, maintains resist resolution, and ensures accurate formation of fine patterns and alignment marks, enhancing the controllability of pattern processing and CD accuracy.
Implementation Method 1
when forming the etching mask film, shielding is performed using a shielding plate so as to prevent the etching mask film from being formed at least at a side surface of the substrate
Implementation Method 2
allowing the light-shielding film to be exposed for grounding and preventing charge-up
Implementation Method 3
In the resist pattern formation using the EB writing, a problem of charge-up is raised
Data Source
AI summary
In a method of manufacturing a mask blank adapted to be formed with a resist pattern by electron beam writing and having a light-shielding film and an etching mask film of an inorganic-based material resistant to etching of the light-shielding film which are formed in this order on a transparent substrate, when forming the etching mask film, shielding is performed using a shielding plate so as to prevent the etching mask film from being formed at least at a side surface of the substrate.