Al-Sc Sputter Targets With Refined Microstructure for AlScN Deposition
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Solution Overview
Problem
Existing methods for fabricating aluminum-scandium sputter targets result in coarse microstructures with compositional variations and the formation of intermetallic phases, leading to reduced performance and process control during deposition of AlScN films and structures.
Innovation Solution
A method involving localized heating and rapid cooling of Al-Sc powder layers to form a metastable Al-Sc alloy target, free of Al3Sc, Al2Sc, and AlSc2 intermetallics, using additive manufacturing techniques such as selective laser melting, to achieve a refined microstructure and controlled composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hot pressing fine pure aluminum and fine pure scandium powder is performed above the melting point of aluminum, then the target blank can be formed, but coarse discrete second phase particles are formed resulting in compositional variations and coarse multiphase microstructure
Solution Approach 1:
The invention changes the thermal processing parameters by performing hot pressing at temperatures below the melting point of aluminum (e.g., 400-600°C) rather than above it. This parameter change prevents the formation of coarse intermetallic phases while still enabling adequate bonding and densification of the powder compact, thereby achieving both manufacturability and compositional uniformity
Solution Approach 2:
The invention uses pre-alloyed Al-Sc powder as the starting material instead of mixing pure Al and pure Sc powders. This ensures homogeneous distribution of scandium atoms within the aluminum matrix at the particle level before pressing, preventing segregation and formation of coarse second phase particles during processing
2Manufacturing precision
If pre-alloyed Al—Sc powder is hot pressed to form a target blank, then compositional variation is reduced, but melting and slow cooling during hot-pressing still results in the formation of coarse second phase particles
Solution Approach 1:
The invention changes the temperature parameter by conducting hot pressing below the melting point of aluminum, preventing the melt-solidify cycle that causes coarse intermetallic formation. This temperature parameter change maintains compositional uniformity while producing a refined microstructure without coarse second phase particles
Solution Approach 2:
The invention employs a two-stage processing approach: first hot pressing at moderate temperature to achieve densification and bonding, then subsequent rapid cooling or heat treatment to refine the microstructure. This periodic thermal action prevents coarse phase formation while maintaining compositional uniformity
3Productivity
If Sc and Al metals are melted and cast to form an ingot, then the ingot can be produced, but high melting point intermetallic Al—Sc phases form making it difficult to cast an ingot with a uniform microstructure and limiting scandium levels to less than 10 weight percent
Solution Approach 1:
The invention changes the processing approach from melting and casting to hot pressing of powders at temperatures below the melting point of aluminum. This parameter change eliminates the formation of high melting point intermetallic phases that limit scandium content, enabling production of targets with scandium levels exceeding 10 weight percent with uniform microstructure
Solution Approach 2:
The invention replaces the thermal-metallurgical process of melting and casting with a solid-state hot pressing process. This substitution avoids the formation of coarse intermetallic phases during solidification, enabling production of uniform microstructures with higher scandium content that would be impossible to achieve through conventional casting
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 method produces Al-Sc sputter targets with a uniform, single-phase microstructure, enabling improved deposition of AlScN films with optimal scandium levels and enhanced process control.
Implementation Method 1
heating the particles of the first powder layer to form a first Al—Sc alloy layer and rapidly cooling the first Al—Sc alloy layer
Implementation Method 2
The composition and microstructure of the Al—Sc target may be controlled to deposit AlScN structures with optimal Sc levels. Refining microstructure reduces variations in parameters required for sputter deposition of Al—Sc structures.
Data Source
AI summary
Aluminum-scandium sputter targets with controlled compositions and refined microstructures are disclosed. The composition and microstructure of the Al—Sc target may be controlled to deposit AlScN structures with optimal Sc levels. Refining microstructure reduces variations in parameters required for sputter deposition of Al—Sc structures. The fabrication process may utilize a localized heat source such as a laser, electron beam, electric arc, or the like to build the target layer-by-layer from powder feed stock.