Variable Fluid Extraction Control for Lithography Immersion Gaps
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Solution Overview
Problem
Existing fluid extraction systems in lithographic apparatuses are unable to adapt to changes in substrate height, leading to inappropriate fluid flow rates and potential imaging errors due to gas bubbles in the immersion space.
Innovation Solution
A fluid extraction system with a variable valve and controller that adjusts the flow rate based on substrate properties, fluid handling system properties, and separation distances between the fluid handling and extraction systems, allowing for real-time control of fluid flow rates between maximum and zero flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed fluid extraction system is used, then the system structure is simple, but the fluid flow rate cannot be adapted to changes in substrate height, causing gas bubbles to accumulate in the immersion space
Solution Approach 1:
The fluid extraction system employs a variable flow rate mechanism that dynamically adjusts the fluid extraction rate based on substrate height changes. The controller receives substrate height information and modulates the extraction flow rate accordingly, transforming a static system into a dynamic one that adapts to varying conditions, thereby preventing gas bubble accumulation while maintaining system functionality.
Solution Approach 2:
The system implements a feedback control mechanism where the controller continuously monitors substrate height and adjusts the fluid extraction rate in response. This closed-loop control ensures that the extraction system responds to actual operating conditions, maintaining optimal fluid flow rates and preventing gas accumulation without requiring complete system redesign.
2Reliability
If the fluid extraction flow rate is increased, then gas bubbles are removed more effectively, but fluid may be excessively extracted from the immersion space, affecting image quality
Solution Approach 1:
The system changes the flow rate parameter dynamically based on substrate height and operational conditions. By adjusting this critical parameter rather than maintaining a fixed high extraction rate, the system effectively removes gas bubbles when needed while preventing excessive fluid extraction that would compromise image quality, thus resolving the contradiction between reliability and precision.
Solution Approach 2:
The controller uses feedback from substrate height measurements and operational status to modulate the extraction flow rate. This ensures that fluid is extracted at appropriate rates to remove gas bubbles without over-extraction, maintaining the delicate balance between preventing gas accumulation and preserving image quality through controlled fluid management.
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
Ensures appropriate fluid flow rates for varying substrate heights, preventing gas accumulation and maintaining image quality by dynamically adjusting fluid extraction in response to changing conditions.
Implementation Method 1
The effect of the immersion fluid is to enable imaging of smaller features since the exposure radiation will have a shorter wavelength in the fluid than in gas. The effect of the immersion fluid may also be regarded as increasing the effective numerical aperture (NA) of the system
Data Source
AI summary
A fluid extraction system for a lithographic apparatus, the fluid extraction system configured to extract fluid that a fluid handling system, including a fluid handling structure, is arranged to supply along a flow path that includes a gap between an edge of a substrate and an edge of a surrounding structure of the substrate; and a controller arranged to control the flow rate of the fluid in the flow path in dependence on one or more selected from: a property of the substrate, a property of the fluid handling system, a property of the fluid handling structure, a property of the fluid extraction system, and/or the separation between the fluid handling structure and the fluid extraction system.