MRAM Structure With Stepped Top Electrode for MTJ Stress Control
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Solution Overview
Problem
As MRAM structures are scaled down, there is a need for improved designs that can store more digits in a smaller area while maintaining the integrity of the magnetic tunnel junction (MTJ) and reducing stress on the top electrode, which is critical for reliable operation.
Innovation Solution
The MRAM structure features a top electrode with a larger upper portion and a smaller lower portion, where the upper portion connects to the lower portion, and the widths of the bottom electrode and MTJ are matched with the lower portion, allowing for a two-step formation process that reduces stress on the MTJ and prevents gaps between adjacent MRAMs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the top electrode is made with a larger width to improve electrical contact and reduce resistance, then the electrical performance is improved, but the stress on the MTJ increases and structural integrity deteriorates
Solution Approach 1:
The top electrode is segmented into two distinct portions: a first top electrode portion with a first width and a second top electrode portion with a second width. This segmentation allows each portion to serve different functions - the first portion provides electrical contact while the second portion minimizes stress on the MTJ, thereby resolving the contradiction between electrical reliability and structural integrity.
2Productivity
If MRAM dimensions are scaled down to store more digits in smaller area, then storage density is improved, but manufacturing precision requirements increase and gaps between adjacent MRAMs may form
Solution Approach 1:
The top electrode is designed with different widths at different locations: the first top electrode portion has a first width and the second top electrode portion has a second width. This local quality variation allows the structure to maintain proper dimensions for high-density storage while providing manufacturing tolerance that prevents gaps between adjacent MRAMs, thus resolving the contradiction between storage density and manufacturing precision.
Data Source
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AI summary
A magnetoresistive random access memory (MRAM) structure includes a magnetic tunnel junction (MTJ), and a top electrode which contacts an end of the MTJ. The top electrode includes a top electrode upper portion and a top electrode lower portion. The width of the top electrode upper portion is larger than the width of the top electrode lower portion. A bottom electrode contacts another end of the MTJ. The top electrode, the MTJ and the bottom electrode form an MRAM.