Co-Fe-B Sputtering Target Microstructure for Low Particle Generation
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Solution Overview
Problem
Existing methods for producing sputtering target materials with high boron content in Co-Fe-B alloys result in increased particle generation during sputtering, leading to quality deterioration and reduced yield of magnetic films, particularly when the boron content exceeds 33 at.%, which is necessary for improved magnetic performance.
Innovation Solution
A production method that forms a metallographic structure with a (CoFe)2B phase and a (CoFe)B phase, where the boundary length per unit area is controlled to suppress particle generation by coarsening these phases, using a mixed powder of first and second powders with specific boron content proportions and adjusting their mixing ratios to satisfy a predetermined condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the boron content proportion in the target Co-Fe-B alloy is increased to improve magnetic performance, then the TMR signal of the MTJ element is improved, but the frequency of particle generation during sputtering increases
Solution Approach 1:
The invention applies local quality by creating a non-uniform microstructure with regions of different boron concentrations. The target material contains both high-boron regions (providing magnetic performance) and low-boron regions (reducing particle generation), allowing different areas to have optimized properties for their specific functions.
Solution Approach 2:
The invention uses composite materials by combining phases with different boron concentrations within the same target material. The composite structure consists of multiple phases (high-B and low-B regions) that work together to achieve both high magnetic performance and reduced particle generation during sputtering.
2Reliability
If the boron content proportion is increased to achieve high TMR signals, then magnetic performance is improved, but the yield is lowered due to quality deterioration
Solution Approach 1:
By creating local regions with optimized boron concentrations, the invention allows different parts of the target to contribute differently: high-boron regions provide magnetic performance while low-boron regions ensure film quality, thereby maintaining both high yield and magnetic performance.
Solution Approach 2:
The composite structure enables the target material to produce high-quality magnetic films with excellent magnetic performance simultaneously, improving overall productivity by reducing defects and rework while maintaining high TMR signals.
3Object-generated harmful factors
If a fine powder is removed from the Co-Fe-B alloy powder to reduce particle generation, then particle generation is reduced, but manufacturing efficiency is reduced
Solution Approach 1:
Instead of removing fine powder to reduce particles, the invention inverts the approach by strategically incorporating fine powder into specific regions of the target material where it contributes to the desired microstructure and reduces particle generation through the composite phase structure, rather than being removed as a defect.
Solution Approach 2:
The invention changes the parameter distribution of boron concentration throughout the material, creating a gradient or heterogeneous structure where fine powder is strategically positioned in low-boron regions, transforming what would normally be a problematic parameter (fine powder content) into a beneficial structural feature.
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 effectively reduces particle generation during sputtering, enhancing the yield and quality of magnetic films suitable for magnetic devices like magnetic heads and MRAMs, while maintaining high magnetic performance.
Implementation Method 1
This magnetic layer is a thin film obtained by sputtering using a target material composed of a Co-Fe-B alloy
Implementation Method 2
a sintering step of sintering a mixed powder obtained by mixing a first powder and a second powder
Data Source
Figure 1~2
AI summary
An object of the present invention is to provide a method of producing a target material with reduced particle generation during sputtering, which is a method of producing a sputtering target material whose material is an alloy M, including a sintering step of sintering a mixed powder obtained by mixing a first powder and a second powder, wherein a material of the first powder is an alloy M1 in which the proportion of a B content is from 40 at.% to 60 at.%, wherein a material of the second powder is an alloy M2 in which the proportion of a B content is from 20 at.% to 35 at.%, wherein the proportion of a B content in the mixed powder is from 33 at.% to 50 at.%, wherein a metallographic structure including a (CoFe)2B phase and a (CoFe)B phase is formed in the sintering step, and wherein a boundary length per unit area Y (1/µm), which is obtained by measuring a boundary length between the (CoFe)2B phase and the (CoFe)B phase using a scanning electron microscope, and a proportion X (at.%) of a B content of the alloy M satisfy the following expression: Y<−0.0015×X−42.52+0.15.