Wafer Temperature Control Using Observer-Based Gas MPC
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Solution Overview
Problem
Existing wafer temperature control systems face challenges in maintaining a predetermined temperature, especially in non-measurement target areas like the central portion of a wafer, due to variations in heat transfer rates and the difficulty of temperature measurement and control across the wafer's surface.
Innovation Solution
A wafer temperature control device that uses a gas regulator to control pressure or flow rate, combined with an observer and model predictive control, to estimate and maintain the temperature of non-measurement target areas by measuring adjacent or easily measurable areas, such as the circumferential portion, thereby simplifying the incorporation of non-linear heat transfer behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are provided at both central and circumferential portions of the wafer, then temperature measurement precision is improved, but device complexity increases significantly
Solution Approach 1:
The patent introduces a heat transfer gas (helium or nitrogen) as an intermediary medium to transfer thermal information from the wafer to the plate. By measuring the temperature of the plate that is in thermal contact with the wafer through the gas medium, the system indirectly obtains temperature information without requiring direct temperature sensors on the wafer surface, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent replaces the mechanical/direct contact temperature sensing system with a gas-mediated thermal coupling system. Instead of placing temperature sensors directly on the wafer (mechanical contact), the system uses heat transfer gas to mediate the thermal interaction, allowing temperature measurement through the plate while maintaining wafer integrity and avoiding complex sensor integration on the wafer
2Productivity
If pressure of heat transfer gas is regulated, then heat transfer rate is improved, but temperature uniformity across the wafer deteriorates
Solution Approach 1:
The patent applies different gas pressures to different regions of the wafer-plate interface. The gas pressure is set to be higher at the central portion and lower at the circumferential portion, creating local variations in heat transfer characteristics. This local quality adjustment allows the central region to receive enhanced heat transfer while the periphery maintains appropriate thermal conditions, thereby achieving both improved heat transfer rate and temperature uniformity
Solution Approach 2:
The patent dynamically adjusts the pressure parameter of the heat transfer gas based on the spatial position and thermal requirements of the wafer. By changing the gas pressure parameter from uniform to non-uniform distribution (higher at center, lower at edges), the system optimizes heat transfer efficiency while maintaining temperature uniformity across the wafer surface
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 solution allows for accurate temperature control of non-measurement target areas, improving usability by measuring temperature at one location and maintaining set temperatures across the wafer, even under external disturbances like plasma-induced heat.
Implementation Method 1
a gas is supplied between the plate and the wafer so as to control the temperature of the wafer
Implementation Method 2
a temperature sensor that measures a temperature of either a predetermined measurement target area of the wafer or an area adjacent thereto
Implementation Method 3
based on the measurement temperature from the temperature sensor and on a gas manipulated variable input into the gas regulator or the pressure or flow rate regulated by the gas regulator, estimates a temperature of a non-measurement target area
Implementation Method 4
controls the gas manipulated variable input into the gas regulator using model predictive control
Data Source
AI summary
The present invention is a wafer temperature control device that includes a gas regulator that regulates a pressure or a flow rate of a gas, a temperature sensor that measures a temperature of either a measurement target area of a wafer or of an area adjacent thereto, an observer that, based on the measurement temperature from the temperature sensor and on a gas manipulated variable input into the gas regulator or the pressure or flow rate regulated by the gas regulator, estimates a temperature of a non-measurement target area that is different from the measurement target area of the wafer, and a gas control unit that, based on an estimation temperature for the non-measurement target area estimated by the observer and on a set temperature for the wafer, controls the gas manipulated variable input into the gas regulator using model predictive control.