Molybdenum Sputtering Target Purification for EUV Particle Reduction
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Solution Overview
Problem
Existing molybdenum sputtering targets used in EUV lithography for semiconductor manufacturing suffer from insufficient reduction of metal impurities, particularly tungsten, leading to increased particle generation during sputtering, which affects the yield of EUV mask blanks.
Innovation Solution
A molybdenum sputtering target with reduced metal impurities, specifically tungsten, is produced through a multi-step process involving ion-exchange steps with cation and anion-exchange resins, oxidation, reduction, and pressure firing to achieve a content of 100 ppm or less metal impurities and 50 ppm or less tungsten, with an optimized ratio of tungsten to total metal impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the purity of molybdenum sputtering target is increased to suppress particle generation, then the particle generation during sputtering is reduced, but the manufacturing complexity and cost increase due to the difficulty of separating tungsten from molybdenum
Solution Approach 1:
The patent applies segmentation by dividing the impurity removal process into two distinct stages: first removing tungsten selectively using ion exchange resin, then removing other metal impurities through conventional purification methods. This segmented approach allows each impurity type to be addressed with the most effective method, reducing overall process complexity while achieving high purity
Solution Approach 2:
The patent uses ion exchange resin as an intermediary substance that selectively binds to tungsten ions in the molybdenum solution. This intermediary enables the separation of tungsten from molybdenum without requiring complex physical or chemical processes, thereby reducing manufacturing complexity while effectively removing the最难去除的杂质
2Reliability
If the molybdenum content is increased to 99.99% or higher to reduce particles, then particle generation is suppressed, but the yield in EUV mask blank manufacturing remains insufficient due to residual impurities
Solution Approach 1:
The patent applies parameter changes by establishing specific quantitative thresholds for impurity content (tungsten ≤50 ppm, total metal impurities ≤100 ppm, oxygen ≤50 ppm) rather than simply increasing molybdenum content. This parameter-based approach provides clear manufacturing targets and enables systematic optimization of both purity and yield
3Quantity of substance
If conventional purification methods are used to reduce metal impurities, then some impurities are removed, but tungsten content remains high due to the difficulty of separating tungsten from molybdenum
Solution Approach 1:
The patent applies the extraction principle by selectively removing tungsten from the molybdenum solution using ion exchange resin before proceeding with conventional purification methods. This extraction of the最难去除的杂质 first prevents tungsten from interfering with subsequent purification steps and ensures tungsten content is reduced to ≤50 ppm
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 solution significantly reduces particle generation during sputtering, enhancing the yield and quality of molybdenum films used in EUV mask blanks by minimizing impurities, particularly tungsten.
Implementation Method 1
a first ion-exchange step of bringing a first molybdenum solution into contact with a first ion-exchange resin which is one ion-exchange resin selected from a cation-exchange resin and an anion-exchange resin once or more
Implementation Method 2
an oxidation step of subjecting the precipitate after removal of the solvent from the third molybdenum solution to oxidation treatment to provide a molybdenum oxide powder
Implementation Method 3
a reduction step of reducing the molybdenum oxide powder to provide a molybdenum powder
Implementation Method 4
a firing step of subjecting the molybdenum powder to pressure firing
Data Source
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AI summary
Disclosed is a molybdenum sputtering target having a content of metal impurities of 100 ppm by mass or less, a tungsten content of 50 ppm by mass or less, and an oxygen concentration of 50 ppm by mass or less.