ROLE OF NITROGEN-IONS IN ION-BEAM REACTIVE SPUTTERING OF NBN

Using ion-beam reactive sputtering of a niobium target, we have studied the effects of energeticnitrogen-ion bombardment on the target reaction and on the resulting NbN film properties. Nitrogen is either added into the ion source with the noble gas to obtain a beam of nitrogen and argon ions, or injected directly into the chamber as neutral molecules so the ion beam is composed of essentially all argon. The target reaction rate is seen to be controlled by the adsorbed thermal nitrogen, and only minimally affected by the presence of ionized nitrogen. Thus, argon-ion bombardment of the target is responsible for stimulating the reaction between the adsorbed nitrogen and the metal target producing the NbN layer. However, the film properties are affected by the presence of nitrogen ions. Films grown with N2 added in the ion source have a higher resistivity and lower superconducting transition temperature than films grown with N2 injected directly into the chamber. These differences increase with N2 flow; the differences are attributed to damage of the growing film by energetic nitrogen reflecting from the target, as measured by an energetic-neutral-particle detector. © 1990, American Vacuum Society. All rights reserved.