Emissivity-Corrected Pyrometry for Stable Thin-Film Temperature Control
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Solution Overview
Problem
Existing methods for emissivity correction in pyrometry during thin-film deposition suffer from residual temperature oscillations due to errors in reflectance measurement and calibration, leading to inaccurate temperature control in semiconductor processes.
Innovation Solution
The method involves measuring multiple pairs of emission and reflectance values over several measurement intervals, calculating temperature-dependent factors, and determining a scattered light calibration parameter to compensate for errors, thereby reducing residual temperature oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If emissivity correction is performed using reflectance measurement and Kirchhoff's law, then temperature measurement accuracy is improved, but residual temperature oscillations occur due to measurement errors
Solution Approach 1:
The patent implements a feedback mechanism where the measured reflectance values are continuously used to update the emissivity correction factor. The system monitors the relationship between reflectance and temperature, and dynamically adjusts the correction applied to the pyrometer readings, thereby reducing residual oscillations through continuous self-correction
Solution Approach 2:
The patent changes the parameter being measured from direct temperature to reflectance, and then uses the reflectance values to derive an emissivity correction factor. This indirect measurement approach allows the system to compensate for surface property changes by tracking reflectance variations and applying corresponding corrections to temperature readings
2Measurement precision
If reflectance is measured at the same wavelength as thermal emission, then emissivity determination accuracy is improved, but scattered light interferes with measurement
Solution Approach 1:
The patent extracts the scattered light component from the total measured signal by analyzing the relationship between reflectance and emission measurements. By separating the scattered light contribution from the thermal emission signal, the system can apply corrections that eliminate the harmful interference while preserving the useful thermal radiation information
Solution Approach 2:
The patent uses reflectance measurement as an intermediary to indirectly determine the scattered light component. By measuring reflectance separately and using it to calculate the expected scattered light contribution, the system can subtract this intermediary-derived value from the total signal to obtain a corrected thermal emission measurement
3Measurement precision
If multiple measurement value pairs are measured over several measurement intervals, then correction value accuracy is improved, but measurement time increases
Solution Approach 1:
The patent performs preliminary measurements of multiple emission and reflectance value pairs during the deposition process. These preliminary measurements are taken in advance to establish the relationship between reflectance and emissivity, allowing the system to calculate accurate correction values before they are needed for temperature control, thereby reducing real-time measurement requirements
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 enables more accurate temperature control by reducing residual oscillations to below ±2°C, improving the reproducibility and yield of semiconductor components.
Implementation Method 1
The pyrometry method for non-contact temperature measurement makes use of the relationship between the thermal radiation emitted by the hot measurement object and the temperature of the object, which is described by the known Planck's radiation equation
Implementation Method 2
The known method of emissivity correction is based on determining the missing, unknown emissivity by measuring the reflectance of the surface of the measurement object
Data Source
AI summary
A method for coating a substrate with at least one layer. During deposition of the layer, at least one optical measuring device repeatedly determines successive measurement value pairs on the layer, each containing an emission value corresponding to the radiation power measured at a light wavelength and a reflectance value, which is also measured at a light wavelength. Actual values of a substrate temperature are calculated based on the measurement value pairs and a previously determined correction value. The actual values are used to control a temperature-control device for controlling the substrate temperature to a desired value. To improve the determination of the correction factor, during the measurement and within a plurality of measurement intervals, at least two measurement value pairs are measured and, for each of the measurement intervals, a temperature-dependent factor is determined that is used for the calculation of the correction value.