Hot Seed Layer Coercivity via ALD Alumina and Low-Rate PVD
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Solution Overview
Problem
Current perpendicular magnetic recording technologies face challenges in achieving high coercivity and low anisotropy in hot seed layers for magnetic write poles, which are essential for increasing storage areal density in hard disk drives, and these properties tend to degrade with temperature.
Innovation Solution
A method involving the deposition of seed layers with a body-centered cubic crystal structure, followed by an alumina buffer layer using atomic layer deposition, and a high coercivity magnetic film at a low deposition rate, enhances the coercivity of the hot seed layer, which is stable up to 120°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deposition methods are used for hot seed layers, then the manufacturing process is simple and fast, but the coercivity is insufficient and degrades with temperature
Solution Approach 1:
The patent changes the deposition parameters by using a very low deposition rate (around 1 Angstrom per second) to achieve high coercivity and low anisotropy in the magnetic film. This parameter change resolves the contradiction by prioritizing film quality (coercivity stability) over manufacturing speed, as the low deposition rate allows for better atomic arrangement and magnetic property control.
Solution Approach 2:
The patent creates a composite structure with multiple layers including bcc seed layers, alumina buffer layers, and high coercivity magnetic films. This composite approach resolves the contradiction by combining materials with different functions - the seed and buffer layers provide structural foundation while the magnetic film layer provides the required magnetic properties with high coercivity stability.
2Reliability
If high deposition power is used, then the deposition rate is high, but the coercivity and magnetic properties are degraded
Solution Approach 1:
The patent explicitly changes the deposition power parameter to very low levels, resulting in a deposition rate of around 1 Angstrom per second. This parameter change directly resolves the contradiction by demonstrating that low deposition power produces superior magnetic properties (high coercivity, low anisotropy) compared to high deposition power methods.
3Reliability
If nonmagnetic spacer layers are used to separate the main pole from magnetic shields, then the magnetic field confinement is improved, but the track width precision is challenging to control
Solution Approach 1:
The patent uses atomic layer deposition (ALD) to form the alumina buffer layer, which provides precise thickness control at the nanometer scale. This deposition method resolves the contradiction by enabling accurate control of the nonmagnetic spacer layer dimensions, thereby controlling the track width while maintaining magnetic field confinement.
Solution Approach 2:
The patent changes the deposition method from conventional techniques to atomic layer deposition, which provides superior thickness uniformity and precision. This parameter change in the deposition process enables precise control of the spacer layer dimensions, resolving the track width control challenge while maintaining field confinement.
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 results in significantly improved coercivity of the hot seed layer, both in its as-deposited and post-annealed states, maintaining stability at elevated temperatures, thereby enhancing the performance of magnetic recording writers.
Implementation Method 1
first depositing one or more seed layers having a body-centered cubic (bcc) crystal structure on the write gap
Implementation Method 2
followed by the deposition of a buffer layer of alumina on the seed layer(s). It is important for this buffer layer to be laid down through atomic layer deposition (ALD) so as to achieve maximum conformal coverage
Implementation Method 3
a high coercivity magnetic film is deposited onto the layer of ALD alumina. It is a key feature of the disclosed method and structure that this high coercivity magnetic film be deposited at a very low deposition rate (around 1 Angstrom per second)
Data Source
AI summary
A method of forming a sub-structure, suitable for use as a hot seed in a perpendicular magnetic recording head, is described. A buffer layer of alumina with a thickness of 50-350 Angstroms is formed by atomic layer deposition as a write gap. Thereafter, one or more seed layers having a body-centered cubic (bcc) crystal structure may be deposited on the buffer layer. Finally, a magnetic film made of FeCo or FeNi with a coercivity of 60-110 Oe is deposited on the seed layer(s) by a physical vapor deposition (PVD) method at a rate of 0.48 to 3.6 Angstroms per second. The magnetic film is preferably annealed at 220° C. for 2 hours in a 250 Oe applied magnetic field.