Photomask Cleaning with Ozonated Water for Cross-Linked Resist Removal
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Solution Overview
Problem
Existing photomask manufacturing processes face challenges in effectively removing cross-linked photosensitive polymeric materials and adhesive materials due to their stable structure and large Van der Waals forces, which leads to low resolution and undesired patterns on semiconductor substrates.
Innovation Solution
A method involving ozonated deionized water and an alkaline solution, followed by mechanical impact, is used to oxidize and soften the patterned photoresist layer, allowing for efficient removal of polymeric materials without damaging the underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cleaning methods are used to remove photoresist, then the cleaning process is simple, but cross-linked polymeric materials and adhesive materials remain as residues due to their stable structure and large Van der Waals forces
Solution Approach 1:
The patent employs ozone water (H2O3) as a strong oxidizing agent to effectively remove cross-linked polymeric materials and adhesive materials from photomask surfaces. The ozone water oxidizes these resistant materials, breaking down their stable structures and enabling complete removal without leaving residues, thereby resolving the contradiction between removal completeness and process simplicity.
Solution Approach 2:
The cleaning method uses a composite approach combining ozone water oxidation with alkaline solutions (such as TMAH). This composite cleaning system leverages the oxidizing power of ozone water and the saponification capability of alkaline solutions to tackle different aspects of photoresist and adhesive removal, achieving superior cleaning results while managing process complexity through a coordinated multi-component system.
2Productivity
If strong mechanical impact is applied to remove photoresist, then removal efficiency increases, but damage occurs to underlying layers and critical dimension accuracy deteriorates
Solution Approach 1:
The patent replaces strong mechanical impact methods with chemical oxidation using ozone water. Instead of relying on mechanical force that can damage underlying layers, the ozone water chemically oxidizes and softens the photoresist and adhesive materials, enabling their removal through chemical action rather than mechanical stress. This substitution maintains high removal efficiency while preserving critical dimension accuracy and protecting underlying layers from damage.
Solution Approach 2:
The patent changes the state and properties of cleaning agents by using ozone water, which has different chemical and physical parameters compared to conventional cleaning solutions. The ozone water's strong oxidizing capability and controlled reactivity allow for efficient photoresist removal without the need for aggressive mechanical parameters, thus maintaining manufacturing precision while improving productivity.
3Productivity
If photomask is used without thorough cleaning, then production speed is maintained, but defect rate increases due to residues causing low resolution and undesired patterns
Solution Approach 1:
The patent implements preliminary cleaning action using ozone water oxidation before the photomask enters production. By thoroughly oxidizing and removing all photoresist and adhesive residues in advance, the cleaning process ensures that no contaminants remain to cause defects during subsequent lithography operations. This preliminary action achieves both high production speed and low defect rates by preventing contamination-related failures.
Solution Approach 2:
The use of ozone water as a strong oxidant enables rapid and complete removal of organic residues including cross-linked photoresist and adhesive materials. This accelerated oxidation process achieves thorough cleaning quickly, allowing photomasks to be ready for production immediately after cleaning, thus maintaining high productivity while ensuring defect-free operation through complete residue removal.
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 method achieves a defect rate of 0-1.5% and maintains critical dimension accuracy, improving the photomask's cleanliness and resolution by effectively removing residues, especially at corners and high aspect ratio features.
Implementation Method 1
applying an ozonated deionized water to the first surface, thereby oxidizing polymeric materials on the surface
Implementation Method 2
applying an alkaline solution onto the patterned photoresist
Implementation Method 3
altering molecular bonding of the polymeric materials
Implementation Method 4
providing a mechanical impact to the patterned photoresist
Data Source
AI summary
A method for manufacturing a photomask is provided. The method includes: forming a target layer over a substrate; forming a patterned photoresist layer over the target layer; applying ozonated deionized water to oxidize organic materials over the substrate; applying an alkaline solution to soften the patterned photoresist layer after applying the ozonated deionized water; and removing the softened patterned photoresist layer by mechanical impact.