Dark-field confocal microscopy using differential fractional vortex beams
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Solution Overview
Problem
Conventional confocal microscopy techniques face challenges in detecting interlayer defects in 3D integrated circuits due to insufficient signal-to-noise ratio and limited detection sensitivity, especially for defects smaller than 50 nm.
Innovation Solution
A dark-field confocal microscopy measurement apparatus and method based on a differential fractional vortex beam, which generates two fractional vortex beams with different fractional orders to enhance imaging contrast and sensitivity by differentiating the dark-field images obtained from these beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional confocal microscopy measurement technology is used, then the optical sectioning capability and imaging resolution are achieved, but the signal-to-noise ratio of interlayer defect detection is insufficient and detection sensitivity is limited
Solution Approach 1:
The patent segments the detection process into two distinct channels: a reference channel that captures only surface reflected light, and a sample channel that captures both surface reflected light and interlayer scattered light. By separately acquiring and then subtracting the reference signal from the sample signal, the method isolates the weak interlayer defect signal from the overwhelming surface reflection background, thereby improving defect detection sensitivity
Solution Approach 2:
The patent introduces a reference sample (or reference measurement) as an intermediary element that captures the surface reflection characteristics without containing interlayer defects. This reference signal serves as a mediator that, when subtracted from the sample signal, eliminates the common surface reflection component and reveals the hidden interlayer defect signals
2Measurement precision
If dark-field confocal microscopy measurement technology is used, then surface reflected light and interlayer scattered light are separated, but the response rate to micro-scale defects is low and defects smaller than 50 nm are submerged in background noise
Solution Approach 1:
The patent employs periodic modulation of the illumination light intensity to the sample, while keeping the reference light intensity constant. This periodic variation allows the detection system to distinguish between the modulated sample signal (containing defect information) and the unmodulated reference signal (containing only surface reflection), thereby enhancing the visibility of micro-defects against background noise through differential detection
Solution Approach 2:
The patent performs preliminary acquisition of the reference signal (surface reflection characteristics) before or during the sample measurement process. By having the reference signal ready in advance, the system can immediately subtract it from the sample signal to eliminate background noise, thereby improving the detection capability for micro-defects smaller than 50 nm
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
The method effectively improves the signal-to-noise ratio and sensitivity of defect detection, enabling the identification of defects as small as 50 nm by suppressing common-mode noise and enhancing coherent effects between signal lights of various orders.
Implementation Method 1
a fractional vortex beam module configured to generate first fractional vortex beam and second fractional vortex beam, where the first fractional vortex beam is generated by superposing a first vortex phase and a phase of a blazed grating
Implementation Method 2
the first fractional vortex beam is generated by superposing a first vortex phase and a phase of a blazed grating
Implementation Method 3
reflected light from a semiconductor surface easily overwhelms scattered light from the interlayer defect
Implementation Method 4
scattered light from the interlayer defect
Implementation Method 5
The dark-field confocal microscopy measurement technology can effectively separate surface reflected light and interlayer scattered light
Implementation Method 6
The differential dark-field scattered image determining module is configured to differentiate the first fractional-order dark-field image from the second fractional-order dark-field image to obtain a differential dark-field scattered image
Implementation Method 7
The defect determining module is configured to process the differential dark-field scattered image to obtain a sample defect
Data Source
AI summary
Provided are a dark-field confocal microscopy measurement apparatus and method. The apparatus includes: a fractional vortex beam module configured to generate first fractional vortex beam and second fractional vortex beam; an optical scanning module configured to scan a sample by using the first fractional vortex beam and the second fractional vortex beam to obtain first signal return light and second signal return light respectively; a dark-field detection module configured to perform dark-field detection on the first signal return light and the second signal return light to obtain a first fractional-order dark-field image and a second fractional-order dark-field image respectively; a differential dark-field scattered image determining module configured to differentiate the first fractional-order dark-field image from the second fractional-order dark-field image to obtain a differential dark-field scattered image; and a defect determining module configured to process the differential dark-field scattered image to obtain a sample defect.