Aluminum-Scandium Sputtering Target Microstructure for Crack-Free Deposition
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Solution Overview
Problem
Conventional aluminum scandium alloys used in sputtering targets suffer from non-uniform chemical stoichiometry, porosity, and microstructural defects, leading to target cracking, particulation, and reduced lifetime, which affects the quality and yield of thin film deposition.
Innovation Solution
The development of non-equilibrium aluminum-scandium composites with a ductile first phase and brittle second phase, characterized by specific intermetallic compounds, provides a microstructure that enhances uniformity, minimizes porosity, and prevents cracking, thereby improving target performance and film quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional aluminum scandium alloys are used in sputtering targets, then the target can be manufactured with standard processes, but the target exhibits non-uniform chemical stoichiometry, porosity, and microstructural defects leading to cracking and particulation
Solution Approach 1:
The patent applies composite materials by combining aluminum matrix with scandium-rich intermetallic phases (Al3Sc, Al2Sc, AlSc) to create a multi-phase microstructure. This composite structure allows the ductile aluminum matrix to prevent cracking while the brittle intermetallic phases provide scandium reservoirs that ensure uniform compositional distribution during sputtering, thereby simultaneously improving manufacturing precision and target reliability
Solution Approach 2:
The patent implements local quality by creating regions with different scandium concentrations - the aluminum matrix provides a ductile base structure while scattered intermetallic phases concentrate scandium in specific locations. This local variation in composition ensures that during sputtering, scandium is replenished uniformly across the target surface despite the non-uniform spatial distribution, resolving the contradiction between compositional uniformity and structural integrity
2Reliability
If the scandium content is increased to improve piezoelectric response, then the piezoelectric properties improve, but the target becomes more prone to cracking and particulation
Solution Approach 1:
The composite structure separates the functions of structural support and piezoelectric property provision. The aluminum matrix maintains structural integrity and prevents cracking, while the scandium-rich intermetallic phases provide the necessary scandium content for high-quality piezoelectric films. This allows high scandium content (up to 65 at%) without compromising target strength
Solution Approach 2:
The patent changes the microstructural parameters by controlling phase distribution, particle size (0.5-500 microns), and volume fractions of different phases. By optimizing these parameters, the target can accommodate high scandium content while maintaining structural integrity through the ductile aluminum matrix framework
3Productivity
If the target is operated for extended periods to increase productivity, then wafer output increases, but target failure due to cracking and particulation reduces lifetime
Solution Approach 1:
The localized intermetallic phases act as scandium reservoirs that continuously replenish scandium during sputtering operations. This local scandium supply mechanism prevents compositional degradation over time, allowing extended target operation without loss of film quality or increase in particulation, thereby extending target lifetime while maintaining high productivity
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 composite targets achieve high compositional uniformity, reduced particulation, and extended target lifetime, resulting in higher wafer yields and improved piezoelectric film properties.
Implementation Method 1
The sputtering target and the substrate are placed in proximity to one another within the chamber and the target is bombarded with charged particles or ions. The high energy ions cause a portion of the sputtering target to dislodge and be re-deposited on the substrate.
Data Source
AI summary
An Al—Sc alloy sputtering target. The target comprising from 1.0 at % to 65 at % scandium and from 35 at % to 99 at % aluminum and having a microstructure including a first aluminum matrix phase and a second phase dispersed uniformly therethrough. The second phase comprises one or more compounds corresponding to the formula ScxAly, where x is from 1 to 2 and y is from 0 to 3.