Microsphere Spectroscopy Focus Control for 10 nm Alignment
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Solution Overview
Problem
Existing spectroscopic measuring apparatuses face challenges in measuring ultra-miniaturized semiconductor devices due to the optical diffraction limit, and the optical nanojet effect generated by microspheres requires a different focus alignment method.
Innovation Solution
A spectroscopic measuring apparatus with a first and second objective lens, where the second lens has a microsphere, uses a light intensity function to determine the focal position by moving the second objective lens vertically downward and setting a threshold value based on the light intensity spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microsphere is used to overcome the optical diffraction limit, then measurement precision is improved, but focus alignment becomes more difficult
Solution Approach 1:
The system uses a feedback mechanism where the spectrum obtained during vertical scanning is analyzed to generate a light intensity function. The focal position is determined by detecting the threshold value of this function, creating a closed-loop feedback system that automatically adjusts the objective lens position to achieve optimal focus alignment with the microsphere.
Solution Approach 2:
The system performs self-alignment by automatically determining the focal position through spectral analysis. The light intensity function and its threshold value provide self-service capability, eliminating the need for manual focus adjustment and enabling the system to automatically adapt to the microsphere's optical characteristics.
2Measurement precision
If the second objective lens with microsphere is moved vertically downward to obtain focus, then measurement accuracy is improved, but risk of collision with sample increases
Solution Approach 1:
The system performs preliminary spectral scanning by moving the second objective lens vertically downward to obtain the light intensity function and determine the focal position before actual measurement. This preliminary action identifies the optimal focal position and prevents collision by establishing safe operating parameters in advance.
Solution Approach 2:
The system replaces direct mechanical contact-based focusing with optical-based focus determination. By using spectral analysis and light intensity function threshold detection, the system determines focal position optically rather than through mechanical trial-and-error movement, thereby preventing sample collision.
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 ultra-precise auto focusing with 10 nm-level accuracy, preventing collisions and ensuring repeatable measurements in a 100-nm-scale fine measurement area.
Implementation Method 1
a microsphere-assisted spectroscopic measuring technology using a photonic nanojet effect generated from a microsphere having a size of several microns has been introduced
Implementation Method 2
A spectrum is obtained while moving the second objective lens vertically downward
Data Source
AI summary
In a focus control method of a spectroscopic measuring apparatus, the spectroscopic measuring apparatus having a first objective lens and a second objective lens equipped with a microsphere is provided. A sample is placed on a stage. A spectrum is obtained while moving the second objective lens vertically downward. A light intensity function that changes with a distance from a sample surface is obtained from the spectrum. A focal position of the second objective lens is determined from a threshold value of the light intensity function.