SOT-MTJ MRAM Hard-Mask Fabrication for Compact Field Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current magnetoresistive random access memory (MRAM) devices face issues such as high chip area, high cost, high power consumption, and sensitivity to temperature variations, limiting their effectiveness in magnetic field sensor applications.
Innovation Solution
A method for fabricating MRAM devices involves forming a magnetic tunneling junction (MTJ) on a substrate, adding a spin orbit torque (SOT) layer, and creating inter-metal dielectric (IMD) layers, followed by a series of patterning and etching processes using multiple hard masks to optimize device structure and minimize surface damage during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional MRAM device structures are used, then magnetic field sensing function is achieved, but chip area is large
Solution Approach 1:
The device is segmented into distinct functional layers (MTJ layer, SOT layer, electrode layers) with each performing a specific function. The MTJ layer provides magnetic field sensing while the SOT layer enables efficient magnetization switching, allowing compact integration without compromising sensing reliability
Solution Approach 2:
The patent transitions from planar device structures to vertically stacked three-dimensional architecture. By stacking the MTJ layer, SOT layer, and electrode layers vertically, the device achieves high functionality in a reduced footprint, directly addressing the chip area reduction goal
2Ease of manufacture
If conventional MRAM fabrication processes are used, then device functionality is achieved, but manufacturing cost is high
Solution Approach 1:
The patent combines multiple functions into integrated layers: the MTJ layer simultaneously serves as both the magnetic tunneling junction for sensing and the magnetic storage element, while the SOT layer integrates both spin-orbit torque generation and magnetization switching functions. This functional integration reduces the number of separate fabrication steps and material depositions, lowering manufacturing cost while maintaining structural precision
Solution Approach 2:
The patent optimizes fabrication parameters including layer thicknesses (e.g., MTJ layer thickness of 5-20 nm, SOT layer thickness of 10-50 nm), deposition temperatures, and annealing conditions to achieve precise magnetic and electrical properties. By carefully controlling these parameters, the device achieves high manufacturing precision using standard semiconductor fabrication processes
3Use of energy by moving object
If conventional MRAM devices are used, then data storage function is achieved, but power consumption is high
Solution Approach 1:
The patent replaces conventional current-through-MTJ switching mechanisms with spin-orbit torque (SOT) switching. Instead of passing high current directly through the MTJ stack (which consumes significant power), the SOT layer generates spin currents that exert torque on the MTJ magnetization remotely. This mechanical-to-spin torque substitution dramatically reduces power consumption while maintaining reliable magnetization switching and data retention
Solution Approach 2:
The SOT layer acts as an intermediary between the electrical input and the MTJ magnetization state. Rather than directly switching the MTJ with high current, the electrical current first generates spin polarization in the SOT layer, which then mediates the magnetization switching of the MTJ. This intermediary mechanism reduces energy dissipation and power consumption while achieving reliable data storage
4Measurement precision
If conventional magnetic field sensors are used, then magnetic field detection is achieved, but sensitivity is limited and temperature sensitivity is high
Solution Approach 1:
The patent employs composite material structures including CoFeB/CoFeP/MgO stacks in the MTJ layer, where different materials contribute complementary properties: CoFeB and CoFeP provide high spin polarization and low damping for enhanced sensitivity, while MgO provides high barrier quality and thermal stability. This composite structure achieves high magnetic field sensitivity while maintaining temperature stability
Solution Approach 2:
The patent optimizes critical parameters including the thickness and composition of the MTJ barrier layer (5-20 nm), the SOT layer material composition, and the magnetic anisotropy energy density. By carefully tuning these parameters, the device achieves high sensitivity to magnetic field changes while the magnetic tunneling junction's inherent resistance change provides temperature compensation, reducing sensitivity to temperature variations
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 reduces chip area, lowers costs, and enhances sensitivity while minimizing temperature effects, resulting in an improved MRAM device with better performance and reliability.
Implementation Method 1
a magnetic tunneling junction (MTJ) on a substrate
Implementation Method 2
forming a spin orbit torque (SOT) layer on the MTJ
Data Source
AI summary
A method for fabricating a semiconductor device includes the steps of forming a magnetic tunneling junction (MTJ) on a substrate, forming a spin orbit torque (SOT) layer on the MTJ, forming an inter-metal dielectric (IMD) layer around the MTJ and the SOT layer, forming a first hard mask on the IMD layer, forming a semiconductor layer on the first hard mask, and then patterning the first hard mask.