MEMS Coriolis Mass Flow Control for Low-Flow Gas Exchange
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current mass flow controllers, such as thermal or pressure-based systems, are inadequate for applications requiring low gas flow rates and fast gas exchange times in substrate processing systems, particularly for processes like chemical vapor deposition (CVD), atomic layer deposition (ALD), and atomic layer etching (ALE).
Innovation Solution
A mass flow controller assembly incorporating a microelectromechanical (MEMS) Coriolis flow sensor that measures mass flow rate and density, utilizing a semiconductor material tube vibrated at a resonant frequency, with a non-metallic coating to prevent gas contamination and a controller to adjust flow rates accurately, allowing for precise control of gas flow rates as low as 10 sccm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal or pressure-based mass flow controllers are used, then the device structure is simple, but the measurement precision and control accuracy for low gas flow rates are insufficient
Solution Approach 1:
The patent replaces thermal or pressure-based mechanical measurement systems with a MEMS Coriolis flow sensor that uses microelectromechanical vibrating elements. The Coriolis effect provides direct mass flow measurement through vibration frequency and phase detection, achieving high precision for low flow rates while maintaining a relatively compact structure through microfabrication techniques
Solution Approach 2:
The patent changes the measurement parameter from thermal or pressure-based indirect measurement to direct mass flow measurement using the Coriolis effect. By vibrating the MEMS sensor at resonant frequency and detecting phase shifts and frequency changes caused by mass flow, the system achieves superior measurement accuracy for low gas flow rates
2Speed
If conventional mass flow controllers are used, then the device is easier to operate, but the gas exchange time is slow
Solution Approach 1:
The patent employs a dynamically vibrating MEMS sensor that operates at resonant frequency. The dynamic vibration allows for rapid response to flow changes, enabling fast gas exchange times. The resonant oscillation provides inherent sensitivity to mass flow changes, allowing quick detection and response to flow rate variations without complex control mechanisms
3Object-affected harmful factors
If a metallic tube is used for the flow sensor, then the structural strength is high, but gas contamination occurs
Solution Approach 1:
The patent uses a composite structure consisting of a metallic or ceramic tube substrate coated with a non-metallic material layer. The underlying tube provides structural strength and mechanical support, while the non-metallic coating (such as polymer or ceramic coating) prevents gas contamination and chemical reactions. This composite approach simultaneously achieves both structural integrity and chemical inertness
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 MEMS Coriolis flow sensor provides accurate measurements of mass flow rate and density independent of temperature and pressure, enabling precise control of gas flow in substrate processing systems, enhancing the efficiency of low-flow rate applications and reducing noise from vibrations.
Implementation Method 1
A microelectromechanical (MEMS) Coriolis flow sensor is arranged in the cavity, includes an inlet fluidly coupled by at least one of the plurality of internal passages to the first inlet of the housing and is configured to measure at least one of a mass flow rate and density of fluid flowing through the MEMS Coriolis flow sensor
Implementation Method 2
utilizing a semiconductor material tube vibrated at a resonant frequency
Data Source
AI summary
A mass flow controller assembly includes a housing defining a cavity, a plurality of internal passages, a first inlet, a first outlet, a second inlet, and a second outlet. A valve is connected to the housing, has an inlet fluidly coupled to the second outlet of the housing and an outlet fluidly coupled to the second inlet of the housing. The valve is configured to control fluid flow from the second outlet of the housing to the second inlet of the housing. A microelectromechanical (MEMS) Coriolis flow sensor is arranged in the cavity, includes an inlet fluidly coupled by at least one of the plurality of internal passages to the first inlet of the housing and is configured to measure at least one of a mass flow rate and density of fluid flowing through the MEMS Coriolis flow sensor. An outlet of the MEMS Coriolis flow sensor is fluidly coupled by at least one of the plurality of internal passages to the second outlet of the housing. The second inlet of the housing is fluidly coupled by at least one of the plurality of internal passages to the first outlet of the housing.