Amorphous NiTa Underlayer for Perpendicular Magnetic Write Head
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Solution Overview
Problem
In perpendicular magnetic recording systems, the use of a metal oxide underlayer like alumina insulates the electroplating structure, reducing current-carrying capacity and limiting the formation of a main pole with low coercivity.
Innovation Solution
A nonmagnetic metallic amorphous underlayer, such as an amorphous NiTa or NiNb alloy, is deposited to reset the growth between the side gap layer and the pole seed layer, allowing for improved current conduction and magnetic properties without insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a metal oxide underlayer like alumina is used, then the growth of the NiCr/CoFe pole seed layer is improved, but the electroplating structure is insulated from the Ru side gap layer, reducing current-carrying capacity
Solution Approach 1:
A thin layer of amorphous metallic underlayer (NiTa or NiNb alloy) is introduced as an intermediary between the Ru side gap layer and the NiCr/CoFe pole seed layer. This intermediary layer serves dual functions: it provides excellent growth substrate for the pole seed layer while simultaneously maintaining electrical conductivity to allow current flow from the Ru side gap layer, thus resolving the contradiction between growth quality and current-carrying capacity
Solution Approach 2:
The patent employs a composite structure combining metal oxide (alumina) insulation layers with amorphous metallic underlayer (NiTa/NiNb) conductive layers. This composite material approach allows the system to simultaneously achieve electrical insulation where needed (between coil and pole) and electrical conductivity where needed (through the electroplating seed structure), resolving the contradiction between insulation and conduction requirements
2Manufacturing precision
If a metal oxide underlayer like alumina is used, then the pole seed layer growth is excellent, but the coercivity of the main pole cannot be reduced to desired low levels
Solution Approach 1:
The amorphous metallic underlayer acts as a mediator that decouples the crystalline orientation influence from the Ru side gap layer while providing a growth-friendly surface for the NiCr/CoFe pole seed layer. This mediator layer allows the pole seed layer to achieve excellent growth characteristics without inheriting the high coercivity associated with direct growth on crystalline Ru, thus enabling low coercivity in the subsequent electroplated CoFe main pole
3Reliability
If the Ru side gap layer is used as electroplating seed, then current conduction is available, but the crystalline orientation effect negatively impacts the CoFe main pole properties
Solution Approach 1:
The amorphous metallic underlayer serves as a mediator that blocks the transmission of crystalline orientation effects from the Ru side gap layer to the CoFe main pole, while simultaneously maintaining the electrical conductivity pathway for electroplating current. This resolves the contradiction by allowing current conduction through the Ru layer while preventing unwanted crystalline orientation influence on the magnetic properties of the CoFe pole
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 approach enhances the magnetic properties of the main pole by promoting soft magnetic characteristics and improving current conduction, resulting in a write head with better magnetic recording capabilities.
Implementation Method 1
A nonmagnetic metallic amorphous underlayer is then deposited on the side gap layer
Implementation Method 2
The NiCr/CoFe bilayer is known to promote soft magnetic properties desirable for the subsequently electroplated CoFe main pole
Implementation Method 3
The metallic amorphous underlayer, unlike metal oxides such as alumina that were used in the prior art, does not insulate the electroplating CoFe layer from the metallic side gap layer. This allows better current conduction normal to the layers
Implementation Method 4
The main pole may be electroplated onto a pole seed layer, such as a NiCr/CoFe bilayer
Data Source
AI summary
A perpendicular magnetic recording write head has a main pole that is typically CoFe electroplated into a generally trapezoidal shaped alumina trench. A metallic side gap layer is deposited into the alumina trench to adjust the trench width to the desired main pole dimension. A nonmagnetic metallic amorphous underlayer, preferably an amorphous NiTa alloy or an amorphous NiNb alloy, is then deposited on the side gap layer. A pole seed layer, such as a NiCr/CoFe bilayer, is deposited into the trench onto the metallic amorphous underlayer prior to electroplating the CoFe main pole. The metallic amorphous underlayer serves to reset the growth between the side gap layer and the NiCr/CoFe pole seed layer. The metallic amorphous underlayer does not insulate the electroplating CoFe layer from the metallic side gap layer, which allows for better current conduction normal to the layers, resulting in a main pole with improved magnetic properties.