Foreline Bypass for Flame Inhibition in Vacuum Pumping
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Solution Overview
Problem
Vacuum pumps in semiconductor processes face risks of explosion due to flammable gas mixtures and reduced clearances from corrosion and material deposition, leading to potential damage and downtime.
Innovation Solution
A foreline system with an isolation valve and bypass that inhibits flame propagation by initially routing the waste stream through the bypass to create an evacuated region, and then opening the valve when pressure drops below a critical value to allow direct flow, reducing the risk of flame propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pumping mechanism operates with close tolerances to prevent fluid leakage, then pumping efficiency is improved, but the risk of component clashing and ignition source generation increases
Solution Approach 1:
The system divides the foreline into two separate flow paths: a primary path through the isolation valve and a secondary bypass path. This segmentation allows the waste stream to be routed through the bypass during high-risk conditions (initial operation with potential flammable atmospheres), preventing flame propagation to the process chamber while maintaining pumping efficiency through the primary path during normal operation.
Solution Approach 2:
The bypass acts as an intermediary flow path between the process chamber and pumping mechanism. By introducing this intermediate route with flame propagation inhibition means, the system provides a safe alternative path that mediates the harmful interaction between the pumping mechanism (potential ignition source) and the waste stream (potential flammable atmosphere).
2Reliability
If material deposits accumulate on rotor and stator surfaces, then corrosion resistance is improved, but component clearances are reduced leading to increased ignition risk
Solution Approach 1:
The system performs preliminary action by routing the waste stream through the bypass path before the pumping mechanism begins full operation. This preliminary routing through the flame propagation inhibition means establishes a safe condition that prevents ignition sources from affecting the process chamber, addressing the ignition risk before it can manifest during normal pumping operation.
Solution Approach 2:
The bypass with flame propagation inhibition means provides preliminary anti-action by preventing flame propagation in advance. Rather than reacting to an ignition event after it occurs, the system proactively blocks the potential propagation path during the initial high-risk operation phase, counteracting the harmful effect before it can spread to the process chamber.
3Speed
If the isolation valve is opened during initial operation, then evacuation speed is improved, but flame propagation risk to the process chamber increases
Solution Approach 1:
The foreline is segmented into two parallel paths allowing the system to achieve both goals simultaneously: the primary path through the isolation valve provides high evacuation speed, while the secondary bypass path with flame propagation inhibition means provides safety. The bypass acts as a protective segment that can be activated independently to prevent flame propagation while the main evacuation continues through the open isolation valve.
Solution Approach 2:
The bypass with flame propagation inhibition means serves as a beforehand cushioning measure. It is prepared in advance and can be activated to protect the process chamber from flame propagation during the initial high-risk evacuation phase, cushioning against potential harm while allowing rapid evacuation to proceed through the main path.
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
Minimizes the hazardous potential of explosions by preventing flame propagation from the pumping mechanism to the process chamber, ensuring safer operation and reducing downtime by optimizing evacuation efficiency.
Implementation Method 1
by initially routing the waste stream through the bypass to create an evacuated region, and then opening the valve when pressure drops below a critical value
Data Source
AI summary
Apparatus and a method are provided for inhibiting the propagation of a flame front that is ignited by a pumping mechanism which draws a waste stream from a process chamber. The apparatus comprises a foreline for conveying the waste stream which is drawn from the process chamber to the pumping mechanism. The foreline comprises an isolation valve for selectively isolating the pumping mechanism from the process chamber and a bypass positioned around the isolation valve. The apparatus further comprises a controller for actuating the isolation valve. The controller is configured to cause the isolation valve to be closed when the waste stream is initially drawn from the process chamber. During which time the waste stream is conveyed to the pumping mechanism via the bypass, the bypass comprises means for inhibiting propagation of a flame front therethrough. The controller is also configured to cause the isolation valve to be opened once a pressure within a region upstream of the isolation valve has been reduced below a value at which propagation of a flame front within the waste stream can be sustained.