MRAM Landing Pad Interconnect for Vertical Resistance Reduction
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Solution Overview
Problem
Conventional MRAM devices face challenges in scaling and embedding due to current-carrying restrictions on narrow wires, leading to increased patterning complexity and potential damage to prior interconnect structures during fabrication.
Innovation Solution
The formation of a landing pad structure in an intermediary wiring layer that extends through multiple interconnect levels, connecting the magnetic tunnel junction (MTJ) to underlying conductors without exposing them, allowing for customized patterning and reduced vertical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional MRAM devices are fabricated with narrow wires to decrease device and wiring sizes, then device scaling is improved, but current-carrying restrictions increase and patterning complexity increases
Solution Approach 1:
The patent transitions from planar 2D interconnect architecture to a 3D vertical architecture by forming landing pads that extend through multiple interconnect levels (first, second, and third wiring layers). This dimensional change allows current to flow vertically through the landing pad structure rather than horizontally through narrow wires, resolving the current-carrying capacity limitation while maintaining scaled device footprint.
Solution Approach 2:
The interconnect structure is segmented into distinct functional regions: lower wiring layer conductors, intermediary wiring layer landing pads, and upper wiring layer connections. This segmentation allows each layer to be optimized independently - the landing pads provide robust vertical current paths while the upper/lower wiring layers handle lateral routing, reducing overall patterning complexity despite multi-layer fabrication.
2Volume of moving object
If conventional MRAM devices use narrow wires for interconnects, then device scaling is improved, but current-carrying capacity deteriorates
Solution Approach 1:
The patent resolves the current-carrying capacity limitation by transitioning from horizontal 2D wire routing to vertical 3D landing pad structures. The landing pads extend through multiple interconnect levels providing robust vertical current paths with larger cross-sectional area, enabling sufficient current flow to switch MRAM cell states while maintaining scaled device footprint.
Solution Approach 2:
The landing pads act as intermediary structures between the lower wiring layer conductors and upper wiring layer connections. These intermediary elements provide the necessary current-carrying capacity bridge, allowing current to flow from lateral wires through vertical landing pads to reach the MTJ structure without requiring narrow wires to carry excessive current distances.
3Reliability
If via is formed on top of MTJ to couple MTJ to upper metallization line in conventional MRAM, then connection is established, but risk of damaging prior interconnect structures increases
Solution Approach 1:
The landing pad structure is formed in advance during the interconnect fabrication sequence, extending through multiple wiring layers before the final upper wiring layer patterning. This preliminary formation establishes robust connection paths early in the process, allowing subsequent MTJ and contact formation to proceed without risking damage to previously formed interconnect structures.
Solution Approach 2:
The landing pad structure is nested within the interconnect stack, with the conductive material embedded in the intermediary wiring layer and extending vertically. This nested configuration protects the connection structure within the dielectric matrix of the interconnect layers, shielding it from damage during subsequent processing steps while maintaining electrical connectivity.
Data Source
AI summary
A magnetic random access memory (MRAM) device includes a conductor disposed in an insulating material of a lower wiring layer, a magnetic tunnel junction (MTJ) structure formed in an upper wiring layer, and a landing pad formed in an intermediary wiring layer between the lower and upper wiring layers, the landing pad extending from a top surface of the conductor to a height above the intermediary wiring layer, wherein the landing pad connects the MJT structure to the conductor.