Wavelength-Selective Overlay Measurement for Semiconductor Lithography
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Solution Overview
Problem
Conventional overlay measuring systems in semiconductor chip fabrication face errors due to refraction or scattering of visible light with wavelengths similar to overlay pattern line widths, leading to inaccurate overlay compensation values and decreased yield rates in photolithography processes.
Innovation Solution
An overlay measuring apparatus that generates visible light with multiple wavelengths, selects a single wavelength for incident light, and uses image signals to acquire and store overlay pattern images, selecting clear images to project with specific colors, thereby reducing errors caused by refraction or scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If visible light with multiple wavelengths is used to image overlay patterns, then the imaging capability is improved, but measurement precision deteriorates due to refraction and scattering errors
Solution Approach 1:
The patent segments the white light into multiple discrete wavelength components using a diffraction grating, allowing the imaging unit to capture overlay pattern images at different wavelengths separately. This segmentation enables selective use of wavelengths that avoid refraction and scattering issues while maintaining comprehensive imaging capability.
Solution Approach 2:
The patent changes the wavelength parameter of light used for imaging by selecting specific wavelengths from the spectrum. The imaging unit captures images at multiple wavelengths, and the system selects wavelengths that minimize refraction and scattering effects, thereby improving measurement precision while maintaining imaging capability.
2Illumination intensity
If white light with multiple wavelengths is used for overlay pattern imaging, then the imaging quality is improved, but overlay measurement accuracy deteriorates due to wavelength-dependent refraction and scattering
Solution Approach 1:
The patent extracts specific wavelength components from white light using a diffraction grating and selects only those wavelengths that do not cause refraction or scattering errors. By taking out the problematic wavelength components and retaining only the suitable ones, the system maintains high imaging quality while ensuring accurate overlay measurements.
Solution Approach 2:
The system changes the wavelength parameter by capturing images at multiple discrete wavelengths and selecting the optimal wavelength for measurement. This parameter change allows the system to avoid wavelengths that cause refraction and scattering while maintaining sufficient illumination intensity for high-quality imaging.
3Device complexity
If overlay patterns are measured using conventional single-wavelength light, then measurement simplicity is maintained, but measurement precision deteriorates due to refraction and scattering errors
Solution Approach 1:
The patent introduces dynamic wavelength selection capability to the measurement system. The imaging unit can switch between different wavelengths, and the system dynamically selects the optimal wavelength for each measurement based on the overlay pattern characteristics. This dynamic approach maintains operational simplicity while significantly improving measurement precision.
Solution Approach 2:
The patent makes the measurement system universal by enabling it to operate at multiple wavelengths. The imaging unit and control system are designed to handle multiple wavelength inputs, allowing the system to adapt to different measurement conditions and pattern types while maintaining a relatively simple overall structure.
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 approach enhances the accuracy of overlay compensation values, improving the yield rate of photolithography processes by minimizing errors associated with light refraction and scattering, resulting in more precise pattern formation on semiconductor chips.
Implementation Method 1
Conventional overlay measuring systems in semiconductor chip fabrication face errors due to refraction or scattering of visible light with wavelengths similar to overlay pattern line widths
Implementation Method 2
Conventional overlay measuring systems in semiconductor chip fabrication face errors due to refraction or scattering of visible light with wavelengths similar to overlay pattern line widths
Implementation Method 3
uses visible light reflected from the plurality of overlay patterns to project the overlay patterns with a predetermined color
Data Source
AI summary
An overlay measuring apparatus includes a light source which generates visible light with a plurality of wavelengths, an optical module which selects visible light with a single wavelength from the visible light generated by the light source, makes the visible light with a single wavelength incident on a plurality of overlay patterns, and uses visible light reflected from the plurality of overlay patterns to project the overlay patterns with a predetermined color, an imaging unit which acquires images of the plurality of overlay patterns according to individual wavelengths of the visible light and acquires corresponding image signals, and a control unit which outputs a control signal to the optical module so that the optical module can project the overlay pattern with a specific color using information associated with the individual wavelengths of the visible light that is used to project the overlay pattern image selected by a selection unit.