NITROGEN (N 2 ) IMPLANTATION TO SUPPRESS GROWTH OF INTERFACIAL OXIDE IN MOCVD BST AND SPUTTERED BST FILMS Renee Nieh, Wen-Jie Qi, Yongjoo Jeon, Byoung Hun Lee, Aaron Lucas, Laegu Kang, Jack C. Lee, Mark Gardner*, and Mark Gilmer* Microelectronics Research Center, University of Texas at Austin, Austin, TX 78758 "Advanced Micro Devices, Austin, TX 78741 ABSTRACT Ba 0 * 5 Sr 05 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, SixOy, 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 lxl014 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- to 10-5 A/cm--lower than oxynitrides with comparable EOTs. INTRODUCTION Aggressive scaling of the MOS transistor has forced the gate oxide thickness into direct tunneling current regimes. As a result, focus has turned toward using oxynitrides, nitrides, and high-k materials as a gate oxide replacement. With a dielectric constant around 300, Ba 0 5 SrofTiO 3 (BST) is one of these high-k gate dielectric candidates. However, like many other high-k materials, when BST is deposited onto Si, an interfacial layer, SixOy, forms between them. Growth of this layer is a result of reaction and interdiffusion between the BST and Si [1]. This interfacial layer is often thick enough to cancel out any scaling benefits gained from using BST as the gate dielectric. In order to scale down the equivalent oxide thickness (EOT) of BST, it is imperative that the growth of the interfacial layer be suppressed or reduced. The implantation of nitrogen (N 2 ) into the Si substrate was investigated as a method to reduce the formation of the interfacial layer between BST and Si. Previous studies have used selective nitrogen implantation to grow gate oxides of different thickness simultaneously [2]. In addition, nitrogen implantation has been shown to reduce oxidation rates by 20-30% [3,4]. Figure 1 demonstrates the effects of nitrogen implantation dose on Si0 2 thickness grown during a rapid thermal processing (RTP) 02 ambient anneal. As expected, SiO 2 was the thickest for samples with no N 2 implantation, and SiO 2 thickness decreased with increasing implant dose. This study evaluated the effects of N 2 implant dose and annealing conditions on the EOT of both RF sputtered and Metal Oxide Chemical Vapor Deposition (MOCVD) BST films. High frequency C-V curves were measured using a HP 4194, and EOT values were extracted from these curves. X-ray photoelectron spectroscopy (XPS) yielded atomic concentration profiles, and X-ray diffraction (XRD) provided crystallinity of the BST films. Leakage currents were measured using a HP 4156. 521 Mat. Res. Soc. Symp. Proc. Vol. 567 0 1999 Materials Research Society