Diamond-Shaped MRAM Pillars for Void-Free Dielectric Gapfill
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Solution Overview
Problem
Conventional MRAM devices face challenges in dielectric gapfill between memory cell pillars, leading to void formation that can cause shorts during metallization due to the use of straight vertical sidewalls in conventional memory cell pillars.
Innovation Solution
The fabrication of MRAM devices with diamond shaped memory cell pillars that have a tapered profile, allowing for void-free dielectric gapfill by employing different encapsulation layers and low aspect ratio inter-pillar spaces, achieved through a method that builds pillars from the bottom-up, using a combination of interlayer dielectrics and encapsulation layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional straight vertical sidewalls are used in memory cell pillars, then fabrication is simpler, but dielectric gapfill creates voids leading to shorts
Solution Approach 1:
The patent applies asymmetry by transitioning from symmetric straight vertical sidewalls to asymmetric diamond-shaped sidewalls with specific taper angles (e.g., 15-45 degrees). This asymmetric geometry creates wider gaps at the top and bottom of pillars, enabling complete dielectric filling without voids while maintaining fabrication feasibility through controlled epitaxial growth processes.
Solution Approach 2:
The patent changes the geometric parameters of the pillar sidewalls by introducing taper angles and diamond-shaped profiles. This parameter modification transforms the gapfill process by creating optimal spacing that prevents void formation, thereby improving reliability without significantly complicating the manufacturing process.
2Reliability
If diamond shaped profile is used, then dielectric gapfill is improved without voids, but fabrication complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming the diamond-shaped pillar profile through controlled epitaxial growth before the dielectric gapfill process. This preliminary geometric preparation ensures that subsequent dielectric deposition automatically fills gaps completely without voids, simplifying the overall process by eliminating the need for complex void-prevention techniques during gapfill.
Solution Approach 2:
The patent replaces complex mechanical void-prevention mechanisms with a geometric solution. Instead of using complex gapfill process control or additional structural elements to prevent voids, the diamond-shaped profile inherently guides complete dielectric filling through its geometry, reducing fabrication complexity.
3Ease of manufacture
If uniform encapsulation layers are used, then fabrication is simpler, but adhesion and capacitance control is limited
Solution Approach 1:
The patent applies local quality by implementing different encapsulation layer configurations at different locations along the pillar height. Specifically, different dielectric materials or thicknesses are applied to the bottom versus top portions of the diamond-shaped pillars, enabling localized optimization of adhesion and capacitance properties while maintaining overall manufacturing simplicity.
Data Source
AI summary
MRAM device structures and techniques for fabrication thereof with improved dielectric gapfill and individually configurable bottom and top encapsulation layers are provided. In one aspect, an MRAM device includes: memory cell pillars having a diamond shaped profile; and an interlayer dielectric fully filling gaps between the memory cell pillars. For instance, each of the memory cell pillars can include a reference layer, a free layer, a tunnel barrier between the reference layer and the free layer, a first encapsulation layer alongside the reference layer, and a second encapsulation layer alongside the free layer; and an interlayer dielectric fully filling gaps between the memory cell pillars. Optionally, the first encapsulation layer can include an oxide dielectric material, and the second encapsulation layer can include a nitride dielectric material. A method of fabricating the present MRAM devices is also provided.