Thermal Assist Magnetic Head Inspection via Cantilever Vibration
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Solution Overview
Problem
Existing methods for inspecting thermal assist type magnetic head elements fail to accurately measure near-field light and its components, such as excitation light, due to low detection sensitivity and inability to separate near-field light from other light components, which affects the spatial intensity distribution and writing track width of hard disks.
Innovation Solution
An inspection apparatus and method using a scanning probe microscope with a cantilever equipped with a magnetic film and noble metal film, capable of adjusting probe height and vibration amplitude, and employing a lock-in amplifier to extract scattered light components, allowing for high-sensitivity measurement of near-field light and excitation light components by controlling the cantilever's vibration and position relative to the specimen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a scanning probe microscope is used to detect near-field light, then the spatial distribution of light spots can be measured, but the detection sensitivity of near-field light significantly deteriorates
Solution Approach 1:
The cantilever is vibrated at a predetermined frequency to generate vibration-induced scattered light. This vibration technique allows the system to distinguish near-field light signals from background noise by detecting light scattered during the vibration cycle, thereby significantly improving detection sensitivity while maintaining spatial distribution measurement capability
Solution Approach 2:
The cantilever vibration is performed periodically at a specific frequency, and the scattered light is detected during this periodic motion. The periodic vibration creates a time-varying scattering pattern that can be separated from static background light, enabling high-sensitivity detection of near-field light spatial distribution
2Ease of operation
If near-field light and other light components are detected under the same condition, then the detection process is simple, but near-field light and other light components cannot be separated from each other
Solution Approach 1:
By vibrating the cantilever at a predetermined frequency, the system generates vibration-induced scattered light that is distinct from static light components. This allows near-field light and other light components to be separated through frequency-based detection, while the overall process remains operationally simple
Solution Approach 2:
The periodic vibration of the cantilever creates a time-varying detection pattern that enables separation of near-field light from other light components. The periodic nature allows the system to isolate near-field light signals through frequency filtering while maintaining operational simplicity
3Reliability
If the cantilever vibration amplitude is increased to improve detection sensitivity, then the detection of near-field light improves, but the vibration may interfere with the scanning accuracy
Solution Approach 1:
The cantilever is vibrated at a predetermined frequency with controlled amplitude. This vibration enables high detection sensitivity for near-field light while the frequency control ensures that the vibration does not interfere with the scanning accuracy, allowing simultaneous achievement of both detection sensitivity and scanning precision
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 accurate measurement of near-field light generation areas and writing magnetic fields with high sensitivity, improving detection of near-field light and excitation light components, thereby enhancing the spatial intensity distribution and positional accuracy of thermal assist light in magnetic head elements.
Implementation Method 1
a vibration driving unit that vibrates the cantilever with a predetermined period and a predetermined amplitude in a vertical direction relative to the surface of the specimen
Implementation Method 2
a displacement detecting unit that detects the vibration of the cantilever by irradiating the surface of the cantilever opposite to the surface of the cantilever, on which the probe is formed, with light and detecting light reflected from the cantilever
Implementation Method 3
a lock-in amplifier to which a frequency signal allowing the vibration driving unit to vibrate the cantilever with a predetermined period or a signal of an integer multiple of the frequency signal is input as a reference signal and which extracts a scattered light component of the near-field light and a scattered light component of the leaking light from a detection signal
Implementation Method 4
a scattered light detecting unit that detects scattered light generated from the surface of the probe of the cantilever by near-field light, which is generated from the near-field light emitting portion of the thermal assist type magnetic head element
Data Source
AI summary
To detect near-field light, which is generated by a thermal assist type magnetic head element, and leaking light with high sensitivity and to more accurately obtain the spatial intensity distribution of a near-field light generation area, an inspection apparatus for a thermal assist type magnetic head element is adapted so that a distance between a cantilever and the surface of a specimen and the excitation amplitude of the cantilever are set to be small to detect near-field light with high sensitivity by the suppression of an influence of other light components, a distance between the cantilever and the surface of the specimen and the excitation amplitude of the cantilever are set to be large to detect other light components present in the vicinity of near-field light with high sensitivity by the suppression of an influence of the amount of detected near-field light when other light components are measured.