Thermal processing is a semiconductor manufacturing process which heats silicon wafers. It can range from as low as 100 C to a temperature of 1200 C or higher and can be done in less than a few seconds. For the cooling process, however, the temperature must be brought down slowly so as not to break the wafer due to thermal shock. These high and fast heating rates are attained through the use of high intensity lamps. It is used for a wide variety of applications in semiconductor manufacturing.
There are several difficulties that come with thermal processing. Perhaps the biggest challenge is being able to accurately measure and control the temperature of the wafer. Methods such as using a thermocouple to monitor the ambient are not valid, as the ramp rates established by the high temperature keep the wafer from reaching thermal equilibrium with the process chamber. Because of this, other strategies must be employed. One such method uses in situ pyrometry to affect real time control.
Another problem is that thermal processing is expensive. With rising operating temperatures and no currently satisfactory low enough input in calories/ton, this problem is getting more and more serious. In most thermal processing, the temperatures of discharged products are high. To lower that temperature, coolers are used. Most coolers work inversely as dryers, however, and have a higher capacity per unit installed.
Thermal processing equipment is always supplied in an integrated system. This consists of the following:
An optional cooling system may also be provided.
The process of thermal processing is used for a wide variety of applications concerning the semiconductor and its fabrication. Uses for this process include dopant activation, thermal oxidation, metal reflow, and chemical vapor deposition.