CPP-GMR Device Work Function Control Layer
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Solution Overview
Problem
Current CPP-GMR devices face challenges with high resistance values leading to increased stray capacitance and noise, which degrade high-frequency response, and require high voltages to achieve large MR ratios, causing spin torque issues that affect magnetization direction and noise generation.
Innovation Solution
A CPP-GMR device with a spacer layer comprising a first and second nonmagnetic metal layer and an n-type semiconductor layer, where a work function control layer is introduced between these layers to control electron concentration and reduce junction resistance, allowing for a thicker semiconductor layer while maintaining low area resistivity and high MR performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the thickness of the tunnel barrier layer is reduced to lower resistance, then resistance decreases, but pinholes occur and magnetic couple increases causing noise and performance degradation
Solution Approach 1:
A nonmagnetic metal intermediate layer is introduced between the tunnel barrier layer and the magnetic layers. This intermediary layer serves multiple functions: it prevents direct magnetic coupling between the tunnel barrier and magnetic layers (reducing noise), provides a buffer against pinhole formation, and maintains electrical conductivity. The intermediate layer effectively decouples the conflicting requirements of low resistance and high reliability.
Solution Approach 2:
The device employs a composite multilayer structure combining tunnel barrier layer, nonmagnetic metal intermediate layer, and magnetic layers. Each layer is optimized for its specific function: the tunnel barrier provides magnetoresistive effect, the intermediate layer provides mechanical and magnetic buffering, and the magnetic layers provide signal detection. This composite structure resolves the contradiction by distributing functions across multiple specialized components.
2Measurement precision
If high voltage is applied to achieve large MR ratio, then MR performance improves, but spin torque increases affecting magnetization direction and generating noise
Solution Approach 1:
The nonmagnetic metal intermediate layer acts as a mediator that reduces the direct interaction between the applied voltage and the magnetic layers. By inserting this nonmagnetic layer, the spin torque transmitted to the magnetic layers is reduced, allowing for better control of magnetization direction while maintaining MR ratio performance.
Solution Approach 2:
The invention changes the material parameters of the intermediate layer (selecting specific nonmagnetic metals with appropriate thicknesses) to optimize the balance between MR ratio and spin torque. By adjusting the thickness and material composition of the intermediate layer, the device achieves large MR ratios without excessive spin torque effects.
3Reliability
If the semiconductor layer is made thicker to reduce pinholes, then reliability improves, but area resistivity increases degrading device performance
Solution Approach 1:
The nonmagnetic metal intermediate layer serves as an intermediary that allows the semiconductor layer to be optimized for reliability (thicker to prevent pinholes) without penalizing electrical performance. The intermediate layer provides an additional conduction path and reduces the impact of any resistance increase in the thicker semiconductor layer.
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 configuration achieves improved MR performance with reduced noise and spin torque influence, enabling better high-frequency response and stability in the CPP-GMR device.
Implementation Method 1
a work function control layer which controls a concentration of electrons at a junction between the first and second nonmagnetic metal layers and the semiconductor layer
Implementation Method 2
a CPP-GMR device having a CPP (current perpendicular to plane) structure which comprises a spacer layer
Data Source
AI summary
The invention provides a CPP-GMR device comprising a spacer layer. The spacer layer comprises a first nonmagnetic metal layer and a second nonmagnetic metal layer, each formed of a nonmagnetic metal material, and a semiconductor layer interposed between the first nonmagnetic metal layer and the second nonmagnetic metal layer, and further comprises a work function control layer formed between the first nonmagnetic metal layer and the semiconductor layer and/or between the second nonmagnetic metal layer and the semiconductor layer. The semiconductor layer is an n-type semiconductor, and the work function control layer is made of a material having a work function smaller than that of said first nonmagnetic metal layer, and said second nonmagnetic metal layer. It is thus possible to obtain by far more improved advantages.