FePt Sputtering Target with AgCu Alloy for Particle Reduction
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Solution Overview
Problem
Current FePt-based sputtering targets face challenges in achieving high density and reducing particle generation during sputtering due to thermal expansion mismatches between FePt alloys and additives like C or BN, leading to defects and density deterioration.
Innovation Solution
Incorporating a AgCu alloy with a low melting point as a sintering additive to increase target density and reduce particle generation, with specific compositional ranges for Ag, Cu, Pt, C, BN, and metal oxides to enhance magnetic properties and insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If C or BN is added as a nonmagnetic phase to FePt alloy to form magnetic recording layer, then magnetic insulation between grains is improved, but thermal expansion mismatch causes compressive stress and particle generation during sputtering
Solution Approach 1:
The patent introduces AgCu alloy as an intermediary material between the FePt magnetic phase and C/BN nonmagnetic phase. This intermediary layer reduces the thermal expansion mismatch stress by providing a gradual transition in thermal expansion coefficients, preventing particle generation while maintaining the magnetic insulation function of C/BN.
Solution Approach 2:
The patent creates a composite sputtering target consisting of FePt alloy, C/BN nonmagnetic phase, and AgCu alloy additive. This composite structure combines the magnetic insulation properties of C/BN with the stress-mitigating properties of AgCu, achieving both magnetic insulation and particle reduction simultaneously.
2Volume of stationary object
If sintering temperature is increased to improve target density, then density is improved, but compressive stress on C or BN increases causing physical defects and particle generation
Solution Approach 1:
The patent changes the thermal expansion parameter by introducing AgCu alloy with intermediate thermal expansion properties. This parameter change allows the system to maintain density improvement at lower sintering temperatures, avoiding the compressive stress that would otherwise occur at higher temperatures.
Solution Approach 2:
The AgCu alloy undergoes phase transition during sintering, transforming from powder to dense metallic phase that fills voids and binds particles together. This phase transition occurs at lower temperatures than conventional sintering, achieving density improvement without excessive thermal stress on C/BN.
3Reliability
If multiple targets (C target and FePt alloy target) are used to form magnetic recording layer, then magnetic insulation is achieved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the C target and FePt alloy target into a single integrated sputtering target. The C/BN nonmagnetic phase and FePt magnetic phase are combined in one target structure, eliminating the need for separate targets and simplifying the manufacturing process while maintaining magnetic insulation through the C/BN phase distribution.
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 resulting FePt-based sputtering target achieves high density and significantly reduces particle generation during sputtering, enabling efficient deposition of magnetic thin films with improved magnetic insulation and stability.
Implementation Method 1
Incorporating a AgCu alloy with a low melting point as a sintering additive to increase target density
Implementation Method 2
FePt-based sintered sputtering target... when sputtered with magnetron sputtering equipment
Data Source
AI summary
An FePt-based sintered sputtering target containing C and/or BN, wherein an area ratio of AgCu alloy grains on a polished surface of a cross section that is perpendicular to a sputtered surface of the sputtering target is 0.5% or more and 15% or less. An object of this invention is to provide a sputtering target capable of reducing particles generation during sputtering and efficiently depositing a magnetic thin film of a magnetic recording medium.