The influence of target history and deposition geometry on RF magnetron sputtered LiCoO2 thin films

Thin LiCoO2 films, typically used as cathode layers in thin-film solid-stat e batteries were RF magnetron sputter-deposited using targets that were eit her freshly produced, or had seen over 100 h of sputter erosion. The substr ates, as received (100) silicon wafers, were either held stationary or were rocked back and forth under the target. Film texturing, grain size, compos ition, and thickness were examined using X-ray diffraction (synchrotron lig ht source), inductively coupled plasma-mass spectroscopy (ICP-MS), Rutherfo rds backscattering spectrometry (RBS) and stylus profilometry. Films that w ere sputtered from the heavily used target were, on average, lithium-defici ent, while films deposited using the fresh target were slightly lithium-ric h. Film thickness, composition, and type of crystallographic texture varied radially, in the plane of the film in the stationary substrate case, in a pattern that reflected the sputter target erosion ring. For films deposited with substrate motion, an ovular area was defined on the film in which com position, and texturing were essentially uniform. The Li/Co ratio in the ta rget and subsequent films was found to decrease over many hours of sputteri ng. Possible causes for the compositional and orientational variations obse rved are discussed. (C) 2001 Elsevier Science B.V All rights reserved.