Flow Rate Controller Output Accuracy via Diaphragm Pressure
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Solution Overview
Problem
Existing methods for obtaining the output flow rate of a flow rate controller in substrate processing apparatuses face challenges in accuracy due to reliance on upstream pressure measurements, leading to significant errors in calculating the actual output flow rate.
Innovation Solution
A method involving a diaphragm mechanism and a tank is used to adjust the pressure in a second pipe downstream of the flow rate controller, allowing for precise calculation of the output flow rate using pressure and temperature values in the tank, thereby accounting for downstream pressure effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the output flow rate is calculated using only upstream pressure measurement, then the measurement system is simple, but the calculation accuracy is poor due to large errors
Solution Approach 1:
A diaphragm mechanism is introduced as an intermediary component between the flow rate controller and the tank. The diaphragm transmits downstream pressure information to the calculation system, enabling accurate flow rate determination without directly measuring downstream pressure. This mediator resolves the contradiction by providing accurate measurement data while maintaining system simplicity.
Solution Approach 2:
The patent replaces direct mechanical pressure measurement in the downstream line with a diaphragm-based pressure transmission system. The diaphragm converts downstream pressure into a measurable form that can be used for calculation, substituting a complex direct measurement system with a simpler indirect measurement approach that achieves the same or better accuracy.
2Measurement precision
If the diaphragm mechanism and tank system is used to measure downstream pressure, then the output flow rate accuracy is improved, but the device complexity increases
Solution Approach 1:
The diaphragm mechanism serves multiple functions: it transmits downstream pressure information, isolates the measurement system from the gas flow path, and enables accurate flow rate calculation. The tank also serves dual purposes as both a pressure reference and a measurement chamber. This multi-functionality reduces the need for additional components, offsetting the added complexity.
3Measurement precision
If calibration is performed frequently to correct flow rate errors, then the measurement accuracy is maintained, but the processing time is increased
Solution Approach 1:
The system performs preliminary calibration by establishing the relationship between upstream pressure, downstream pressure (via diaphragm), and actual flow rate before normal operation. This preliminary action creates a calibration curve or lookup table that can be used during normal processing, reducing the need for frequent recalibration and minimizing time loss.
Solution Approach 2:
The system implements feedback by continuously monitoring both upstream and downstream pressures and using this information to correct flow rate calculations in real-time. The feedback mechanism allows the system to maintain accuracy without frequent manual calibration, as the dual-pressure measurement provides continuous correction data.
Data Source
AI summary
A method of obtaining the output flow rate of the flow rate controller according to an aspect is provided. The method including a first step of outputting gas whose flow rate is adjusted according to a designated set flow rate from the flow rate controller, in a state where the diaphragm mechanism is opened; a second step of adjusting the diaphragm mechanism so that the pressure in the second pipe is the target pressure value, in a state where the output of gas from the flow rate controller is continued in the first step; and a third step of obtaining the output flow rate of the flow rate controller by using a pressure value and a temperature value in the tank, after the pressure in the second pipe is set to the target pressure value in the second step.