MTJ Stack Fabrication for MRAM Chip Area Reduction
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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 semiconductor device is fabricated using a magnetic tunneling junction (MTJ) stack with a pinned layer, barrier layer, and free layer, where the critical dimension of the free layer differs from that of the pinned layer, and a cap layer formation process to create multiple MTJs with optimized dimensions and spacers for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic field sensor technologies (AMR sensors, GMR sensors, MTJ sensors) are used, then magnetic field sensing function is achieved, but chip area is large and cost is high
Solution Approach 1:
The sensor structure is divided into multiple MTJ stacks arranged in a specific pattern, with each stack contributing to the overall sensing function. The segmented design allows for compact integration while maintaining sensing capability through the collective response of multiple junctions.
Solution Approach 2:
Multiple functional layers are nested within a compact vertical structure, with MTJ stacks integrated into a multi-layered sensor architecture. The pinned layer, barrier layer, and free layer are nested in sequence, enabling high-density integration in a small footprint.
2Measurement precision
If conventional magnetic field sensor technologies are used, then magnetic field sensing function is achieved, but power consumption is high
Solution Approach 1:
The sensor utilizes changes in magnetic parameters (magnetization direction, resistance states) to detect external magnetic fields without requiring continuous power input. The MTJ structure maintains its magnetic states passively, consuming minimal power for readout operations.
3Measurement precision
If conventional magnetic field sensor technologies are used, then magnetic field sensing function is achieved, but sensitivity is limited and temperature stability is poor
Solution Approach 1:
The sensor employs composite magnetic structures with multiple layers having different magnetic properties (pinned layer with fixed magnetization, free layer with variable magnetization). This composite approach enhances sensitivity while the symmetric configuration compensates for temperature-induced variations.
Solution Approach 2:
The MTJ structure utilizes asymmetric magnetic layer configurations where the pinned layer and free layer have different magnetic characteristics, enabling enhanced sensitivity to external fields while the overall symmetric device layout provides temperature compensation.
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 approach reduces chip area, cost, and power consumption while enhancing sensitivity and temperature stability, resulting in a more efficient MRAM device for magnetic field sensing applications.
Implementation Method 1
Magnetoresistance (MR) effect has been known as a kind of effect caused by altering the resistance of a material through variation of outside magnetic field
Data Source
AI summary
A method for fabricating semiconductor device includes the steps of first forming a magnetic tunneling junction (MTJ) stack on a substrate, in which the MTJ stack includes a pinned layer on the substrate, a barrier layer on the pinned layer, and a free layer on the barrier layer. Next, part of the MTJ stack is removed, a first cap layer is formed on a sidewall of the MTJ stack, and the first cap layer and the MTJ stack are removed to form a first MTJ and a second MTJ.