MRAM Upper Electrode Geometry for Ion Implantation and MTJ Patterning
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Solution Overview
Problem
In the manufacturing of magnetoresistive random access memory (MRAM) devices, existing methods face challenges in effectively forming a lower electrode and magnetic tunnel junction (MTJ) structure with precise control over the upper electrode's dimensions and shape, which affects the device's electrical characteristics and patterning accuracy.
Innovation Solution
A method involving sequential etching processes to form an upper electrode with specific portions of varying widths and slopes, and a via structure with a concave lower surface, allowing for precise patterning of the lower electrode and MTJ structure while minimizing electrical shorts and magnetic field interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the upper electrode is formed with uniform width, then the manufacturing process is simple, but the ion implantation is obstructed and patterning precision deteriorates
Solution Approach 1:
The upper electrode is divided into multiple width portions (first width portion, second width portion, third width portion) with different widths along the vertical direction. This segmentation allows the electrode to perform multiple functions: providing electrical connection while enabling ion implantation through the narrower second width portion, and maintaining structural integrity through the wider first and third width portions.
Solution Approach 2:
The upper electrode's width varies along the vertical direction rather than being uniform, creating a three-dimensional structure with different cross-sectional areas at different heights. This dimensional variation resolves the conflict between maintaining electrode integrity and allowing ion implantation by exploiting the vertical dimension.
2Manufacturing precision
If the upper electrode width is reduced to allow ion implantation, then patterning precision improves, but electrical conductivity and signal strength deteriorate
Solution Approach 1:
The upper electrode is segmented into different width portions where the first and third width portions have greater width to ensure electrical conductivity and signal strength, while the second width portion has reduced width to allow ion implantation. This segmentation allows simultaneous optimization of electrical performance and patterning precision.
Solution Approach 2:
Different portions of the upper electrode have different local qualities (widths) suited for different functions. The wider portions provide electrical connectivity, while the narrower portion enables ion implantation, allowing each region to be optimized for its specific function.
3Device complexity
If a single etching process is used, then the manufacturing process is simple, but the upper electrode cannot achieve the desired complex width variations
Solution Approach 1:
The etching process is segmented into multiple sequential steps (first, second, and third etching processes), each removing material to create a specific width portion of the upper electrode. This process segmentation enables precise control over the complex three-dimensional shape of the electrode.
Solution Approach 2:
The mask pattern is formed in advance with specific geometry to guide the sequential etching processes. The preliminary mask formation establishes the framework for achieving the desired width variations in the upper electrode through the subsequent etching steps.
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 solution enables improved electrical characteristics and effective patterning of MRAM devices by ensuring the upper electrode's design does not obstruct ion implantation, allowing for precise formation of the lower electrode and MTJ structure, thereby enhancing the device's performance and reliability.
Implementation Method 1
an ion-beam etching (IBE) process using the upper electrode as an etching mask may be performed on the lower electrode layer and the MTJ structure layer
Data Source
AI summary
A magnetoresistive random access memory (MRAM) device and a method of manufacturing the same, the device including a substrate; a memory unit including a lower electrode, a magnetic tunnel junction (MTJ) structure, and an upper electrode sequentially stacked on the substrate; a passivation pattern on a sidewall of the memory unit; a via on the memory unit and contacting the upper electrode; and a wiring on the via and contacting the via, wherein a center portion of the upper electrode protrudes from a remaining portion of the upper electrode in a vertical direction substantially perpendicular to an upper surface of the substrate.