Pressure Flow Controller Gas Concentration Detection by Pressure Drop
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Solution Overview
Problem
Conventional pressure-type flow rate control devices in semiconductor manufacturing require a separate concentration measuring device to accurately control the concentration of source gases in mixed gases, increasing apparatus size and cost.
Innovation Solution
A method that uses a pressure-type flow rate control device with a restriction portion, upstream valve, and pressure sensor to detect pressure drop characteristics after the upstream valve is closed, allowing for concentration detection of a specified gas in a mixed gas without a separate concentration measuring device, by comparing detected pressure drop characteristics with stored reference characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate concentration measuring device is added to accurately detect source gas concentration in mixed gases, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The pressure sensor originally designed for flow rate control is made to perform dual functions: maintaining flow rate control while simultaneously detecting source gas concentration through pressure drop characteristics analysis. This eliminates the need for a separate concentration measuring device.
Solution Approach 2:
The flow rate control device itself generates the measurement signal by utilizing its own pressure sensor to detect pressure drops that occur when the upstream valve is closed, allowing the system to self-diagnose gas concentration without external measuring equipment.
2Measurement precision
If a separate concentration measuring device is added to accurately detect source gas concentration, then measurement precision is improved, but cost increases
Solution Approach 1:
The pressure sensor is repurposed to serve both flow rate control and concentration measurement functions, eliminating the need to manufacture and install separate concentration measuring equipment, thereby reducing overall system cost.
Solution Approach 2:
The system uses its existing pressure sensor and valve mechanisms to generate and detect pressure drop signals for concentration measurement, avoiding additional manufacturing costs for external measuring devices.
3Device complexity
If pressure drop characteristics are used for concentration detection, then device complexity is reduced, but measurement precision must be maintained
Solution Approach 1:
The controller measures pressure drops, compares them with reference values, and uses this feedback to determine gas concentration. This closed-loop approach ensures accurate concentration detection while using only existing device components.
Solution Approach 2:
The system detects concentration changes by monitoring variations in pressure drop parameters when the upstream valve is closed. Different gas compositions produce distinct pressure drop characteristics that the controller analyzes to determine concentration.
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 precise detection of source gas concentration in mixed gases within the pressure-type flow rate control device, eliminating the need for a separate concentration measuring device and reducing apparatus size and cost.
Implementation Method 1
detecting, by the pressure sensor, one or more pressure drop characteristics occurring after the upstream valve is changed from open to closed
Data Source
AI summary
A method for detecting the concentration of a specified gas contained in a mixed gas includes, in a pressure-type flow rate control device including a restriction portion, an upstream valve provided upstream of the restriction portion, and a pressure sensor for measuring the pressure between the restriction portion and the upstream valve, a step of flowing the mixed gas from the upstream side of the upstream valve in a state in which the pressure on the downstream side of the restriction portion is lower than the pressure on the upstream side of the restriction portion, a step of determining with a pressure sensor pressure drop characteristics occurring after the upstream valve is changed from an open to a closed state, and a step of determining the concentration of the specified gas in the mixed gas based on the pressure drop characteristics.