DLC Thickness Calculation via Interferometric Modulation
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Solution Overview
Problem
Existing interferometric techniques fail to accurately measure the thickness of a diamond-like carbon (DLC) layer on magnetic-head sliders when its thickness is unknown, which is common, leading to imprecise calculations of critical parameters like ALR and PTR.
Innovation Solution
A method is developed to calculate the DLC thickness using a linear relationship between modulation and reflectivity, expressed through explicit equations involving known optical parameters, allowing for the correction of interferometric measurements by solving for the DLC thickness using modulation data from two object surfaces with known optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional interferometric measurement is used to measure the DLC layer thickness, then the measurement process is simple and rapid, but the measurement precision is insufficient when the DLC thickness is unknown
Solution Approach 1:
The patent applies preliminary action by first performing an initial interferometric scan to obtain modulation data, then using this data to calculate the DLC thickness before correcting the surface profile. This preliminary measurement and calculation step enables subsequent precise correction, resolving the contradiction between measurement precision and method complexity.
Solution Approach 2:
The patent introduces an intermediary calculation process that uses the measured modulation data and known optical parameters to determine the DLC thickness. This intermediary step serves as a bridge between the raw interferometric measurement and the corrected surface profile, enabling precise thickness measurement without directly complicating the measurement apparatus.
2Manufacturing precision
If interferometric measurement is performed through a DLC layer of unknown thickness, then the measurement can be carried out, but the calculation of ALR and PTR parameters becomes imprecise
Solution Approach 1:
The patent applies feedback by using the measured modulation data to calculate the DLC thickness, then using this calculated thickness to determine the phase change on reflection, and finally using this phase change information to correct the surface profile and recalculate ALR and PTR parameters. This feedback loop recovers the lost phase information and significantly improves manufacturing precision.
Solution Approach 2:
The patent changes the parameter of DLC thickness from unknown to known by calculating it from modulation data. This parameter change enables the subsequent calculation of phase change on reflection and correction of surface profile, directly improving the accuracy of ALR and PTR parameters while recovering the previously lost phase information.
3Ease of manufacture
If the DLC layer thickness is assumed to be known, then the correction can be simplified, but this assumption is often not valid in practice
Solution Approach 1:
The patent applies self-service by enabling the measurement system to determine the DLC thickness itself through modulation data analysis, rather than relying on external assumptions or separate measurement processes. This self-determined thickness value maintains correction process simplicity while ensuring reliability, as the system generates its own calibration information from the measurement data.
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 method enhances the precision of DLC thickness calculation, improving the accuracy of ALR and PTR parameters to an RMS of 0.55 nm or better, refining the profile data beyond previous techniques, and providing a straightforward correction for interferometric measurements.
Implementation Method 1
interferometric measurement
Implementation Method 2
absolute value of reflectivity
Data Source
AI summary
An explicit relationship is developed between the ratio of average interferometric modulation produced by diamond-like carbon (DLC)-coated magnetic-head surfaces and the thickness of the DLC layer. Accordingly, the thickness of the DLC layer is calculated in various manners from modulation data acquired for the system using object surfaces of known optical parameters.