Semiconductor Wafer Temperature Controller with Feedback Error Reset
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Solution Overview
Problem
Existing temperature control methods for semiconductor wafers using model following servo control often result in reference model outputs that do not completely conform to the setpoint, leading to potential errors in temperature control.
Innovation Solution
A temperature controller with multiple control loops and detectors that calculates manipulated variables based on a reference model, where the slowest response loop is set to 100% and the others follow, searching for an optimal pattern to reach the setpoint quickly, and includes a feedback control mechanism to reset errors when the reference model output reaches a predetermined time or temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If model following servo control is used to control temperature adjusters, then the temperature can reach the setpoint quickly, but the reference model output does not completely conform to the setpoint, causing temperature errors
Solution Approach 1:
The patent introduces a feedback mechanism where the error between the reference model output and the actual temperature setpoint is detected and fed back to the manipulated variable calculator. This feedback loop continuously adjusts the manipulated variables to eliminate the error, ensuring that the temperature control precision is maintained while preserving the fast response characteristics of the model following servo control.
Solution Approach 2:
The patent performs preliminary optimization of the reference model by searching for the optimal manipulated variable pattern in advance (either online or offline) to minimize the error between the reference model output and the setpoint. This preliminary action ensures that the reference model is as accurate as possible before being used for temperature control, thereby reducing temperature errors while maintaining fast response.
2Productivity
If the manipulated variable is saturated to reach setpoint at maximum speed, then the throughput is improved, but the temperature may overshoot or not conform exactly to the setpoint
Solution Approach 1:
The feedback mechanism detects the error between the reference model output and the setpoint even when the manipulated variable is saturated. By continuously feeding back this error and adjusting the manipulated variables accordingly, the system can maintain maximum speed response while correcting any overshoot or inaccuracy, thus preserving both high throughput and temperature precision.
Solution Approach 2:
The patent dynamically adjusts the manipulated variables based on the error feedback and the optimal pattern search results. This dynamic adjustment allows the system to operate at maximum speed when the error is large (improving throughput) while automatically fine-tuning the manipulated variables when approaching the setpoint (maintaining precision), thereby resolving the contradiction between speed and accuracy.
Data Source
AI summary
A manipulated variable calculator having a plurality of control loops and configured to calculate manipulated variables to be respectively given to a plurality of temperature adjusters includes: a reference model output generator configured to generate a reference model that is a response output until reaching a temperature setpoint when, in the plurality of control loops, a manipulated variable of a control loop having the slowest response speed is defined as 100%; a simulator configured to sequentially search for a switching time to determine a manipulated variable pattern; a reference model configured to generate a reference model output based on the searched switching time; and a control switching unit configured to switch to a feed-back control using an error between the reference model outlet and the temperature setpoint when the reference model outlet reaches a predetermined time or a predetermined temperature after the reference model outlet starts.