EUV Collector Mirror Protection via Buffer Gas Ion Slowing
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Solution Overview
Problem
In EUV light sources for high-volume manufacturing, the collector mirror's lifetime is reduced due to debris such as high-energy ions, neutral atoms, and clusters from the plasma, which degrade the mirror's surface and reduce reflectivity, leading to efficiency and downtime issues.
Innovation Solution
A Gas Management System is implemented, using a flowing gas with a high pressure (above 100mTorr) and a composition like hydrogen to slow ions below 30eV before they reach the collector mirror, and a multi-channel structure to direct EUV radiation while minimizing ion energy and absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vacuum environment is used in the EUV light source chamber, then EUV light transmission is improved, but ion energy is reduced and debris damage to the collector mirror is minimized
Solution Approach 1:
A buffer gas (such as hydrogen, helium, or nitrogen) is introduced as an intermediary substance between the plasma source and the collector mirror. This buffer gas interacts with ions through elastic collisions, transferring kinetic energy and slowing ions down before they reach the collector mirror. The buffer gas acts as a mediator that protects the collector mirror from direct ion impact while allowing the vacuum environment to maintain EUV light transmission.
Solution Approach 2:
The patent changes the pressure parameter of the chamber by introducing buffer gas at controlled pressures (typically 10-100 mTorr). This pressure change modifies the ion energy and flux characteristics without fundamentally altering the vacuum state. The buffer gas density is adjusted to optimize ion slowing while minimizing EUV absorption, creating an optimal balance between protecting the collector mirror and maintaining light transmission.
2Reliability
If buffer gas is introduced to slow ions, then collector mirror protection is improved, but EUV light absorption increases
Solution Approach 1:
The patent optimizes the buffer gas pressure parameter to balance ion slowing and EUV absorption. By controlling the pressure to typical ranges of 10-100 mTorr, the system achieves sufficient ion energy reduction while keeping EUV absorption minimal. This parameter optimization is achieved through careful selection of buffer gas type and pressure level, allowing the system to operate at the optimal point where collector mirror protection is maximized and light transmission is maintained.
Solution Approach 2:
The patent uses inert or reactive buffer gases (such as hydrogen, helium, nitrogen, or their combinations) that create a controlled atmospheric environment in the chamber. These gases are selected specifically for their ability to slow ions effectively while having minimal impact on EUV light transmission. The buffer gas atmosphere serves as a protective medium that can be carefully controlled to achieve the desired balance.
3Object-affected harmful factors
If high pressure gas is used to slow ions, then ion energy reduction is improved, but gas flow resistance increases and EUV transmission is reduced
Solution Approach 1:
The patent introduces buffer gas at controlled pressures (typically 10-100 mTorr) rather than high pressures. This parameter selection allows sufficient ion slowing to occur while maintaining acceptable gas flow characteristics and minimal EUV absorption. The pressure level is optimized to achieve the desired ion energy reduction without creating excessive flow resistance or complicating the gas management 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 system significantly reduces ion flux and extends the collector mirror's lifetime by suppressing ion energy, maintaining reflectivity and improving operational efficiency in high-volume manufacturing environments.
Implementation Method 1
a flowing gas with a high pressure (above 100mTorr) and a composition like hydrogen to slow ions below 30eV before they reach the collector mirror
Implementation Method 2
a multi-channel structure to direct EUV radiation while minimizing ion energy and absorption
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Devices and corresponding methods of use are described herein which may comprise an enclosing structure defining a closed loop flow path and a system generating a plasma at a plasma site, e.g. laser produced plasma system, where the plasma site may be in fluid communication with the flow path. For the device, a gas may be disposed in the enclosing structure which may include an ion-stopping buffer gas and / or an etchant. A pump may be provided to force the gas through the closed loop flow path. One or more heat exchangers removing heat from gas flowing in the flow path may be provided. In some arrangements, a filter may be used to remove at least a portion of a target species from gas flowing in the flow path.