Emissivity-Corrected Pyrometry for Substrate Temperature Control
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Solution Overview
Problem
Existing methods for determining substrate temperature during thin-film deposition suffer from residual oscillations due to incomplete emissivity correction, leading to inaccurate temperature control and reduced reproducibility in semiconductor production.
Innovation Solution
The method involves transforming emissivity and reflectance values into new values that oscillate with the same angular frequency, allowing for precise calculation of substrate temperature and reduction of residual oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If emissivity correction is performed using conventional methods, then temperature measurement is enabled, but residual oscillations remain due to angular frequency mismatch between emissivity and reflectance curves
Solution Approach 1:
The patent transforms the emissivity or reflectance values by applying a temporal transformation that modifies their angular frequency. Specifically, the measurement values are transformed using a transformation factor that adjusts the angular frequency of the oscillating curve to match between emissivity and reflectance measurements, thereby eliminating the mismatch that causes residual temperature oscillations.
Solution Approach 2:
The patent introduces transformed measurement values as an intermediary between the raw emissivity/reflectance measurements and the final temperature calculation. These transformed values serve as a mediator that reconciles the angular frequency difference between the two measurement curves, allowing for more accurate temperature determination without the harmful residual oscillations.
2Productivity
If emissivity values and reflectance values are used directly in temperature calculation, then temperature values can be determined, but residual oscillations occur due to phase shifts between oscillating curves
Solution Approach 1:
The patent applies temporal transformation to the emissivity or reflectance values before they are used in temperature calculation. This preliminary action of transforming the measurement values corrects the angular frequency mismatch in advance, preventing residual oscillations from occurring in the final temperature measurement and ensuring accurate temperature control throughout the deposition process.
3Adaptability or versatility
If measurement wavelengths for emissivity and reflectance are slightly different, then both measurements can be performed, but the angular frequencies of the oscillating curves differ
Solution Approach 1:
The patent compensates for the wavelength difference by transforming the temporal characteristics of the measurement curves. The transformation factor adjusts the angular frequency of the oscillating curve derived from one measurement (emissivity or reflectance) to match the other, thereby eliminating the precision loss that would result from using slightly different wavelengths.
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 significantly reduces residual temperature oscillations, improving the accuracy and reproducibility of substrate temperature control, which is critical for semiconductor deposition processes.
Implementation Method 1
an emissivity value UE,i that corresponds to the thermal radiation output measured at a first wavelength
Implementation Method 2
a reflectance value UR,i measured at a second wavelength and differs only slightly at most from the first wavelength
Implementation Method 3
The pyrometry method for non-contact temperature measurement makes use of the equation 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 4
The emissivity is determined with the help of Kirchhoff's law for the case of opaque substrates as ε=1−ρ
Data Source
AI summary
A method for coating a substrate, in which emissivity values (UE,n) and reflectance values (UR,n) are determined using pyrometers in order to control the temperature of the substrate. Since the wavelengths of the two pyrometers differ slightly, the raw temperature determined from the emissivity value (UE,n) cannot be optimally compensated for using the reflectance value (UR,n). The angular frequencies (ωE, ωR) of the curves of the two values (UE,n) and (UR,n) oscillating over time t differ slightly from one another, leading to an oscillation of the actual temperature value. To counteract this phenomenon, values modified by a numerical time transformation are used rather than the measured values.