Raw Material Vapor Concentration Control With Dead-Time MPC
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Solution Overview
Problem
Conventional concentration control systems in semiconductor manufacturing face challenges in reducing the number of PID control parameter adjustments due to dead time responses in gas replacement, leading to suboptimal response performance and increased man-hours for adjustments.
Innovation Solution
Implementing a concentration control device that uses model predictive control for flow rate adjustments in the raw material vaporization system, incorporating a prediction model with dead time considerations to improve response performance and reduce the need for PID parameter optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PID control is used for flow rate control, then the control system is simple to implement, but the response performance is degraded due to dead time in gas replacement
Solution Approach 1:
The patent changes the control methodology from conventional PID control to model predictive control (MPC). This parameter change in control strategy allows the system to explicitly account for dead time in the gas replacement process through its prediction model, thereby improving response performance while maintaining implementation feasibility through automated model identification
Solution Approach 2:
The model predictive control performs preliminary prediction of future system behavior based on the identified model including dead time characteristics. By predicting the impact of control actions before they fully manifest, the system can pre-adjust control inputs to compensate for the dead time delay in gas replacement, improving response performance
2Loss of time
If PID control parameters are optimized to improve response performance, then the response time can be reduced, but the number of adjustment steps increases
Solution Approach 1:
The system performs automated model identification through one-time identification experiments, allowing the control model to self-adjust to the specific system characteristics. This self-service approach eliminates the need for manual PID parameter optimization steps while capturing the dead time effects inherent in the gas replacement process
Solution Approach 2:
The patent replaces manual mechanical adjustment of PID parameters with automated model identification and predictive control algorithms. This substitution eliminates the iterative adjustment process while maintaining or improving response performance through computationally-driven control optimization
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
This approach enhances response speed and reduces overshoot while significantly reducing the number of control parameter adjustments, improving process reproducibility and efficiency in concentration control.
Implementation Method 1
the concentration of IPA is measured by an analyzer using non-dispersive infrared absorption spectroscopy (NDIR)
Implementation Method 2
a vaporization tank that stores a liquid or solid raw material, a carrier gas supply path for supply of a carrier gas to the vaporization tank, a raw material gas lead-out path for leading-out of a raw material gas obtained by vaporizing the raw material
Data Source
AI summary
A concentration control device enables concentration control at high speed and with suppressed overshoot and is used in a raw material vaporization system that introduces a carrier gas into a liquid or solid raw material contained in a vaporization tank, vaporizes the carrier gas, and supplies a raw material gas generated by vaporization. The concentration control device includes flow rate control equipment that controls a flow rate of the carrier gas, a concentration measurement unit that measures a concentration of the raw material gas, and a flow rate control unit that controls a flow rate operation amount input to the flow rate control equipment by model predictive control based on a target concentration value of the raw material gas and a measured concentration value of the concentration measurement unit.