Pyrometer Calibration via Wafer Light Absorption
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Solution Overview
Problem
Current methods for calibrating pyrometers in thermal processing chambers are time-consuming and require opening the chamber, making them inefficient for routine use and high-temperature measurements.
Innovation Solution
A method involving a calibration wafer with a reflective plane, where light energy is directed and detected to determine absorption and temperature, allowing for rapid calibration of pyrometers without opening the chamber, using a system with a controller to adjust the temperature measurement device based on detected light energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods using embedded thermocouples are used, then temperature measurement accuracy is improved, but calibration time increases substantially and chamber integrity is compromised
Solution Approach 1:
The patent replaces mechanical contact-based temperature measurement (thermocouples) with optical-based measurement (pyrometers). This substitution eliminates the need for physical contact with the wafer, enabling non-contact temperature measurement and calibration. The pyrometer measures thermal radiation from the wafer surface to determine temperature, avoiding the time-consuming thermocouple calibration process while maintaining measurement accuracy.
Solution Approach 2:
The patent uses a reference wafer with known thermal properties as a standard for calibration. By measuring the temperature of this reference wafer using the pyrometer and comparing it to expected values, the system can be calibrated without opening the chamber or using embedded thermocouples. This copying approach allows rapid verification and calibration of the temperature measurement system.
2Measurement precision
If pyrometers are calibrated using embedded thermocouples, then temperature measurement accuracy is improved, but chamber integrity and purity are compromised
Solution Approach 1:
The patent replaces mechanical contact-based measurement systems with optical measurement systems. The pyrometer measures temperature remotely through the chamber window without requiring physical access to the wafer or opening the chamber. This eliminates contamination risks and maintains chamber integrity while achieving accurate temperature measurement through optical detection of thermal radiation.
Solution Approach 2:
The patent introduces an optical window as an intermediary between the pyrometer and the wafer. This window allows thermal radiation to pass from the wafer to the pyrometer while maintaining the sealed chamber environment. The intermediary enables non-contact measurement without compromising chamber integrity or purity.
3Speed
If rapid thermal processing is performed, then processing speed is improved, but temperature measurement and control become more challenging
Solution Approach 1:
The patent implements continuous temperature monitoring during rapid thermal processing using the pyrometer. The system continuously measures wafer temperature throughout the heating and cooling cycles, enabling real-time feedback control. This continuous measurement capability is essential for managing the thermal transients in rapid processing, allowing the system to track temperature changes at high speed and maintain precise control despite the rapid rate of temperature change.
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
Enables accurate and rapid calibration of pyrometers across a range of temperatures, including high temperatures, improving the efficiency and integrity of thermal processing without disrupting the chamber environment.
Implementation Method 1
determining the absorption of the wafer based on the detected energy
Implementation Method 2
detecting light energy comprising at least one ray of light that has traversed a path within the wafer and has been reflected at a reflective plane
Data Source
AI summary
Methods and apparatus for wafer temperature measurement and calibration of temperature measurement devices may be based on determining the absorption of a layer in a semiconductor wafer. The absorption may be determined by directing light towards the wafer and measuring light reflected from the wafer from below the surface upon which the incident light impinges. Calibration wafers and measurement systems may be arranged and configured so that light reflected at predetermined angles to the wafer surface is measured and other light is not. Measurements may also be based on evaluating the degree of contrast in an image of a pattern in or on the wafer. Other measurements may utilize a determination of an optical path length within the wafer alongside a temperature determination based on reflected or transmitted light.