Immersion Lithography Liquid Diverter for Refractive Index Stability
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Solution Overview
Problem
Temperature gradients in immersion liquids during lithographic processes can cause imaging defects due to the temperature dependency of the refractive index, and leaching of resist into the liquid can lead to transport issues and aberrations.
Innovation Solution
A lithographic projection apparatus with a liquid diverter to promote liquid flow across the space between the substrate and the projection system, reducing recirculation and temperature gradients by ensuring laminar flow and minimizing contact between the resist and the immersion liquid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is immersed in a liquid with high refractive index to enable imaging of smaller features, then the resolution and depth of focus are improved, but temperature gradients arise causing imaging defects and resist leaching problems
Solution Approach 1:
The patent extracts and removes the harmful heated liquid from the optical path using a wiper blade. The wiper blade physically removes the liquid that has been heated by the projection beam, preventing it from causing temperature gradients and imaging defects while allowing fresh, cool liquid to replace it.
Solution Approach 2:
The patent converts the harmful effect of heated liquid into a beneficial circulation pattern. By using the wiper blade to remove heated liquid and allowing fresh liquid to flow in, the system creates a controlled liquid circulation that prevents temperature gradients while maintaining the immersion benefit for resolution.
2Quantity of substance
If a liquid confinement system is used to supply liquid locally, then the liquid volume is reduced, but recirculation zones form causing temperature gradients
Solution Approach 1:
The patent introduces dynamic liquid flow management by using a wiper blade that actively moves across the liquid surface during substrate scanning. This dynamic action prevents static recirculation zones and maintains uniform liquid composition by continuously replacing heated liquid with fresh liquid.
Solution Approach 2:
The wiper blade operates continuously during the scanning process, ensuring continuous removal of heated liquid and continuous supply of fresh liquid. This continuous action prevents the formation of recirculation zones and maintains uniform liquid composition throughout the exposure process.
3Manufacturing precision
If the projection beam is absorbed by the immersion liquid to enable imaging, then the imaging function is achieved, but heat is generated causing temperature gradients
Solution Approach 1:
The wiper blade extracts and removes the heated liquid from the optical path, preventing the accumulated heat from causing temperature gradients. The removed liquid is replaced by fresh, cool liquid, maintaining thermal stability.
Solution Approach 2:
The wiper blade acts as an intermediary between the heated liquid and the optical path. It removes the harmful heated liquid and replaces it with cool liquid, mediating the thermal interaction and preventing temperature gradients from forming.
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 solution reduces imaging defects by maintaining a stable refractive index and preventing resist leaching, thereby enhancing the precision and consistency of the lithographic process.
Implementation Method 1
reducing recirculation and temperature gradients by ensuring laminar flow
Implementation Method 2
immerse the substrate in the lithographic projection apparatus in a liquid having a relatively high refractive index... The effect of the liquid may also be regarded as increasing the effective NA of the system and also increasing the depth of focus
Data Source
AI summary
A immersion lithographic apparatus is disclosed in which one or more liquid diverters are positioned in a space surrounded by a liquid confinement structure. A function of the liquid diverter(s) is to hinder the formation of one or more recirculation zones of immersion liquid which may lead to variations in refractive index of the immersion liquid in the space and thereby imaging errors.