Wafer Temperature Estimation Using Movable Sensor and Mixing Ratio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing heat treatment apparatuses for semiconductor wafers face challenges in accurately and quickly controlling temperature in the low temperature range of 100 to 400°C due to significant differences between detected temperatures by sensors and the actual wafer temperature, leading to prolonged heating times.
Innovation Solution
A heat treatment apparatus and method utilizing a combination of three temperature sensors – one externally, one internally, and a movable sensor with a temperature estimation section that calculates the wafer temperature using a mixing ratio formula (T=T1×(1−α) + T2×α, α>1) to accurately estimate and control the wafer temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional temperature sensor is used to detect wafer temperature, then the sensor structure is simple, but the temperature detection precision is poor in the low temperature range of 100 to 400°C due to large difference between detected temperature and actual wafer temperature
Solution Approach 1:
The patent introduces a movable temperature sensor that acts as an intermediary, physically contacting the wafer surface to directly detect its temperature. This mediator overcomes the limitation of non-contact sensors that cannot accurately measure wafer temperature in the low temperature range, providing precise temperature data without requiring complete redesign of the heating system.
Solution Approach 2:
The movable temperature sensor is nested within the holding tool structure, allowing it to be carried into and out of the processing container along with the holding section. This nesting approach enables the sensor to access the wafer for temperature measurement while maintaining a compact overall structure and avoiding excessive device complexity.
2Productivity
If the wafer is heated from room temperature to set temperature using conventional methods, then the heating system is simple, but the time required for temperature stabilization is excessively long
Solution Approach 1:
The patent implements a feedback control system where the movable temperature sensor continuously monitors the actual wafer temperature, and this information is fed back to the control section. The control section adjusts the heater power based on the temperature difference between the set point and actual temperature, enabling rapid and accurate temperature stabilization while preventing overheating.
Solution Approach 2:
The temperature control system transitions from a static, open-loop heating approach to a dynamic, closed-loop control system. The heater power is dynamically adjusted based on real-time temperature feedback, allowing the system to rapidly respond to temperature changes and achieve stabilization much faster than conventional fixed-power heating methods.
3Ease of operation
If the movable temperature sensor remains in the processing container after wafer removal, then the temperature measurement is convenient, but the sensor contamination and damage risk increase
Solution Approach 1:
The temperature sensor is designed to be movable rather than fixed, allowing it to dynamically change position between two states: inside the processing container during measurement and outside during storage. This dynamic capability enables the sensor to be retracted to a safe position after measurement, preventing contamination and damage while maintaining measurement convenience during operation.
Solution Approach 2:
The holding tool is designed to automatically carry the temperature sensor out of the processing container immediately after wafer removal. This preliminary action of retracting the sensor prevents it from remaining in the harsh processing environment, thereby preventing contamination and damage before they can occur, while maintaining ease of operation during the measurement phase.
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 approach allows for rapid and precise temperature control of semiconductor wafers, reducing stabilization time by 30% to 50% in the low temperature range, where the absorption wavelength of wafers is short and thermal response is low.
Implementation Method 1
a heating section, provided outside the processing container, for externally heating the processing container
Implementation Method 2
a first temperature sensor, provided between the heating section and the processing container, for detecting the temperature of the heating section; a second temperature sensor, fixed in the processing container, for detecting the interior temperature of the processing container; a third temperature sensor to be carried into and out of the processing container along with the holding section
Implementation Method 3
a temperature estimation section for selecting two of the first temperature sensor, the second temperature sensor and the third temperature sensor, and estimating the temperature of the object to be processed based on detection temperatures from the two temperature sensors
Data Source
AI summary
A heat treatment apparatus including: a processing container for processing wafers held in a boat; heaters for heating the processing container; and a control section for controlling the heaters. Heater temperature sensors are provided between the heaters and the processing container, in-container temperature sensors are provided in the processing container, and movable temperature sensors are provided in the boat. The temperature sensors are connected to a temperature estimation section. The temperature estimation section selects two of the three types of temperature sensors, e.g. the movable temperature sensors and the in-container temperature sensors, and determines the temperature of a wafer according to the following formula: T=T1×(1−α)+T2×α, α>1, where T1 and T2 represent detection temperatures of the selected temperature sensors, and α represents a mixing ratio.