Radiation Damage

Abstract

Ion implantation is a violent process, a large amount of the projectile kinetic energy is transferred to the atoms of the target displacing them from the lattice sites. The knowledge of the damage created by the implanted ions is of extreme relevance for the planning of the subsequent thermal annealing. It is necessary to eliminate or to reduce drastically the presence of defects in the active zones of the device before the implementation of the implantation process in the industrial fabrication of the devices. This chapter will treat and describe the damage resulting just after the implant. The evolution and the annealing of extended defects will be described in the next chapter, although a region of overlap exists between them. Implants are usually performed at room temperature and as seen in chapter 2, in spite of the adopted precautions, temperature rise is possible during the implant itself. Even at room themperature some defects, in particular point defects, are mobile and may interact among themselves or with preexisting damage giving rise to a variety of extended defects only in part related to the distribution of damage for a OK substrate implant. This part will be considered at the end of this chapter. The next paragraphs describe the slowing down of the projectile, the damage distribution and the related defect distribution under particular assumptions. For clarity a brief description of the most common defects in silicon is also presented.