Czerny-Turner Spectrometer with Narrow Bandpass Filter
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Solution Overview
Problem
Current semiconductor process monitoring technologies face challenges in achieving high resolution and signal-to-noise ratios, particularly in detecting small changes in Angstrom-scale layers and complex process chemistries, due to limitations in spectrometer resolution and out-of-band light rejection, which hinder robust process control and data accuracy.
Innovation Solution
A compact very high resolution spectrometer system utilizing a modified Czerny-Turner configuration with narrow pass band filters and selective optical components, capable of achieving resolutions up to 0.025 nm, is developed to enhance the detection of individual molecular rovibrational emission lines and improve out-of-band light rejection, enabling more precise monitoring of semiconductor processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spectrometer resolution is used, then device complexity is reduced, but measurement precision deteriorates due to inability to detect small changes in Angstrom-scale layers
Solution Approach 1:
The spectrometer is divided into modular components including a Czerny-Turner configuration with separate dispersion elements and detector arrays. This segmentation allows high resolution to be achieved through coordinated modular components rather than a monolithic complex system, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent employs a two-dimensional detector array that captures spectral data across multiple wavelengths simultaneously, adding a dimensional approach to resolution. This allows high spectral resolution to be achieved through spatial distribution of detection elements rather than increasing optical path length or complexity.
2Measurement precision
If conventional out-of-band light rejection is used, then device complexity is reduced, but measurement precision deteriorates due to inability to reject out-of-band light
Solution Approach 1:
A narrow bandpass filter is introduced as an intermediary optical element between the light source and the detector. This filter selectively transmits only the desired wavelength range while blocking out-of-band light, achieving high rejection ratios without requiring complex multi-stage filtering systems.
Solution Approach 2:
The optical system employs wavelength-selective components that provide different transmission characteristics at different wavelengths. The narrow bandpass filter provides high rejection for out-of-band wavelengths while maintaining high transmission for the target wavelength, achieving local optimization of optical quality without overall system complexity.
3Measurement precision
If very high resolution spectrometer is used, then measurement precision is improved for detecting molecular rovibrational emission lines, but device complexity increases
Solution Approach 1:
The Czerny-Turner spectrometer configuration is designed to handle multiple spectral ranges and detection requirements through a single universal optical path. The same dispersion elements and detector array can be used for various semiconductor process monitoring applications, achieving high resolution without requiring application-specific complex optical systems.
Solution Approach 2:
The patent uses a detector array that captures spectral information across multiple wavelengths simultaneously, creating a digital copy of the spectrum. This allows high resolution to be achieved through computational analysis of the digital spectrum rather than requiring proportionally complex optical dispersive elements.
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 system provides improved signal-to-noise ratios and increased sensitivity to plasma and chemical changes, allowing for more accurate process control and characterization of semiconductor processes, particularly in fast pulsed plasmas and complex structures, within a compact and cost-effective package.
Implementation Method 1
filtering the optical signal using a narrow pass band filter
Implementation Method 2
processing the filtered optical signal using a selective combination of optical components based on a desired resolution
Data Source
AI summary
An optical instrument of very high resolution is provided that can be used for monitoring semiconductor processes. Very high resolution may be considered in this application space to be resolutions sufficient to permit resolving of individual molecular rovibrational emission lines. In one example an optical instrument is provided that includes: (1) an optical interface that receives an optical fiber, (2) a narrow band pass filter that filters out a portion of an optical signal received via the optical fiber, (3) optical components that are selectively combined to process at least a portion of the unfiltered optical signal, wherein the optical components include a sensor that receives the unfiltered optical signal, and (4) one or more processors that process electrical signals from the sensor. The optical instrument can be a spectrometer suitable for a process control instrument.