Predictive Multi-Loop Control for Wafer Temperature Distribution
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Solution Overview
Problem
Existing temperature control methods for semiconductor wafers struggle to maintain a desired distribution in transient states, especially when disturbances occur, leading to deviations in temperature distribution due to varying response speeds among control loops.
Innovation Solution
A control device with multiple control parts, including a prediction part and a generation part, predicts future control amounts and generates target values for control targets with different response speeds, ensuring that operation amounts match target values for each control cycle, even when disturbances affect the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a reference trajectory is determined using a normative model from the slowest response control loop, then the optimal operation amount pattern can be obtained, but the temperature distribution deviates from the desired distribution when disturbances occur or response changes
Solution Approach 1:
The patent applies preliminary action by predicting future control amounts of the slowest response control loop in advance for each control cycle, and generating future target values for other control loops based on these predictions. This allows the system to proactively adjust to disturbances and response changes before they cause significant deviations, maintaining temperature distribution accuracy while achieving optimal settling time.
Solution Approach 2:
The patent implements feedback by continuously updating the prediction of future control amounts based on actual system response and using this information to generate adjusted future target values. This closed-loop approach ensures that when disturbances occur or response characteristics change, the system can adapt and maintain the desired temperature distribution across all control loops.
2Ease of operation
If the operation amount is calculated using a fixed reference trajectory, then the control process is simple, but the distribution of control amounts deviates from the desired distribution in transient states when disturbances occur
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed reference trajectory to a dynamic prediction-based target value generation system. The future target values are continuously updated based on predicted future control amounts of the slowest response loop, allowing the system to adapt to changing conditions while maintaining computational efficiency through the use of predictive models rather than complex real-time calculations.
3Stability of the object's composition
If the control loop with the slowest response speed is used to generate the reference trajectory, then other loops can follow this trajectory, but the overall settling time is prolonged due to the slow response characteristic
Solution Approach 1:
The patent applies preliminary action by predicting the future control amounts of the slowest response loop in advance and generating target values for other loops based on these predictions. This allows faster loops to start adjusting earlier according to predicted trajectories, reducing the overall settling time while maintaining the uniformity of control amount distribution that would otherwise be dictated by the slowest loop's actual response.
Data Source
AI summary
Multiple control parts include a first control part and a second control part other than the first control part, the first control part showing the slowest response speed of a control amount with respect to a target value. A control device includes: a prediction part for predicting a future control amount for a first control target by using a first model indicating dynamic characteristics of the first control target corresponding to the first control part for each control cycle; and a generation part for generating a future target value of a second control target corresponding to the second control part from the future control amount. The second control part determines an operation amount for the second control target based on the future target value.