Segmented MRAM Sputtering Target Prevents 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 results in defects and yield issues in MRAM device fabrication.
Innovation Solution
The formation of sputtering targets with multiple sub-targets bonded to a back plate, where each sub-target is sized below a threshold to prevent cracking, reducing the likelihood of particle contamination and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sputtering targets with high boron content are used, then the magnetic properties and functionality of MRAM devices are improved, but the targets become brittle and prone to cracking leading to particle generation and contamination
Solution Approach 1:
The sputtering target is divided into multiple sub-targets that are bonded together on a back plate. Each sub-target has dimensions below a threshold size that prevents cracking during sputtering operations. This segmentation maintains the necessary magnetic properties while eliminating the structural integrity issues associated with large, monolithic high-boron targets.
Solution Approach 2:
The target structure parameters are changed from a single large target to multiple smaller sub-targets with specific dimensional constraints. By controlling the size parameters of individual sub-targets to remain below a critical threshold, the material maintains its magnetic functionality while avoiding the brittleness and cracking problems that occur in larger targets.
2Area of stationary object
If larger sputtering targets are used to cover the substrate area, then the deposition coverage is improved, but cracking and particle generation increase
Solution Approach 1:
The large target area requirement is satisfied by arranging multiple sub-targets in a configuration that collectively covers the substrate. Each sub-target remains below the critical size threshold that causes cracking, while the ensemble of sub-targets provides sufficient coverage area for the substrate, thus eliminating particle contamination while maintaining deposition coverage.
Solution Approach 2:
Multiple small sub-targets are bonded together on a common back plate to form a composite target structure. This merging of multiple crack-free sub-targets creates an effective large-area target that covers the substrate without exhibiting the cracking and particle generation problems of monolithic large targets.
3Device complexity
If monolithic sputtering targets are used for simplicity, then the device complexity is reduced, but cracking and manufacturing reliability deteriorate
Solution Approach 1:
The target is segmented into multiple sub-targets bonded to a back plate, which adds structural complexity but eliminates cracking and improves sputtering reliability. The modular nature of sub-targets allows for easier handling and replacement, offsetting the increased assembly complexity with operational simplicity and enhanced manufacturing reliability.
Solution Approach 2:
The sputtering target is constructed as a composite structure with multiple sub-targets bonded to a back plate. This composite architecture combines the magnetic properties needed for MRAM fabrication with a structurally sound configuration that prevents cracking, thereby improving overall target reliability and sputtering operation stability.
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 effectively reduces or eliminates target cracking, minimizing particle contamination and improving the yield and reliability of MRAM device fabrication by using sub-targets sized below a determined threshold, thereby ensuring stable sputtering operations.
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
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 no greater than a threshold target size. A given sub-target characterized by a size no greater than the threshold target size exhibits no crack formation in a sputtering operation. Each of the plurality of sub-targets is in direct contact with one or more adjacent sub targets.