Grain-Refined Magnetic Layer for TMR Sensor Resistance Uniformity
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Solution Overview
Problem
Tunneling magnetoresistive sensors face issues with high surface roughness in ferromagnetic layers, leading to increased thickness of barrier layers and subsequent unit-to-unit variation in tunneling resistance, which degrades performance characteristics.
Innovation Solution
Incorporating a grain refining agent, such as boron, niobium, or hafnium, into the magnetic layer to achieve a grain-refined surface with reduced roughness, which in turn improves the conformality of the barrier layer and reduces device-to-device variation in magnetoresistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the barrier layer thickness is increased to ensure freedom from holes or defects, then electrical breakdown is prevented, but surface roughness is replicated and tunneling resistance variation increases
Solution Approach 1:
The ferromagnetic layer is prepared in advance with a controlled grain structure and optimized surface properties before the barrier layer is deposited. This preliminary preparation ensures that the barrier layer can be applied at optimal thickness without suffering from excessive roughness, preventing both electrical breakdown and resistance variation simultaneously
2Ease of manufacture
If the ferromagnetic layer surface roughness is high, then magnetic material deposition is easier, but barrier layer conformality deteriorates and performance decreases
Solution Approach 1:
The surface roughness parameter of the ferromagnetic layer is optimized to an intermediate value that balances ease of deposition with barrier layer conformality. The grain structure parameters are also controlled to achieve the desired surface characteristics without excessive roughness
Data Source
AI summary
A magnetic sensor includes a magnetic layer comprising magnetic material and a grain refining agent. The magnetic layer having a grain-refined magnetic layer surface. A layer adjacent the magnetic layer has a layer surface that conforms to the grain-refined magnetic layer surface.