Self-Verification Mass Flow Controller Using Pressure Sensors
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Solution Overview
Problem
Mass flow controllers (MFCs) often become out of calibration during semiconductor manufacturing processes, leading to lower yields or complete failure, as existing systems require offline testing and do not continuously verify accuracy in real time.
Innovation Solution
A pressure-based mass flow control system that includes a control valve, controller, and a source of fluid for real-time verification, using pressure and temperature sensors to calculate and adjust flow rates, allowing for self-verification and potential recalibration during process steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offline testing with mass flow verifiers is used to test MFC accuracy, then measurement precision is improved, but productivity deteriorates due to process interruption and time loss
Solution Approach 1:
The system performs preliminary calibration using a known reference flow rate before the actual manufacturing process begins. This preliminary action establishes a baseline for accuracy verification, allowing the MFC to be tested against the reference value without interrupting the main production process. The controller stores this reference measurement and uses it for continuous verification during operation.
Solution Approach 2:
The system enables continuous accuracy verification by automatically comparing the MFC's measured flow rate against the stored reference flow rate during the entire manufacturing process. This continuous monitoring occurs without stopping the process, maintaining productivity while ensuring the MFC remains within acceptable accuracy tolerances throughout production.
2Reliability
If offline testing is performed to verify MFC calibration, then reliability is improved through accurate detection, but loss of time increases due to process interruption
Solution Approach 1:
The system performs preliminary calibration using a known reference flow rate before the actual manufacturing process begins. This preliminary action establishes a baseline for accuracy verification, allowing the MFC to be tested against the reference value without interrupting the main production process. The controller stores this reference measurement and uses it for continuous verification during operation.
Solution Approach 2:
The system implements a feedback mechanism where the controller continuously compares the MFC's measured flow rate against the stored reference flow rate. When the measured value deviates from the reference by more than a predetermined tolerance, the system generates an alert or error signal, enabling timely intervention while maintaining process continuity.
3Productivity
If real-time verification is implemented using pressure and temperature sensors, then productivity is improved through continuous monitoring, but device complexity increases
Solution Approach 1:
The system uses pressure and temperature sensors as intermediary measurement devices to indirectly verify MFC accuracy. Instead of requiring direct flow rate measurement with complex equipment, the system measures easily obtainable parameters (pressure and temperature) and uses the ideal gas law to calculate flow rate. This intermediary approach simplifies the verification system while enabling continuous monitoring.
Solution Approach 2:
The system replaces complex mechanical flow measurement devices with electronic sensing and calculation. Instead of using mechanical mass flow verifiers that require physical connection and process interruption, the system uses electronic pressure and temperature sensors combined with computational methods (ideal gas law) to verify MFC accuracy, reducing mechanical complexity while enabling real-time operation.
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 continuous accuracy verification and recalibration of MFCs in real time, preventing calibration drift and ensuring consistent flow rates, thereby reducing the risk of product failure and increasing yield.
Implementation Method 1
a flow restrictor to generate chocked flow condition for flow measurement
Implementation Method 2
a pressure sensor for providing a pressure measurement signal representative of the measured pressure of fluid upstream to the flow restrictor
Implementation Method 3
a temperature sensor for providing a temperature measurement signal representative of the measured temperature of fluid in the system
Data Source
AI summary
A mass flow control system can be self verified for its accuracy when controlling a flow to a process. The system comprises: a control valve for controlling the flow of fluid through the system as a function of a control signal; a controller for generating the control signal as a function of measured flow of fluid through the system and a targeted flow set point; a pressure sensor for measuring the controlling fluid pressure for use in measuring and verifying the flow rate; and a source of fluid for providing a known volume of fluid for use in verifying the system accuracy anytime between steps of the flow control process.