Radiation Thermometer Infrared Absorption Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in accurately measuring the temperature of a semiconductor wafer during thermal treatment in an ammonia atmosphere, where ammonia absorbs infrared light, leading to incorrect temperature readings with radiation thermometers.
Innovation Solution
A thermal treatment apparatus equipped with a chamber, light irradiation units, a gas supplying unit, a radiation thermometer, and a control unit that uses conversion tables to accurately measure temperature by selecting the appropriate table based on the treatment gas atmosphere, including the use of a filter to discard absorbed infrared wavelengths and ensure precise temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature measurement is performed using a radiation thermometer in an ammonia atmosphere, then temperature measurement capability is provided, but measurement precision deteriorates due to infrared absorption by ammonia
Solution Approach 1:
The patent changes the measurement parameters by using multiple wavelength bands for infrared measurement. Instead of using a single wavelength that is absorbed by ammonia, the system measures infrared radiation at multiple wavelengths and processes these measurements to compensate for ammonia absorption, thereby maintaining accurate temperature measurement in ammonia atmosphere
Solution Approach 2:
The patent introduces an intermediary computational process that uses the measured infrared intensities at multiple wavelengths to calculate the actual temperature. This computational intermediary compensates for the harmful ammonia absorption effect by comparing measurements across different wavelengths and applying correction algorithms
2Reliability
If closed-loop control is performed based on radiation thermometer output, then temperature control capability is provided, but control reliability deteriorates when measurement is encumbered by ammonia
Solution Approach 1:
The patent implements feedback control using multiple wavelength measurements. The system continuously monitors infrared radiation at multiple wavelengths, processes these measurements to compensate for ammonia absorption, and uses the corrected temperature information to adjust the heating control, thereby maintaining reliable temperature control despite the presence of ammonia
Solution Approach 2:
The control system changes from using a single wavelength measurement to using multiple wavelength measurements as the basis for feedback control. This parameter change enables the system to distinguish between temperature-related infrared radiation and ammonia absorption effects, improving control reliability
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
Enables accurate temperature measurement of semiconductor wafers in ammonia atmospheres by compensating for infrared absorption, allowing for proper control of heating processes and preventing overheating.
Implementation Method 1
a radiation thermometer configured to measure temperature of the substrate by receiving infrared light emitted from the substrate
Implementation Method 2
Ammonia absorbs infrared used by the radiation thermometer in the measurement, and thus the intensity of infrared received by the radiation thermometer decreases
Implementation Method 3
The wavelength of light emitted by the xenon flash lamp is shorter than the wavelength of light emitted by a conventional halogen lamp, and substantially matches with the basic absorption band of a semiconductor wafer made of silicon. Thus, when emitted onto the semiconductor wafer by the xenon flash lamp, only a small amount of flash light is transmitted, and thus the temperature of the semiconductor wafer rapidly increases
Data Source
AI summary
An atmosphere of ammonia that absorbs infrared light in a wavelength band overlapping with the measurement wavelength band of a radiation thermometer is formed in a chamber in which a semiconductor wafer is thermally treated. A filter that selectively transmits infrared light having a wavelength not overlapping with the absorption wavelength band of ammonia is installed between an optical lens system and a detector of the radiation thermometer to avoid influence of the infrared light absorption by ammonia. A conversion table corresponding to the installed filter is selected from a plurality of conversion tables representing a correlation between energy of infrared light incident on the radiation thermometer and temperature of a black body, and is used at the radiation thermometer. Accordingly, the temperature of the semiconductor wafer can be accurately measured in the atmosphere of ammonia.