Photo Mask Cleaning Preventing Arcing Damage
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Solution Overview
Problem
During the photo mask cleaning process, static electricity is generated due to the rapid flow of chemicals, leading to arcing and damage to the metal patterns, which can cause faults in the exposure process.
Innovation Solution
A method and apparatus where the chemical is initially applied to the non-pattern area of the photo mask while it is stationary, and then the nozzle moves to the center of the pattern area to discharge the chemical, ensuring the entire surface is wetted before rotation, thereby preventing arcing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chemical is rapidly ejected to the center of the mask during cleaning, then cleaning efficiency is improved, but static electricity accumulates and causes arcing that damages the metal pattern
Solution Approach 1:
The patent applies preliminary action by first weting the entire mask surface with chemical before the rapid ejection phase. This pre-wetting step reduces static electricity accumulation during the subsequent high-speed cleaning phase, preventing arcing damage while maintaining cleaning efficiency
Solution Approach 2:
The cleaning process is segmented into distinct phases: a pre-treatment phase where chemical is supplied to the entire mask surface, and a main cleaning phase where chemical is rapidly ejected to the center. This segmentation allows each phase to optimize for its specific function while mitigating the harmful effects of rapid chemical ejection
2Manufacturing precision
If chemical is supplied to the entire mask surface at once, then uniform cleaning is achieved, but static electricity generation increases leading to arcing
Solution Approach 1:
The pre-wetting step applies chemical to the entire mask surface in advance, creating a uniform base layer that prevents static electricity accumulation during the main cleaning phase. This preliminary action achieves both uniform cleaning and static electricity prevention
Solution Approach 2:
The cleaning process uses periodic action by alternating between slow chemical supply for pre-wetting and rapid chemical ejection for main cleaning. This periodic variation in chemical supply rate allows uniform coverage while managing static electricity generation
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 effectively prevents arcing and subsequent damage to the metal patterns during the cleaning process, ensuring the integrity of the photo mask for subsequent exposure processes.
Implementation Method 1
a chemical (a sulfuric peroxide mixture: SPM) is ejected to the center of the mask or a portion of the mask that is close to the center, and the applied chemical removes contaminants on the substrate
Implementation Method 2
static electricity is generated at a periphery of a chemical ejection hole as the chemical rapidly flows on the mask
Implementation Method 3
the generated static electricity is confined by the metal pattern, and the metal pattern is damaged when arcing is generated due to the accumulated static electricity
Data Source
AI summary
Disclosed is a method for cleaning a photo mask. The method includes a pre-treatment operation of wetting a chemical on an entire surface of the photo mask in a state in which the photo mask is stopped, and a cleaning operation of supplying the chemical to a pattern area of the photo mask in a state in which the photo mask is rotated.