Low Temperature Pyrometry Calibration for Substrate Control
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Solution Overview
Problem
Conventional optical pyrometers fail to reliably measure substrate temperatures in the range of 300-500°C due to insufficient emission intensity and emissivity variation, leading to process degradation, non-repeatability, and drift in semiconductor processing.
Innovation Solution
A method involving multiple-point calibration of pyrometers using polynomial or linear curve fitting to compensate for emissivity variations, combined with the use of highly sensitive photodetectors like InAs, InGaAs, or PbS diode photodetectors at wavelengths between 2-4.8 micrometers, to accurately measure and control substrate temperatures between 300-1200°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical pyrometers are used to measure substrate temperature, then measurement is feasible at high temperatures (650-1200°C), but measurement reliability deteriorates at low temperatures (300-500°C) due to insufficient emission intensity
Solution Approach 1:
The patent applies parameter changes by selecting a specific wavelength range (2-4.8 micrometers) optimized for low-temperature detection. This wavelength parameter is specifically chosen to maximize emission intensity detection at low temperatures while minimizing interference from lamp radiation, thereby resolving the contradiction between measurement reliability and temperature range.
2Measurement precision
If conventional pyrometry is used at low temperatures, then temperature measurement is attempted, but measurement accuracy deteriorates due to emissivity variation of the support plate and strong lamp radiation interference
Solution Approach 1:
The patent extracts and eliminates harmful factors by using a wavelength range (2-4.8 micrometers) that specifically avoids strong lamp radiation interference. This extraction of the harmful wavelength component allows accurate temperature measurement at low temperatures without the degradation caused by lamp radiation and emissivity variation.
3Measurement precision
If multiple pyrometers with calibration are used, then temperature measurement precision is improved across wide temperature range, but device complexity increases
Solution Approach 1:
The patent applies universality by designing a pyrometer system that can accurately measure temperatures across a wide range (300-1200°C) using a single optimized wavelength range (2-4.8 micrometers). This multi-functional approach eliminates the need for multiple specialized pyrometers, thereby maintaining measurement precision while reducing device complexity.
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
Achieves stable closed-loop temperature control with high precision and repeatability across a wide temperature range, improving temperature uniformity and reducing errors caused by emissivity variations and lamp radiation interference.
Implementation Method 1
measuring a temperature of the substrate with a first pyrometer disposed over the substrate, measuring a temperature of the support plate with a second pyrometer disposed below the support plate
Data Source
AI summary
Embodiments of the present invention generally relate to methods and apparatus for measuring, calibrating, and controlling substrate temperature during low temperature and high temperature processing. In one embodiment, the method includes epitaxially forming a layer stack on a substrate placed on a support plate, measuring a temperature of the substrate with a first pyrometer disposed over the substrate, measuring a temperature of the support plate with a second pyrometer disposed below the support plate, calibrating the first pyrometer at multiple temperature points based on actual temperature readings of the substrate to generate a first set of calibrated temperature readings associated with the substrate, calibrating the second pyrometer using the set of calibrated temperature readings as a reference to generate a second set of calibrated temperature readings associated with the support plate, and controlling a power supplied to a heat source configured to heat the substrate based on the second set of calibrated temperature readings.