MTJ Etch Structure to Prevent Sidewall Residue Damage
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Solution Overview
Problem
Conventional MRAM manufacturing methods damage magnetic tunnel junctions (MTJs) during the etching process due to the formation of by-products on the sidewalls, leading to pattern shifting and reduced performance.
Innovation Solution
A single etch operation is used to form the top electrode, MTJ, and bottom electrode, eliminating the need for a second etch operation and thereby preventing damage to the MTJ, while a cap layer protects the MRAM cells without additional spacer layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple etch operations are used to form bottom electrodes and MTJs separately, then manufacturing precision can be controlled, but the MTJ sidewalls accumulate by-products and residues causing pattern shifting and performance degradation
Solution Approach 1:
The patent combines the etching of bottom electrode and MTJ into a single etch operation. The etch pattern simultaneously defines both structures, eliminating sequential etching steps. This merging approach prevents by-product accumulation on MTJ sidewalls that occurs with multiple separate etch operations, while maintaining manufacturing precision through the unified etch process design.
Solution Approach 2:
The patent extracts and removes the harmful by-products from the MTJ sidewalls using a cleaning step positioned between the single etch operation and subsequent processing. This extraction of contaminants eliminates the pattern shifting and performance degradation caused by residue accumulation, allowing the benefits of single-etch manufacturing to be realized without the harmful side effects.
2Reliability
If a second etch operation is performed to etch bottom electrodes, then electrical insulation between bottom electrodes is achieved, but the MTJ may be damaged by the second etch
Solution Approach 1:
The patent merges the electrical insulation function into the single etch operation that forms both the bottom electrode and MTJ. The etch pattern is designed to create isolated bottom electrode regions with proper spacing, achieving electrical insulation without requiring a separate etch step that would expose the MTJ to additional damage risks.
Solution Approach 2:
The patent performs the electrical insulation patterning during the initial single etch operation, before any subsequent processing steps. By establishing the isolated bottom electrode structure upfront, the design eliminates the need for later etching operations that could damage the MTJ, while still achieving the required electrical insulation between adjacent devices.
3Reliability
If additional spacer layers are added to protect MRAM cells, then protection during manufacturing is improved, but device complexity increases
Solution Approach 1:
The patent employs a cap layer that forms conformally on the sidewalls of the MTJ and bottom electrode structures. This cap layer serves as a self-protecting element that automatically provides the necessary protection during subsequent manufacturing steps without requiring additional spacer layers or complex protective structures to be added.
Solution Approach 2:
The cap layer performs multiple functions simultaneously: it protects the MTJ sidewalls during manufacturing processing, serves as an etch stop layer, and can be used as a seed layer for subsequent deposition. This multi-functionality eliminates the need for separate dedicated protection structures, reducing device complexity while maintaining manufacturing protection.
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 ensures the sidewalls of the MTJ remain clean, maintaining the integrity and performance of the MRAM cells by avoiding the formation of residues on the MTJ sidewalls, thus enhancing the manufacturing process and reducing defects.
Implementation Method 1
a first magnetic layer and a second magnetic layer, wherein the first magnetic layer and the second magnetic layer have a first relative magnetization orientation
Implementation Method 2
magnetic tunnel junction (MTJ) arranged between the top and bottom electrodes
Data Source
AI summary
A device includes a semiconductor substrate, a bottom conductive line, a bottom electrode, a magnetic tunneling junction (MTJ), and a residue. The bottom conductive line is over the semiconductor substrate. The bottom electrode is over the bottom conductive line. The MTJ is over the bottom electrode. The residue of the MTJ is on the sidewall of the bottom electrode and is spaced apart from the bottom conductive line.