Substrate Freeze Cleaning to Prevent Photomask White Haze
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Solution Overview
Problem
Freeze cleaning methods for substrates used in photomasks can lead to partial oxidation of the halftone film, causing defects like white haze due to potential differences between different film materials on the substrate.
Innovation Solution
A substrate processing method that forms a solidified film on the substrate, melts it selectively based on material type, and uses a controlled liquid and gas supply to neutralize static electricity and remove foreign matter without causing oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If freeze cleaning is performed on a substrate with different film materials, then foreign matter is removed, but partial oxidation occurs causing white haze defects
Solution Approach 1:
The patent applies preliminary action by grounding the substrate before freeze cleaning to remove static electricity in advance. This prevents oxidation during the cleaning process by eliminating the electrostatic field that would otherwise cause oxygen to be attracted to charged regions of the substrate, thereby preventing white haze defects before they can form.
Solution Approach 2:
The patent creates an inert environment by controlling the atmospheric conditions during freeze cleaning. By managing the gas environment and eliminating electrostatic fields that would attract oxygen, the process effectively creates a protective atmosphere that prevents oxidation of the substrate and film materials during the cleaning operation.
2Device complexity
If static electricity is not neutralized during freeze cleaning, then cleaning process is simple, but potential differences cause oxidation defects
Solution Approach 1:
The grounding step is performed as a preliminary action before the main freeze cleaning process. This simple preparatory step removes static electricity in advance, preventing oxidation defects without adding significant complexity to the overall cleaning process.
3Productivity
If different regions of the substrate are cleaned simultaneously, then processing time is reduced, but non-uniform cleaning and defects occur
Solution Approach 1:
The patent segments the cleaning process by region, treating different areas of the substrate differently based on their specific requirements. The system divides the substrate into multiple regions and applies customized cleaning parameters to each, ensuring uniform cleaning results while maintaining efficient processing through automated regional control.
Solution Approach 2:
The patent applies local quality by customizing cleaning parameters for different regions of the substrate. Each region receives cleaning conditions optimized for its specific characteristics, such as film material type and contamination level, resulting in uniformly high cleaning quality across the entire substrate surface.
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
Effectively removes foreign matter and neutralizes static electricity, reducing defects like white haze by minimizing potential differences between film materials, ensuring precise and reliable substrate cleaning.
Implementation Method 1
freeze cleaning that freezes a cleaning liquid supplied on a substrate for photomasks
Implementation Method 2
melts it selectively based on material type
Data Source
AI summary
According to an embodiment, a substrate processing method includes forming a liquid film on a substrate including a first region provided with a first film on an outermost surface thereof and a second region provided with a second film on an outermost surface thereof, the first film and the second film being different from each other in material. The method further includes forming a solidified film by solidifying the liquid film. The method further includes causing the solidified film on the first region to melt prior to the solidified film on the second region.