Reticle Defect Inspection Focal Point Correction
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Solution Overview
Problem
Existing reticle defect inspection apparatuses face challenges in achieving high detection sensitivity due to focal point shifts caused by varying reticle thickness, especially when attempting simultaneous inspection of transmission and reflection using different wavelengths, leading to blurring and reduced contrast.
Innovation Solution
A reticle defect inspection apparatus with a focusing lens driving mechanism to correct focal point shifts in the transmitted illumination optical system, allowing for simultaneous detection of transmitted and reflected light while maintaining high precision by separating and adjusting the illumination areas to prevent overlap and blurring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If different wavelengths are used for transmitted light inspection and reflected light inspection, then defect detection sensitivity is improved, but optical system design becomes more difficult and aberration control becomes harder
Solution Approach 1:
The patent changes the wavelength parameter from using different wavelengths for transmission and reflection to using a single wavelength for both inspection methods. This simplifies the optical system design while maintaining defect detection sensitivity by adjusting other optical parameters to compensate for the wavelength constraint.
2Device complexity
If a single wavelength is used for both transmitted light and reflected light inspection, then optical system design is simplified, but focal point shifts occur due to varying reticle thickness causing image blurring
Solution Approach 1:
The patent segments the illumination into two separate areas: a transmitted light illumination area and a reflected light illumination area. By spatially separating these illumination zones and using a single wavelength for both, the system avoids focal point shifts and image blurring while maintaining optical design simplicity. The separation ensures that transmitted and reflected light paths do not interfere with each other.
3Productivity
If transmitted light and reflected light illumination areas overlap, then inspection efficiency is improved, but image blurring occurs reducing detection accuracy
Solution Approach 1:
The patent divides the illumination area into distinct transmitted light and reflected light zones that do not overlap. This spatial segmentation prevents image blurring and maintains detection accuracy while still enabling simultaneous inspection of both transmission and reflection modes, thereby preserving inspection efficiency.
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 high-sensitivity defect inspection by correcting focal point shifts, ensuring clear and distinct images of both transmission and reflection, thereby improving detection accuracy and precision.
Implementation Method 1
a transmitted light obtained by a first inspection light transmitted through a sample
Implementation Method 2
a reflected light obtained by a second inspection light reflected by a sample
Data Source
AI summary
A reticle defect inspection apparatus that can carry out a defect inspection with high detection sensitivity are provided. The apparatus includes an optical system of transmitted illumination for irradiating one surface of a sample with a first inspection light, an optical system of reflected illumination for irradiating another surface of the sample with a second inspection light, and a detecting optical system that can simultaneously detect a transmitted light obtained by the first inspection light being passed through the sample and a reflected light obtained by the second inspection light being reflected by the sample. And the optical system of transmitted illumination includes a focusing lens driving mechanism for correcting a focal point shift of the transmitted light resulting from thickness of the sample.