Liquid Immersion Exposure Apparatus Charging Suppression
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Solution Overview
Problem
Liquid immersion exposure apparatuses in photolithography processes face issues with charging, leading to exposure defects and defective devices due to charge accumulation in the liquid and contacting members, which can result in foreign material adsorption and defects during the exposure process.
Innovation Solution
The exposure apparatus employs a liquid supply system that fills the optical path with a liquid and includes a fluid supply to adjust the specific resistance of the liquid in the immersion space, using materials like carbon dioxide to decrease the specific resistance and suppress charging, along with a recovery system to manage the fluid and gas within the immersion space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid is used to fill the optical path in exposure apparatus, then exposure quality is improved, but charging occurs leading to foreign material adsorption and exposure defects
Solution Approach 1:
The patent changes the electrical parameter (specific resistance) of the liquid by adding ions through fluid supply. This transforms the liquid from a high-specific-resistance state (prone to charging) to a low-specific-resistance state (conductive, dissipates charge), thereby eliminating the harmful charging effect while preserving the exposure quality improvement benefits of liquid immersion
Solution Approach 2:
The patent introduces fluid (containing ionizable materials) as an intermediary substance that modifies the electrical properties of the immersion liquid. This intermediary enables charge dissipation without directly interfering with the optical path or exposure process, resolving the contradiction between maintaining liquid immersion benefits and preventing charging-related defects
2Object-affected harmful factors
If fluid supply is added to control specific resistance, then charging is suppressed, but device complexity increases
Solution Approach 1:
The fluid supply system serves multiple functions: it controls specific resistance to prevent charging, maintains liquid properties in the optical path, and can be integrated with existing liquid supply infrastructure. This multi-functionality justifies the added complexity by addressing several requirements simultaneously
Solution Approach 2:
The system uses naturally occurring ionizable materials in the fluid that automatically dissociate into ions upon contact with the immersion liquid, providing self-regulating charge control without requiring complex external control mechanisms. The fluid itself performs the function of charge management through its chemical properties
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 effectively reduces charging in the liquid and contacting members, minimizing exposure defects and the production of defective devices by preventing foreign material adsorption and maintaining the properties of the liquid in the optical path.
Implementation Method 1
a fluid supply port that supplies a fluid including a material capable of changing the specific resistance of the liquid to at least a part of a space around a liquid immersion space that is formed by the liquid
Implementation Method 2
a liquid supply port that supplies the liquid in order to fill an optical path of the exposure light emitted from the emission surface with the liquid
Data Source
AI summary
An exposure apparatus exposes a substrate with exposure light via a liquid. The exposure apparatus includes an optical system including an emission surface from which the exposure light is emitted; a liquid supply port that supplies the liquid in order to fill an optical path of the exposure light emitted from the emission surface with the liquid; and a fluid supply port that supplies a fluid including a material capable of changing the specific resistance of the liquid to at least a part of a space around a liquid immersion space that is formed by the liquid.