Dual-Meter Mass Flow Controller Real-Time Calibration

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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 do not continuously monitor calibration settings in real time.

Innovation Solution

A mass flow controller system with first and second flow meters, upstream and downstream proportional control valves, and a system processor/controller that generates a control signal to maintain setpoint flow rates, includes a closed-loop pressure controller to regulate pressure and verify flow rates using thermal and pressure sensing, allowing for real-time calibration checks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If off-line testing with mass flow verifiers is used to test MFC calibration, then measurement precision is improved, but productivity deteriorates because the MFC must be taken out of service for testing

Engineering Contradiction:

Improvecalibration test accuracyVSAvoidprocess continuity

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The system enables continuous calibration verification by implementing real-time monitoring of flow rates through dual mass flow meters during normal semiconductor manufacturing operations. The MFC remains in service while its calibration is continuously verified, eliminating the need for off-line testing and maintaining uninterrupted production.

Inventive Principle:

Principle #20Continuity of useful action

2Reliability

If real-time monitoring of MFC calibration is implemented, then reliability is improved, but device complexity increases due to additional sensors and control systems

Engineering Contradiction:

Improvecalibration accuracy maintenanceVSAvoidsystem structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system performs self-verification by using a second mass flow meter to monitor the flow rate controlled by the MFC. The controller compares the setpoint flow rate with the actual flow rate measured by the second meter, enabling the system to automatically detect calibration drift without external intervention or complex additional hardware.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The second mass flow meter serves multiple functions: it acts as both a flow measurement device for process control and a verification device for calibration monitoring. This multi-functionality reduces the need for separate dedicated calibration testing equipment, thereby limiting the increase in system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Loss of time

If continuous calibration monitoring is performed, then loss of time is reduced by early detection of calibration drift, but use of energy increases due to continuous operation of additional sensors and processors

Engineering Contradiction:

Improvedetection time of calibration driftVSAvoidenergy consumption of monitoring system

Core Design Contradiction:

Loss of timeVSUse of energy by moving object

Solution Approach 1:

The system replaces periodic mechanical off-line testing with electronic continuous monitoring using mass flow meters and a digital controller. This substitution enables real-time detection of calibration drift, significantly reducing the time loss associated with undetected calibration errors, while the energy consumption is managed through efficient electronic sensing and processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 system ensures continuous monitoring and self-calibration of MFCs, minimizing the impact of upstream pressure disturbances and preventing calibration-related failures, thereby improving yield and reducing costs.

Implementation Method 1

The first flow meter is constructed and arranged to measure the flow rate of the mass of a gas through the mass flow controller as a function of thermal sensing mass flow

Methodology Applied

Scientific EffectThermal sensing mass flow: Thermal Radiation

Implementation Method 2

The second flow meter is constructed and arranged to measure flow rate of the mass of the gas through the mass flow controller as a function of measured rate of decay of the gas pressure when allowed to flow from a predefined volume

Methodology Applied

Scientific EffectPressure decay measurement: Pressure Gradient

Data Source

PatentUS10606285B2System for and method of monitoring flow through mass flow controllers in real time

Publication Date: 2020.03.31 MKS INSTR INC

AI summary

A mass flow controller comprises: a first flow meter constructed and arranged to measured flow rate of mass through the mass flow controller; a second flow meter constructed and arranged to measure flow rate of mass through the mass flow controller; a control valve constructed and arranged so as to control the flow rate of mass through the mass flow controller in response to a control signal generated as a function of the flow rate as measured by one of the flow meters; and a system controller constructed and arranged to generate the control signal, and to provide an indication when a difference between the flow rate of mass as measured by the first flow meter and the flow rate of mass as measured by the second flow meter exceeds a threshold.