Effect of Sr-ruthenate seed layer on dielectric properties of SrTiO3 thin films prepared by plasma-enhanced atomic layer deposition

Abstract

The effect of a strontium ruthenate seed layer on the dielectric properties of SrTiO(3) thin films was investigated. The SrTiO(3) thin films were deposited by plasma-enhanced atomic layer deposition using titanium tetra-isopropoxide and bis(dipivaloylmethanato) strontium as precursors and oxygen as an oxidant. A strontium ruthenate seed layer was formed through the deposition of ultrathin SrO and a postannealing process. The SrTiO(3) thin films deposited on a seed layer, prepared by deposition of 2.7 nm SrO and postannealing prior to SrTiO(3) deposition, showed considerably enhanced dielectric properties in comparison to SrTiO(3) films deposited on Ru directly; that was attributed to enhancement of the films' crystallinites and a reduction of low-k interfacial layers. For optimization of seed-layer formation, the dependency of the inserted SrO layer thickness on the dielectric properties of the SrTiO(3) films was investigated for a SrO thickness range of 0.27 to 5.4 nm. The 10 nm thick SrTiO(3) thin film on the seed layer formed by deposition of a 1.35 nm thick SrO layer and postannealing exhibited a dielectric constant of about 75 [equivalent oxide thickness similar to 0.5 nm], which meets the requirement of dynamic random access memory 40 nm technology. (C) 2008 The Electrochemical Society.