Flowing Gas Ion Shield for EUV Collector Mirror
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing EUV light sources face significant challenges due to ion debris, which degrades the collector mirror's reflectivity, leading to a short lifetime and increased downtime in high-volume manufacturing environments, as the ions with high energies cause erosion of the multi-layer coating, reducing the mirror's effectiveness.
Innovation Solution
The introduction of a flowing gas, such as hydrogen or halogen, between the plasma and the optic to reduce ion energy below 100eV, effectively mitigating ion debris and extending the collector mirror's lifetime by using a gas pressure sufficient to scatter and stop ions before they reach the optic, thereby reducing ion flux and maintaining EUV reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a collector mirror is used to collect and direct EUV light, then EUV light can be effectively collected and directed to an intermediate location, but the high-energy ions from the plasma will erode the multi-layer coating, reducing reflectivity and mirror lifetime
Solution Approach 1:
A gas flow (hydrogen, deuterium, or halogen) is introduced as an intermediary medium between the plasma and the collector mirror. This gas flow serves as a mediator that interacts with the high-energy ions through scattering and charge exchange processes, reducing ion energy to below 100 eV before ions reach the mirror surface, thereby protecting the multi-layer coating from erosion while maintaining EUV light collection efficiency
Solution Approach 2:
The patent changes the energy parameter of ions by introducing a gas flow that reduces ion energy from keV range to below 100 eV through scattering and charge exchange. This parameter change transforms the harmful high-energy ions into low-energy ions that do not erode the mirror coating, extending mirror lifetime to over 10^12 pulses
2Reliability
If gas pressure is increased to reduce ion energy, then ion flux to the mirror is reduced, but EUV light absorption by the gas increases
Solution Approach 1:
The patent optimizes the gas pressure parameter to a specific range (10-100 mTorr) where the gas density is sufficient to reduce ion energy through scattering and charge exchange, but not so high as to cause significant EUV light absorption. This parameter optimization balances ion mitigation with EUV transmission, achieving both reduced ion flux and acceptable light transmission
Solution Approach 2:
The gas flow is introduced locally in the region between the plasma and the collector mirror, creating a localized zone of reduced ion energy. The gas pressure and flow rate are controlled to provide ion protection only in the critical path where ions would otherwise reach the mirror, while minimizing gas presence in the EUV light path to reduce absorption
3Reliability
If the distance between plasma and optic is increased, then ion energy is reduced through longer travel path, but the system size and complexity increase
Solution Approach 1:
Instead of increasing the distance between plasma and optic, the patent introduces a gas flow as an intermediary that actively reduces ion energy over a shorter distance. The gas molecules provide scattering centers and charge exchange partners that rapidly decelerate ions, achieving the same ion energy reduction effect that would otherwise require a much longer vacuum path, thereby compacting the system
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 ion energy and flux, extending the collector mirror's lifetime to over 10^12 pulses, equivalent to about 1 year of operation in a high-volume manufacturing environment, while maintaining high EUV transmission and reflectivity.
Implementation Method 1
using a gas pressure sufficient to scatter and stop ions before they reach the optic
Implementation Method 2
reduce ion energy below 100eV, effectively mitigating ion debris
Implementation Method 3
gas pressure sufficient to operate over the distance, d, to reduce ion energy below 100eV
Implementation Method 4
scatter and stop ions before they reach the optic
Implementation Method 5
The energetic radiation generated during de-excitation and recombination of these ions is emitted from the plasma
Implementation Method 6
LPP light sources generate EUV radiation by depositing laser energy into a source element
Implementation Method 7
converting a material into a plasma state that has at least one element with one or more emission lines in the EUV range
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A device is disclosed which may comprise a system generating a plasma at a plasma site, the plasma producing EUV radiation and ions exiting the plasma. The device may also include an optic, e.g., a multi-layer mirror, distanced from the site by a distance, d, and a flowing gas disposed between the plasma and optic, the gas establishing a gas pressure sufficient to operate over the distance, d, to reduce ion energy below a pre-selected value before the ions reach the optic, hi one embodiment, the gas may comprise hydrogen and in a particular embodiment, the gas may comprise greater than 50 percent hydrogen by volume.