Mask Blank Optical Specification Control via Transmittance Feedback
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Solution Overview
Problem
Mask blanks deviate from optical specifications due to transmittance variation in synthetic quartz glass substrates, leading to pattern defects in transfer targets, especially with shorter exposure wavelengths like 193 nm, where the transmittance decreases to 80% or less, causing issues in fine and elaborate mask patterns.
Innovation Solution
A system that includes substrate and mask blank information storage and communication between manufacturing departments to ensure accurate optical characteristic data exchange, allowing for precise control of transmittance and phase difference variations in both the substrate and thin film planes, thereby preventing deviations from optical specifications and pattern defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the exposure wavelength is reduced to 193 nm for miniaturization of semiconductor devices, then the resolution and manufacturing precision are improved, but the transmittance of the mask blank substrate decreases to 80% or less due to absorption, causing variation in optical characteristics and pattern defects
Solution Approach 1:
The patent applies parameter changes by measuring and managing the transmittance of individual mask blank substrates at the specific exposure wavelength (193 nm), then adjusting process parameters such as thin film formation conditions based on each substrate's characteristics. This ensures that optical characteristics remain stable despite the reduced transmittance caused by shorter wavelength exposure
Solution Approach 2:
The patent implements feedback by measuring the transmittance of each mask blank substrate and using this information to adjust subsequent manufacturing processes. The system feeds back the optical characteristic data to control the thin film formation process, ensuring consistent optical properties are achieved despite variations in substrate transmittance at 193 nm wavelength
2Adaptability or versatility
If synthetic quartz glass is used as the mask blank substrate material, then the substrate can be used for both KrF (248 nm) and ArF (193 nm) excimer lasers, but the transmittance varies significantly at 193 nm due to manufacturing variations in the glass
Solution Approach 1:
The patent measures the transmittance of each synthetic quartz glass substrate at 193 nm and uses this measured parameter to adjust the thin film formation process. By changing process parameters based on individual substrate characteristics, the patent achieves precise transmittance control despite variations in the glass material itself
Solution Approach 2:
The patent performs preliminary measurement of substrate transmittance before thin film formation, allowing the manufacturing process to be adjusted in advance based on each substrate's optical characteristics. This preliminary action ensures that subsequent processes are optimized for each specific substrate, preventing transmittance variations from affecting final product quality
3Ease of manufacture
If the transmittance variation in the substrate is not controlled, then the manufacturing process is simpler, but the mask blank deviates from optical specifications and causes pattern defects in transfer targets
Solution Approach 1:
The patent implements a feedback system where transmittance measurements of individual substrates are used to adjust manufacturing parameters. This feedback loop ensures optical specification compliance without requiring complete process redesign, maintaining relative manufacturing simplicity while achieving precise optical control
Solution Approach 2:
The patent changes process parameters such as thin film thickness and formation conditions based on measured substrate transmittance values. This approach maintains ease of manufacture by using standard processes with adjustable parameters rather than requiring entirely new manufacturing methods, while ensuring optical specifications are met
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 ensures that mask blanks meet optical specifications, preventing pattern defects in transfer targets by accurately managing transmittance and phase difference variations, even in the short wavelength region, thus ensuring high-quality semiconductor device production.
Implementation Method 1
the transmittance (transmittance in a plate thickness direction) sometimes decreases to 80% with the 6025 size (plate thickness: 6.35 mm) due to absorption by the substrate itself with respect to the exposure light caused by manufacturing variation in synthetic quartz glass
Data Source
AI summary
A mask blank manufacturing department manufactures a mask blank by forming a thin film to be a mask pattern on a mask blank transparent substrate. When providing the mask blank to a mask manufacturing department, the mask blank manufacturing department provides optical characteristic information (transmittance variation) of the mask blank transparent substrate and optical characteristic information (transmittance variation and/or phase difference variation) of the mask blank to the mask manufacturing department. The optical characteristic information of the mask blank transparent substrate is provided to the mask blank manufacturing department from a materials processing department that manufactures mask blank transparent substrates.