MRAM Top Electrode Direct Coupling via Spacer and Etch Stop
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Solution Overview
Problem
Conventional magnetoresistive random-access memory (MRAM) cells have a large height due to the use of contacts or vias between electrodes, which is not compatible with the vertical spacing between adjacent metal layers, and this can lead to shorting issues and increased manufacturing costs.
Innovation Solution
The solution involves directly coupling the top electrode to the overlying metal line without a via or contact, using a wide sidewall spacer and an overhanging etch stop layer to prevent metal overflow and reduce the overall height of the MRAM cell, thereby aligning it with the vertical spacing between metal layers and minimizing the risk of shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contacts or vias are used between electrodes in conventional MRAM cells, then electrical connection is achieved, but the cell height increases and becomes incompatible with vertical spacing between metal layers
Solution Approach 1:
The patent removes the via or contact structure from between the top electrode and the overlying metal line. By directly coupling the top electrode to the metal line without an intermediate via, the unnecessary height component is extracted from the cell structure, reducing overall cell height while maintaining electrical connectivity.
Solution Approach 2:
The patent merges the top electrode directly with the overlying metal line by eliminating the via structure. This direct coupling combines what were previously separate components (electrode and metal line connected via via) into a more integrated structure, reducing the vertical distance and improving compatibility with metal layer spacing.
2Reliability
If via or contact structures are used, then electrical connection is established, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and removes the via or contact structure from the manufacturing process. By eliminating this intermediate component, the number of fabrication steps is reduced, manufacturing complexity is lowered, and production costs are decreased, while the direct coupling maintains the necessary electrical connection.
Solution Approach 2:
The patent performs preliminary planning to directly couple the top electrode with the metal line in the initial structure design, avoiding the need for subsequent via formation steps. This preliminary action of designing a direct interface eliminates the need for additional oxidation prevention layers and other protective coatings that would be required for via structures.
3Reliability
If taller cell structure with vias is used, then electrical connection is achieved, but risk of shorting between adjacent metal layers increases
Solution Approach 1:
The patent removes the via structure that creates a tall vertical path through the cell. By extracting this height-increasing component and replacing it with a direct horizontal coupling, the vertical distance that could potentially lead to shorting is eliminated, reducing the risk of electrical interference between adjacent metal layers.
Solution Approach 2:
The patent transitions from a vertical connection approach (via extending upward from the electrode) to a horizontal or planar connection approach (direct coupling at the same vertical level). This dimensional change from vertical to lateral coupling reduces the vertical height and the associated shorting risk while maintaining electrical connectivity.
Data Source
AI summary
Some embodiments relate to a method for manufacturing a magnetoresistive random-access memory (MRAM) cell. The method includes forming a spacer layer surrounding at least a magnetic tunnel junction (MTJ) layer and a top electrode of the MRAM cell; etching the spacer layer to expose a top surface of the top electrode and a top surface of a spacer formed by the spacer layer; forming an upper etch stop layer over the top electrode top surface and the spacer top surface; and forming an upper metal layer in contact with the top electrode top surface of the MRAM cell. A width of the upper etch stop layer is greater than a width of a bottom surface of the upper metal layer.