MFC Verification Using a Calibration Tank for Low-Flow Process Gases
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Solution Overview
Problem
Existing methods for verifying the supply flow rate of process gases, especially at low flow rates below 10 sccm and for metal gases, are time-consuming and face challenges due to temperature sensitivity and residual gas issues.
Innovation Solution
A process gas supply control verification method that involves supplying a process gas to a calibration tank through a bypass gas supply line, measuring the changing state of the tank, and calculating the supply flow rate using a correction factor and measurements of pressure, temperature, and leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional verification methods are used for low flow rates below 10 sccm, then verification accuracy can be maintained, but verification time becomes excessively long
Solution Approach 1:
The patent introduces a calibration tank as an intermediary device between the MFC and the process chamber. The calibration tank accumulates process gas at low flow rates, allowing verification to be performed by measuring pressure changes over time rather than directly measuring extremely low flow rates. This mediator enables accurate verification of low flow rates without requiring excessively long measurement periods.
Solution Approach 2:
The patent transforms the verification approach by changing the measurement parameter from direct flow rate measurement to pressure change measurement. By monitoring how pressure changes in the calibration tank over time, the system can indirectly determine flow rate with high accuracy. This parameter transformation allows verification to be completed in reasonable time while maintaining precision.
2Measurement precision
If verification is performed for metal gases, then complete verification can be achieved, but temperature sensitivity and residual gas interfere with accurate measurement
Solution Approach 1:
The patent extracts the verification process from the process chamber environment and performs it in a dedicated calibration tank. This separation removes the interfering factors (temperature sensitivity and residual gas issues) from the measurement environment. The calibration tank provides a controlled environment where these harmful factors are minimized or eliminated, enabling accurate verification of metal gases.
Solution Approach 2:
The calibration tank creates an inert verification environment that is isolated from the process chamber conditions. By performing verification in this controlled atmosphere, the system eliminates interference from residual gases and temperature fluctuations that would otherwise affect metal gas measurements. The inert environment ensures that only the MFC's flow control performance is being measured.
3Device complexity
If MFC verification is performed without a bypass system, then system complexity is reduced, but verification capability for process gases is lost
Solution Approach 1:
The patent segments the gas supply system into two independent paths: a process gas supply line to the process chamber and a bypass gas supply line to the calibration tank. This segmentation allows verification to be performed independently without affecting normal process operations. The bypass system can be activated or deactivated as needed, providing verification capability while maintaining relatively simple system architecture.
Solution Approach 2:
The bypass gas supply line and calibration tank serve multiple functions: they enable MFC verification, provide a controlled environment for measurement, and can be integrated into existing process gas supply systems. This multi-functionality adds verification capability without requiring a completely separate verification system, thus limiting the increase in overall system complexity.
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
This method allows for accurate and efficient verification of mass flow controller operations for low flow process gases, including metal gases, reducing verification time and ensuring reliable gas supply.
Implementation Method 1
The MFC can precisely control the supply flow rate by detecting changes in gas pressure depending on the supply pressure of a process gas and environmental conditions.
Implementation Method 2
supplying the process gas to a calibration tank through a bypass gas supply line; measuring the changing state of the calibration tank
Data Source
AI summary
Proposed are a substrate processing system and a process gas supply control verification method and, more particularly, to a technology to verify the operation of a mass flow controller (MFC) that supplies a process gas for semiconductor processing at an appropriate flow rate according to a recipe.