Flow-Through Pressure Sensor Assembly for MFC Dead Volume Removal
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Solution Overview
Problem
Pressure-based Mass Flow Controllers (MFCs) suffer from dead volume issues due to their closed loop design, leading to stagnant gas mixtures that can affect downstream processes in semiconductor manufacturing, especially when switching between gas types.
Innovation Solution
A system is introduced to induce gas flow through the reservoirs of the MFC's transducer assembly, incorporating a flow-through path between reservoirs to displace stagnant gas, thereby preventing unwanted gas mixtures by ensuring complete replacement of old gas with new gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a closed loop design is used in pressure-based MFCs, then measurement precision is improved, but dead volume increases causing stagnant gas mixtures
Solution Approach 1:
The reservoir is divided into two separate communication paths: one path for pressure sampling (through the transducer) and another flow-through path for gas exchange. This segmentation allows the measurement function to be preserved while creating a dedicated pathway that eliminates stagnant gas volumes.
Solution Approach 2:
A flow-through restrictor is introduced as an intermediary element in the gas path between reservoirs. This restrictor controls and directs gas flow through the reservoir, ensuring complete gas exchange while maintaining the pressure sampling functionality for accurate flow measurement.
2Reliability
If purge gas is circulated through MFC to remove atmospheric moisture, then reliability is improved, but dead volume prevents complete gas replacement
Solution Approach 1:
The flow-through path enables continuous gas circulation and exchange through the reservoir. Instead of relying on intermittent purge cycles that leave stagnant gas in dead volumes, the design maintains continuous flow that constantly refreshes the gas in the reservoir, ensuring complete replacement of atmospheric moisture and enabling reliable process operation.
3Device complexity
If multiple gas species are flowed through a single MFC to reduce hardware cost, then device complexity is reduced, but gas exchange efficiency decreases due to dead volume
Solution Approach 1:
The stagnant dead volume is extracted or removed from the system by creating a dedicated flow-through path that bypasses the traditional closed reservoir design. This extraction of the problematic dead volume element allows rapid gas exchange to occur, enabling efficient switching between multiple gas species through a single MFC and reducing the overall number of devices needed.
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 flow-through path effectively removes dead volume, ensuring rapid and complete gas exchange, reducing the risk of gas mixtures and improving process reliability in semiconductor manufacturing.
Implementation Method 1
A flow through path provides for a path for fluid flow between and through the two reservoirs
Data Source
AI summary
A system for removing dead volume in a sensor assembly of a mass flow controller is presented. The system comprises a valve assembly communicable coupled to the sensor assembly. The valve assembly is in fluid communication with fluid in a primary flow path and the sensor assembly is in fluid communication with fluid in the primary flow path. The sensor assembly comprises a pressure transducer having a first reservoir and another pressure transducer having a second reservoir. The first reservoir has a port in fluid communication with fluid in a sampled flow path. The second reservoir is coupled to a second pressure transducer and is fluidly coupled to the first reservoir through a flow through path. The second reservoir also includes another port for communicating the flow of fluid from the flow through path to another flow path. A flow rate restrictor is disposed in the flow through path.