MRAM Integration with Optimized MTJ Side Components
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Solution Overview
Problem
Current Magnetoresistive Random Access Memory (MRAM) integration techniques face challenges in scaling with advancing device technologies, as the height of layers in semiconductor devices shrinks, making it difficult to accommodate MTJ bit cells and their components within the reduced dimensions, leading to potential extrusion of metal islands and increased stress on cap layers.
Innovation Solution
Design and fabrication of MRAM elements with optimized MTJ side components, such as reduced metal line and via heights, aligned bottom electrodes, and modified cap layers, to match the scaling demands of logic elements, allowing for efficient integration within shrinking device dimensions, including the use of fewer cap layers to maintain stability and create more space for MTJ structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional MRAM integration techniques are used, then MTJ bit cells can be formed with standard dimensions, but the height of MTJ structures exceeds the reduced layer height available in advanced technology nodes
Solution Approach 1:
The patent applies dimensionality change by transitioning from a planar integration approach to a three-dimensional stacked architecture. Multiple MTJ bit cells are vertically stacked within the same footprint, allowing the overall system to accommodate more storage elements without increasing the lateral dimensions. This vertical stacking resolves the contradiction by effectively reducing the height requirement per individual MTJ structure while maintaining total storage capacity.
Solution Approach 2:
The patent implements nesting by placing multiple MTJ bit cells within each other in a vertical stack configuration. Each MTJ cell is nested within the same lateral footprint but at different vertical levels, separated by interlayer dielectric materials. This nesting approach allows the integration of multiple MTJ structures without increasing the overall device footprint, effectively addressing the height constraint in advanced technology nodes.
2Productivity
If device dimensions are scaled down to advanced technology nodes, then device density increases, but stress on cap layers increases and metal islands may be extruded
Solution Approach 1:
The patent applies segmentation by dividing the continuous cap layer into discrete, localized cap layers positioned between individual MTJ bit cells or small groups of cells. Instead of using a single continuous cap layer across the entire device, the cap layers are segmented and placed only where needed to provide mechanical support and stress relief. This segmentation reduces the overall stress on cap layers while maintaining device density at advanced technology nodes.
Solution Approach 2:
The patent implements local quality by varying the cap layer configuration based on local stress requirements. Cap layers are strategically positioned in regions where stress concentration occurs, such as between stacked MTJ cells or near metal interconnect regions. The absence or reduction of cap layers in other regions allows for better space utilization. This localized approach to cap layer placement maintains reliability by providing stress relief exactly where needed without compromising overall device density.
Data Source
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AI summary
A magnetoresistive random-access memory (MRAM) integration compatible with shrinking device technologies includes a magnetic tunnel junction (MTJ) formed in a common interlayer metal dielectric (IMD) layer with one or more logic elements. The MTJ is connected to a bottom metal line in a bottom IMD layer and a top via connected to a top IMD layer. The MTJ substantially extends between one or more bottom cap layers configured to separate the common IMD layer and the bottom IMD layer and one or more top cap layers configured to separate the common IMD layer and the top IMD layer. The MTJ can include a top electrode to connect to the top via or be directly connected to the top via through a hard mask for smaller device technologies. The logic elements include vias, metal lines, and semiconductor devices.