Spectrometric Optical System with Dual-Lamp Source and Dynamic Integration
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Solution Overview
Problem
Current spectrometric methods face challenges in achieving high signal-to-noise ratio (SNR) across a wide spectral range, particularly from DUV to NIR, due to limited dynamic range of light detectors and instability of light sources, which affects the precision of measurements in applications like semiconductor process characterization.
Innovation Solution
A method that combines a Deuterium lamp and a Quartz-Tungsten-Halogen lamp to provide a stable light source for spectrometric measurements, with adjustable integration time of the light detector to optimize SNR within the limited dynamic range, allowing for seamless signal combination across the entire spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single light source is used to cover a wide spectral range, then the spectral coverage is improved, but the stability and signal-to-noise ratio deteriorate
Solution Approach 1:
The patent divides the broadband light source into multiple narrowband sources (Deuterium lamp for UV, Xe lamp for visible/NIR) that each operate within their optimal spectral ranges. This segmentation allows each source to maintain high stability and SNR in its designated range while collectively covering the full spectral bandwidth through coordinated operation.
2Measurement precision
If the integration time of the light detector is increased, then the signal-to-noise ratio is improved, but the measurement time and risk of saturation increase
Solution Approach 1:
The patent implements dynamic adjustment of integration time based on the measured signal level and reflectance characteristics of the article. The system automatically selects optimal integration time values to achieve required SNR while preventing detector saturation, adapting to different measurement conditions in real-time.
Solution Approach 2:
The system changes the integration time parameter according to the spectral characteristics and reflectance of the measured article. By adjusting this temporal parameter dynamically, the system optimizes the balance between SNR and measurement time for each specific measurement scenario.
3Adaptability or versatility
If the dynamic range of the light detector is increased, then the measurement range is improved, but the device complexity and cost increase
Solution Approach 1:
Instead of using a single detector with extremely high dynamic range, the patent segments the measurement into multiple stages with different integration times. This approach achieves effective high dynamic range coverage by combining multiple measurements taken at different exposure levels, avoiding the need for a single complex high-range detector.
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 measurement system's performance by maintaining a high SNR and stability, enabling accurate broadband spectral measurements by optimizing integration time based on the article's reflectance and spectral characteristics, even when the dynamic range is limited.
Implementation Method 1
a first light source being a Deuterium lamp (D2)
Implementation Method 2
a second light source being a Quartz-Tungsten-Halogen lamp (QTH)
Implementation Method 3
a light detection system that transforms light returned from the illuminated article into an electrical signal
Data Source
AI summary
A system and method for use in spectrometric measurements of an article using selecting an optimal integration time range of the light detection system during which the measurement is to be applied, the optimal integration time being that at which a required value of signal to noise ratio (SNR) of the measurements is obtainable.