Thermally stable very thin Ag films for electrodes

Low-resistivity metals such as Cu and Ag have been investigated for substitution of Al alloy films in the electrodes of thin film transistor used in active matrix liquid crystal displays. Though Ag has the drawback of agglomerating easily during heat treatment, improved thermal stability by modification of the Ag film into an Al/Ag/Al structure has been confirmed. In this paper, the surface morphology and electrical resistivity of this structure with various Ag layer thicknesses (from 95 to 50 nm) are investigated. The Al/Ag/Al structure showed excellent stability after annealing at 600 S C in vacuum, even with reduced thickness. The resistivity of the Al/Ag(95 nm)/Al film and of the Al/Ag(50 nm)/Al film after annealing were 1.8 and 2.4 mu Omega cm, respectively. For comparison, properties of Ag films with the same thickness were investigated, but these films became discontinuous after annealing due to agglomeration. Modified Ag films maintained excellent properties after annealing, even when the Ag layer thickness was reduced. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3071968]