EUV Photomask Plasma Cleaning for Contamination Removal
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Solution Overview
Problem
In extreme ultraviolet lithography, photomasks suffer from hydrocarbon contamination due to heat-generated decomposition and volatilization of photoresist during EUV exposure, leading to proximity and critical dimension uniformity drift and white spot defects, which are difficult to completely remove during cleaning operations.
Innovation Solution
A method involving plasma processing, specifically using oxygen or hydrogen plasma to remove carbon-based residues from the photomask surfaces, either after exposure or during storage, to maintain the photomask's performance and prevent contamination buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If photomask is used for EUV lithography exposure, then semiconductor device production efficiency increases, but hydrocarbon contamination accumulates on photomask surface
Solution Approach 1:
The patent applies preliminary action by performing plasma cleaning on the photomask before it accumulates significant hydrocarbon contamination. The cleaning process is proactively applied at scheduled intervals or when contamination reaches a threshold level, preventing the contamination from severely impacting lithography performance. This proactive approach maintains photomask quality and ensures consistent semiconductor device production efficiency.
2Object-affected harmful factors
If photomask cleaning operations are performed, then hydrocarbon contamination is reduced, but cleaning completeness is insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing plasma cleaning parameters including power density, gas composition (oxygen, hydrogen, or nitrogen plasma), pressure, and treatment duration. By carefully controlling these parameters, the process achieves thorough hydrocarbon removal while preventing damage to the photomask's sensitive multilayer structure and absorber patterns. This balanced parameter optimization enables effective contamination removal with high cleaning completeness.
3Duration of action of stationary object
If photomask service life is extended, then production cost decreases, but contamination accumulation increases
Solution Approach 1:
The patent applies periodic action by implementing scheduled plasma cleaning cycles during photomask usage. Instead of allowing contamination to accumulate continuously, the photomask undergoes periodic plasma treatment at intervals determined by exposure count or contamination monitoring. This periodic maintenance approach extends the photomask's functional service life by systematically removing hydrocarbon contamination before it reaches critical levels that would require mask replacement.
4Manufacturing precision
If plasma processing is applied to remove contamination, then pattern sharpness is maintained, but processing complexity increases
Solution Approach 1:
The patent applies mechanics substitution by replacing mechanical or chemical cleaning methods with plasma processing. Plasma cleaning uses ionized gas species to chemically etch and remove hydrocarbon contamination without physical contact, avoiding mechanical damage to the photomask's fine patterns. This substitution maintains pattern sharpness and critical dimension uniformity while the process complexity is managed through automated plasma reactor systems and integrated cleaning workflows.
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 plasma cleaning method effectively reduces white spot defects and critical dimension uniformity drift, extending the photomask's service life and improving semiconductor device yield by maintaining pattern sharpness and uniformity, with a significant increase in the number of exposures before unacceptable drift occurs.
Implementation Method 1
The reflective photomask having the contamination is plasma processed in the plasma processing chamber to remove the contamination from the surface
Implementation Method 2
The plasma includes oxygen plasma or hydrogen plasma
Data Source
AI summary
A method includes placing a photomask having a contamination on a surface thereof in a plasma processing chamber. The contaminated photomask is plasma processed in the plasma processing chamber to remove the contamination from the surface. The plasma includes oxygen plasma or hydrogen plasma.