Magnetoresistive Element Etching for STT-MRAM Scalability
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Solution Overview
Problem
In spin-injection-writing magnetic memory technologies, such as STT-MRAM, the scalability of magnetoresistive elements poses challenges in reducing the current required for magnetization inversion, and existing ion beam etching methods often result in re-deposition and damage, leading to electrically short failures and degradation of the magnetoresistive element's characteristics.
Innovation Solution
The use of a two-step ion beam etching process with varying acceleration voltages and angles, where the first etching process employs a low acceleration voltage and large incident angle to pattern the magnetoresistive element without re-deposition, followed by a second etching process with a high acceleration voltage and small incident angle to remove etching residue and prevent damage, thereby forming an ideal shape without electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ion beam etching is used to pattern magnetoresistive elements, then etching can be performed, but re-deposition and damage occur leading to electrically short failures and degradation of element characteristics
Solution Approach 1:
The patent divides the single etching process into two distinct steps: a first etching step that patterns the magnetoresistive element, and a second etching step that removes etching residue. This segmentation allows each step to be optimized independently, preventing re-deposition damage while achieving precise patterning and maintaining element reliability.
Solution Approach 2:
The patent introduces an intermediary cleaning step between the first and second etching processes. This intermediary step removes etching residue that would otherwise cause re-deposition damage in subsequent processing, thereby preventing electrically short failures and maintaining element characteristics without compromising etching precision.
2Use of energy by moving object
If magnetoresistive element size is reduced to improve scalability, then current required for magnetization inversion decreases, but etching damage and re-deposition become more significant
Solution Approach 1:
By segmenting the etching process into two steps with an intermediary cleaning step, the patent enables precise patterning of smaller magnetoresistive elements without the re-deposition damage that would be particularly harmful at reduced dimensions. This allows continued scaling while maintaining element integrity.
Solution Approach 2:
The patent converts the potentially harmful etching residue into a removable intermediate state. By intentionally allowing residue formation in the first step and then systematically removing it in the second step, the process prevents the residue from causing re-deposition damage, thereby enabling smaller element sizes without increased etching damage.
3Device complexity
If single-step etching is used to simplify the process, then manufacturing complexity is reduced, but etching residue causes re-deposition and element damage
Solution Approach 1:
The patent segments the etching process into two steps with an intermediary cleaning step, which adds process complexity but enables precise control over etching residue removal. This segmentation achieves superior element shape precision and prevents re-deposition damage, outweighing the increased manufacturing complexity.
Solution Approach 2:
The patent maintains continuous useful action by immediately following the first etching step with an intermediary cleaning step that removes residue before it can cause damage. This continuous process ensures that etching precision is maintained throughout the manufacturing sequence without interruption or compromise.
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 the current required for magnetization inversion, enhances etching selectivity, and prevents re-deposition and damage, resulting in improved scalability and reliability of the magnetoresistive elements in magnetic memory technologies.
Implementation Method 1
a first etching process is performed by ion beam etching (IBE); and then a second etching process is performed
Data Source
AI summary
According to one embodiment, a magnetic memory includes a transistor having first and second diffusion layers in a semiconductor substrate and a gate electrode between the first and second diffusion layers, a first insulating layer on the semiconductor substrate, the first insulating layer covering the transistor, a first contact plug in the first insulating layer, the first contact plug connected to the first diffusion layer, a second contact plug in the first insulating layer, the second contact plug connected to the second diffusion layer, a magnetoresistive element on the first insulating layer, the magnetoresistive element connected to the first contact plug, an electrode on the magnetoresistive element, and an impurity region in the first insulating layer, the second contact plug, and the electrode.