Nitrogenated Cu/Ag Under-layers for Magnetoresistive Sensor Grain Orientation
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Solution Overview
Problem
Magnetoresistive sensors face challenges in achieving optimal crystalline grain growth and orientation when depositing layers over existing shield lead structures, which hinders their sensitivity and data density performance.
Innovation Solution
A CPP magnetoresistive sensor with an under-layer structure comprising a first sub-layer of Ta, a second sub-layer of Cu, and a third sub-layer of Ag, deposited using specific Argon and Nitrogen gas mixtures to achieve a preferred crystalline texture, supporting a ferromagnetic free layer with a body-centered cubic structure for enhanced magnetoresistive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deposition methods are used over shield lead structures, then device complexity is reduced, but crystalline grain growth and orientation are suboptimal
Solution Approach 1:
The patent applies preliminary action by depositing the Cu/Ag under-layer structure with specific crystalline orientations (Cu (100) and Ag (100) textures) before depositing the magnetic alloy layers. This pre-established textured foundation promotes optimal grain growth in subsequent layers, resolving the contradiction by preparing the substrate in advance to enable better crystalline development without requiring complex in-situ control during magnetic layer deposition.
Solution Approach 2:
The Cu/Ag under-layer structure serves as an intermediary between the shield lead structure and the magnetic alloy layers. This intermediate layer with controlled (100) texture mediates the crystalline growth process, providing a template that promotes favorable grain orientation in the magnetic layers while isolating them from the complex shield lead structure below, thus improving manufacturing precision without directly complicating the final device structure.
2Reliability
If favorable magnetic alloys are deposited, then magnetoresistive sensitivity increases, but crystalline grain structure deteriorates
Solution Approach 1:
The Cu/Ag under-layer acts as an intermediary that decouples the relationship between magnetic alloy deposition and crystalline grain structure formation. By providing a pre-textured (100) surface, it allows favorable magnetic alloys to be deposited with their inherent high sensitivity properties while the under-layer controls the crystalline grain structure, thus resolving the contradiction between achieving high sensitivity and maintaining optimal grain structure.
Solution Approach 2:
The patent segments the deposition process into distinct functional layers: the Cu/Ag under-layer responsible for crystalline template formation, and the magnetic alloy layers responsible for magnetoresistive functionality. This segmentation allows each layer to be optimized independently - the under-layer for crystalline orientation and the magnetic layers for sensitivity - thereby resolving the contradiction between these two competing requirements.
3Reliability
If under-layer structure is added to promote (100) texture, then magnetoresistive sensitivity improves, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by controlling the deposition conditions (nitrogen content in process gas, deposition sequence) of the Cu and Ag layers to achieve specific crystalline orientations. By changing these deposition parameters, the under-layer develops strong (100) textures that template the magnetic layers, improving sensitivity while keeping the structural complexity manageable through controlled material properties rather than complex geometries.
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 solution enables favorable crystalline grain structure and orientation, leading to increased magnetoresistive sensitivity and performance by promoting high magneto-resistance values and lattice matching, thereby improving sensor performance and data density.
Implementation Method 1
a spin valve sensor structure that allows favorable alloys to be used with optimal crystalline grain structure and orientation
Implementation Method 2
Certain alloys have shown promise for increasing the performance of such magnetoresistive sensors. However, depositing such layers over available shield lead structure has resulted in less than optimal crystalline grain growth in these magnetic alloys
Implementation Method 3
a spin valve sensor, also referred to as a giant magnetoresistive (GMR) sensor
Implementation Method 4
depositing the layers in an Argon (Ar) plus nitrogen (N2) process gas mixture
Data Source
AI summary
A magnetoresistive sensor that has a free layer with a face centered cubic, 100 crystal orientation formed on an underlayer structure that has been deposited in the presence of nitrogen. The free layer can be constructed of CoFe, Co2(Mn(1-y)Fey)X (where 0≦y≦1 and X is Si, Ge, Sn, Al, Ga, or a combination thereof), CoFeX (where X is Si, Ge, Sn, Al, Ga, or a combination thereof). The under-layer can include a layer of Ta, a Cu layer formed over the layer of Ta and deposited using a process gas comprising about 20 percent nitrogen and a layer of Ag deposited over the layer of Cu and deposited using a process gas comprising about 50 to 100 percent nitrogen.