Closed-Loop Gas Sampling for Precise FOUP Contamination Monitoring
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Solution Overview
Problem
Existing gas concentration measurement methods in semiconductor container environments, such as FOUPs and reticle pods, are not repeatable and precise due to changes in gas concentration caused by sample removal and introduction of clean air, leading to inaccurate contamination monitoring and potential defects in wafers or reticles.
Innovation Solution
A non-destructive gas analyzing system using spectroscopy units, particularly cavity ring-down spectroscopy, transfers gas samples to and from the container through a closed loop, maintaining constant gas concentration for precise and repeatable measurements without altering the gas properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gas samples are removed from the container for analysis, then gas concentration can be measured, but the gas concentration changes due to sample removal and clean air introduction, leading to inaccurate contamination monitoring
Solution Approach 1:
The patent extracts only a small portion of the gas sample from the container for analysis while maintaining the majority of the gas environment intact. The gas sample is taken through a sampling port without completely removing or replacing the container's atmosphere, thus preserving gas concentration stability while enabling measurement.
Solution Approach 2:
The patent introduces an intermediary sampling system that includes a sampling port, tubing, and analysis chamber. This intermediary system allows gas concentration measurement without direct contact between the container's gas environment and the external environment, preventing contamination and concentration changes during sampling.
2Reliability
If clean air is introduced to replace removed gas samples, then the container remains pressurized, but the introduced clean air alters the gas concentration and dilutes contaminants
Solution Approach 1:
The patent extracts and analyzes gas samples without introducing replacement air into the container. The sampling system is designed to take out gas for analysis while maintaining the container's pressure balance through the sampling process itself, eliminating the need for clean air introduction that would dilute contaminants.
Solution Approach 2:
The patent employs a feedback mechanism where gas concentration measurements are continuously monitored and used to adjust sampling rates and container pressure maintenance. This feedback loop ensures accurate contaminant concentration measurement while maintaining stable pressure conditions without introducing diluting clean air.
3Measurement precision
If conventional gas analysis methods are used, then gas concentration can be determined, but the measurements are not repeatable due to changing gas composition during sampling
Solution Approach 1:
The patent implements continuous gas sampling and analysis rather than discrete sampling events. The gas concentration measurement is performed continuously through a sampling port, ensuring that the measurement process does not disrupt the gas composition and that repeatable measurements can be taken at any time without changing the baseline conditions.
Solution Approach 2:
The patent designs a self-regulating sampling system that automatically maintains container pressure and gas composition during measurement. The system self-adjusts to take samples without external intervention that would alter gas concentration, ensuring that measurements are repeatable and not affected by sampling operations.
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
Enables effective, precise, and repeatable determination of gas concentrations within containers, allowing for timely contamination recognition and monitoring of container conditions, such as outgassing behavior and gasket wear, thereby enhancing semiconductor manufacturing yield.
Implementation Method 1
A non-destructive gas analysing unit, particularly a spectroscopy unit, for determining a concentration of at least one component of an amount of gas
Implementation Method 2
at least two mirrors provided in the cavity configured to reflect the laser light such that the laser light circulates multiple times within the cavity
Data Source
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AI summary
The invention relates to a method for determining a concentration of at least one component of a gas in a container (210) adapted and configured to hold wafers or reticles, comprising the steps of: transferring an amount of gas from the container (210) to a non-destructive gas analysing unit (220); determining a concentration of the amount of gas by means of the non-destructive gas analysing unit (220); and returning the amount of gas from the non-destructive gas analysing unit (220) to the container (210).