MRAM MTJ Element Lower Electrode Contact Plug Seam Void
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Solution Overview
Problem
As semiconductor devices, such as MRAM, are downscaled, the increasing aspect ratio of contact holes leads to seams or voids in contact plugs, which can cause degradation in the characteristics of MTJ elements due to stepped parts formed in the MTJ elements when they are formed on these defective plugs.
Innovation Solution
The MRAM configuration includes MTJ elements formed above an interlayer dielectric film, with a lower electrode connecting the MTJ element to a contact plug and a sidewall film covering the side surface of the MTJ element, ensuring it does not overlap with the contact plugs and maintaining electrical connection, thus avoiding the negative impact of seams or voids in the contact plugs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If contact plugs are made with higher aspect ratio to accommodate downscaling, then integration density is improved, but seams or voids occur in contact plugs leading to stepped parts in MTJ elements
Solution Approach 1:
A lower electrode is introduced as an intermediary component between the contact plug and the MTJ element. This lower electrode serves as a mediator that receives the electrical connection from the contact plug and provides a stable base for the MTJ element, thereby isolating the MTJ element from the defects (seams or voids) in the contact plug and preventing stepped parts from forming in the MTJ element.
2Device complexity
If MTJ elements are formed directly on contact plugs to maintain electrical connection, then device complexity is reduced, but stepped parts are formed in MTJ elements causing characteristic degradation
Solution Approach 1:
The lower electrode acts as an intermediary layer that decouples the MTJ element from the contact plug. This allows the MTJ element to be formed on a flat, stable surface (the lower electrode) rather than directly on the defective contact plug, preventing stepped parts while maintaining the electrical connection path through the lower electrode to the contact plug.
Solution Approach 2:
The electrical connection path is segmented into two distinct parts: the contact plug that provides external electrical access, and the lower electrode that provides a stable foundation for the MTJ element. This segmentation allows each component to be optimized independently - the contact plug for electrical connection and the lower electrode for structural stability - thereby preventing the transmission of defects from the contact plug to the MTJ element.
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 configuration prevents the formation of stepped parts in the MTJ elements, thereby suppressing degradation and allowing the MRAM to maintain normal operation and performance even during downscaling, ensuring reliable data storage and retrieval.
Implementation Method 1
stores therein data by a change in a magnetic resistance caused by spin-polarized tunneling
Implementation Method 2
The MTJ element can be switched into a low resistance state or a high resistance state depending on the magnetization orientations of the two ferromagnetic layers
Implementation Method 3
the spin-transfer torque writing has advantages in higher integration, lower power consumption, and higher performance because of the property of a spin-transfer torque device that a spin injection current is smaller in an amount for magnetization reversal
Data Source
AI summary
A memory includes a semiconductor substrate. Cell transistors are on the substrate. Contact plugs each of which is buried between the adjacent cell transistors and electrically connected to a diffusion layer between the adjacent cell transistors. An interlayer dielectric film buries gaps between the contact plugs. A storage element is provided not above the contact plugs but above the interlayer dielectric film. A sidewall film covers a part of a side surface of the storage element, and is provided to overlap with one of the contact plugs as viewed from above a surface of the semiconductor substrate. A lower electrode is provided between a bottom of the storage element and the interlayer dielectric film and between the sidewall film and one of the contact plugs, and electrically connects the storage element to one of the contact plugs.