Mass Flow Controller Inlet Pressure Reporting Across Valve States
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Solution Overview
Problem
Existing mass flow controllers (MFCs) lack effective in situ verification and calibration methods, leading to potential out-of-calibration issues during semiconductor fabrication processes, which can result in lower product yield and significant expenses.
Innovation Solution
A mass flow controller (MFC) with integrated pressure sensors and a controller that toggles between flow-based and pressure-based feedback control modes, using rate-of-pressure-decay measurements for initial flow control and downstream pressure measurements for verification, allowing continuous and accurate flow regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional pressure-based MFCs are used without in situ verification, then device complexity is reduced, but manufacturing precision and reliability deteriorate due to potential out-of-calibration issues
Solution Approach 1:
The patent combines flow control and verification functions into a single integrated MFC device. The controller merges flow-based feedback control and pressure-based feedback control into one system, eliminating the need for separate verification equipment while maintaining high precision through dual-mode operation
Solution Approach 2:
The patent implements feedback control by having the controller continuously monitor chamber pressure via the pressure sensor and adjust the control valve accordingly. The controller toggles between flow-based feedback (using pressure decay rate) and pressure-based feedback (using absolute pressure readings), ensuring continuous calibration and high flow control precision without adding external verification devices
2Measurement precision
If the pressure sensor continuously updates inlet pressure readings, then measurement precision is improved, but reliability worsens when the upstream valve is closed and pressure is not representative
Solution Approach 1:
The patent implements dynamic pressure reading selection where the controller adjusts the inlet pressure reporting strategy based on the upstream valve state. When the upstream valve is open, the controller uses real-time pressure sensor readings; when the valve is closed, the controller switches to using the last valid reading from buffer memory. This dynamic adaptation ensures reliable and accurate pressure measurements under varying operational conditions
3Productivity
If flow-based feedback control is used during upstream valve closure, then productivity is maintained through continuous control, but measurement precision deteriorates due to pressure decay not representing actual flow conditions
Solution Approach 1:
The patent implements periodic switching between flow-based feedback control and pressure-based feedback control modes. The controller alternates between using pressure decay rate measurements and absolute pressure readings, allowing the system to maintain continuous productivity while periodically verifying and correcting flow measurements against reliable pressure-based references, thus preventing cumulative measurement errors
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 self-verification and calibration of MFCs during operations, ensuring continuous and stable flow control without disrupting process conditions, thereby maintaining high product yield and reducing operational costs.
Implementation Method 1
a pressure sensor that detects fluid pressure in the chamber
Implementation Method 2
In pressure-based feedback control, a pressure upstream of the pressure drop element, as detected by the second pressure sensor, is monitored
Implementation Method 3
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
Data Source
AI summary
Mass flow control (MFC) devices capable of reporting inlet pressure and methods of reporting inlet pressure are provided. A mass flow controller (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 sensor that detects fluid pressure in the chamber. The MFC further includes a controller configured to control actuation of the upstream valve. The controller is configured to toggle between two modes of reporting a measured inlet pressure. In a first mode, the controller reports a measured inlet pressure based on a reading from the pressure sensor and storing the reading to a buffer when the upstream valve is open. In a second mode, the controller reports the measured inlet pressure based on the reading stored to the buffer when the upstream valve is closed.