Lithographic Gas Barrier System for Measurement Stability
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Solution Overview
Problem
Lithographic apparatuses face challenges in maintaining measurement accuracy and pattern transfer precision due to local fluctuations in ambient gas characteristics, which affect measurement and projection radiation beams, leading to positioning inaccuracies and imaging errors.
Innovation Solution
A lithographic apparatus with a barrier system that reduces ambient gas inflow into a protected volume by establishing a gas curtain with a turbulent flow from curtain openings and a less turbulent inner entrainment gas flow from inner openings, radially inward of the curtain openings, to stabilize the gas environment and minimize refractive index variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the lithographic apparatus operates at high scanning speeds to improve throughput, then productivity increases, but measurement accuracy and pattern transfer precision deteriorate due to gas fluctuations affecting radiation beams
Solution Approach 1:
The gas barrier system is segmented into multiple functional components: a gas curtain generated by curtain openings and an inner gas flow from inner openings. This segmentation allows independent optimization of each component's function, with the outer curtain providing bulk protection and the inner flow providing stable measurement conditions
Solution Approach 2:
A gas curtain is introduced as an intermediary substance between the ambient environment and the measurement radiation beam path. This gas barrier mediates the interaction between high-speed operation and measurement accuracy by reducing gas fluctuations that would otherwise directly affect the radiation beams
2Measurement precision
If a gas barrier is introduced to protect the measurement volume from ambient gas fluctuations, then measurement precision improves, but device complexity increases due to additional barrier components
Solution Approach 1:
The gas barrier system serves multiple functions simultaneously: it protects the measurement volume from ambient gas fluctuations, provides a stable refractive index environment for radiation beams, and maintains protection during high-speed scanning operations. This multi-functionality reduces the need for separate systems for each protective function
Solution Approach 2:
The system utilizes changes in gas flow parameters (velocity, turbulence level, pressure) to achieve different protective functions. The curtain gas provides high-velocity bulk protection while the inner entrainment gas provides low-velocity stable conditions, with each parameter optimized for its specific function
3Reliability
If high velocities are used for the gas curtain to effectively block ambient gas, then the barrier effectiveness improves, but turbulence increases causing gas fluctuations that affect measurement accuracy
Solution Approach 1:
The gas barrier is segmented into two distinct flow regions: an outer high-velocity turbulent curtain for effective blocking, and an inner low-velocity laminar flow for stability. This segmentation allows each region to be optimized for its specific function without compromise
Solution Approach 2:
The inner low-velocity gas flow acts as an intermediary between the outer turbulent curtain and the measurement volume. It buffers the turbulence from the curtain while maintaining the protective barrier's effectiveness, providing a stable gas environment for accurate measurements
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 configuration enhances the stability of the gas environment within the protected volume, reducing noise and velocity variations, thereby improving measurement accuracy and reducing recovery time after fast movements, allowing for higher scanning speeds while maintaining precision.
Implementation Method 1
a flow of curtain gas from at least one curtain opening so as to establish a gas curtain enclosing part of the protected volume
Implementation Method 2
a flow of inner entrainment gas from at least one inner entrainment opening for being entrained into the flow of curtain gas
Data Source
AI summary
An apparatus has a first component with a first surface and a second component with a second surface, wherein the first and second components can undergo relative movement. The first surface and the second surface face each other. The first surface accommodates a barrier system to provide a barrier to reduce or prevent an inflow of ambient gas into a protected volume of gas between the first and second surfaces. The barrier system includes a curtain opening adapted for a flow of curtain gas therefrom for establishing a gas curtain enclosing part of the protected volume, and an inner entrainment opening, located inward of the curtain opening with respect to the protected volume, adapted for a flow of inner entrainment gas therefrom for being entrained into the flow of curtain gas. The apparatus is configured such that the inner entrainment gas flow is less turbulent than the curtain gas flow.