Formation of Defects During Ion-Assisted Growth of Thin Films from the Vapor Phase

Abstract

ABSTRACTDuring ion-assisted growth of thin films from the vapor phase, defect generation and incorporation are of paramount interest. In many cases the wish is to obtain as defect free films as possible, however, in some applications a certain, controllable, defect content is desirable. In this paper experimental results on defect incorporation as a function of ion energy and growth temperature are presented. Results for poly- and single crystalline TiN films as well as for epitaxial Mo/V superlattice films are given. As the ion energy and/or ion flux are increased the amount of defects increases. At low temperatures the defects consist predominantly of point defect clusters and incorporated primary ions while at higher temperatures redistribution of point defects and incorporated primary ions results in dislocation loops and gas bubbles, respectively. However, for low ion energies where the energy transferred to the growing film surface is not high enough to cause atomic displacement events, reduction of defect densities can also be obtained. Furthermore, in the case of Mo/V superlattices it is demonstrated that interfacial mixing and increased interface roughness occurs at ion energies ≥ 25 eV. In the absence of an applied substrate bias the interface widths are determined to be 0.3 nm. For higher energies the widths becomes progressively larger and at a bias of 225 V an interface width of > 0.9 rum is obtained.