Ag Alloy Sputtering Target Composition for High-Reflectivity Layers
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Solution Overview
Problem
Existing silver-based alloys for reflective layers suffer from reduced reflectivity and increased film resistivity due to the addition of alloying elements, and are prone to arcing during the sputtering process, which can lead to layer defects.
Innovation Solution
A sputtering target comprising an AgXAl alloy with 0.20 to 0.80 wt.-% of alloying metal X (In, Sn, or Bi) and 100 to 300 ppm-wt. of Al, produced through a direct melting process under vacuum or inert gas conditions, ensuring homogeneous distribution and low oxide content, thereby enhancing reflectivity and reducing arcing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alloying elements (In, Sn, Sb, Bi) are added to silver to improve corrosion resistance, then corrosion resistance is improved, but reflectivity deteriorates
Solution Approach 1:
The invention changes the concentration parameter of aluminum from trace impurity levels (<0.5 ppm-wt.) to a specific range (100-300 ppm-wt.), which fundamentally alters the optical properties of the alloy. This parameter change enables the aluminum to form a protective oxide layer that prevents oxidation of the reflective metal components, thereby maintaining reflectivity while preserving corrosion resistance.
Solution Approach 2:
Aluminum acts as an intermediary element that mediates between the conflicting requirements of corrosion resistance and reflectivity. The aluminum forms a protective oxide barrier that prevents direct oxidation of the silver and alloying elements (In, Sn, Sb, Bi), thereby preserving their reflective properties while maintaining corrosion protection.
2Reliability
If alloying elements are added to silver to improve corrosion resistance, then corrosion resistance is improved, but film resistivity increases
Solution Approach 1:
The invention changes the concentration parameter of aluminum to a specific range (100-300 ppm-wt.) that optimizes both corrosion resistance and electrical conductivity. This precise parameter control ensures that the aluminum forms sufficient protective oxide while maintaining low film resistivity, unlike higher concentrations of alloying elements that would increase resistivity.
3Manufacturing precision
If impurity elements like aluminum are kept at very low contents to minimize oxide introduction, then oxide content is reduced, but reflectivity deteriorates due to oxidation of alloying elements
Solution Approach 1:
Aluminum serves as a sacrificial intermediary that preferentially oxidizes to form a protective barrier, preventing oxidation of the reflective metal components (silver, indium, tin, antimony, bismuth). This intermediary action maintains low oxide content that affects reflectivity while preventing oxidation of the reflective elements.
Solution Approach 2:
The invention converts the typically harmful effect of aluminum oxidation (introduction of oxides that reduce reflectivity) into a beneficial protective mechanism. The aluminum oxide layer formed at 100-300 ppm-wt. concentration acts as a protective barrier that prevents oxidation of the reflective metal components, thereby preserving reflectivity while providing corrosion resistance.
4Productivity
If sputtering targets with higher oxide contents are used, then material deposition is faster, but layer defects occur due to arcing and micro-arcing
Solution Approach 1:
The invention changes the oxide content parameter to a controlled low level (100-300 ppm-wt. aluminum producing minimal oxides) that prevents arcing and micro-arcing during sputtering. This parameter control ensures stable deposition processes without the harmful electrical discharges that cause layer defects, while maintaining adequate corrosion protection.
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 AgXAl alloy achieves improved reflectivity and reduced film resistivity, with minimal arcing and uniform layer thickness, while maintaining high corrosion resistance and adhesion to substrates.
Implementation Method 1
Sputtering targets made of silver-based alloys are known and are often used to produce thin films/layers for glazing applications such as for coating glass, or as reflective-layers in optical storage media and displays.
Implementation Method 2
a process for the production of said sputtering target wherein an AgXAl alloy is formed by the addition of Al to the Ag metal or AgX alloy
Implementation Method 3
produced through a direct melting process under vacuum or inert gas conditions, ensuring homogeneous distribution and low oxide content
Data Source
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AI summary
The present invention relates to a sputtering target based on silver (Ag) and comprising one alloying metal, selected from the group consisting of indium (In), tin (Sn), antimony (Sb) and bismuth (Bi), and a low amount of aluminum (Al), to a process for the production thereof and to layers obtained by sputtering of such a target.