Perpendicular Magnetic Recording Write Head with Tapered Pole Tip
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Solution Overview
Problem
Current perpendicular magnetic recording (PMR) technologies face challenges in achieving narrow track widths and strong write fields, particularly in reaching areal densities beyond 1 Tb/in^2, due to limitations in main pole design and the lack of effective methods for fabricating main poles and spin torque oscillators (STOs) with similar narrow track widths for microwave assisted magnetic recording (MAMR) applications.
Innovation Solution
A PMR write head design featuring a main pole with a trimmed width and leading edge taper, achieved through an ion milling process, which generates a write field of approximately 15000 Oe while minimizing side track erasure, and includes a STO and side shields to enhance writing performance and suppress fringing fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the main pole width is reduced to achieve narrow track width, then the track width is improved, but the write field strength deteriorates due to small pole tip area and pole tip saturation
Solution Approach 1:
The patent applies local quality by creating a non-uniform pole tip structure where the pole width varies along the pole height. The pole tip region has a narrower width than the upper pole region, concentrating magnetic flux at the pole tip to enhance write field strength while maintaining narrow track width. This is achieved through selective etching or deposition processes that modify the pole tip geometry locally.
Solution Approach 2:
The patent transitions from a two-dimensional view of pole width to a three-dimensional pole tip structure by introducing vertical dimensionality. The pole tip is shaped with specific angular orientations (e.g., 45-degree angles) relative to the pole axis, creating a conical or pyramidal geometry that concentrates flux in the vertical dimension while controlling horizontal track width.
2Manufacturing precision
If ion milling is used to trim the pole tip to define track width, then the manufacturing precision is improved, but the device complexity increases due to additional process steps
Solution Approach 1:
The patent applies preliminary action by pre-forming the pole tip geometry through controlled etching or deposition before the final ion milling step. The pole tip is prepared with a preliminary shape (e.g., through selective removal of sacrificial layers or controlled deposition angles) that guides the subsequent ion milling process, reducing the complexity of achieving the final precise geometry.
Solution Approach 2:
The patent employs self-service by designing the pole tip structure to self-align during fabrication. The ion milling process automatically defines the track width based on the pole tip geometry and masking layer alignment, eliminating the need for separate alignment and trimming steps. The structure itself guides the fabrication process to achieve the desired precision.
3Force
If the main pole is made thinner at the air bearing surface to provide large head field, then the write field is improved, but the structural stability deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the pole structure into distinct regions: an upper pole region with larger cross-section for structural stability and a pole tip region with narrower width for enhanced head field. The transition between these regions is achieved through controlled etching or deposition, creating a stepped or tapered interface that maintains both stability and field strength.
Solution Approach 2:
The patent employs composite materials by using different magnetic layer compositions or structures in the upper pole region versus the pole tip region. The upper region may use materials optimized for structural integrity and flux generation, while the pole tip region uses materials optimized for flux concentration and head field strength, creating a composite structure that balances stability and performance.
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 design enables the fabrication of narrow track widths of around 50 nm or less with high head fields, effectively addressing the limitations of existing technologies by providing a large write field and minimizing side track erasure, thus supporting areal density growth in MAMR applications.
Implementation Method 1
a pole tip having a first distance between a trailing edge and leading edge at the air bearing surface (ABS) and a tapered side that extends from the leading edge to a bottom surface of the main pole
Data Source
AI summary
A main pole layer having at least a leading taper and trimmed pole tip portion is described. The leading taper increases head field up to ≧15000 Oe even for narrow track widths approaching 50 nm. For MAMR applications, a STO and trailing shield are sequentially formed on a trailing pole tip side. Furthermore, full side shields may be added to reduce fringing field. A preferred embodiment includes both of a leading taper and trailing taper at the pole tip where leading taper angle is between 20° and 60° and trailing taper angle is from 10° to 45°. A method is provided for forming various embodiments of the present invention. A key feature is that milling depth at an effective neck height distance is greater than or equal to the pole tip thickness. A self aligned STO may be formed by the same ion milling step that defines track width.