EUV Contamination Protection Duct with Gas Flow and Electrostatic Deflection
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Solution Overview
Problem
Conventional contamination control systems for extreme ultraviolet (EUV) systems, such as actinic mask inspection and lithographic systems, are inadequate in protecting optical components from contaminants due to the limitations of air-based ventilation at atmospheric pressures and existing vacuum pumping or crossflow gas jet methods, which can degrade imaging performance.
Innovation Solution
The apparatus employs a duct system that uses a low-pressure gas flow to sweep contaminants away from optical surfaces, combined with thermophoretic and electrostatic protection methods to effectively reduce contamination in EUV systems. The duct system includes a source of low-pressure gas with high transmission rates for EUV light, and intermediate openings that facilitate contaminant removal, while thermophoretic protection utilizes temperature gradients and electrostatic protection generates charges to direct contaminants away from sensitive components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If vacuum pumping is used for contamination protection, then contaminants are removed from the vacuum chamber, but contaminants cannot be effectively protected in areas close to optical components such as near surfaces of optics, masks or detectors
Solution Approach 1:
The vacuum chamber is divided into multiple sealed zones (first zone, second zone, third zone) with different pressure levels. The first zone contains the optical components and is maintained at a higher pressure than the second zone, which is in turn at a higher pressure than the third zone. This segmentation allows localized contamination control near optical components without compromising the overall vacuum environment.
Solution Approach 2:
A barrier layer (such as a membrane or wall) is introduced between zones of different pressures. This intermediary structure allows pressure differentiation while maintaining system integrity, enabling the first zone to be protected from contaminants in the second and third zones through the barrier while still allowing vacuum pumping to operate in the lower pressure zones.
2Object-affected harmful factors
If crossflow gas jets are used to blow away contaminants, then contamination protection is provided, but density gradients are produced that degrade imaging performance
Solution Approach 1:
Different pressure conditions are applied to different zones of the system. The first zone containing optical components is maintained at a higher pressure than subsequent zones, creating a pressure gradient that naturally directs contaminants away from sensitive areas without requiring high-speed gas jets that would create density gradients and degrade imaging.
Solution Approach 2:
The mechanical action of high-speed gas jets is replaced with a pressure differential system. Instead of using kinetic energy from fast-moving gas to deflect contaminants, the system uses static pressure differences to create a controlled environment where contaminants are prevented from reaching optical components, thereby avoiding density gradient formation.
3Object-affected harmful factors
If air-based ventilation is used at atmospheric pressure, then contamination control is achieved, but EUV light is not sufficiently transmitted by air at atmospheric pressure
Solution Approach 1:
The pressure parameter is changed across different zones of the system. The first zone containing optical components is maintained at a higher pressure (closer to atmospheric) to provide contamination control through ventilation, while subsequent zones are maintained at progressively lower pressures to allow EUV light transmission. This parameter change resolves the contradiction by applying different pressure conditions in different spatial locations.
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 significantly reduces contaminants on optical surfaces, maintaining high imaging performance by effectively removing water vapor, hydrocarbons, and particulate matter, and providing enhanced protection through controlled gas flow, temperature gradients, and electrostatic charges, ensuring reliable operation of EUV systems.
Implementation Method 1
The apparatus employs a duct system that uses a low-pressure gas flow to sweep contaminants away from optical surfaces
Implementation Method 2
thermophoretic protection utilizes temperature gradients to direct contaminants away from sensitive components
Implementation Method 3
electrostatic protection generates charges to direct contaminants away from sensitive components
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
An apparatus for use with extreme ultraviolet (EUV) light comprising A) a duct having a first end opening, a second end opening and an intermediate opening intermediate the first end opening the second end opening, B) an optical component disposed to receive EUV light from the second end opening or to send light through the second end opening, and C) a source of low pressure gas at a first pressure to flow through the duct, the gas having a high transmission of EUV light, fluidly coupled to the intermediate opening. In addition to or rather than gas flow the apparatus may have A) a low pressure gas with a heat control unit thermally coupled to at least one of the duct and the optical component and/or B) a voltage device to generate voltage between a first portion and a second portion of the duct with a grounded insulative portion therebetween.