Wafer Temperature Estimation via Heat Transfer Gas Pressure Control
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Solution Overview
Problem
Existing wafer temperature control systems struggle to accurately estimate and maintain the temperature of a wafer in a low-pressure environment due to the non-linear relationship between the wafer temperature and the pressure of the heat transfer gas, leading to inaccuracies in controlling the wafer to a target temperature.
Innovation Solution
A wafer temperature control device that includes a pressure regulator, a nearby temperature sensor, a temperature estimation observer, and a controller, which uses a non-linear relationship between the wafer temperature and the pressure of the heat transfer gas to accurately estimate and control the wafer temperature by adjusting the pressure of the heat transfer gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is provided on the stage to measure temperature near the wafer, then the temperature near the wafer can be measured, but the wafer temperature cannot be estimated with sufficient accuracy due to the non-linear relationship between wafer temperature and heat transfer gas pressure
Solution Approach 1:
The patent introduces a temperature estimation observer as an intermediary computational system that processes measurements from the nearby temperature sensor and pressure regulator data to estimate the actual wafer temperature. This observer acts as a mediator between the measurable stage temperature and the desired wafer temperature, using a thermal model that accounts for the non-linear heat transfer characteristics through the heat transfer gas.
Solution Approach 2:
The patent changes the approach from directly measuring wafer temperature to estimating it through a mathematical model that incorporates multiple parameters including nearby temperature, heat transfer gas pressure, and thermal conductivity relationships. The observer dynamically adjusts the estimation based on pressure variations and thermal model parameters to accurately track wafer temperature despite the non-linear relationship.
2Temperature
If the pressure of heat transfer gas is regulated to promote heat transfer, then heat transfer efficiency is improved, but it remains difficult to measure the wafer temperature directly
Solution Approach 1:
The patent replaces the mechanical/direct measurement approach with a computational estimation system. Instead of attempting to physically measure the wafer temperature directly (which is difficult due to the vacuum environment and non-linear heat transfer), the system uses a mathematical observer that substitutes physical measurement with computational modeling based on available sensor data and thermal physics principles.
Solution Approach 2:
The temperature estimation observer serves as an intermediary that bridges the gap between the controllable parameters (pressure regulator settings, nearby temperature) and the desired output (wafer temperature). This computational mediator translates indirect measurements into accurate wafer temperature estimates without requiring direct contact with the wafer surface.
3Manufacturing precision
If conventional temperature control methods are used without considering non-linear pressure-temperature relationship, then the control system is simpler, but the wafer temperature cannot be controlled to target temperature with high accuracy
Solution Approach 1:
The patent implements a feedback mechanism through the temperature estimation observer that continuously monitors the estimated wafer temperature and adjusts the pressure regulator control accordingly. The observer provides real-time feedback about the thermal state, allowing the control system to compensate for non-linear effects and maintain accurate temperature control despite the complex pressure-temperature relationship.
Solution Approach 2:
The system performs preliminary computational action by using the temperature estimation observer to predict the wafer temperature based on current pressure and temperature conditions. This preliminary estimation allows the control system to anticipate temperature changes and adjust pressure regulation proactively, improving control accuracy before deviations occur.
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 system enables precise estimation and control of the wafer temperature to a target temperature by correcting the temperature setting using a non-linear relationship, reducing estimation errors and maintaining the wafer at a consistent temperature.
Implementation Method 1
a nearby temperature sensor configured to measure a temperature near the wafer
Implementation Method 2
supplying a heat transfer gas, such as helium gas, between the plate and the wafer
Implementation Method 3
promoting the transfer of heat from the plate being subjected to the temperature adjustment to the wafer by supplying a heat transfer gas
Data Source
AI summary
The present invention is a wafer temperature control device for controlling the temperature of a wafer by regulating the pressure of a heat transfer gas, the wafer temperature control device being capable of estimating the temperature of the wafer with sufficient accuracy and controlling the temperature of the wafer to a target temperature, and including: a pressure regulator configured to regulate the pressure of the heat transfer gas; a nearby temperature sensor configured to measure a nearby temperature of the wafer, a temperature estimation observer configured to estimate the temperature of the wafer based on the nearby temperature measured by the nearby temperature sensor and a manipulated pressure variable input to the pressure regulator or the pressure regulated by the pressure regulator, and a controller configured to control the manipulated pressure variable based on a temperature setting and an estimated wafer temperature estimated by the temperature estimation observer.