Double Hard-Mask Mill Back for Near Field Transducer Fabrication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional methods for fabricating near field transducers (NFTs) in energy-assisted magnetic recording face challenges in accurately controlling the writer gap and NFT thickness due to issues like over-milling and shadow effects, leading to inconsistent NFT shapes and limited disk size.
Innovation Solution
A double hard-mask mill back method is employed, involving multiple patterned hardmask layers and etch processes to precisely form the pin and disk sections of the NFT, allowing for independent control of disk and pin thicknesses and eliminating the limitations of traditional fabrication techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional milling process is used to form pin section, then NFT structure can be formed, but writer gap cannot be controlled accurately due to over-milling
Solution Approach 1:
The patent applies preliminary action by forming the pin section of the NFT before forming the disk section. The pin section is milled first to establish a precise reference plane, then the disk section is formed on top of it. This sequential approach allows the writer gap to be defined by the pin section height rather than being affected by over-milling of the disk section, thereby improving writer gap control accuracy.
2Manufacturing precision
If photolithography is used to form hole for disk section, then disk section can be formed, but writer gap layer material is etched away by developer
Solution Approach 1:
The patent introduces an intermediary protective layer (such as a second hardmask layer or spin-on-glass) over the writer gap layer before photolithography. This protective layer acts as a barrier that prevents the photolithography developer from etching away the writer gap layer material while still allowing the photolithography process to form the disk section pattern, thus preventing material loss and improving writer gap control.
3Manufacturing precision
If lift-off process is used to form disk section, then NFT can be completed, but NFT thickness cannot be controlled accurately due to shadow effect
Solution Approach 1:
The patent applies preliminary action by first forming the pin section with a defined height, then forming the disk section on top of the pin section. This establishes a reference plane that allows subsequent etching processes to accurately control the NFT thickness relative to the pin section, eliminating the shadow effect problem that occurs when attempting to define thickness from a flat substrate surface.
4Length of moving object
If traditional photolithography is used, then hole can be formed, but disk size is limited to diameter larger than 250 nm
Solution Approach 1:
The patent transitions from two-dimensional photolithography patterning to three-dimensional nanosphere lithography. By using self-assembled nanospheres as masks, the method enables precise formation of sub-250 nm disk features that cannot be achieved with conventional photolithography, thus reducing the minimum disk size while maintaining manufacturing precision through the self-organizing nature of the nanosphere assembly process.
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 enables accurate control of the NFT writer gap, disk thickness, and pin thickness, allowing for smaller disk sizes and consistent NFT shapes, thereby improving the fabrication process and enhancing the performance of energy-assisted magnetic recording devices.
Implementation Method 1
performing an etch process on the NFT metal layer via the first patterned hardmask, the etch process forming the NFT having the disk section and the pin section
Data Source
AI summary
A method of forming a near field transducer (NFT) for energy assisted magnetic recording is disclosed. A structure comprising an NFT metal layer and a first hardmask layer over the NFT metal layer is provided A first patterned hardmask is formed from the first hardmask layer, the first patterned hardmask disposed over a disk section and a pin section of the NFT to be formed. An etch process is performed on the NFT metal layer via the first patterned hardmask, the etch process forming the NFT having the disk section and the pin section.