张世广118-119-B07.doc

118 CHAPTER 3 The Semiconductor in Equilibrium Impurity Atom Ion Implantation Ina second method of doping,high-energy impurity ions are implanted into the beam of impurity ions are accelerated to energies ranging from 1 keV to1 MeV and impinges the surface of the a process is referred to as ion primary advantages of ion implantation are the more precise control and reproducibility of impurity doping and the lower processing pared to diffusion. Figure shows a basic schematic of an ion implantation depth of ration or projected range isa function of the implanted ions since there isa certain randomness in the interaction of the implanted ions with the host semiconductor shows a typical impurity performing several implants at different energies,it is possible to create a region that is almost uniformly doped. When energetic ions impinge on the semiconductor,they lose their energy bya series of collisions with the semiconductor a result of this interaction,semiconductor atoms are displaced from their normal single-crystal damaged region is created in the semiconductor and most of the implanted ions are not located in substi t utional activate the implanted ion and repair the damaged area,the semiconductor must be annealed at an elevated temperature