EUV Mask Blank Surface Smoothing via Laser Melting
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Solution Overview
Problem
Current substrate treatment processes for EUV mask blanks generate defects such as pits, scratches, bumps, and particles, which are not effectively addressed by existing polishing and cleaning methods, leading to a need for improved surface smoothing techniques to achieve defect-free surfaces for extreme ultraviolet lithography.
Innovation Solution
A method involving the use of a laser to scan and melt the surface of a glass substrate with a softening point temperature, forming a molten mass to fill pits and scratches, and depositing a metal smoothing layer with a lower melting point than the substrate to cover and smooth out defects, followed by cooling to achieve a smooth surface with an average roughness of less than 0.15 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chemical mechanical planarization (CMP) and cleaning processes are used to treat substrate surfaces, then the substrate is prepared for coating, but defects such as pits, scratches, bumps and particles are generated on the surface
Solution Approach 1:
The patent applies phase transition by melting the substrate surface using laser energy to transform it from solid to liquid state, allowing the molten material to flow and fill defects, then cooling it back to solid to create a smooth, defect-free surface
Solution Approach 2:
The patent replaces the mechanical CMP process with a thermal-laser based process. Instead of using mechanical abrasion and chemical reactions, the invention uses laser-induced melting and solidification to smooth the surface, eliminating the generation of mechanical defects
2Manufacturing precision
If the substrate surface is melted and re-solidified to smooth defects, then surface roughness is reduced, but the process requires precise control of temperature and cooling rates
Solution Approach 1:
The patent utilizes parameter changes by controlling the laser power, scanning speed, and cooling rate to achieve the desired surface smoothness. By adjusting these parameters, the process can be optimized to melt and resolidify the surface without creating new defects or causing substrate damage
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
The method effectively reduces surface roughness to less than 0.15 nm, minimizing defects and preparing a smooth surface for the deposition of EUV reflective multilayers, enhancing the quality of EUV mask blanks by filling and smoothing pits, scratches, bumps, and particles.
Implementation Method 1
scanning a surface of a glass substrate comprising pits and scratches with a laser
Implementation Method 2
melting the surface to form a molten mass to fill the pits and scratches
Implementation Method 3
cooling the molten mass and forming a cooled, smooth surface
Implementation Method 4
cooling the molten mass and forming a cooled, smooth surface
Implementation Method 5
melting the metal smoothing layer to form a molten mass; filling the pits and scratches with the molten mass
Data Source
AI summary
Extreme ultraviolet (EUV) mask blanks and methods for their manufacture, and production systems therefor are disclosed. The method for forming an EUV mask blank comprises smoothing out surface defects on a surface of a substrate.