Ru Hard Mask for MRAM Data Density
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Solution Overview
Problem
Magnetic random-access memory (MRAM) technologies face challenges in achieving high data density and reducing parasitic electrical resistance, particularly due to the limitations of existing hard mask layers in magnetoresistive tunnel junction (MTJ) elements.
Innovation Solution
The use of a Ruthenium (Ru) hard mask layer in MRAM structures, which does not form insulating oxides and is highly resistant to ion etching and chemical mechanical polishing, allowing for thinner layers and reduced shadowing effects, thereby enabling closer spacing of memory elements and increased data density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional hard mask layers are used in MTJ elements, then the structure provides sufficient etch resistance, but the layers must be thicker which increases parasitic electrical resistance and limits data density
Solution Approach 1:
The patent changes the material parameter of the hard mask layer from traditional materials (such as TaN or SiN) to Ruthenium (Ru), which has fundamentally different properties: Ru provides sufficient ion etch resistance while being highly conductive and not forming insulating oxides. This material substitution allows the hard mask layer to be made thinner, reducing parasitic resistance while maintaining etch protection during fabrication processes.
2Reliability
If traditional hard mask layers are used in MTJ elements, then the structure provides adequate protection during fabrication, but the thicker layers create shadowing effects that prevent closer spacing of memory elements
Solution Approach 1:
By changing the material parameter to Ruthenium, the hard mask layer achieves high etch resistance with a thinner thickness. This reduces the shadowing effect during ion etching processes, allowing ions to reach the bottom of narrower trenches more effectively. Consequently, memory elements can be spaced closer together, increasing data density while maintaining adequate fabrication protection.
3Object-affected harmful factors
If Ru hard mask layer is used to reduce thickness and parasitic resistance, then data density increases, but the layer must maintain sufficient resistance to ion etching and chemical mechanical polishing
Solution Approach 1:
The patent selects Ruthenium based on its unique combination of properties: high ion etch resistance, resistance to chemical mechanical polishing, and excellent electrical conductivity. By changing the material parameter to Ru, the layer can be made thinner to reduce parasitic resistance and enable closer element spacing, while Ru's inherent resistance to ion etching and CMP processes ensures sufficient protection is maintained during fabrication.
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
The Ru hard mask layer enhances data density by allowing memory elements to be spaced closer together while maintaining low parasitic resistance, ensuring efficient data storage and reduced electrical interference.
Implementation Method 1
Ruthenium (Ru) hard mask layer in MRAM structures, which does not form insulating oxides and is highly resistant to ion etching
Implementation Method 2
highly resistant to ion etching and chemical mechanical polishing
Data Source
AI summary
A magnetic memory element has a Ru hard mask layer. The use of Ru advantageously allows for closer spacing of adjacent magnetic memory elements leading to increased data density. In addition, the use of Ru as a hard mask reduces parasitic electrical resistance by virtue of the fact that Ru does not oxidize in ordinary manufacturing environments. The magnetic memory element can be formed by depositing a plurality of memory element layers, depositing a Ru hard mask layer, depositing a RIEable layer over the Ru hard mask layer, and forming a photoresist mask over the hard mask layer. A reactive ion etching can be performed to transfer the image of the photoresist mask onto the RIEable layer to form a RIEable mask. An ion etching can then be performed to transfer the image of the RIAable mask onto the underlying Ru hard mask and underlying memory element layers.