Imaging Apparatus Using Diffraction Grids and Time Delay Integration
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Solution Overview
Problem
Conventional optical semiconductor inspection apparatuses face challenges in improving optical resolution due to difficulties in securing sufficient transmission coefficients and suppressing aberration over a wide wavelength range, leading to increased inspection time and limited resolution capabilities.
Innovation Solution
The proposed imaging apparatus employs a configuration with a first and second diffraction grid positioned at conjugate focal planes of the illumination and imaging optical systems, respectively, and a stage for sample movement, using a time delay integration method to synchronize the photographing of reflected light, thereby improving optical resolution and reducing imaging time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical inspection methods are used with deep UV light and high NA objective lens, then optical resolution is improved, but inspection time increases and transmission coefficient becomes insufficient
Solution Approach 1:
The inspection process is segmented into multiple passes: a first inspection at higher speed with relaxed resolution requirements, followed by a second inspection only in regions of interest identified from the first pass. This segmentation allows the system to maintain high overall inspection speed while still achieving high resolution where needed.
Solution Approach 2:
Instead of applying high NA and deep UV illumination to the entire wafer surface, the system applies high resolution inspection partially only to regions of interest (defect candidates) identified by the initial lower resolution pass. This partial application of excessive action (high NA illumination) reduces total inspection time while maintaining measurement precision where required.
2Measurement precision
If wide wavelength band light is used to improve resolution, then frequency range resolution is enhanced, but transmission coefficient and aberration control become difficult
Solution Approach 1:
The system uses different illumination wavelengths locally: deep UV light (193nm or 248nm) is applied specifically at defect candidate regions where high frequency resolution is needed, while other regions use broader spectrum illumination. This local application of specific wavelength quality maintains transmission coefficient overall while achieving high frequency range resolution where required.
Solution Approach 2:
The system dynamically changes the wavelength parameter of illumination light based on inspection needs. By switching between deep UV wavelengths (193nm, 248nm) and adjusting the wavelength band, the system optimizes both transmission coefficient and frequency range resolution for different inspection scenarios without compromising overall reliability.
3Measurement precision
If high NA objective lens is used to improve resolution, then optical resolution is enhanced, but aberration suppression becomes extremely difficult
Solution Approach 1:
The inspection is segmented into two stages: first a rapid scan with lower NA to identify regions of interest, then a focused high NA inspection only in those regions. This segmentation allows the use of high NA lenses (increasing device complexity) without requiring aberration suppression across the entire field of view, thereby reducing the practical complexity of aberration management.
Solution Approach 2:
The high NA objective lens is applied partially only to regions of interest rather than the entire inspection field. This partial application reduces the burden of aberration suppression complexity while maintaining high optical resolution where it matters most, avoiding the need for extremely complex aberration correction systems across the full field.
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 configuration enhances optical resolution and reduces imaging time by effectively utilizing structured illumination and synchronized image capture, allowing for improved frequency range resolution without the need for extensive image processing.
Implementation Method 1
a first diffraction grid positioned at a conjugate focal plane of a sample of an illumination optical system and transmitting the illumination light toward a sample
Implementation Method 2
a photographing unit to receive the reflected light from the sample through the second diffraction grid and synchronized with a movement of the sample according to the stage to photograph in time delay integration method
Data Source
AI summary
An imaging apparatus includes an illumination light source to output an illumination light, an illumination optical system to transmit the illumination light toward a sample, an imaging optical system to transmit light reflected from the sample, a stage to move the sample in a predetermined transfer direction, and a photographing unit to receive the reflected light. The imaging apparatus may include one or more diffraction grids located at conjugate focal planes of the sample. The operation of the photographing unit may be synchronized with a movement of the sample by the stage to obtain an image in accordance with a time delay integration method.