Probe Cantilever Deformation Correction for Interferometer Height Accuracy
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Solution Overview
Problem
Conventional scanning probe microscopes inaccurately measure height changes due to the angular deflection of the cantilever, which affects the interferometer's height measurements, especially when the cantilever bends to control the tip position, leading to errors in height estimation.
Innovation Solution
A method and apparatus that involve arranging the probe in calibration positions to measure deformation, generating interference calibration values, and processing these values to determine a correction factor for height measurements, accounting for the cantilever's shape changes between measurement times, thereby correcting the estimated height changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the cantilever is used to control the tip position through bending, then the probe can achieve precise positioning, but the angular deflection of the cantilever causes errors in interferometer height measurements
Solution Approach 1:
The patent performs a calibration routine before actual measurements to determine a correction factor. The cantilever is positioned at multiple calibration positions with known deformations, and the interferometer measurements are compared against reference values to establish a correction relationship. This preliminary calibration action accounts for the angular deflection effects before real measurements begin.
Solution Approach 2:
The patent implements a feedback mechanism where the measured height values from the interferometer are corrected using the calibration-derived correction factor. The system continuously applies this correction to compensate for the angular deflection of the cantilever, ensuring that the final height measurements are accurate despite the cantilever's bending during operation.
2Productivity
If conventional interferometer measurement is used without correction, then the measurement process is simple and fast, but the height measurements contain errors due to cantilever angular deflection
Solution Approach 1:
The calibration routine is performed once beforehand to establish the correction factor, rather than continuously during measurements. This preliminary action separates the complex calibration process from the routine measurement process, maintaining high measurement speed while improving accuracy through the applied correction.
Solution Approach 2:
The patent changes the measurement parameters by introducing a correction factor that adjusts the raw interferometer readings. This parameter transformation allows the system to maintain the simplicity and speed of conventional interferometry while compensating for systematic errors through mathematical correction of the measurement values.
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 provides accurate height measurements by accounting for cantilever deformation, improving the precision of scanning probe microscopy and related applications by correcting for the artefacts caused by cantilever bending, especially for shorter cantilevers.
Implementation Method 1
operate an interferometer to reflect a sensing beam with the probe (or cantilever) at each calibration position thereby generating a reflected sensing beam, combine the reflected sensing beam with a reference beam to generate an interferogram, and generate an interference calibration value for each calibration position by measuring the interferogram
Data Source
AI summary
A method of performing a measurement routine on a probe, the probe comprising a cantilever extending from a support. An interferometer is operated to reflect a sensing beam with the cantilever thereby generating a reflected sensing beam and combine the reflected sensing beam with a reference beam to generate an interferogram. The interferometer generates a first interference measurement value at a first measurement time by measuring the interferogram and a second interference measurement value at a second measurement time by measuring the interferogram, The cantilever deforms to form a different shape between the measurement times. A change in height of the probe between the measurement times is estimated in accordance with a difference between the first and second interference measurement values, and corrected in accordance with the difference in shape of the cantilever between the measurement times.