EUV Source Module Buffer Gas Spectral Purity
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Solution Overview
Problem
Existing EUV lithographic apparatuses face challenges in effectively mitigating particulate debris and suppressing wavelengths outside the EUV range, such as ultra-violet and infra-red radiation, using gaseous spectral purity filters.
Innovation Solution
A source module is introduced that utilizes a buffer gas with at least 50% transmission for EUV radiation and at least 70% absorption for secondary radiation, which can be cooled using passive or circulation-based cooling methods, to enhance EUV enrichment and debris mitigation, employing light atomic weight elements like C2H4, NH3, or SiH3Cl to improve spectral purity and suppress unwanted radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a gaseous spectral purity filter comprising ZrCl4 is used to enrich the EUV beam, then the EUV wavelength enrichment is improved, but the filter cannot effectively mitigate particulate debris and suppress wavelengths outside the EUV range
Solution Approach 1:
The patent changes the chemical composition parameter of the gaseous filter from ZrCl4 to a mixture containing H2, He, Ne, Ar, or Kr. This parameter change enables the filter to simultaneously achieve EUV transmission, debris mitigation, and suppression of unwanted wavelengths, resolving the technical contradiction by finding a gas composition that satisfies multiple requirements at once.
2Manufacturing precision
If a spectral purity filter is introduced to improve beam quality, then the spectral purity is improved, but the device complexity increases
Solution Approach 1:
The gaseous filter system is designed to perform multiple functions simultaneously: it acts as a spectral purity filter for EUV enrichment, a debris mitigation barrier, and a suppressor of unwanted wavelengths. By combining these functions into a single gaseous medium rather than requiring separate filters for each function, the patent reduces overall system complexity while maintaining high spectral purity.
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 buffer gas effectively transmits EUV radiation while absorbing secondary radiation, improving the spectral purity and enrichment of the EUV beam, thereby enhancing the performance of the EUV lithographic apparatus by mitigating particulate debris and unwanted wavelengths.
Implementation Method 1
The buffer gas has at least 50% transmission for the EUV radiation and at least 70% absorption for the secondary radiation
Implementation Method 2
The buffer gas may be cooled. In order to cool the buffer gas, the source may comprise a passive element constructed and arranged to cool the buffer gas. Also, the source may comprise a circulation unit constructed and arranged to cool the buffer gas
Data Source
AI summary
A source module for use in a lithographic apparatus is constructed to generate extreme ultra violet (EUV) and secondary radiation, and includes a buffer gas configured to cooperate with a source of the EUV radiation. The buffer gas has at least 50% transmission for the EUV radiation and at least 70% absorption for the secondary radiation.