Magnetic Head Read Sensor Stripe Height Control via Segmented ELG Patterning
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Solution Overview
Problem
The incorporation of a rear bias material in magnetic heads can cause electrical shorts with electronic lapping guides, leading to errors in estimating the true stripe height of read sensors, which misguides the lapping process and affects the accuracy of magnetic head manufacturing.
Innovation Solution
A method is developed where the backside edge of the read sensor and the electronic lapping guide are formed in separate patterning steps, allowing independent optimization and avoiding electrical shorts, with the stripe height offset between them characterized using test devices to control the lapping process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rear bias material is deposited behind the backside edge of electronic lapping guides, then the magnetic bias field is provided to the read sensor, but electrical shorts occur through the thin backside insulating layer causing errors in stripe height estimation
Solution Approach 1:
The patent divides the formation of read sensor backside edge and ELG backside edge into separate patterning steps. The read sensor backside edge is formed in a first patterning step, and the ELG backside edge is formed in a second patterning step. This segmentation allows the rear bias material to be deposited and patterned without causing electrical shorts to the ELG, while still providing the necessary magnetic bias field to the read sensor.
2Ease of manufacture
If the backside edges of read sensor and electronic lapping guide are formed in the same patterning step, then the manufacturing process is simplified, but electrical shorts occur causing misguidance of the lapping process
Solution Approach 1:
The patent segments the patterning process into distinct steps: a first patterning step for forming the read sensor backside edge, and a second patterning step for forming the ELG backside edge. This segmentation prevents electrical shorts that would occur if both edges were formed in the same step, thereby ensuring accurate stripe height estimation while maintaining a manageable manufacturing process.
Solution Approach 2:
The patent performs preliminary actions by forming the read sensor backside edge in the first patterning step before forming the ELG backside edge in the second patterning step. This preliminary formation allows subsequent deposition and patterning of rear bias material without causing electrical shorts to the ELG, ensuring accurate stripe height control.
3Device complexity
If the thin backside insulating layer is used with rear bias material, then the magnetic head structure is achieved, but electrical shorts occur through the insulating layer
Solution Approach 1:
The patent segments the formation process to prevent electrical shorts through the thin backside insulating layer. By forming the read sensor backside edge separately from the ELG backside edge, the rear bias material can be deposited and patterned without creating conductive paths through the insulating layer to the ELG, maintaining both structural integrity and electrical insulation.
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 final stripe height of the read sensor by decoupling the formation of the read sensor and electronic lapping guide backside edges, minimizing errors and optimizing the manufacturing process.
Implementation Method 1
depositing a sensor layer stack including at least one free layer over a substrate
Implementation Method 2
depositing an electronic lapping guide (ELG) layer over the substrate
Implementation Method 3
lapping the read sensor and the ELG to provide an air bearing surface of a read sensor
Data Source
AI summary
A method of forming a magnetic head includes forming a read sensor stripe, depositing an electronic lapping guide (ELG) layer over the substrate in an ELG region, forming a backside edge of a read sensor by patterning the read sensor stripe in a first patterning step, forming a backside insulator layer and a rear bias magnetic material portion over the backside edge of the read sensor, forming a backside edge of an ELG by patterning the ELG layer in the ELG region in a second patterning step, simultaneously forming a front side edge of the read sensor and a front side edge of the ELG, and lapping the read sensor and the ELG to provide an air bearing surface of a read sensor. The physical stripe height offset can be determined for each flash field by correlating device conductance and ELG conductance.