Dual Resolution Spectrometer for Semiconductor Thin Film Measurement
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Solution Overview
Problem
Existing spectrometers used in semiconductor device manufacturing lack sufficient resolution, particularly in the short wavelength region, which affects the precision of measurements such as thickness and Critical Dimension (CD) of thin films.
Innovation Solution
A dual resolution spectrometer is introduced, featuring a diffraction grating with a higher grating density and two mirrors with different focal lengths, allowing for the separation and detection of light in two wavelength regions with different resolutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional spectrometer with a single diffraction grating is used, then the device structure is simple, but the wavelength resolution in the short wavelength region is insufficient
Solution Approach 1:
The spectrometer is divided into multiple functional sections: a first diffraction grating for initial wavelength separation, a mirror for reflecting and focusing light, and a second diffraction grating for further wavelength separation. This segmentation allows each component to specialize in specific wavelength ranges, achieving high resolution in the short wavelength region while maintaining overall system functionality.
Solution Approach 2:
A mirror is introduced as an intermediary component between the first and second diffraction gratings. This mirror reflects and focuses the dispersed light from the first grating onto the second grating, enabling the light to undergo sequential wavelength separation. The intermediary mirror facilitates the transition between two diffraction stages, achieving enhanced resolution without requiring a single complex grating.
2Measurement precision
If the diffraction grating density is increased to improve resolution, then the wavelength resolution increases, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of using a single high-density diffraction grating that would be difficult to manufacture, the system segments the diffraction function across two gratings with moderate densities. The first grating performs initial separation, and the second grating performs fine separation, achieving equivalent or superior resolution to a single high-density grating but with easier fabrication for each individual component.
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 dual resolution spectrometer significantly increases the wavelength resolution in the short wavelength region by up to four times, enhancing the precision of semiconductor device measurements and improving the reliability of thickness and CD measurements.
Implementation Method 1
The diffraction grating disperses light from the first mirror according to a wavelength of the light from the first mirror
Implementation Method 2
The first mirror reflects light from the slit to a diffraction grating
Data Source
AI summary
A dual resolution spectrometer includes a slit plate comprising a slit receiving light reflected from a measurement target. The slit plate directs the light reflected from the measurement target to a first mirror. The first mirror reflects light from the slit to a diffraction grating. The diffraction grating disperses light from the first mirror according to a wavelength of the light. The diffraction grating directs light in a first wavelength region to a second mirror and directs light in a second wavelength region to a third mirror. The second mirror reflects the light in the first wavelength region to a detector. The third mirror reflects the light in the second wavelength region to the detector. The detector detects the light in the first wavelength region and the light in the second wavelength region with different resolutions from each other.