Multilayer SOT Electrode Etching via Resistivity Segmentation
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Solution Overview
Problem
Legacy MRAM manufacturing processes face challenges in precisely etching spin-orbit torque (SOT) electrodes due to their thinness, leading to over-etching and increased interconnect resistance, which affects the operating efficiency of MRAM devices.
Innovation Solution
Implementing a multilayer SOT electrode with a low resistivity top layer and a high resistivity bottom layer, where the high resistivity layer acts as an etch stop, allowing for precise etching and maintaining a low impedance interconnect to the magnetic free layer, enabling efficient spin current generation and bidirectional switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thin SOT electrode is used to reduce interconnect resistance, then the operating efficiency is improved, but the etching precision deteriorates leading to over-etching
Solution Approach 1:
The SOT electrode is segmented into multiple layers with different resistivity values. The first SOT electrode layer has lower resistivity than the second layer, allowing the thin first layer to provide low interconnect resistance while the thicker second layer serves as an etch stop to prevent over-etching during manufacturing processes.
Solution Approach 2:
Different regions of the SOT electrode structure are assigned different electrical resistivity properties. The first layer (adjacent to the magnetic free layer) has lower resistivity to minimize interconnect resistance and improve spin current generation, while the second layer has higher resistivity to provide etching protection. This local differentiation of electrical properties resolves the contradiction between low resistance and etching precision.
2Productivity
If the SOT electrode is made thinner to reduce resistance, then the operating efficiency is enhanced, but the manufacturing yield decreases due to over-etching
Solution Approach 1:
The SOT electrode is divided into multiple layers where the first thin layer provides low resistance for high operating efficiency, while the second thicker layer provides etching protection to maintain manufacturing yield. This segmentation allows both conflicting requirements to be satisfied simultaneously.
Solution Approach 2:
The SOT electrode uses a composite structure with layers of different materials or material compositions having distinct resistivity characteristics. This composite approach enables the structure to exhibit both low overall resistance (through the conductive first layer) and high etching resistance (through the protective second layer), thereby improving both operating efficiency and manufacturing yield.
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 relaxes etching constraints, improves manufacturing yield, and enhances the operating efficiency of MRAM devices by ensuring accurate etching and maintaining low interconnect resistance while allowing for repeatable bidirectional switching of magnetic polarity.
Implementation Method 1
For in-plane polarized magnetic films, electron spin currents arising from the spin-Hall effect (SHE) within heavy metal has been shown to apply spin-transfer torques to a magnet.
Implementation Method 2
Multi-layer spin orbit torque electrodes for perpendicular magnetic random access memory
Data Source
AI summary
Embodiments herein relate to a system, apparatus, and/or process for producing a spin orbit torque (SOT) electrode that includes a first layer with a first side to couple with a free layer of a magnetic tunnel junction (MTJ) and a second layer coupled with a second side of the first layer opposite the first side, where a value of an electrical resistance in the first SOT layer is lower than a value of an electrical resistance in the second SOT layer and where a current applied to the SOT electrode is to cause current to preferentially flow in the first SOT layer to cause a magnetic polarization of the free layer to change directions. During production of the SOT electrode, the second layer may act as an etch stop.