Embedded MRAM Top Contact Structure for Short-Circuit Isolation
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Solution Overview
Problem
Current manufacturing processes for forming top contacts in magnetoresistive random-access memory (MRAM) devices lead to short circuits between ferromagnetic layers and/or electrodes, causing reliability and performance issues, and limit the integration of MRAM structures into advanced node technologies due to increased stack height and shadowing effects during etching.
Innovation Solution
A MRAM device structure with a top contact design that includes a first portion directly above the magnetic tunnel junction (MTJ) stack surrounded by a metal oxide layer, and a second portion partially above the metal oxide layer, along with a via contact design that ensures coplanar surfaces and alignment with conductive vias, using conformal dielectric layers and selective deposition of metal oxide to prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the top electrode is made tall to prevent short circuits, then reliability is improved, but the total height of the MTJ stack increases creating challenges for shadowing effects in ion-beam-etching and high aspect ratio for reactive-ion-etching
Solution Approach 1:
A conformal dielectric layer is introduced as an intermediary between the top electrode and the top contact. This dielectric layer extends laterally beyond the top electrode, creating an isolation barrier that prevents short circuits without requiring the top electrode to be taller. The intermediary layer thus provides the necessary electrical isolation while maintaining a compact stack height suitable for advanced node technologies.
2Reliability
If the top electrode is made tall to prevent short circuits, then reliability is improved, but this places limits on the fitting of MTJ stacks into narrow intermetal dielectric spacing
Solution Approach 1:
The conformal dielectric layer acts as an intermediary isolation structure that provides lateral coverage beyond the top electrode edges. This allows the top contact to be formed at a lower elevation without risking short circuits, thereby enabling tighter intermetal dielectric spacing while maintaining reliable electrical isolation. The mediator layer effectively decouples the isolation function from the electrode height.
3Ease of manufacture
If conventional top contact formation is used, then manufacturing simplicity is maintained, but short circuits occur between ferromagnetic layers and electrodes
Solution Approach 1:
The conformal dielectric layer is formed preliminarily before the top contact is deposited. This preliminary action of extending the dielectric layer laterally beyond the top electrode creates a pre-established isolation barrier that guides subsequent top contact formation. The top contact can then be formed using conventional processes without requiring complex adjustments, while the pre-positioned dielectric layer ensures electrical isolation is maintained.
Data Source
AI summary
Embodiments of present invention provide a method of forming a MRAM structure. The method includes forming at least one magnetic tunnel junction (MTJ) stack on top of a supporting structure; forming a conformal liner surrounding a sidewall of the MTJ stack; forming a first dielectric layer surrounding the conformal liner; selectively forming a metal oxide layer on top of the conformal liner and the first dielectric layer, the metal oxide layer having at least a first opening that exposes a top surface of the MTJ stack; and forming a top contact contacting the top surface of the MTJ stack through the first opening in the metal oxide layer. An MRAM structure formed thereby is also provided.