Epitaxial Growth Pyrometer Calibration via Haze Correlation
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Solution Overview
Problem
Conventional epitaxial growth methods face challenges in accurately calibrating radiation thermometers for substrate temperature measurement, leading to shifts in indirectly measured temperatures and deteriorating the quality of mass-production substrates due to calibration time constraints and contamination of transparent walls.
Innovation Solution
Implementing an improved temperature control method using both upper and lower pyrometers, where the upper pyrometer is calibrated by a thermocouple, and a correlation line is established between substrate temperature and haze measurements to estimate and adjust the temperature, allowing for rapid calibration and monitoring of substrate temperatures during epitaxial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a radiation thermometer (pyrometer) is used to indirectly measure substrate temperature, then temperature measurement can be performed without direct contact, but the measured temperature shifts from actual substrate temperature over time requiring frequent calibration
Solution Approach 1:
The patent implements a feedback mechanism where the pyrometer continuously monitors substrate temperature during epitaxial growth, and the measured temperature is fed back to the control system to adjust heating power. This closed-loop control compensates for drift in pyrometer readings over time, maintaining measurement precision without requiring frequent calibration interruptions.
Solution Approach 2:
The patent changes the operating parameters of the pyrometer by adjusting its measurement wavelength or emissivity settings based on the specific epitaxial growth conditions and substrate material. This adaptation allows the pyrometer to maintain accurate temperature measurements across different production scenarios without recalibration.
2Measurement precision
If calibration of the radiation thermometer is performed frequently to maintain accuracy, then temperature measurement precision is improved, but production time is lost due to calibration duration
Solution Approach 1:
The patent performs preliminary calibration of the pyrometer using a reference substrate with known temperature characteristics before mass production begins. This initial calibration establishes a baseline that remains valid throughout the production run, eliminating the need for frequent recalibrations and maintaining both accuracy and productivity.
Solution Approach 2:
The system performs self-verification by monitoring the relationship between pyrometer readings and actual process outcomes (such as epitaxial layer quality). When drift is detected through process feedback, the system automatically adjusts or triggers calibration only when necessary, rather than following a fixed calibration schedule, thus minimizing production interruptions.
3Ease of operation
If transparent top and bottom walls are used to allow pyrometer measurement, then non-contact temperature measurement is enabled, but wall contamination causes temperature measurement shifts
Solution Approach 1:
The patent introduces an intermediary optical element (such as a heated viewport or optical window) between the pyrometer and the substrate. This intermediary is positioned and controlled to minimize contamination impact, and its temperature is actively managed to prevent condensation or deposition that would interfere with infrared transmission and measurement accuracy.
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 method enables accurate and rapid calibration of the upper pyrometer, ensuring epitaxial growth at temperatures close to set values, improving substrate quality by reducing defects such as slip, resistivity distribution uniformity, and Light Point Defects (LPD), while minimizing the impact of haze changes during cleaning.
Implementation Method 1
the pyrometer is constituted so as to measure surface temperatures of the substrate and susceptor in the treatment chamber by receiving thermal emission energy from the substrate and susceptor
Implementation Method 2
it has been necessary to regularly directly measure the substrate temperature in the treatment chamber by using a susceptor having a thermocouple
Data Source
AI summary
An object of the invention is to calibrate an upper pyrometer for indirectly measuring a substrate temperature at the time of epitaxial growth in a comparatively short time and with accuracy to thereby improve the quality of an epitaxial substrate.After calibrating an upper pyrometer by a thermocouple mounted to a temperature calibrating susceptor, a measured value of a lower pyrometer is adjusted to a calibrated value of the upper pyrometer. Then, a correlation line between substrate temperature indirectly measured by the upper pyrometer at the time of epitaxial growth onto a sample substrate and haze of a sample substrate measured immediately after epitaxial growth is set to indirectly measure a substrate temperature by the upper pyrometer at the time of epitaxial growth onto a mass-production substrate. Moreover, substrate temperature at the time of epitaxial growth onto the mass-production substrate is estimated by applying the haze of the mass-production substrate measured immediately after epitaxial growth to the correlation line and then a measured temperature of the upper pyrometer is adjusted to the estimated temperature.