Dual Asymmetric Optimal Control for Gas Flow Ratio Precision
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Solution Overview
Problem
Current flow ratio controller systems face challenges in maintaining precise control of gas flow ratios across multiple channels with minimal pressure drop and consistent response times, especially when distributing gas to multiple shower head fixtures in semiconductor processing, leading to inefficiencies and difficulties in maintaining even gas application on wafers.
Innovation Solution
A four-channel gas delivery system utilizing dual asymmetric optimal (DAO) control modules and a virtual DAO control module to control the flow ratios between four outlet channels, generating bias signals to maintain optimal valve conductance and ensure consistent response times across all channels, thereby reducing pressure drop and improving control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a flow ratio controller is used to divide gas flow among multiple secondary flow paths, then the gas flow can be distributed in predetermined ratios, but the pressure drop across the valves becomes significantly high
Solution Approach 1:
The patent applies asymmetric control strategies where different control methods are used for different valve positions. Specifically, one valve is controlled to remain mostly closed while another is controlled to remain mostly open, creating an asymmetric operating point that minimizes pressure drop while maintaining precise flow ratio control. This is achieved through the dual antisymmetric optimal (DAO) control algorithm that independently optimizes each valve's position rather than treating them symmetrically.
Solution Approach 2:
The system dynamically adjusts valve positions and control parameters to optimize performance. The DAO control algorithm continuously monitors flow ratios and adjusts valve conductance parameters in real-time, changing operating parameters to maintain optimal pressure drop characteristics while achieving precise flow distribution. The bias signal generation dynamically modifies control parameters based on desired flow ratios.
2Manufacturing precision
If conventional flow ratio control systems are used, then flow ratios can be stabilized after initial setting, but the flows take time to stabilize and response is slow
Solution Approach 1:
The system implements feedback control through the DAO algorithm that continuously monitors actual flow ratios and adjusts valve positions accordingly. Flow sensors provide real-time feedback on gas flow rates, and the control system uses this information to make dynamic adjustments, ensuring rapid stabilization and consistent response times. The feedback loop operates independently for each channel, enabling parallel optimization.
Solution Approach 2:
The control system transitions from static valve positioning to dynamic control where valve positions are continuously adjusted based on real-time conditions. The DAO algorithm provides dynamic response by independently controlling each valve's conductance in real-time, allowing the system to adapt quickly to changing conditions and achieve rapid stabilization without the delays associated with conventional sequential adjustment methods.
3Ease of operation
If fixed valve positions are used in secondary flow lines, then the system can be simpler to operate, but it becomes difficult to set up and requires difficult initial determination of valve positions
Solution Approach 1:
The system replaces fixed valve positions with dynamic control capabilities. Instead of requiring manual setup and fixed positioning during manufacturing, the DAO control algorithm enables automated adjustment of valve positions during operation. This dynamic approach eliminates the need for difficult initial setup while maintaining operational simplicity, as the system self-adjusts to achieve desired flow ratios.
Solution Approach 2:
The control system performs self-adjustment through the DAO algorithm that automatically determines optimal valve positions based on real-time flow measurements. Rather than requiring external intervention for setup and calibration, the system uses its own sensors and control algorithms to self-optimize performance, eliminating complex setup procedures while maintaining ease of operation.
4Stress or pressure
If asymmetric control is applied to minimize pressure drop, then one valve can be kept mostly closed and another mostly open, but this creates imbalance in the control system
Solution Approach 1:
The system deliberately introduces asymmetry in valve positioning as a control strategy. The DAO algorithm intentionally sets different operating points for different valves, with one valve positioned mostly closed and another mostly open. This asymmetric configuration is not a deviation from balance but rather the optimized balance point that minimizes pressure drop while maintaining stable flow ratio control.
Solution Approach 2:
The control system dynamically adjusts valve conductance parameters to achieve optimal asymmetric positions. By changing the control parameters independently for each valve, the system finds the asymmetric operating point that balances pressure drop minimization with flow ratio stability. The bias signal generation continuously adapts parameters to maintain this optimized asymmetric balance.
Data Source
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AI summary
A four channel gas delivery system. The system comprises an inlet channel; four outlet channels; four control valves, each valve being arranged so as to control the flow from the inlet channel through a corresponding one of the outlet channels; and a flow ratio control system. The flow ratio control system includes two dual antisymmetric optimal (DAO) control modules. The DAO control modules are configured and arranged so as to control the respective control valves so as to control the relative ratios of flow from the inlet channel through the four outlet channels. The flow ratio control system also includes a virtual DAO control module configured and arranged so as to control the ratio of flow between the two DAO control modules.