Pressure-Based Fluid Flow Splitting for Fast Ratio Control
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Solution Overview
Problem
Current flow ratio controllers (FRCs) in the semiconductor industry face challenges in quickly adjusting flow ratios among multiple channels, often taking multiple seconds, which can impact process quality due to their reliance on mass flow controllers (MFCs designed for standalone flow rate control rather than ratio control.
Innovation Solution
A system with an inlet pressure sensor, controllable valves, and outlet pressure sensors, controlled by a system that determines and adjusts valve positions using a lookup table or equation to achieve desired flow ratios within one second, independent of total flow rate, allowing rapid adjustment of flow ratios without the need for temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mass flow controllers (MFCs) are used to control flow in each channel of the FRC, then flow rate control is achieved, but transition time to change flow ratios becomes multiple seconds
Solution Approach 1:
The patent extracts the flow control function from MFCs and implements it separately using controllable valves. Each valve is independently controlled based on upstream and downstream pressure measurements, eliminating the need for MFCs to calculate and adjust flow rates iteratively. This separation allows rapid valve positioning without the computational overhead of MFC-based ratio control.
Solution Approach 2:
The patent replaces the electronic control system of MFCs with a pressure-based mechanical control system. By measuring pressures upstream and downstream of each valve and using these measurements to directly control valve positions, the system achieves faster response times without the iterative calculations required by MFC-based control.
2Measurement precision
If MFCs are used in FRC for ratio control, then flow rate measurement is available, but coordination among MFCs becomes complex and time-consuming
Solution Approach 1:
The patent introduces pressure sensors as intermediary devices that measure upstream and downstream pressures to directly control valve positions. This intermediary measurement approach simplifies the control logic by using pressure ratios rather than requiring complex coordination among multiple MFCs to achieve desired flow ratios.
Solution Approach 2:
Each valve controls its own channel based on local pressure measurements upstream and downstream of that valve. This self-service approach eliminates the need for centralized coordination among multiple controllers, as each valve independently adjusts its position based on its own pressure feedback to maintain the desired flow ratio.
3Measurement precision
If iterative processes are used to establish flow ratios, then accurate ratio control is achieved, but transition time increases to multiple seconds
Solution Approach 1:
The patent performs preliminary measurements of upstream and downstream pressures before adjusting valve positions. By having pressure sensors continuously monitor pressures and using these pre-measured values to directly determine valve positions, the system eliminates iterative adjustment cycles and achieves accurate flow ratios in a single control action.
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
Enables rapid and accurate adjustment of flow ratios among multiple channels, reducing transition times to less than one second, improving process quality by eliminating the need for iterative processes and temperature measurements, and maintaining stability even with varying total flow rates.
Implementation Method 1
an inlet pressure sensor positioned in the inlet, coupled to the fluid flow, that measures the inlet pressure and generates inlet pressure signal; a plurality of outlet pressure sensors, each positioned downstream of each of the controllable valves, that measures the downstream pressure and generates an outlet pressure signal
Data Source
AI summary
A method and apparatus for the controlled splitting of a fluid flow into multiple channels, where an input command specifies the flow in each channel as a percentage of the total flow. The flow in each channel is controlled by a valve capable of moving to a specified position, where the position is determined as a function of the specified percentage, the pressure upstream of the valve, and the pressure downstream of the valve.