Explanation of Temperature Calibration Technology for High Temperature Annealing Furnace Thermometer

It is reported that the high-temperature annealing furnace adopts a closed-loop control system composed of an accelerated digital PLD temperature controller, thermocouple, pyrometer, and heat source to correctly control the temperature. By collaborative control of halogen lamps in different regions, the temperature difference in each region can be compensated during the temperature control process, keeping the temperature of different regions on the substrate unchanged. Due to its installation at the bottom of the cavity, the pyrometer can only receive radiation from the back of the substrate and cannot receive radiation from the lamp. Therefore, a pyrometer can accurately measure the temperature of the substrate. The temperature calibration principle of this pyrometer is as follows:
1. Introduction to Pyrometer:
The pyrometer introduced in this article is a thermal radiation optical pyrometer. When the pyrometer receives infrared radiation from the measured object, the optical signal is filtered, photoelectric converted, and amplified to become an analog signal, which is then transmitted to the signal interface circuit module of the sensor. This module performs A/D conversion on the signal and converts it into a digital signal that can be recognized by the computer. The digital signal fed back to the computer is referred to as the pyrometer feedback value in the following text.
2. Temperature calibration table:
According to relevant laws, the temperature of an object is related to its radiation and spectral emissivity. For high-temperature annealing furnaces, the amount of radiation received by the pyrometer mainly depends on factors such as substrate material, doping, natural oxide layer on the surface, and substrate temperature. For the same type of substrate (i.e. substrates with the same material, doping, and surface natural oxide layer), the amount of radiation received by the pyrometer is related to the substrate temperature. Therefore, for the same type of substrate, the feedback value of the pyrometer corresponds one-to-one with the substrate temperature. This correspondence constitutes temperature calibration data, and a temperature calibration table is used to store the relationship data between multiple substrate temperatures and feedback values from a pyrometer. Different temperatures correspond to different feedback values of the pyrometer. The high-temperature annealing furnace computer can calculate the actual temperature of the substrate based on the signal value feedback from the pyrometer and the temperature calibration table.