Membrane Humidification for Lithography Temperature Stability
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Solution Overview
Problem
High evaporation rates of immersion liquids in lithographic apparatuses lead to cooling effects and temperature variations, necessitating high humidity gas purging to maintain stability, especially in 'all wet' systems and liquid confinement systems with increasing gas flow rates.
Innovation Solution
A humidifying apparatus utilizing a hydrophilic membrane to efficiently humidify gas by controlling the temperature of a liquid on one side of the membrane, allowing vapor to pass through and humidify the gas on the other side, with a system that includes conduits for guiding gas and liquid, and optional temperature conditioning for precise humidity control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high flow rates of gas are used to maintain immersion liquid, then evaporation is prevented and temperature stability is improved, but the complexity of the liquid supply system increases
Solution Approach 1:
A gas-permeable, liquid-impermeable membrane is introduced as an intermediary component between the gas supply system and the immersion liquid. The membrane allows controlled gas flow through its structure to reach the immersion liquid while preventing direct liquid flow, thereby stabilizing temperature and preventing evaporation without requiring complex liquid supply infrastructure.
Solution Approach 2:
The invention utilizes pneumatic principles by employing a gas-permeable membrane that allows gas molecules to pass through while blocking liquid. Gas is supplied at controlled pressure and flow rates through the membrane to the immersion liquid, enabling temperature stabilization and evaporation prevention through pneumatic control rather than complex hydraulic liquid supply systems.
2Reliability
If gas flow rate is increased to prevent evaporation, then temperature stability improves, but energy consumption increases
Solution Approach 1:
The invention changes the physical parameters of gas delivery by using a gas-permeable membrane with specific pore sizes and surface properties. This allows the gas flow rate to be optimized at the molecular level through membrane selection rather than high-volume bulk flow, reducing energy consumption while maintaining sufficient gas delivery to prevent evaporation and stabilize temperature.
3Reliability
If a gas-permeable liquid-impermeable membrane is used to deliver gas to immersion liquid, then evaporation is prevented and temperature stability is improved, but the device complexity increases
Solution Approach 1:
The invention employs porous membrane materials with carefully selected pore sizes and surface characteristics that are gas-permeable but liquid-impermeable. These commercially available porous membranes provide the required selective permeability through their inherent material structure, avoiding the need for complex mechanical or chemical systems while effectively delivering gas to the immersion liquid for evaporation prevention and temperature stabilization.
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 solution effectively minimizes temperature variations by maintaining high humidity levels, reducing the need for large amounts of immersion liquid and minimizing disturbances to optical sensors, while allowing for flexible adjustment of moisture levels in the purge gas.
Implementation Method 1
a membrane; a first conduit for guiding gas to one side of said membrane; a second conduit for guiding liquid to the other side of said membrane
Implementation Method 2
wherein said membrane has a surface which is liquidphilic to said liquid
Implementation Method 3
a liquid temperature conditioner for conditioning the temperature of a liquid; wherein the temperature of said gas on the other side of said membrane is influenced by the temperature of liquid on the one side of said membrane
Data Source
AI summary
A humidifying apparatus is disclosed in which gas is provided to a first side of a membrane and liquid to a second side of the same membrane. The membrane is non-porous to the liquid but porous to vapour of the liquid and is liquidphilic to said liquid.