MRAM Electrode Co-Deposition to Prevent MTJ Pillar Re-Sputtering
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Solution Overview
Problem
Conventional MRAM device fabrication methods lead to re-sputtering of metal layers during etching, causing shorts and edge roughness in magnetic tunnel junction pillars, which negatively impact the electrical performance and yield of MRAM devices.
Innovation Solution
A method is developed where the electrode metal for both the top and bottom electrodes is deposited in a single process after forming the magnetic tunnel junction pillar, using a metal nitride liner and an amorphous or low-grain-boundaries dielectric material as a hardmask to prevent re-sputtering and edge roughness, resulting in smoother pillar surfaces and improved device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polycrystalline hardmasks are used during the etching process, then the etching can proceed effectively, but re-sputtering occurs leading to shorts in the MTJ pillar and uneven edges
Solution Approach 1:
The patent changes the physical state of the hardmask material from polycrystalline to amorphous. This parameter change eliminates grain boundaries that cause uneven etching and re-sputtering, resulting in smooth pillar edges and preventing shorts while maintaining effective etching progression
Solution Approach 2:
The patent employs a composite structure combining amorphous hardmask material with specific etching conditions. The amorphous material serves as a protective layer that prevents re-sputtering of metal layers while allowing controlled etching, thus improving both reliability and productivity
2Manufacturing precision
If conventional deposition processes are used for electrodes, then multiple deposition steps are required, but this increases process complexity and time
Solution Approach 1:
The patent merges the deposition of top and bottom electrodes into a single deposition step. By using a through-silicon via structure as a placeholder during deposition, both electrodes can be formed simultaneously in one process, reducing complexity while maintaining precise electrode formation
Solution Approach 2:
The through-silicon via structure serves as an intermediary element that enables single-step deposition. It acts as a placeholder that allows the deposition material to reach and form both the top and bottom electrodes simultaneously, simplifying the overall process
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 eliminates re-sputtering issues, reduces shorting, and enhances the electrical performance and yield of MRAM devices by creating smooth, even surfaces on the magnetic tunnel junction pillars.
Implementation Method 1
conformally depositing an electrode material over a magnetic tunnel junction (MTJ) pillar
Data Source
AI summary
A method to form a semiconductor structure for a magnetoresistive random-access memory (MRAM) device where the material for the top electrode and the bottom electrode is deposited in a single process. The method includes conformally depositing an electrode material over a magnetic tunnel junction (MTJ) pillar, under the MTJ pillar, around a spacer encapsulating and extending above the MTJ pillar. The method includes recessing the electrode material to form a thinner portion of the electrode material over the MTJ pillar. The thinner portion of the electrode material forms a thinner portion of the electrode material over the MTJ pillar that is a top electrode. The portion of the electrode material under the MTJ pillar forms a bottom electrode that is thicker than the top electrode.