Narrow Trackwidth Magnetic Sensor Liftoff Process
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Solution Overview
Problem
Current manufacturing processes face challenges in producing magnetic sensors with narrow trackwidths reliably and uniformly due to issues like shadowing effects and mask deformation, which limit data density and track density in magnetic disk drives.
Innovation Solution
A method involving the deposition of sensor layers, formation of mask structures, and ion milling to define narrow trackwidths without using organic image transfer layers, allowing for a hard mask layer with low ion milling rates and Si hard mask deposition by processes other than spin coating to prevent high temperature curing, facilitating the creation of sensors with reduced dimensions and minimizing shadowing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mask liftoff processes are used to define narrow trackwidth sensors, then mask removal is achieved, but shadowing effects and mask deformation occur leading to poor manufacturing precision
Solution Approach 1:
The mask structure is divided into multiple layers: a first mask layer (e.g., photoresist) that defines the overall sensor area and a second mask layer (e.g., metal or polymer) that defines the narrow trackwidth. This segmentation allows each layer to perform its specific function without interfering with the other, preventing shadowing effects and deformation during liftoff.
Solution Approach 2:
A hard mask layer (e.g., silicon nitride or carbon) is introduced as an intermediary between the sensor layers and the first mask layer. This hard mask layer serves as a protective barrier during ion milling and provides a stable structure that prevents deformation during the liftoff process, enabling precise narrow trackwidth definition.
2Ease of manufacture
If organic image transfer layers are used to facilitate mask liftoff, then mask removal is easier, but high temperature curing is required which may damage sensor layers
Solution Approach 1:
The first mask layer is designed as a disposable photoresist layer that is easily removed after serving its purpose of defining the sensor area. This layer does not need to be reused or recovered, so using conventional photoresist with standard curing temperatures is acceptable. The critical narrow trackwidth is defined by the second mask layer which is not removed.
Solution Approach 2:
The mask formation process uses multiple deposition techniques with different temperature requirements. The hard mask layer is deposited by sputtering or atomic layer deposition at low temperatures, and the photoresist is applied and patterned at room temperature. This parameter change approach allows mask formation without high temperature curing that could damage sensor layers.
3Stability of the object's composition
If spin coating is used to deposit hard mask layers, then uniform deposition is achieved, but high temperature curing is required which may cause mask deformation
Solution Approach 1:
The spin coating process is replaced with alternative deposition methods such as sputtering, atomic layer deposition (ALD), or dip coating. These methods achieve uniform hard mask layer deposition without requiring high temperature curing, thereby preventing mask structure deformation while maintaining layer uniformity.
Solution Approach 2:
The mask structure uses composite materials with different properties: a soft photoresist layer for easy pattern transfer and a hard metal or polymer layer for structural stability. The hard mask layer is deposited at low temperatures using sputtering or ALD, creating a composite structure that combines the ease of photoresist patterning with the dimensional stability of hard materials without requiring high temperature curing.
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
Enables the reliable and uniform production of magnetic sensors with very narrow trackwidths, enhancing data density and reducing process variations, while maintaining mask integrity and preventing deformation.
Implementation Method 1
An ion milling is performed to remove portions of the sensor material that are not covered by the first mask structure
Data Source
AI summary
A method for manufacturing a magnetic read sensor allows for the construction of a very narrow trackwidth sensor while avoiding problems related to mask liftoff and shadowing related process variations across a wafer. The process involves depositing a plurality of sensor layers and forming a first mask structure. The first mask structure has a relatively large opening that encompasses a sensor area and an area adjacent to the sensor area where a hard bias structure can be deposited. A second mask structure is formed over the first mask structure and includes a first portion that is configured to define a sensor dimension and a second portion that is over the first mask structure in the field area.