Flow Rate Controller Output Calculation Using Pressure Rise
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Solution Overview
Problem
Conventional methods for calculating the output flow rate of pressure type flow rate controllers in gas supply systems for substrate processing apparatuses are prone to errors due to large internal volumes of processing vessels and temperature changes, and alternative methods using external flow rate measuring devices increase costs.
Innovation Solution
A method that calculates the output flow rate using previously known volumes within the gas supply system and the rise rate of pressure measurement values over time, employing pressure type flow rate controllers with orifices and pressure gauges, and controlling valves to stabilize and measure pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the conventional build-up method is used to calculate the output flow rate of the flow rate controller, then the calculation can be performed using the processing vessel, but the large internal volume of the processing vessel introduces error factors such as temperature difference and time-dependent changes
Solution Approach 1:
The patent extracts the measurement function from the processing vessel by using a separate, smaller measurement vessel. This removes the processing vessel's problematic characteristics (large volume, temperature gradients, time-dependent changes) from the flow rate measurement process, thereby improving measurement precision without adding external expensive devices
Solution Approach 2:
The system is segmented into a gas supply system with flow rate controllers and a separate measurement system using a measurement vessel. This segmentation allows the measurement function to be performed in a controlled, small-volume environment rather than relying on the large processing vessel, reducing measurement errors
2Measurement precision
If a flow rate measuring device is provided within the gas supply system to calculate the output flow rate, then the calculation accuracy improves, but the cost of the gas supply system increases
Solution Approach 1:
The measurement vessel serves multiple functions: it acts as both a collection vessel for the gas and a measurement chamber for flow rate calculation. By making the vessel multi-functional, the patent avoids adding dedicated expensive measurement devices while still achieving accurate flow rate calculation
Solution Approach 2:
The system uses its own existing components (measurement vessel, pressure gauge, temperature sensor) to perform the flow rate measurement function. The gas supply system measures its own output using readily available components rather than requiring external specialized measurement equipment, thereby reducing cost
3Productivity
If the conventional build-up method is used with the processing vessel, then the output flow rate can be calculated, but temperature differences within the processing vessel and changes with time introduce errors
Solution Approach 1:
The patent performs preliminary measurement in a small measurement vessel under controlled conditions before the gas is supplied to the large processing vessel. This preliminary action allows accurate flow rate calculation to be performed under stable conditions, and the results can then be used to control the flow rate controllers for subsequent processing
Solution Approach 2:
The patent changes the volume parameter from the large processing vessel volume to a small measurement vessel volume for the measurement process. This parameter change fundamentally improves measurement reliability by eliminating the temperature gradients and time-dependent changes that occur in large vessels, while still enabling flow rate calculation capability
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 calculation of output flow rates using existing components in the gas supply system, reducing errors and costs associated with external measuring devices.
Implementation Method 1
an output flow rate of the flow rate controller as the measurement target is calculated from an internal pressure of the processing vessel
Implementation Method 2
an output flow rate of the flow rate controller as the measurement target is calculated from an internal pressure of the processing vessel, an internal temperature of the processing vessel and a previously known internal volume of the processing vessel
Data Source
AI summary
A gas, whose flow rate is adjusted by a flow rate controller as a measurement target, is supplied into a processing vessel in a state that a third valve of the gas supply system provided at an upstream side of the processing vessel is opened. While the gas is continuously supplied, the third valve is closed after a pressure measurement value of a pressure gauge within a flow rate controller for pressure measurement is stabilized. After the third valve is closed, an output flow rate of the flow rate controller as the measurement target is calculated from a previously known volume of the gas supply system in which the gas supplied through the flow rate controller as the measurement target is collected and a rise rate of the pressure measurement value of the pressure gauge within the flow rate controller for pressure measurement with respect to time.