FIB Micromachining Thickness Measurement via Optical Interference
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Solution Overview
Problem
Current methods for determining the thickness of samples micromachined using a Focused Ion Beam (FIB) are inaccurate and introduce electron dose-related artefacts, requiring complex and expensive dual beam systems.
Innovation Solution
An integrated system combining a FIB exposure system with a light optical system for non-destructive thin-film optical interferometry, allowing for precise measurement of sample thickness without electron irradiation, using optical interference to determine the distance between sample surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SEM imaging is used to determine sample thickness, then thickness measurement is possible, but electron dose introduces artefacts and alters the sample
Solution Approach 1:
The patent replaces the electron beam-based SEM imaging system with a light optical system that uses visible or UV light for thickness measurement. This substitution eliminates electron irradiation entirely, avoiding the introduction of artefacts while maintaining the ability to measure sample thickness through optical interference methods.
Solution Approach 2:
The patent introduces light as an intermediary medium for thickness measurement instead of using electrons directly. By using optical interference of light waves reflected from the sample surfaces, the system achieves non-contact thickness measurement without the harmful effects of electron beam irradiation on the sample.
2Measurement precision
If dual beam SEM/FIB system is used, then thickness measurement without electron artefacts is possible, but system complexity and cost increase
Solution Approach 1:
The patent extracts the thickness measurement function from the complex dual beam SEM/FIB system and implements it using a separate, simpler light optical system. This allows the FIB system to focus solely on micromachining while the optical system independently handles thickness measurement, reducing overall system complexity.
Solution Approach 2:
The patent makes the light optical system a universal addition that can be integrated with existing FIB systems to provide both micromachining and thickness measurement capabilities. The optical system serves multiple purposes including thickness measurement and potential imaging, eliminating the need for expensive dual beam configurations.
3Productivity
If FIB imaging is used to monitor micromachining, then process monitoring is possible, but sample material is removed and heavy ions are implanted
Solution Approach 1:
The patent replaces FIB imaging with light optical imaging for process monitoring. This substitution eliminates the harmful effects of ion beam irradiation, preventing sample material removal and heavy ion implantation while maintaining the ability to monitor the micromachining process in real-time.
Solution Approach 2:
The patent introduces light as an intermediary for process monitoring instead of using the FIB. Optical interference techniques allow non-contact monitoring of the sample during micromachining, providing real-time feedback without the destructive effects of ion beam irradiation.
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 provides a precise and non-destructive means to measure sample thickness, avoiding electron-induced artefacts and eliminating the need for expensive dual beam systems, offering improved control over FIB micromachining.
Implementation Method 1
analyzing the light collected by the light collecting optics and establishing a measure for the modulation of an intensity of said collected light due to an optical interference of said light from a first surface of the sample and light from a second surface of the sample
Data Source
AI summary
A method and an apparatus for micromachining samples are provided. The apparatus includes an integral combination of a sample holder, a focused ion beam (FIB) exposure system for projecting a FIB onto a sample, and a light optical microscope (LM). The LM is configured for imaging or monitoring the sample during and/or after FIB exposure. The method includes the steps of using the LM projecting light towards the sample and collecting reflected and/or transmitted light from said sample; analyzing the collected light and establishing a measure for the modulation of an intensity of said collected light due to an optical interference of light from a first surface of the sample and light from a second surface of the sample; and using the measure for the modulation of the intensity for establishing a measure for the distance between said first surface and said second surface.