Effect of Sr–Ruthenate Seed Layer on Dielectric Properties of SrTiO[sub 3] Thin Films Prepared by Plasma-Enhanced Atomic Layer Deposition

Abstract

The effect of a strontium ruthenate seed layer on the dielectric properties of SrTi O3 thin films was investigated. The SrTi O3 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 SrTi O3 thin films deposited on a seed layer, prepared by deposition of 2.7 nm SrO and postannealing prior to SrTi O3 deposition, showed considerably enhanced dielectric properties in comparison to SrTi O3 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 SrTi O3 films was investigated for a SrO thickness range of 0.27 to 5.4 nm. The 10 nm thick SrTi O3 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 ∼0.5 nm], which meets the requirement of dynamic random access memory 40 nm technology. © 2008 The Electrochemical Society.