Precise Control of Temperature Rising Speed of Wafer during Rapid Thermal Processing
In rapid thermal processing of a semiconductor wafer, it is important to keep a given temperature rising speed of the wafer during the temperature rising process. 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 heating rate of the halogen lamp heaters was controlled by computer to keep a given temperature rising speed of 50 °C/s with a controlling time interval of 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 found that a combined method of control with prepared correlation and PID (proportional integral derivative) control is a good method to decrease 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 of 50 °C/s from 330 °C to 370 °C. We also measured the effects of artificial control delay time and measuring error of the monitoring temperature on the error of the temperature rising speed.