EFEM Inert Gas Control for Bottom Purge Nitrogen Waste
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Solution Overview
Problem
Conventional EFEM systems waste nitrogen gas by excessively supplying it into the housing during the bottom purge process, leading to increased pressure and unnecessary gas discharge, even when oxygen concentration and humidity levels remain unchanged.
Innovation Solution
An EFEM control system that adjusts the inert gas supply amount based on the oxygen concentration and the status of the purge process, subtracting the in-container inert gas supply amount from the total supply amount to prevent excessive gas usage, maintaining a slightly positive pressure within the housing while minimizing gas waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen gas is continuously supplied into the housing during the bottom purge process, then the oxygen concentration and humidity levels are maintained at optimal values, but the nitrogen gas is wasted due to excessive supply and subsequent discharge
Solution Approach 1:
The control unit monitors oxygen concentration and humidity levels in real-time and adjusts the nitrogen gas supply rate accordingly. When levels are optimal, the supply rate is reduced or stopped, preventing waste. When levels deviate from targets, the supply rate is increased to restore optimal conditions. This closed-loop feedback control eliminates continuous excessive supply while maintaining reliability.
Solution Approach 2:
The nitrogen gas supply rate is dynamically adjusted based on current environmental conditions rather than being supplied at a constant rate. The system transitions between different supply states (high rate, low rate, stopped) depending on whether oxygen concentration and humidity are within target ranges, optimizing gas usage while maintaining process reliability.
2Reliability
If nitrogen gas is supplied at a high rate into the housing, then the oxygen concentration is rapidly reduced to target levels, but the pressure increases causing unnecessary gas discharge
Solution Approach 1:
The nitrogen gas supply rate is dynamically adjusted based on current oxygen concentration levels. When oxygen concentration is high, a higher supply rate is used to rapidly reduce it. When oxygen concentration approaches target levels, the supply rate is automatically reduced to maintain pressure balance and prevent excessive discharge. This dynamic adjustment optimizes both control effectiveness and pressure management.
Solution Approach 2:
The system changes the nitrogen gas supply rate parameter based on oxygen concentration measurements. By adjusting this parameter dynamically, the system achieves rapid oxygen reduction when needed while preventing pressure buildup that would cause unnecessary gas discharge, thus resolving the contradiction between control speed and pressure stability.
3Reliability
If the nitrogen gas supply amount is increased to maintain low oxygen concentration, then the cleanliness of the substrate transfer space is improved, but the cost and waste of nitrogen gas increases
Solution Approach 1:
The control unit uses feedback from oxygen concentration and humidity sensors to adjust nitrogen gas supply. When cleanliness indicators (low oxygen, low humidity) are achieved, the supply is reduced or stopped, maintaining cleanliness while eliminating waste. When indicators deteriorate, supply is increased to restore cleanliness. This feedback mechanism ensures cleanliness is maintained at minimum necessary gas consumption.
Solution Approach 2:
The system monitors its own environmental conditions and autonomously adjusts nitrogen gas supply to maintain optimal cleanliness. By self-regulating based on real-time measurements, the system ensures substrate transfer space cleanliness is maintained while minimizing nitrogen gas consumption, eliminating the need for continuous excessive supply.
Data Source
AI summary
An EFEM includes a housing having a substantially closed substrate transfer space in the housing and a control part configured to perform a control of supplying an inert gas into at least the housing. The control part includes an inert gas total supply amount setting part configured to set a total supply amount of the inert gas to be supplied into the housing; a door open/purge determination part configured to determine whether a container door of a substrate storage container is in an open state and whether a purge device is performing a purge process; and an in-housing inert gas supply amount calculation part configured to calculate a supply amount of the inert gas to be supplied into the housing. The supply amount of the inert gas to be supplied into the housing is determined according to an inert gas supply amount command value determined based on a calculation result.