Patterned Magnetic Disk Diffraction Grating Alignment
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Solution Overview
Problem
Current hard disk media manufacturing lacks a coordinate reference for accurately detecting the center and direction of the disk, which is essential for precise alignment during the inspection and manufacturing process, especially with the introduction of patterned media that requires increased recording density and defect detection.
Innovation Solution
Incorporating a diffraction grating pattern with a repetitive configuration and varying pitch on the circumference of the disk, allowing for the detection of the center and direction using diffracted light, enabling accurate alignment with a disk holding stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffraction grating pattern is added to the disk surface for alignment detection, then the measurement precision of disk center and direction is improved, but the device complexity increases due to additional pattern formation steps
Solution Approach 1:
The alignment detection function is merged with the existing data track formation process by integrating the diffraction grating pattern into the same magnetic layer structure. This allows the alignment marks to be formed simultaneously with the data tracks during the magnetic recording process, eliminating the need for separate alignment mark formation steps and reducing overall device complexity.
Solution Approach 2:
The magnetic layer serves multiple functions: it stores data information and simultaneously provides the diffraction grating pattern for alignment detection. This multi-functionality reduces the need for additional components and simplifies the overall disk structure while maintaining high measurement precision for center and direction detection.
2Productivity
If optical scatterometry is used for high-speed inspection of the whole disk surface, then the productivity is improved, but the measurement precision of defect types deteriorates since defect configurations cannot be specified
Solution Approach 1:
The inspection process is segmented into two stages: first, optical scatterometry performs high-speed screening of the entire disk surface to detect the presence of defects; second, SEM or AFM performs detailed examination of specific defect locations to identify defect types. This segmentation allows the system to maintain high productivity while achieving precise defect characterization.
Solution Approach 2:
The diffraction grating pattern serves as an intermediary reference system that enables precise coordinate mapping between the optical inspection system and the subsequent SEM/AFM examination. By providing a known geometric reference, the system can accurately locate defects detected by optical scatterometry and guide the high-precision instruments to those specific locations, thereby maintaining both speed and accuracy.
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 precise detection and alignment of the disk center and direction, facilitating comprehensive surface inspection and defect specification without reducing throughput, thereby improving the inspection efficiency and accuracy.
Implementation Method 1
a diffraction grating pattern is formed as an alignment pattern
Data Source
AI summary
Embodiments of the invention provide patterned media in which the center and the direction of the disk can be detected. According to one embodiment, patterned media has a bit pattern including convex portions of a magnetic material on one surface or both surfaces of a nonmagnetic substrate having a central hole. A diffraction grating pattern is formed as an alignment pattern in the inner circumference (or outer circumference) of the patterned media. The diffraction grating pattern is a pattern having a repetitive configuration, and includes a pattern with a repetitive pitch different from that in other portions, or a portion having no pattern, at least one region on a circumference. The diffraction grating pattern is irradiated with detection light and diffracted light is detected, thereby a center and a direction of the disk can be detected.