Precise Control Method of Temperature Rising Speed of Wafer During Rapid Thermal Processing With Lamp Heaters Available to Purchase

In rapid thermal processing of a semiconductor wafer, temperature-rising-time is the same order of heating-time, and so keeping a given temperature-rising-speed of the wafer during the temperature-rising process is important. We made an experimental apparatus to measure the temperature-rising-speed of a ceramic ball of 2 mm in diameter heated with four halogen lamp heaters. The temperature change of the ceramic ball was measured and the heating rate of the halogen lamp heaters was controlled by a personal computer to keep a given temperature-rising-speed 50°C/s with controlling-time-interval 0.1 s. We examined the effect of various heating control methods on the error of the temperature-rising-speed of the ceramic ball. We tested the PID-control, the control with a prepared correlation, and the combined method of control with prepared correlation and PID-control. We found that the combined method is a good method to decease the error of the temperature-rising-speed. The average error of the temperature-rising-speed is 0.5°C/s and the repetition error is almost zero for the temperature-rising-speed 50°C/s during 330°C to 370°C. We also measured the effects of artificial control-delay-time and measuring-error of the monitor temperature on the error of the temperature-rising-speed.