Vortex-Illumination Confocal Microscopy for Sub-50 nm Defect Detection
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Solution Overview
Problem
Conventional optical dark-field confocal microscopy lacks the necessary signal-to-noise ratio for detecting nano-scale defects smaller than 50 nm due to beam diffraction and multiple scattering effects, limiting the detection scale and defect detection rate.
Innovation Solution
A dark-field confocal microscopy apparatus and method utilizing vortex illumination aperture scanning and dark-field lock-in detection, incorporating a vortex illumination generation module, aperture scanning module, sample scanning module, and dark-field lock-in detection module to enhance sensitivity for nano-scale defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical dark-field confocal microscopy is used, then surface and subsurface detection capability is provided, but signal-to-noise ratio is insufficient for detecting nano-scale defects smaller than 50 nm
Solution Approach 1:
The patent changes the illumination mode from conventional dark-field to vortex illumination, introducing a topological charge parameter to the light field. This parameter change creates a donut-shaped intensity profile with a dark center, which enhances the scattering signal from nano-scale defects while suppressing the background, thereby improving both measurement precision and signal-to-noise ratio for defects smaller than 50 nm
Solution Approach 2:
The patent implements periodic scanning of the vortex illumination beam across the sample using a scanning galvanometer. This periodic action modulates the scattering signal from defects at a specific frequency, which is then detected by lock-in amplification to extract weak signals from noise, resolving the contradiction between detection sensitivity and signal-to-noise ratio
2Measurement precision
If vortex illumination aperture scanning is implemented, then detection sensitivity for defects smaller than 50 nm is enhanced, but device complexity increases
Solution Approach 1:
The patent introduces a spiral phase plate as an intermediary component that imparts orbital angular momentum to the incident laser beam, transforming it into vortex illumination. This simple optical element achieves the complex illumination pattern without requiring complex optical systems, thereby enhancing detection sensitivity while minimizing the increase in device complexity
Solution Approach 2:
The patent replaces complex mechanical illumination systems with a combination of a simple spiral phase plate and standard laser components. This substitution achieves vortex illumination using primarily optical elements rather than complex mechanical beam shaping systems, reducing device complexity while maintaining enhanced detection sensitivity
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 highly-sensitive detection of defects smaller than 50 nm by controlling beam propagation with vortex illumination and using lock-in amplification to highlight and amplify oscillation signals from nano-scale defects.
Implementation Method 1
The vortex illumination generation module is configured to generate vortex illumination
Implementation Method 2
the objective lens is configured to: focus the split beam output by the beam expander onto the sample, and collect the signal return light to be incident on the non-polarizing beam splitter
Implementation Method 3
the photomultiplier is configured to convert a light signal of the received scattered light into an electric signal
Implementation Method 4
the lock-in amplifier is configured to perform lock-in amplification processing on the electric signal output by the photomultiplier
Data Source
AI summary
This application relates to the technical field of optical precision measurement and discloses a dark-field confocal microscopy measurement apparatus and method based on aperture scanning of vortex illumination. The apparatus includes a vortex illumination generation module, a vortex illumination aperture scanning module, a sample scanning module, and a dark-field lock-in detection module. On one hand, the vortex illumination aperture scanning module enables the light spot focused on the sample to scan a small range of the sample, generating oscillating signals that highlight the scattering signal of nano-scale defects on the sample. On the other hand, highly-sensitive oscillation signal detection is achieved using the dark-field lock-in detection module. In the present disclosure, the small-range aperture scanning of vortex illumination is combined with the dark-field lock-in detection to realize highly-sensitive detection of defects smaller than 50 nm.