Mark C. Gilmer

Nitrogen (N2) implantation to suppress growth of interfacial oxide in MOCVD BST and sputtered BST films

Ba 0.5 Sr 0.5 TiO 3 (BST) is one of the high-k candidates for replacing SiO 2 as the gate dielectric in future generation devices. The biggest obstacle to scaling the equivalent oxide thickness (EOT) of BST is an interfacial layer, Si x O y , which forms between BST and Si. Nitrogen (N 2 ) implantation into the Si substrate has been proposed to reduce the growth of this interfacial layer. In this study, capacitors (Pt/BST/Si) were fabricated by depositing thin BST films (50A) onto N 2 implanted Si in order to evaluate the effects of implant dose and annealing conditions on EOT. It was found that N 2 implantation reduced the EOT of RF magnetron sputtered and Metal Oxide Chemical Vapor Deposition (MOCVD) BST films by ∼20% and ∼33%, respectively. For sputtered BST, an implant dose of 1×10 14 cm −;2 provided sufficient nitrogen concentration without residual implant damage after annealing. X-ray photoelectron spectroscopy data confirmed that the reduction in EOT is due to a reduction in the interfacial layer growth. X-ray diffraction spectra revealed typical polycrystalline structure with (111) and (200) preferential orientations for both films. Leakage for these 50A BST films is on the order of 10 −8 to 10 −5 A/cm 2 —lower than oxynitrides with comparable EOTs.