Antisymmetric Optimal Gas Flow Ratio Controller
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Solution Overview
Problem
Existing flow ratio controllers for semiconductor processing tools face challenges in stabilizing gas flow ratios across multiple channels, experiencing high pressure drops and poor control performance, especially when handling downstream blockages, and are difficult to set up due to nonlinear valve curves and limited dynamic range.
Innovation Solution
A multiple-channel gas delivery system with a flow ratio controller that includes flow sensors and actively controlled valves, utilizing a multiple antisymmetric optimal (MAO) controller to maintain preselected flow ratios across secondary channels relative to the total flow, ensuring optimal valve conductance and minimizing pressure drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a flow ratio controller is used to divide gas flow to multiple locations, then the gas flow can be precisely metered and delivered to multiple channels, but the pressure drop across the controller becomes high
Solution Approach 1:
The patent implements dynamic control of multiple valves rather than static positioning. The MAO control algorithm continuously adjusts valve positions based on real-time flow measurements and control objectives, allowing the system to adapt to changing conditions and minimize pressure drop while maintaining precise flow ratios.
Solution Approach 2:
The system changes the control parameter from simple on/off valve control to continuous valve position control with optimized opening percentages. The MAO algorithm determines optimal valve positions that achieve desired flow ratios while minimizing total valve conductance and pressure drop across the system.
2Ease of manufacture
If conventional control algorithms are used for flow ratio control, then the system setup is straightforward, but the control performance is poor when handling downstream blockages
Solution Approach 1:
The system implements feedback control by continuously measuring actual flow rates through flow meters and comparing them to target values. The MAO control algorithm uses this feedback information to adjust valve positions in real-time, enabling the system to compensate for downstream blockages and maintain reliable flow ratio control.
Solution Approach 2:
The MAO control algorithm performs preliminary optimization by pre-calculating optimal valve positions based on desired flow ratios before actual gas flow begins. This preliminary action allows the system to be prepared for various operating conditions including potential blockages, improving reliability without complicating the physical setup.
3Ease of operation
If the valve positions are fixed to simplify control, then the system is easier to operate, but the settling time becomes long and dynamic response is slow
Solution Approach 1:
The system transitions from fixed valve positions to dynamic valve control where the MAO algorithm continuously optimizes valve positions based on current operating conditions. This dynamic approach reduces settling time by actively adjusting valves during the transient phase rather than relying on fixed positions that require long stabilization periods.
Solution Approach 2:
The patent replaces simple mechanical fixed-position valve control with an intelligent control system that uses algorithms (MAO) to determine optimal valve positions. This substitution of mechanical simplicity with computational intelligence achieves both ease of operation through automation and fast dynamic response through real-time optimization.
4Device complexity
If linear time invariant control is used, then the control structure is simple, but the dynamic range is insufficient for multiple channels
Solution Approach 1:
The MAO control algorithm changes from linear control parameters to nonlinear optimization parameters. It dynamically adjusts valve positions based on the specific flow ratio requirements for each channel, allowing the system to adapt to a wide range of operating conditions and achieve sufficient dynamic range for controlling multiple channels with different flow requirements.
Solution Approach 2:
The control system segments the overall flow control problem into individual channel control objectives. The MAO algorithm independently optimizes valve positions for each channel based on its specific flow ratio requirement, allowing each channel to operate within its optimal dynamic range while maintaining coordinated control across all channels.
Data Source
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AI summary
A multiple-channel gas delivery system comprises a primary channel, at least three secondary channels and a flow ratio controller. The controller receives gas through the primary channel and controls the ratio of the flow rate of the gas through each of the secondary channels relative to the total flow rate entering the system. The flow ratio controller includes a valve for each of the secondary channels. Each secondary channel has a feedback control loop to regulate its flow to achieve flow ratio set points. The feedback control loops always put each of the valves in a position such that the total valve conductance of the valves is maximized, the fastest settling times for flows and flow ratios through the secondary channels is achieved, and the pressure drop through the flow ratio controller is minimized. The flow ratio controller implements an algorithm that does not explicitly indicate which valve is at a fully open position, but guarantees that at least one valve is at a fully open position.