Many materials and devices at various stages of manufacture cannot withstand sustained levels of heat. In Rapid Thermal Processing (RTP), samples are rapidly heated and cooled thereby limiting their exposure. Furthermore, rapidly heating samples can significantly improve throughput. A properly designed thermal profile is very important in this case because the thermal stress that is imparted during rapid heating can be significant, so controlled cooling is often employed.
There are a wide range of applications that require rapid heating cycles. These include but are not limited to post-ion implant anneal, ohmic contact formation, and film crystallization. During ion implantation, dopant atoms are accelerated towards the sample at keV energies where they implant themselves at various depths at interstitial lattice sites. This process causes damage to the lattice which must be repaired.
By rapidly heating the sample, atoms diffuse and return to their proper positions in the lattice, eliminating the defects. This process also moves the dopant atoms to lattice sites where they form covalent bonds and contribute electrons or holes to the host lattice band structure. To form ohmic contacts, heat is applied causing the metal to diffuse into the material and form alloys with the surface layers of the substrate. Ohmic contacts have very minimal contact resistance and a linear current-voltage relationship. Finally, films can be re-crystalized and alloyed by exposing them to elevated temperatures for short periods. Many materials and devices at various stages of manufacture cannot withstand sustained levels of heat making RTP an ideal tool for all of the aforementioned processes.