Amorphous Hf Layer for CPP-GMR Sensor Uniformity
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Solution Overview
Problem
Conventional CPP-GMR spin valve structures with metal spacers exhibit low MR ratios and non-uniformity due to rough surface morphology and large grain size in CCP layers, leading to poor device performance in high-density recording applications.
Innovation Solution
A CCP forming layer configuration using an amorphous metal, alloy, or oxide layer, such as Hf or Zr, is deposited on a Cu spacer, followed by plasma treatment and ion-assisted oxidation to form a smoother, more uniform metal oxide template with segregated Cu metal paths, enhancing the MR ratio and device uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional CCP layer with AlOx template is used, then the device structure is simple, but the surface morphology is rough and grain size is large leading to poor device uniformity
Solution Approach 1:
The patent employs a composite CCP forming layer structure consisting of multiple metal layers (e.g., CoFeB, Ru, Ta) combined with oxide layers. This composite structure enables the formation of a smoother surface morphology and finer grain size after oxidation, directly improving device uniformity while maintaining structural complexity through functional material combinations
Solution Approach 2:
The patent utilizes ion-assisted oxidation (IAO) process parameters to transform the CCP forming layer into a metal oxide template with controlled grain size and surface morphology. By adjusting oxidation conditions and ion assistance parameters, the process achieves smoother surfaces and more uniform grain structures, resolving the uniformity issue without requiring fundamentally different layer structures
2Reliability
If a CCP layer with large grain size is used, then the manufacturing process is simple, but the MR ratio is low due to poor electron scattering control
Solution Approach 1:
The patent applies ion-assisted oxidation with specific energy and flux parameters to control the grain size and distribution in the metal oxide template. This parameter control during oxidation creates finer and more uniform grains, improving electron scattering control and thereby enhancing the MR ratio while maintaining manufacturing feasibility
Solution Approach 2:
The use of composite CCP forming layers with specific metal combinations (CoFeB, Ru, Ta) provides controlled grain growth characteristics during oxidation. The composite structure enables finer grain size and more uniform distribution, which improves electron scattering control and increases the MR ratio
3Manufacturing precision
If a rough surface morphology CCP layer is used, then the deposition process is straightforward, but the Cu metal paths are non-uniform leading to poor device performance
Solution Approach 1:
The patent employs ion-assisted oxidation parameters to transform the CCP forming layer into a metal oxide template with smoother surface morphology. The ion assistance provides directional energy that promotes uniform oxidation and grain formation, creating smoother surfaces that guide more uniform Cu metal path formation during subsequent processing
Solution Approach 2:
The composite CCP forming layer structure with multiple metal and oxide layers provides controlled surface evolution during oxidation. The specific material combinations enable smoother surface morphology development, which directly influences the uniformity of Cu metal paths formed in the resulting metal oxide template
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 significantly improves the MR ratio and resistance uniformity across the wafer, achieving more uniform Cu metal paths and better device performance compared to conventional CCP schemes with AlOx templates.
Implementation Method 1
followed by plasma treatment and ion-assisted oxidation to form a smoother, more uniform metal oxide template
Implementation Method 2
followed by plasma treatment and ion-assisted oxidation to form a smoother, more uniform metal oxide template
Implementation Method 3
form a smoother, more uniform metal oxide template with segregated Cu metal paths
Data Source
AI summary
A method is described for forming a confining current path (CCP) spacer in a CPP-GMR sensor. A first Cu spacer, an amorphous metal/alloy layer such as Hf, a second Cu spacer, and an oxidizable layer such as Al, Mg, or AlCu are sequentially deposited on a ferromagnetic layer. A pre-ion treatment (PIT) and ion assisted oxidation (IAO) transform the amorphous layer into a first metal oxide template and the oxidizable layer into a second metal oxide template both having Cu metal paths therein. A third Cu layer is deposited on the second metal oxide template. The amorphous layer promotes smoothness and smaller grain size in the oxidizable layer to minimize variations in the metal paths and thereby improves dR/R, R, and dR uniformity by 50% or more.