Mass Flow Controller Temperature Compensation
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Solution Overview
Problem
Conventional mass flow controllers do not adequately account for temperature changes, leading to variations in response time when controlling gas flow rates, which can affect the timing and quality of gas supply in semiconductor manufacturing equipment.
Innovation Solution
A mass flow controller that includes a thermometer to measure gas temperature and adjusts the control signal to compensate for temperature differences, ensuring the valve opening is optimized to maintain consistent flow rates, thereby reducing response time changes due to temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mass flow controller uses a conventional flow control valve without temperature compensation, then the device structure remains simple, but the response time varies significantly with temperature changes
Solution Approach 1:
The control means performs preliminary action by calculating and storing correction values for different temperature conditions in advance. When temperature changes occur, the system retrieves and applies the appropriate correction value immediately, rather than calculating it in real-time. This preliminary preparation of correction data enables fast response time compensation without adding complex real-time computation requirements.
Solution Approach 2:
The invention changes the control parameter by introducing temperature-dependent correction values that modify the relationship between control signal and valve opening. The control means adjusts the valve opening based on both the control signal and the current temperature condition, using stored correction values to compensate for temperature effects. This parameter change approach maintains consistent response time across different temperatures while keeping the hardware structure simple.
2Manufacturing precision
If the mass flow controller applies temperature-based correction to maintain consistent response time, then the flow rate control accuracy improves, but the control algorithm complexity increases
Solution Approach 1:
The control means performs preliminary action by calculating and storing correction values for different temperature conditions in advance. When temperature changes occur, the system retrieves and applies the appropriate correction value immediately, rather than calculating it in real-time. This preliminary preparation of correction data enables fast response time compensation without adding complex real-time computation requirements.
Solution Approach 2:
The invention uses copying by storing correction values in a lookup table or memory structure. Instead of performing complex real-time calculations, the control means copies the pre-calculated correction value corresponding to the current temperature condition and applies it to the control signal. This copying approach simplifies the real-time control algorithm while maintaining high accuracy.
3Speed
If the mass flow controller uses a piezoelectric element to change valve opening proportionally to voltage, then the control response is linear and predictable, but the response time increases when temperature differs from reference temperature
Solution Approach 1:
The invention changes the control parameter by introducing temperature-dependent correction values that modify the relationship between control signal and valve opening. The control means adjusts the valve opening based on both the control signal and the current temperature condition, using stored correction values to compensate for temperature effects. This parameter change approach maintains consistent response time across different temperatures while keeping the hardware structure simple.
Solution Approach 2:
The control means incorporates feedback by measuring the actual temperature and using it to select appropriate correction values. The system continuously monitors temperature conditions and adjusts the control signal accordingly, creating a closed-loop control system that maintains consistent valve response characteristics across different temperature conditions.
Data Source
AI summary
A control means configured to perform flow rate control in which the control means outputs a control signal to a flow control valve to control a valve opening such that a measured flow rate of gas measured by a flow meter matches a set flow rate adjusts intensity of the control signal such that an absolute value of a change amount of the valve opening becomes larger as measured temperature of the gas measured by a thermometer becomes further higher than reference temperature, while the absolute value of the change amount of the valve opening becomes smaller as the measured temperature becomes further lower than the reference temperature. Thereby, change of response time on changing the valve opening of the flow control valve due to the difference between the measured temperature of the gas and the reference temperature can be reduced.