Mask Substrate Frame Geometry for Deformation Control
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Solution Overview
Problem
In semiconductor device production, masks deform when chucked to exposure apparatuses, leading to accuracy issues in pattern transfer processes, especially with ArF and EUV exposure technologies where short wavelengths exacerbate the impact of mask deformation.
Innovation Solution
A substrate for mask blanks with a specific geometric configuration and surface flatness is used to minimize deformation, featuring a frame-shaped region with controlled height differences and flatness, allowing for precise pattern transfer without significant distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional mask substrate is used, then the mask can be manufactured with standard processes, but the mask deforms when chucked to the exposure apparatus, reducing transfer accuracy
Solution Approach 1:
The mask substrate surface is divided into distinct regions: a large inner region (132mm×132mm) for pattern formation and a frame-shaped peripheral region with specific height differences. This segmentation allows the central pattern area to maintain high flatness while the peripheral frame provides structural support and deformation control during chucking.
Solution Approach 2:
Different regions of the mask substrate are given different surface heights and flatness characteristics. The inner region has high flatness (100nm or less) for precise pattern transfer, while the frame-shaped peripheral region has controlled height differences (100nm or less) to provide mechanical stability during handling and chucking operations.
2Measurement precision
If shorter wavelength exposure light (EUV) is used, then higher resolution patterns can be transferred, but mask deformation has a greater impact on transfer accuracy
Solution Approach 1:
The frame-shaped peripheral region is designed in advance to compensate for deformation forces that will occur during chucking. The specific height differences and geometric configuration of the frame structure pre-establish stress distribution patterns that prevent deformation of the inner region during exposure, ensuring that the high-resolution patterns remain accurate.
3Area of stationary object
If the mask substrate is made larger to accommodate larger patterns, then more circuit elements can be processed, but the mask becomes more prone to deformation during chucking
Solution Approach 1:
The mask substrate employs an asymmetric design where the inner region (132mm×132mm) is smaller than the overall substrate, surrounded by a frame-shaped peripheral region with specific height differences. This asymmetric configuration optimizes the balance between usable pattern area and structural support, allowing larger substrates to maintain stability during chucking while providing sufficient area for complex circuit patterns.
Data Source
AI summary
In a substrate for use as a mask blank including a first main surface, a normal region, a frame-shaped region and inner region are present on the first main surface. The frame-shaped region includes first to fourth corner region and first to fourth middle region. The inner region has a flatness of 100 nm or less, the flatness being determined on the basis of a least-squares plane PP1 of the normal region. When one of the corner regions is referred to as an n-th corner region and two middle regions nearest to the n-th corner region are respectively referred to as a first near middle region and a second near middle region, the specific relationship regarding the surface profile is satisfied in the n-th corner region and the first and second near middle regions.