Ion Implantation in Semiconductors: Lattice Disorder and Electrical Effects

Ion implantation techniques have been used to form p-n junctions and device structures. The anneal characteristics are influenced by reordering of the lattice, radiation damage effects, and the lattice location of the implanted species. Hall effect and channeling techniques have been used to evaluate the nature of the implanted layer. Anneal data suggests that there is similarity in the disorder produced in ion implanted and fast neutron irradiated silicon. In both cases, localized regions of disorder are produced around the track of the incident ion or recoil lattice atom. The nature of the disordered region has not yet been defined. In ion implanted samples at doses ¿ 1014/cm2 at room temperature an amorphous layer is formed which anneals at significantly higher temperatures than the isolated regions of disorder produced at lower doses. In annealed samples, Group V dopant atoms occupy substitutional sites while Group III elements have a significant fraction on regular interstitial sites. Hall measurements on implanted samples also reveal differences between Group III and V dopant elements. One of the difficulties experienced in evaluating the electrical characteristics of implanted layers is that the anneal temperatures lie above the range of studies on fast neutron irradiated silicon.