Multi-Tapered MRAM Top Electrode for ILD Void Prevention
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Solution Overview
Problem
In high-performance magnetoresistive random access memory (MRAM) devices based on perpendicular magnetic tunnel junction (MTJ) structures, the challenge is to achieve well-defined interfaces and effective interface control to prevent voids in the interlevel dielectric (ILD) between pillars, which can lead to shorts.
Innovation Solution
The implementation of a magnetoresistive random access memory (MRAM) device with a pillar structure featuring a bottom electrode, a magnetic tunnel junction (MTJ) with a reference layer, a free layer, and a tunnel barrier, and a top electrode with multiple recessed tiers. Each tier of the top electrode has a smaller footprint than the tier below it, reducing the risk of voids in the ILD gapfill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flat top electrodes are used in MTJ pillar structures, then the manufacturing process is simpler, but voids form in the interlevel dielectric (ILD) between pillars leading to shorts
Solution Approach 1:
The top electrode is divided into multiple tiers (first tier, second tier, third tier) with progressively smaller footprints. This segmentation creates a stepped profile that eliminates voids in the ILD gapfill by providing a tapered transition zone, thereby preventing shorts while maintaining manufacturing feasibility through sequential deposition and etching steps.
2Reliability
If the top electrode footprint is reduced to improve dielectric isolation, then ILD voids are reduced, but the contact area for electrical connection decreases
Solution Approach 1:
The top electrode structure transitions from a two-dimensional flat planar design to a three-dimensional multi-tiered stepped configuration. By utilizing the vertical dimension, the electrode achieves reduced horizontal footprint for better isolation while maintaining adequate contact area through the stacked tiers, each contributing to the overall electrical connection path.
Data Source
AI summary
A magnetoresistive random access memory (MRAM) includes a pillar structure having a bottom electrode and a magnetic tunnel junction (MTJ) having a reference layer, a free layer and a tunnel barrier disposed between the reference layer and the free layer. The MTJ is disposed on the bottom electrode. A top electrode is disposed on the MTJ. The top electrode includes two or more tiers wherein each tier successively includes a smaller footprint.