In-situ Dielectric Capping for MTJ Sidewall Oxidation and Stress
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Solution Overview
Problem
The down-scaling of integrated circuits leads to oxidation and inherent stress issues in magnetic tunnel junctions (MTJs) of MRAM devices, affecting their performance, particularly causing sloped R-H loops and undesirable stress directions/magnitudes.
Innovation Solution
Forming a dielectric capping layer on the sidewalls of MTJ cells in-situ during etching, which compensates for inherent stresses and prevents oxidation by maintaining a vacuum environment, using a production tool with etching and deposition chambers to ensure minimal exposure to external substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MTJ layers are etched to form MTJ cells during down-scaling, then device density is improved, but sidewall oxidation occurs causing sloped R-H loops
Solution Approach 1:
A dielectric capping layer is formed on the sidewalls of MTJ cells before they are exposed to external environment. This preliminary protective action prevents oxidation during subsequent processing steps, maintaining perfect square R-H loops even as device density increases through down-scaling
Solution Approach 2:
The dielectric capping layer creates an inert protective environment around the MTJ cell sidewalls, isolating them from oxygen and preventing oxidation. This allows the MTJ cells to maintain their magnetic properties and produce ideal square R-H loops during high-density scaling
2Productivity
If MTJ layers are etched to form MTJ cells during down-scaling, then device density is improved, but inherent stress issues occur affecting performance
Solution Approach 1:
The dielectric capping layer applies a counteracting stress to compensate for the inherent stress generated during MTJ cell formation. By selecting appropriate dielectric materials and layer thicknesses, the stress from the capping layer balances the intrinsic stress in the MTJ stack, enabling reliable operation at scaled dimensions
Solution Approach 2:
The inherent stress in MTJ cells is managed by changing the stress parameters of the dielectric capping layer. By adjusting the material composition, thickness, and deposition conditions of the capping layer, the stress state of the MTJ cell can be optimized for scaled device dimensions
3Reliability
If vacuum environment is maintained during etching and capping formation, then oxidation is prevented, but process complexity increases
Solution Approach 1:
The etching of MTJ layers and the formation of the dielectric capping layer are combined into a single continuous vacuum process sequence. By merging these steps without breaking vacuum, the process prevents oxidation while managing complexity through integrated tool design that performs multiple functions in one vacuum environment
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 method substantially eliminates sidewall oxidation, aligns easy axes for improved switching uniformity, and enhances MRAM performance by reducing inherent stresses, resulting in perfect square R-H loops and improved reliability.
Implementation Method 1
forming a dielectric capping layer on sidewalls of the MTJ cell, wherein the dielectric capping layer has a non-neutral stress compensating for the inherent stresses in the MTJ cell
Implementation Method 2
By forming a dielectric capping layer to protect the sidewalls of the MTJ cells before the MTJ cells are exposed to external environment, the adverse oxidation of the MTJ cells is substantially eliminated
Data Source
AI summary
A method of forming an integrated circuit includes forming magnetic tunnel junction (MTJ) layers; etching the MTJ layers to form a MTJ cell; and forming a dielectric capping layer on sidewalls of the MTJ cell, wherein the step of forming the dielectric capping layer is in-situ performed with the step of etching the MTJ layers.