Pressurized Liquid Injection for EUV Mask Substrate Cleaning
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Solution Overview
Problem
Conventional cleaning methods for mask blank substrates, such as high speed shear flow and megasonic cleaning, struggle to effectively remove small foreign substances and can generate latent defects on the glass substrate surface, particularly in EUV reflective mask blanks where high surface defect sensitivity is critical.
Innovation Solution
A method involving the use of pressurized cleaning liquid containing bubbles or cleaning particles, injected through a nozzle with a slit or pinhole opening, to detach and remove particles from the substrate surface, including those smaller than 100 nm, while minimizing the risk of latent defect generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cleaning methods (high speed shear flow or megasonic cleaning) are used, then cleaning capability is provided, but small foreign substances (particles smaller than 100 nm) cannot be effectively removed and latent defects are generated on the glass substrate surface
Solution Approach 1:
The invention changes the cleaning mechanism from conventional shear flow or megasonic cleaning to pressurized cleaning liquid injection. By adjusting parameters such as liquid pressure (0.1-10 MPa), flow rate, and injection angle (30-60 degrees), the cleaning method achieves high removal rate for small particles (60 nm or larger) while preventing latent defects. The pressurized liquid creates controlled impact forces that effectively remove particles without generating subsurface damage.
Solution Approach 2:
The invention employs hydraulic principles by using pressurized cleaning liquid (water or water-based solution) injected through a nozzle. The high-pressure liquid stream creates mechanical impact and shear forces that detach particles from the substrate surface. The hydraulic approach replaces conventional mechanical or ultrasonic methods, achieving superior cleaning for sub-100nm particles while maintaining substrate integrity and preventing latent defects.
2Manufacturing precision
If high pressure nozzles are used for cleaning, then foreign substances can be stripped from surfaces, but the complexity of the cleaning system increases
Solution Approach 1:
The invention extracts only the essential cleaning function by using a simple pressurized liquid injection system. Instead of complex multi-component cleaning apparatus, it uses a straightforward setup with a nozzle, pressurized liquid supply, and substrate positioning. This extracted approach maintains high particle removal capability while significantly reducing system complexity compared to conventional high-speed shear flow or megasonic cleaning systems.
3Manufacturing precision
If megasonic cleaning is applied, then cleaning action is provided, but convex defects are generated on the substrate surface
Solution Approach 1:
The invention replaces the ultrasonic vibration mechanism (acoustic field) with a pressurized liquid injection system (mechanical hydraulic field). The pressurized liquid creates direct mechanical impact and shear forces for particle removal without using ultrasonic waves. This substitution eliminates the generation of convex defects associated with megasonic cleaning while maintaining effective cleaning action for small particles.
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 achieves a high removal rate of surface defects, exceeding 98% for particles 60 nm or larger, and prevents latent defects within the glass substrate, ensuring high-quality mask blank substrates with reduced convex defects, thereby improving the accuracy and contrast of transferred patterns.
Implementation Method 1
injecting pressurized cleaning liquid containing bubbles or cleaning particles from a injection nozzle to at least one surface of the substrate
Implementation Method 2
cleaning at least one surface of a substrate located in a liquid by injecting pressurized cleaning liquid containing bubbles or cleaning particles
Implementation Method 3
pressurized cleaning liquid containing bubbles or cleaning particles
Implementation Method 4
high speed shear flow of the ultrapure water injected from the high pressure nozzles are generated near the surfaces of the objects to be cleaned. With the high speed shear flow, fine foreign substances attached to the surfaces of the objects to be cleaned are stripped by breaking the bond with the surfaces
Data Source
AI summary
The present invention is a method of cleaning a substrate, comprising cleaning at least one surface of a substrate located in a liquid by injecting pressurized cleaning liquid containing bubbles or cleaning particles from a injection nozzle to at least one surface of the substrate.