Radiation Thermometer Emissivity Adjustment for Flash Lamp Annealing
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Solution Overview
Problem
In thermal processing of semiconductor wafers, especially when using flash lamp annealing in ammonia atmospheres, temperature measurement by radiation thermometers is inaccurate due to ammonia absorption of infrared light, leading to excessive heating and temperature overshooting.
Innovation Solution
A thermal processing apparatus and method that includes a chamber for the substrate, a light irradiation unit, a gas supply for forming a processing gas atmosphere, a radiation thermometer, and an emissivity determination unit to adjust the set emissivity of the thermometer to account for gas absorption, ensuring accurate temperature measurement by reducing the set emissivity when the measurement wavelength overlaps with the gas's absorption band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature measurement is performed by a radiation thermometer in ammonia atmosphere, then temperature monitoring is enabled, but measurement accuracy deteriorates due to ammonia absorption of infrared light
Solution Approach 1:
The patent changes the measurement wavelength parameter of the radiation thermometer from the conventional infrared range (affected by ammonia absorption) to the visible light range (around 405 nm), where ammonia does not absorb. This parameter change eliminates the harmful absorption effect while maintaining temperature measurement capability through detection of visible light emitted or reflected from the heated substrate.
2Speed
If flash lamp annealing is used to rapidly heat the substrate surface, then heating speed is improved, but temperature control accuracy deteriorates due to measurement errors in ammonia atmosphere
Solution Approach 1:
The patent changes the detection wavelength parameter to visible light range, enabling accurate temperature monitoring during rapid flash lamp annealing processes in ammonia atmosphere, thereby maintaining both high heating speed and accurate temperature control.
Solution Approach 2:
The radiation thermometer provides real-time temperature feedback during flash lamp annealing, allowing the system to control the heating process accurately despite the challenging ammonia atmosphere, by continuously monitoring substrate temperature and adjusting heating parameters accordingly.
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 allows for precise temperature control and accurate measurement of the substrate temperature even in ammonia atmospheres, preventing overheating and ensuring the substrate reaches the target temperature effectively.
Implementation Method 1
a radiation thermometer configured to measure the temperature of the substrate through reception of infrared light emitted from the substrate
Implementation Method 2
Ammonia absorbs infrared used by the radiation thermometer in measurement, and thus the intensity of infrared received by the radiation thermometer decreases
Implementation Method 3
a thermal processing apparatus configured to heat a substrate by irradiating the substrate with light
Data Source
AI summary
A substrate in a chamber is preheated through light irradiation by a halogen lamp and then heated through irradiation with flash light from a flash lamp. Ammonia is supplied to the chamber from an ammonia supply mechanism to form ammonia atmosphere. The temperature of the substrate at heating processing is measured by a radiation thermometer. When the measurement wavelength band of the radiation thermometer overlaps with the absorption wavelength band of ammonia, the set emissivity of the radiation thermometer is changed and set to be lower than the actual emissivity of the substrate. When radiation light emitted from the substrate is absorbed by the ammonia atmosphere, the radiation thermometer can accurately output the temperature of the substrate as a measured value by reducing the set emissivity of the radiation thermometer.