Immersion Lithography Fluid Supply System with Drain Path Control
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Solution Overview
Problem
Temperature variations in the immersion liquid of lithographic apparatuses cause imaging defects due to the high sensitivity of the refractive index to temperature changes, and existing fluid flow control methods are inefficient and prone to contamination.
Innovation Solution
A fluid supply system with a first fluid flow path and a drain fluid flow path, regulated by a controller to vary the fluid flow rate, using passive components and a mass flow controller to achieve precise and flexible flow control, minimizing contamination and thermal disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large body of liquid is used to fill the space between the projection system and substrate, then the liquid provides adequate coverage and cooling, but the liquid must be accelerated during scanning exposure requiring additional or more powerful motors and causing turbulence
Solution Approach 1:
The patent divides the immersion liquid into two separate regions: a stationary bulk liquid region that provides cooling and refractive index stability, and a thin film liquid layer that moves with the substrate during scanning. This segmentation allows the bulk liquid to remain mostly stationary (reducing motor power requirements) while still providing adequate coverage through the thin film that is accelerated with the substrate.
2Quantity of substance
If a large body of liquid is used for immersion, then adequate coverage is provided, but turbulence in the liquid leads to undesirable and unpredictable effects
Solution Approach 1:
By segmenting the liquid into a stationary bulk region and a moving thin film region, the patent eliminates turbulence in the bulk liquid while maintaining adequate coverage through the thin film. The thin film moves synchronously with the substrate without causing turbulence in the larger liquid volume.
3Ease of operation
If existing fluid flow control methods are used to control immersion liquid flow, then flow control is achieved, but the methods are inefficient and prone to contamination
Solution Approach 1:
The patent replaces traditional mechanical flow control devices (valves, pumps) with a passive flow control mechanism based on pressure differential and capillary forces. The flow rate is controlled by adjusting the pressure in the gas seal region, which naturally regulates liquid flow without mechanical components that could cause contamination or inefficiency.
4Device complexity
If temperature control of immersion liquid is not precisely maintained, then system complexity is reduced, but imaging defects occur due to high sensitivity of refractive index to temperature changes
Solution Approach 1:
The patent extracts the temperature control function from the main immersion liquid system by introducing a separate temperature control unit that independently regulates the immersion liquid temperature. This allows precise temperature control without adding complexity to the overall imaging system, as the temperature control operates as a separate, dedicated subsystem.
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 system effectively stabilizes the fluid flow rate, reducing the risk of contamination and thermal fluctuations, enabling precise temperature control and improved imaging quality by minimizing the impact of temperature variations on the refractive index.
Implementation Method 1
The flow rate of liquid through the liquid supply system can be controlled by controlling the pressure differential across the liquid supply system
Implementation Method 2
A porous material can be used to provide a capillary force to the liquid, which can help to control the flow rate of liquid through the liquid supply system
Data Source
AI summary
A fluid supply system for a lithographic apparatus includes a first fluid flow path for fluid between a fluid source and a first component and a drain fluid flow path for fluid flow from a junction in the first fluid flow path to a drain component. A controller is provided to vary a fluid flow rate to the first component from the fluid source by regulating flow of fluid through the drain fluid flow path.