Segmented CoFeB Sputtering Target to Prevent MRAM Cracking
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Solution Overview
Problem
Traditional sputtering targets made of ferromagnetic alloys like CoFeB are brittle and prone to cracking, especially with high boron content, leading to particle generation and contamination during the sputtering process, which causes defects and reliability issues in MRAM devices.
Innovation Solution
The formation of sputtering targets with a plurality of sub-targets bonded to a back plate, where each sub-target is characterized by a size below a threshold target size to prevent cracking, using a method that includes pressing and sintering powders of ferromagnetic materials like CoFeB and bonding them to a back plate, thereby reducing the likelihood of crack formation during sputtering operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sputtering targets with high boron content are used, then the magnetic properties for MRAM are improved, but the targets become brittle and prone to cracking
Solution Approach 1:
The sputtering target is divided into multiple segments or zones with different boron concentrations. The core region contains high boron content for optimal magnetic properties, while the outer regions have lower boron content to provide structural strength and prevent cracking. This segmentation allows the target to maintain both magnetic performance and structural integrity simultaneously.
2Manufacturing precision
If high boron content ferromagnetic alloys are used in sputtering targets, then the magnetic tunnel junction performance is enhanced, but particle generation and contamination increase due to target cracking
Solution Approach 1:
By segmenting the target with varying boron content, the high-boron core provides excellent magnetic layer quality while the low-boron outer regions prevent cracking and reduce particle generation during sputtering operations.
Solution Approach 2:
Different regions of the sputtering target are assigned different local qualities - the core region has high boron content optimized for magnetic properties, while the outer regions have lower boron content optimized for structural stability. This local quality differentiation ensures high magnetic layer quality without excessive particle contamination.
3Reliability
If uniform high boron content is maintained throughout the sputtering target, then magnetic properties are optimized, but the target becomes more susceptible to crack formation
Solution Approach 1:
The target composition is segmented into high-boron and low-boron regions, sacrificing overall compositional uniformity to prevent cracking. The high-boron core maintains magnetic performance while the low-boron outer regions provide crack resistance.
Solution Approach 2:
The target exhibits local quality variations in boron content - high boron in the core for magnetic performance and low boron at the edges for structural stability. This local differentiation resolves the contradiction between magnetic optimization and crack prevention.
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
This approach reduces or eliminates target crack formation, minimizing particle contamination and enhancing yield and reliability by ensuring that sputtering targets do not crack, even with high boron content, thus improving the sputtering process for MRAM devices.
Implementation Method 1
a physical vapor deposition (PVD) process, also known as a sputter deposition or sputtering, deposits thin films by using energetic particles to bombard a target source into the gas phase and onto a substrate
Implementation Method 2
pressing and sintering powders of ferromagnetic materials like CoFeB and bonding them to a back plate
Data Source
AI summary
A sputtering target structure includes a back plate characterized by a first size, and a plurality of sub-targets bonded to the back plate. Each of the sub-targets is characterized by a size that is a fraction of the first size and is equal to or less than a threshold target size. Each sub-target includes a ferromagnetic material containing iron (Fe) and boron (B). Each of the plurality of sub-targets is in direct contact with one or more adjacent sub-targets.