MRAM Seal Ring Peeling Prevention via MTJ Layer
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Solution Overview
Problem
Current STT-MRAM devices suffer from seal ring peeling defects due to via (WT) bar punch through to the underlying metallization layer, which is challenging to prevent with existing etch tuning methods.
Innovation Solution
Replacing the WT bar design with a magnetic tunnel junction (MTJ) layer in the logic region of the MRAM device, forming a metal-filled via and a tunnel junction via with copper, and using a magnetic shield in the seal ring region to prevent seal ring peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If WT bar design is used to connect metallization layer, then electrical connection is achieved, but seal ring peeling defect occurs due to etch punch through
Solution Approach 1:
The patent removes the WT (via) bar structure from the seal ring area entirely. Instead of using a traditional via bar to make the electrical connection, the invention extracts this problematic element and replaces it with an MTJ-based solution that eliminates the etch punch through issue while maintaining the necessary electrical connectivity function.
Solution Approach 2:
The patent changes the fundamental parameter of the connection structure by replacing the WT bar material and geometry with an MTJ stack. This parameter change transforms the connection method from a simple metal via bar to a complex magnetic tunnel junction structure that is inherently resistant to etch punch through while providing the required electrical connection.
2Reliability
If etch tuning is adjusted to prevent punch through, then seal ring protection is improved, but landing precision in logic area deteriorates
Solution Approach 1:
The patent applies local quality by creating different structures for different regions: the seal ring area uses an MTJ-based connection structure that is resistant to etch punch through, while the logic area maintains the traditional WT bar structure optimized for landing precision. This regional differentiation allows each area to have the structure best suited to its specific requirements without compromising the other.
3Ease of manufacture
If traditional WT bar structure is used, then manufacturing process is simple, but seal ring peeling defect occurs
Solution Approach 1:
The patent employs composite materials by replacing the simple metal WT bar with a multi-layer MTJ stack consisting of ferromagnetic layers, insulating tunnel barriers, and capping layers. This composite structure provides both the electrical connection function and the protective function against seal ring peeling, overcoming the limitations of simple metal structures while remaining compatible with existing semiconductor manufacturing processes.
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 approach effectively prevents seal ring peeling and WT punch through, optimizing the seal ring area and ensuring reliable operation of MRAM devices without requiring a reticle change or increasing manufacturing costs.
Implementation Method 1
forming a MTJ layer in the logic region which solves the seal ring peeling issue due to WT etch punch through to the M3 or M5
Data Source
AI summary
A method for forming a MRAM device free of seal ring peeling defect, and the resulting device, are provided. Embodiments include forming magnetic tunnel junction (MTJ) over a metallization layer in a seal ring region of an MRAM device; forming a metal filled via connecting the MTJ and the metallization layer; forming a tunnel junction via over the MTJ; and forming a top electrode over the tunnel junction via.