MTJ Formation Two-Step Etching Tantalum Layer Integrity
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Solution Overview
Problem
Current manufacturing methods for magnetic random access memory (MRAM) face challenges in producing scalable and reliable magneto tunnel junctions (MTJs) due to the thinning of the tantalum layer, leading to defective elements and shorting of the fixed and free layers.
Innovation Solution
A method involving multiple etching steps using photo-resists to define and maintain the width and length of layers in a MTJ stack, ensuring a sufficient tantalum layer thickness for reliable connection, with optional use of a nitride layer for protection and etching with specific gases like CF4 and C2H5OH to maintain layer integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the tantalum layer thickness is reduced to meet manufacturing limitations, then the device can be manufactured with current processes, but the connection reliability deteriorates and shorting occurs between fixed and free layers
Solution Approach 1:
The patent divides the single etching process into two separate etching steps: a first etching step that creates initial openings through the oxide layer, and a second etching step that completes the openings through the tantalum layer. This segmentation allows each step to be optimized independently, ensuring complete penetration while maintaining proper layer thicknesses, thereby preventing shorting while achieving manufacturability.
Solution Approach 2:
The first etching step performs preliminary action by creating openings through the oxide layer before the second etching step completes the openings through the tantalum layer. This preliminary action ensures that the etching process is properly initiated and positioned, allowing the second step to complete penetration reliably without requiring excessive reduction of tantalum layer thickness.
2Productivity
If the tantalum layer thickness is reduced, then manufacturing can proceed with current capabilities, but defective MRAM elements are produced
Solution Approach 1:
By segmenting the etching process into two distinct steps with different target depths, the patent enables complete penetration through the tantalum layer without requiring the layer to be excessively thin. This maintains element quality and reduces defects while allowing manufacturing to proceed with standard layer thicknesses and capabilities.
3Device complexity
If a single etching step is used, then the manufacturing process is simpler, but complete penetration through the oxide and tantalum layers cannot be achieved
Solution Approach 1:
The patent segments the etching process into two steps: the first etching step targets penetration through the oxide layer to a controlled depth, and the second etching step completes the penetration through the tantalum layer. This segmentation achieves complete penetration precision that would be difficult to obtain in a single step, while the added process step is justified by the significant improvement in etching precision and reliability.
Solution Approach 2:
The first etching step performs preliminary action by creating openings through the oxide layer, establishing the correct position and depth before the second etching step completes penetration through the tantalum layer. This preliminary action ensures precise control over the etching process, achieving complete penetration while maintaining manufacturing precision.
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 results in a significantly larger and more reliable tantalum contact layer, enhancing the connection of MTJs to external circuits and reducing the risk of shorting, while maintaining low switching current levels.
Implementation Method 1
An oxide layer is first etched, using a first photo-resist, to leave a portion of the oxide layer
Implementation Method 2
a second photo-resist is deposited on top of and around the portion of the oxide layer
Implementation Method 3
a second etching step is performed on the MTJ stack, using the second photo-resist, to leave a portion of the contact layer, a portion of the free layer and a portion of the barrier layer
Implementation Method 4
A third etching is performed of the MTJ stack, using the portion of the oxide layer, to leave a second portion of the contact layer, a second portion of the free layer and a second portion of the barrier layer
Data Source
AI summary
A method of manufacturing a magnetic memory element includes the steps of performing a first etching an oxide layer is etched, using a first photo-resist, the oxide layer formed on top of a contact layer that is formed on top of a magneto tunnel junction (MTJ), depositing a second photo-resist and second etching to leave a portion of the contact layer used to suitably connect the MTJ to circuits outside of the magnetic memory element.