MTJ Stack Etching to Prevent Sidewall Residue and Pattern Shift
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Solution Overview
Problem
Conventional MRAM manufacturing methods result in the formation of residues on the sidewalls of magnetic tunnel junctions (MTJs) due to re-deposition during etching, which can damage the MTJs and lead to pattern shifting, compromising the integrity and performance of the MRAM cells.
Innovation Solution
A single etch operation is used to form the top electrode, MTJ, and bottom electrode, eliminating the need for a subsequent etch operation that causes residues on the MTJ sidewalls, thereby maintaining the structural integrity and performance of the MTJs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multiple etch operations are used to form the top electrode, MTJ, and bottom electrode separately, then each layer can be etched with optimized parameters, but residues are formed on the MTJ sidewalls causing damage and pattern shifting
Solution Approach 1:
The patent combines multiple separate etch operations into a single etch operation that forms the top electrode, MTJ, and bottom electrode simultaneously. This merging eliminates the re-deposition issue that occurs between separate etch steps, preventing residue formation on MTJ sidewalls and maintaining pattern accuracy while still allowing optimized etch parameters to be applied to the combined structure.
Solution Approach 2:
The patent applies a protective cap layer to the MTJ structure before the etch operation. This preliminary protective action prevents the etch process from damaging the MTJ sidewalls and eliminates the need for subsequent cleanup operations that would otherwise be required to remove residues, thereby maintaining manufacturing precision.
2Ease of manufacture
If conventional multi-step etching is performed, then layer-by-layer formation is achieved, but re-deposition during etching damages MTJs and causes pattern shifting
Solution Approach 1:
The patent merges the formation of top electrode, MTJ, and bottom electrode into a single etch operation. This eliminates the intermediate steps where re-deposition occurs, preventing damage to the MTJ structure and maintaining its integrity while still achieving the desired layer-by-layer formation through the single optimized etch process.
Solution Approach 2:
The patent introduces a cap layer as an intermediary protective element during the etch operation. This cap layer acts as a mediator that protects the MTJ from direct exposure to the etch process and prevents re-deposition damage, thereby maintaining MTJ structural integrity throughout the manufacturing process.
3Manufacturing precision
If separate etch operations are used for top electrode, MTJ, and bottom electrode, then each component can be precisely controlled, but additional etching causes residues and requires extra process steps
Solution Approach 1:
The patent combines the etching of top electrode, MTJ, and bottom electrode into a single operation. This merging reduces the total number of etch steps while maintaining precise dimensional control of each component through optimized etch parameters applied to the combined structure, thereby reducing process complexity without sacrificing manufacturing precision.
Data Source
AI summary
A device includes a bottom electrode, a magnetic tunneling junction (MTJ) stack, a top electrode, and a metal-containing layer. The bottom electrode includes a bottom portion and a top portion over the bottom portion. A width of the top portion is greater than a width of the bottom portion. The MTJ stack is over the top portion of the bottom electrode. The top electrode is over the MTJ stack. The metal-containing layer is on a sidewall of the top portion of the bottom electrode. An interface is between the metal-containing layer and the bottom electrode, and a top surface of the metal-containing layer is lower than a bottom surface of the MTJ stack.