MRAM MTJ Top Contact Structure With Sidewall Spacer Isolation
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Solution Overview
Problem
Current manufacturing processes for high-performance vertical magnetoresistive random-access memory (MRAM) devices face challenges in forming top contacts that can lead to shorts between ferromagnetic layers due to inadequate interface definition, resulting in reliability and performance issues.
Innovation Solution
The proposed solution involves forming a magnetic tunnel junction (MTJ) stack with a top contact surrounded by sidewall spacers, where the top surface of the first sidewall spacer is in direct contact with the top contact, and a second sidewall spacer surrounds the first spacer, using materials like silicon-nitride and other dielectric materials to prevent shorts during the formation of the top contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current manufacturing process is used to form top contact, then device complexity is reduced, but short between ferromagnetic layers occurs due to inadequate interface definition
Solution Approach 1:
The patent divides the contact formation process into multiple stages: forming sidewall spacers around the MTJ stack, creating openings through dielectric layers, and depositing conductive materials in a controlled sequence. This segmentation ensures precise interface definition between the top contact and ferromagnetic layers while preventing shorts through systematic process control.
Solution Approach 2:
The patent performs preliminary actions by first forming sidewall spacers around the MTJ stack before creating the top contact opening. This preliminary structure definition ensures that subsequent contact formation occurs at precisely controlled locations, preventing shorts between ferromagnetic layers while maintaining interface integrity.
2Manufacturing precision
If top contact is formed without sidewall spacers, then manufacturing precision is reduced, but process steps are simplified
Solution Approach 1:
The patent introduces sidewall spacers as intermediary structures that mediate between the MTJ stack and the top contact. These spacers serve as physical guides and barriers that ensure precise contact alignment with ferromagnetic layers while simplifying the overall manufacturing process by providing self-aligned reference structures.
Solution Approach 2:
The patent applies local quality by forming sidewall spacers only at specific locations around the MTJ stack where precise alignment is needed. This localized structure provides manufacturing precision at critical interfaces without adding unnecessary complexity to the entire device structure.
3Reliability
If conventional contact formation is used, then productivity is maintained, but short defects increase reducing yield
Solution Approach 1:
The patent implements beforehand cushioning by forming sidewall spacers and defining opening locations before creating the top contact. This preventive approach cushions against potential short defects by establishing physical barriers and alignment references in advance, thereby improving device yield without significantly impacting manufacturing efficiency.
Data Source
AI summary
Embodiments of present invention provide a method of forming a MRAM structure. The method includes forming a magnetic tunnel junction (MTJ) stack; forming a first dielectric layer to a level above a tunnel barrier layer of the MTJ stack, the first dielectric layer partially covering the MTJ stack with a top surface of the MTJ stack being exposed; depositing an etch-stop layer covering the top surface of the MTJ stack and a top surface of the first dielectric layer; depositing a second dielectric layer covering the etch-stop layer; forming an opening in the second dielectric layer; removing a portion of the etch-stop layer above the top surface of the MTJ stack; and forming a top contact by depositing a conductive material in the opening. An MRAM structure formed thereby is also provided.