Silver Sputtering Target Grain Control for Arcing Reduction
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Solution Overview
Problem
Large-area sputtering targets used in producing high-resolution displays face issues with spark discharges, known as arcing, which lead to defects and reduced production efficiency due to the limitations in power density and material quality, especially when producing large and high-resolution displays with small pixels.
Innovation Solution
A silver-based alloy with a crystal structure of less than 120 μm average grain size, low oxygen content (less than 20 ppm), and high metallic purity (at least 99.99%) is used, combined with induction melting under reducing conditions and the addition of graphite to minimize impurities and oxygen, resulting in a sputtering target that reduces the risk of spark discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power density is increased to improve production rate, then productivity increases, but spark discharges occur causing coating defects
Solution Approach 1:
The patent changes the material parameters of the sputtering target by controlling the crystal grain size to 120 μm or less and limiting oxygen content to 20 ppm or less. These parameter changes reduce the tendency toward spark discharges, allowing higher power density to be applied without causing coating defects, thus resolving the contradiction between productivity and reliability.
2Reliability
If alloy purity is increased to reduce spark discharges, then reliability improves, but manufacturing complexity increases
Solution Approach 1:
The patent specifies precise parameter ranges for alloy composition (oxygen content ≤ 20 ppm, impurity elements ≤ 0.5 ppm each) and crystal grain size (≤ 120 μm). By controlling these parameters within defined ranges rather than requiring absolute purity, the patent achieves reduced spark discharge tendency while keeping the manufacturing process feasible through standard purification and heat treatment methods.
3Reliability
If crystal grain size is reduced to minimize spark discharges, then reliability improves, but manufacturing difficulty increases
Solution Approach 1:
The patent sets the crystal grain size parameter to 120 μm or less, which is sufficiently fine to reduce spark discharge tendency but not so fine as to require excessively complex manufacturing. This parameter can be achieved through conventional heat treatment processes such as annealing at controlled temperatures (e.g., 400-600°C), making the manufacturing process practical and economically viable.
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 effectively minimizes spark discharges and enhances the sputtering process quality, allowing for higher power density and cost-effective production of large-area sputtering targets with improved material purity and grain structure, leading to better coating quality and reduced defects.
Implementation Method 1
the melting is carried out by induction melting under reducing conditions
Implementation Method 2
melting is carried out by induction melting under reducing conditions with an oxygen content of less than 20 ppm by weight
Implementation Method 3
the sputtering process
Data Source
AI summary
Planar sputtering target with an area of greater than 0.3 m 2> or tubular sputtering target with a length of at least 1 m, comprises a silver-based alloy with 0.01-5 wt.% at least one further alloy component comprising indium, tin, antimony or bismuth; and a crystal structure with an average grain size of less than 120 mu m, an oxygen content of less than 50 mg/kg, impurity elements of less than 0.5 mg/kg, which comprises aluminum, lithium, sodium, calcium, magnesium, barium and chromium of, and a metal purity of at least 99.99 wt.%. An independent claim is also included for producing a planar sputtering target with an area of greater than 0.3 m 2> or a tubular sputtering target with a length of at least 1 m, comprising melting an alloy that comprises silver and at least one further alloy component comprising indium, tin, antimony or bismuth; casting the melt into a mold to form a molded article of the silver-base alloy; and forming the molded body to the sputtering target. The melting takes place by induction melting under reducing conditions by adjusting an oxygen content of less than 50 mg/kg.