Mass Flow Controller Self-Verification Using Dual Feedback Control
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Solution Overview
Problem
Existing mass flow control devices in semiconductor fabrication processes lack the capability for in situ self-verification and calibration, leading to potential inaccuracies and yield losses due to out-of-calibration MFCs during processing.
Innovation Solution
A mass flow controller (MFC) with a controller configured to toggle between flow-based feedback control and pressure-based feedback control, utilizing first and second pressure sensors to monitor fluid pressure and pressure upstream of a pressure drop element, allowing for self-verification and recalibration of the MFC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional pressure-based MFC is used, then the device structure is simple, but the measurement precision and reliability deteriorate due to lack of self-verification capability
Solution Approach 1:
The patent combines two different control methods (flow-based feedback control using pressure decay rate and pressure-based feedback control using upstream pressure) into a single MFC device. The controller integrates both control algorithms and switches between them based on operational conditions, enabling self-verification and recalibration without requiring separate verification equipment.
Solution Approach 2:
The patent implements dual feedback control mechanisms: (1) flow-based feedback control that uses the rate of pressure decay in the chamber to determine flow rate, and (2) pressure-based feedback control that uses the upstream pressure of the pressure drop element. Both feedback loops continuously monitor and adjust the control valve to maintain accurate flow control.
2Reliability
If traditional MFC without self-verification is used, then the device complexity is low, but the reliability and productivity worsen due to out-of-calibration operations
Solution Approach 1:
The MFC device performs self-verification and self-calibration using its own internal sensors and control algorithms. The flow-based feedback control method uses the chamber's pressure decay characteristics to verify flow measurements, and the controller can automatically recalibrate by switching between control methods, eliminating the need for external verification equipment or manual calibration.
Solution Approach 2:
The patent changes the control parameter dynamically by switching between flow-based feedback (using pressure decay rate) and pressure-based feedback (using upstream pressure) depending on operational conditions. This parameter switching enables the system to adapt to different scenarios and maintain reliability without requiring complex additional hardware.
3Measurement precision
If flow-based feedback control is implemented, then the measurement precision improves through self-verification, but the use of energy increases due to continuous pressure monitoring
Solution Approach 1:
The controller periodically switches between flow-based feedback control and pressure-based feedback control rather than continuously operating one method. This periodic switching allows the system to verify measurements and recalibrate when needed while conserving energy during normal operation by using the more efficient pressure-based control method.
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
The MFC achieves continuous and accurate mass flow control with in situ self-verification and recalibration capabilities, reducing the risk of yield losses and improving process reliability.
Implementation Method 1
The first pressure sensor detects fluid pressure in the chamber
Implementation Method 2
the second pressure sensor detects fluid pressure downstream of the downstream control valve and upstream of the pressure drop element
Implementation Method 3
a pressure drop element disposed downstream of the downstream control valve
Data Source
AI summary
Mass flow controller (MFC) devices capable of self-verification and methods of providing for self-verifying mass flow control are provided. An MFC includes a chamber configured to receive a fluid, an upstream valve disposed upstream of the chamber, and a downstream control valve disposed downstream of the chamber. The MFC further includes a pressure drop element disposed downstream of the downstream control valve and first and second pressure sensors. A controller of the MFC is configured to control actuation of the downstream control valve by toggling between flow-based feedback control and pressure-based feedback control. In flow-based feedback control, a flow is monitored based on a rate of decay of pressure in the chamber as detected by the first pressure sensor upon closure of the upstream control valve. In pressure-based feedback control, a pressure upstream of the pressure drop element, as detected by the second pressure sensor, is monitored.