Lithographic Sensor Beam Stabilization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithographic apparatuses face errors in sensor readings due to interference from non-uniform fluid flow and temperature variations in the sensor beam path, leading to inaccuracies in measuring properties like position.
Innovation Solution
A lithographic apparatus is designed with a sensor that employs a combination of turbulent and laminar fluid flows to maintain uniform refractive index conditions, using a first outlet for turbulent flow and a second outlet for laminar flow to enclose and stabilize the fluid path, preventing unconditioned gas from entering the sensor beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large body of liquid is used to fill the space between the projection system and substrate, then the refractive index is improved for smaller feature imaging, but turbulence and unpredictable effects occur during scanning exposure
Solution Approach 1:
The patent divides the fluid management into separate functional zones: a liquid supply system provides immersion liquid locally at the imaging field, while a gas flow system separately manages turbulence control and droplet removal. This segmentation allows independent optimization of refractive index requirements and fluid stability without the harmful interactions of a single large liquid body.
Solution Approach 2:
The patent extracts the harmful turbulent effects by introducing a controlled gas flow that removes unwanted liquid droplets and stabilizes the fluid environment in the sensor beam path. The gas flow system takes out the instability caused by liquid turbulence while preserving the beneficial refractive index properties of the immersion liquid at the imaging field.
2Measurement precision
If immersion liquid is supplied to improve refractive index, then imaging of smaller features is enabled, but droplets may interfere with sensor beam path and cause measurement errors
Solution Approach 1:
The patent introduces a gas flow as an intermediary substance between the immersion liquid and the sensor beam path. This gas flow serves multiple functions: it prevents liquid droplets from reaching the sensor, it removes any droplets that do form, and it stabilizes the refractive index environment. The intermediary gas layer protects the sensor while allowing the immersion liquid to remain at the imaging field for high-resolution imaging.
3Productivity
If substrate table is accelerated during scanning exposure, then productivity is improved, but turbulence in the liquid increases causing unpredictable effects
Solution Approach 1:
The patent implements dynamic fluid management where gas flow parameters are adjusted in response to substrate table motion. The gas flow system adaptively controls turbulence and droplet removal based on the acceleration and velocity of the substrate table, maintaining fluid stability even during high-speed scanning operations that improve productivity.
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 approach significantly reduces systematic measurement errors and noise, achieving high refractive index stability and accuracy in position measurements, even during substrate table movement.
Implementation Method 1
a first outlet to provide a turbulent fluid flow along the sensor beam path
Implementation Method 2
a second outlet to provide a laminar fluid flow substantially enclosing the turbulent fluid flow
Implementation Method 3
a first outlet to provide a thermally conditioned fluid with a first flow characteristic to at least part of the sensor beam path
Implementation Method 4
a second outlet to provide a laminar fluid flow substantially enclosing the turbulent fluid flow
Data Source
AI summary
A lithographic apparatus having a first outlet to provide a thermally conditioned fluid with a first flow characteristic to at least part of a sensor beam path, and a second outlet associated with the first outlet and to provide a thermally conditioned fluid with a second flow characteristic, different to the first flow characteristic, adjacent the thermally conditioned fluid from the first outlet.