Mask Inspection Pressure Control for Stable EUV Aberrations
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Solution Overview
Problem
EUV lithography masks experience aberration instability due to fluctuations in environmental pressure, leading to inspection failures and reduced tool availability.
Innovation Solution
Implementing a fan assembly with adjustable power to maintain a stable pressure difference between the inside and outside of the inspection tool, using pressure sensors to monitor and control the environmental pressure, thereby reducing aberration instability and improving inspection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If environmental pressure is not controlled during mask inspection, then the inspection process is simpler, but aberration instability increases leading to inspection failures
Solution Approach 1:
The patent applies the inert atmosphere principle by creating a controlled pressure environment inside the inspection tool that isolates the optical components from external pressure fluctuations. The housing encloses the inspection space and maintains a stable internal pressure, effectively creating an inert environmental condition that prevents pressure-induced aberrations during mask inspection
Solution Approach 2:
The patent implements feedback control through pressure sensors that continuously monitor the internal pressure of the housing and adjust the gas flow accordingly. When pressure deviations are detected, the system automatically modifies the gas flow rate to restore the target pressure, creating a closed-loop control system that maintains stable inspection conditions
2Productivity
If pressure fluctuations occur during inspection, then fewer components are needed, but aberration variations increase reducing tool availability
Solution Approach 1:
The housing creates a stable pressure environment that isolates optical components from external pressure changes, maintaining consistent optical performance throughout the inspection process and preventing aberration-induced inspection failures
Solution Approach 2:
Real-time pressure monitoring and active compensation through gas flow adjustment ensure that internal pressure remains stable, thereby maintaining optical aberration stability and ensuring continuous tool availability for mask inspection
3Reliability
If no pressure control is implemented, then the system is simpler, but inspection failure rate increases
Solution Approach 1:
The enclosed housing with pressure control creates a stable environmental chamber that protects the inspection process from external pressure variations, significantly reducing inspection failures caused by pressure-induced optical aberrations
Solution Approach 2:
The feedback control system using pressure sensors and gas flow adjustment actively maintains target pressure conditions, preventing aberration variations that would otherwise cause inspection failures and thereby improving overall inspection success rate
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
Stabilizes the inspection process by minimizing aberration fluctuations, reducing failure rates, and enhancing tool availability, thus improving the efficiency and accuracy of EUV mask inspections.
Implementation Method 1
introducing a gas flow into the inspection tool
Implementation Method 2
pressure sensors to monitor and control the environmental pressure
Data Source
AI summary
A method for inspecting a mask is provided. The method includes placing the mask on a stage of an inspection tool; using a fan assembly, introducing a gas flow into the inspection tool; performing an environmental pressure control over the inspection tool; and capturing an image of the mask. The environmental pressure control includes monitoring an in-tool pressure inside the inspection tool and an out-tool pressure outside the inspection tool; determining whether the pressure difference between the in-tool pressure and the out-tool pressure is out of an acceptable range; and in response the determination determines that the pressure difference between the in-tool pressure and the out-tool pressure is out of the acceptable range, adjusting the power of the fan assembly.