Plasma Light Source Debris Protection via Buffer Gas Flow
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Solution Overview
Problem
Plasma-based light sources for generating extreme ultraviolet (EUV), vacuum ultraviolet (VUV), and soft X-ray radiation face issues with debris such as target material gas, atomic vapor, high energy ions, and neutrals that degrade component performance and attenuate light, with existing magnetic field solutions being ineffective in stopping neutrals and costly to implement.
Innovation Solution
A system that generates plasma and introduces a flowing buffer gas between the plasma site and components to reduce ion energy below 100 eV, using outlets and pumps to control gas pressure and flow direction, thereby protecting components and increasing light transmission by reducing target material gas concentration along the optical pathway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If magnetic fields are used to deflect charged particles, then ion deflection is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces the magnetic field deflection system with a gas flow-based ion stopping mechanism. By introducing a buffer gas flow between the plasma source and reflective optics, ions are stopped through collisions with gas molecules rather than magnetic deflection, eliminating the need for complex coils while achieving ion protection.
Solution Approach 2:
The buffer gas acts as an intermediary substance between the plasma source and the reflective optics. This gas flow mediates the interaction by absorbing ion energy through collisions, preventing ions from reaching and damaging the optics, while also reducing the concentration of target material gas along the optical pathway.
2Object-affected harmful factors
If buffer gas is introduced for ion stopping, then ion energy reduction is improved, but light transmission is degraded due to gas absorption
Solution Approach 1:
The patent optimizes the buffer gas parameters (type, pressure, flow rate) to achieve the desired balance. By selecting gases with appropriate ion stopping power and minimal EUV absorption, and by controlling the gas pressure and flow rate, the system maximizes ion energy reduction while minimizing light transmission degradation.
Solution Approach 2:
The buffer gas flow is strategically positioned and directed to provide localized protection. The gas flow concentration is higher near the plasma source where ion stopping is most needed, while the optical pathway remains relatively clear. This spatial differentiation of gas density achieves both ion protection and light transmission preservation.
3Illumination intensity
If target material gas concentration is reduced along the optical pathway, then light transmission is improved, but gas flow control complexity increases
Solution Approach 1:
The patent uses pneumatic principles to control gas flow through the chamber. By utilizing pressure differentials, flow guides, and strategic gas injection points, the system creates controlled gas flow patterns that reduce target material gas concentration along the optical pathway while maintaining manageable system complexity through fluid dynamics rather than complex mechanical control.
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
The system effectively reduces ion energy and target material gas concentration, enhancing the operational efficiency and light transmission of plasma-based light sources by using a buffer gas with higher EUV transmission than Xenon, such as Hydrogen, Helium, or Argon, to minimize debris impact on reflective optics and other components.
Implementation Method 1
a flowing gas disposed between the plasma and the component, the gas establishing an average gas pressure, P, over the distance, d, sufficient to reduce ion energy below 100 eV before the ions reach the component
Implementation Method 2
at least one pump removing gas from the chamber, the pump and outlet cooperating to reduce target material gas concentration along the pathway from the plasma to the intermediate location
Implementation Method 3
Plasma-based light sources, such as laser-produced plasma (LPP) sources and discharge-produced plasma (DPP) sources, are often used to generate soft X-ray, extreme ultraviolet (EUV), and/or vacuum ultraviolet (VUV) light
Implementation Method 4
the light emanating from the plasma is often collected via a reflective optic, such as a collector optic (e.g. a near-normal incidence or grazing incidence mirror)
Data Source
AI summary
The present disclosure is directed to plasma-based light sources. Systems and methods are described for protecting components of the light source from plasma generated debris which can include target material gas, atomic vapor, high energy ions, neutrals, micro-particles, and contaminants. Particular embodiments include arrangements for reducing the adverse effects of plasma generated ions and neutrals on light source components while simultaneously reducing in-band light attenuation due to target material gas and vapor.