Flow-Through Pressure Sensor Assembly for MFC Gas Switching
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Solution Overview
Problem
Pressure-based Mass Flow Controllers (MFCs) face inefficiencies in removing dead volumes during gas changes, leading to unwanted gas mixtures and process disruptions due to their closed loop design, where stagnant gas remains in reservoirs and is not effectively displaced by flowing gas.
Innovation Solution
Incorporating a flow through path between reservoirs coupled with pressure transducers, allowing new gas to sweep and displace old gas, thereby eliminating dead volumes and preventing gas mixtures during gas switching in semiconductor manufacturing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a closed loop design with reservoirs is used in pressure-based MFCs, then the device can maintain stable pressure control, but dead volumes form in the reservoirs where stagnant gas is not effectively displaced during gas changes
Solution Approach 1:
The reservoir is divided into two separate chambers (first reservoir and second reservoir) connected by a flow through path. This segmentation allows gas to flow through both chambers, eliminating stagnant dead volumes while maintaining the pressure control function of each chamber. The flow restrictor further segments the flow path to control gas movement between chambers.
Solution Approach 2:
A flow through path is added as a new dimension to the traditional closed loop reservoir design. This creates a through-flow pathway that allows gas to enter and exit the reservoir system, transforming the closed loop into an open flow path while maintaining the pressure stabilization function of the reservoir chambers.
2Reliability
If traditional closed loop reservoir design is used, then pressure stabilization is achieved, but unwanted gas mixtures occur during gas switching due to ineffective displacement of stagnant gas
Solution Approach 1:
The flow through path is pre-configured in the reservoir design to enable continuous gas flow through both chambers. This preliminary structural arrangement ensures that during gas switching, the new gas can immediately sweep through and displace old gas without forming stagnant mixtures, while the pressure stabilization function is already in place through the dual-chamber design.
3Device complexity
If multiple gas species are flowed through a single MFC to reduce hardware cost, then hardware reduction is achieved, but efficient gas replacement becomes more critical to prevent contamination
Solution Approach 1:
The flow through path enables continuous gas flow through both reservoir chambers, creating a continuous sweeping action that efficiently replaces one gas species with another. This continuous flow mechanism ensures that when multiple gas species share a single MFC, the transition between gases is rapid and complete, preventing contamination and enabling reliable multi-gas operation with reduced hardware.
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 design ensures efficient removal of stagnant gas, reducing the risk of unwanted gas mixtures and improving the reliability of gas changes in MFCs, enhancing process stability and reducing hardware costs by allowing multiple gas species to flow through a single MFC.
Implementation Method 1
a flow restrictor disposed in the flow through path
Implementation Method 2
allowing new gas to sweep and displace old gas, thereby eliminating dead volumes
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.