Semiconductor Wafer Temperature Controller with Dynamic Reference Model Switching
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Solution Overview
Problem
Existing temperature control methods for semiconductor wafers face challenges in maintaining uniformity and achieving the shortest time to reach a temperature setpoint, as dynamic characteristics of thermo-modules differ between heating and cooling, leading to suboptimal response speeds when using a single reference model.
Innovation Solution
A temperature controller with multiple control loops and detectors that calculates manipulated variables using a reference model selecting unit to switch between heating and cooling reference models based on current conditions, ensuring optimal manipulated variable patterns for reaching the setpoint quickly while maintaining uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single reference model generated based on heating response is used for both heating and cooling, then the response speed in heating is maximized, but uniformity cannot be kept in cooling because the reference model output precedes the actual output
Solution Approach 1:
The patent divides the single reference model into separate heating reference model and cooling reference model. The manipulated variable pattern searching unit searches for optimal patterns separately for heating and cooling conditions, and the reference model output generator selects and generates output from the appropriate reference model based on current heating or cooling state. This segmentation resolves the contradiction by allowing each reference model to be optimized for its specific thermal condition.
Solution Approach 2:
The patent implements dynamic switching between heating and cooling reference models based on real-time temperature conditions. The reference model output generator dynamically selects which reference model to use (heating or cooling) depending on whether the current temperature is below or above the setpoint, allowing the system to adapt its control characteristics to match the actual thermal state and maintain both speed and uniformity.
2Stability of the object's composition
If the reference model output for cooling is used, then uniformity is ensured, but the response speed becomes slow
Solution Approach 1:
The patent creates distinct heating and cooling reference models with各自 optimized characteristics. The cooling reference model is specifically tuned to match cooling dynamics, ensuring uniformity is maintained while the heating reference model is optimized for fast response. The system segments the control strategy to match thermal conditions.
Solution Approach 2:
The patent changes the parameters of the reference model based on thermal conditions. Different reference models have different dynamic parameters optimized for heating versus cooling. The manipulated variable pattern searching unit searches for optimal patterns with parameters suited to each condition, allowing the system to achieve both uniformity in cooling and fast response in heating.
3Productivity
If multiple reference models are maintained for heating and cooling, then optimal control for both conditions is achieved, but the device complexity increases
Solution Approach 1:
The patent uses a universal manipulated variable pattern searching unit that can search for optimal patterns for both heating and cooling conditions. The reference model output generator serves multiple functions by dynamically selecting between heating and cooling reference models. This multi-functionality approach maintains productivity while managing complexity through shared computational resources.
Solution Approach 2:
The reference model output generator automatically determines which reference model to use based on current temperature conditions without external intervention. The system self-manages the complexity by implementing automatic selection logic that switches between heating and cooling models based on whether the current temperature is below or above the setpoint, reducing the burden on external control systems.
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
The solution allows the semiconductor wafer temperature to follow reference model outputs irrespective of heating or cooling, achieving the setpoint in the shortest time while ensuring uniformity by selecting appropriate reference models and gains for each condition.
Implementation Method 1
In a thermo-module such as Peltier element, the dynamic characteristics sometimes differ in heating and cooling
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 generates 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 reference model selecting unit configured to select the reference model depending on a heating responsiveness and a cooling responsiveness of the temperature adjusters.