EUV Lithography Cavity Drying via Gas Flow Reversal
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Solution Overview
Problem
In EUV lithography apparatuses, the drying of cooling channels is crucial for accurate leak testing, as helium diffusion through frozen cooling liquid drops can hinder leak detection, necessitating effective drying methods to prevent cooling liquid escape and ensure test reliability.
Innovation Solution
A method involving charging the cavity with a dry gas, reversing gas flow direction, and applying pressure surges based on relative humidity to evaporate and freeze remaining liquid, ensuring complete drying by maintaining negative pressure below the vapor pressure limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cavity is dried by conventional methods (without gas flow reversal or pressure surges), then the drying process is simpler, but the drying time is significantly longer and the drying completeness is insufficient
Solution Approach 1:
The gas flow direction is periodically reversed during the drying process, alternating between forward flow and reverse flow to continuously refresh the gas contact with liquid surfaces and enhance evaporation efficiency throughout the cavity
Solution Approach 2:
Pressure surges are applied periodically to change the pressure parameter within the cavity, creating temporary pressure differentials that accelerate liquid evaporation and improve gas-liquid mixing, thereby enhancing the drying rate
2Measurement precision
If the cavity is not thoroughly dried, then the leak test can be performed faster, but helium diffusion through frozen cooling liquid drops hinders leak detection accuracy
Solution Approach 1:
Periodic reversal of gas flow direction ensures continuous contact between dry gas and all liquid surfaces in the cavity, preventing stagnant zones where liquid could remain and later interfere with helium leak detection
Solution Approach 2:
Pressure surges create transient high-pressure conditions that force gas into tight spaces and enhance liquid evaporation, ensuring complete drying and eliminating potential helium diffusion pathways
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 significantly reduces drying time and ensures thorough evaporation of cooling liquid, preventing helium diffusion and enhancing leak test accuracy by ensuring the cavity reaches a dry state.
Implementation Method 1
charging the cavity with a gas, wherein a liquid taken up in the cavity at least partially evaporates
Implementation Method 2
applying a negative pressure to the cavity as soon as the relative humidity of the process exhaust air falls below a specified humidity value during step b), wherein the liquid remaining in the cavity freezes
Implementation Method 3
wherein the liquid remaining in the cavity freezes and sublimates
Data Source
AI summary
A method for drying a cavity provided in a component of a projection exposure apparatus comprises: a) charging the cavity with a gas, wherein a liquid taken up in the cavity at least partially evaporates, and the gas together with the evaporated liquid is transported away out of the cavity as process exhaust air; b) detecting the relative humidity of the process exhaust air, wherein in step a) at least one change of direction of the gas, in which a direction of flow of the gas through the cavity is reversed, and/or at least one pressure surge is performed in dependence on the relative humidity of the process exhaust air; and c) applying a negative pressure to the cavity as soon as the relative humidity of the process exhaust air falls below a specified humidity value during step b).