AVS 54th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS1+TF-TuM

Invited Paper PS1+TF-TuM1
Characteristics for HfO2 Gate Dielectrics Deposited by Remote Plasma ALD Method

Tuesday, October 16, 2007, 8:00 am, Room 606

Session: Plasma Enhanced Atomic Layer Deposition and Plasma Deposition
Presenter: H. Jeon, Hanyang University, South Korea
Authors: S. Kim, Hanyang University, South Korea
H. Jeon, Hanyang University, South Korea
Correspondent: Click to Email

Many high-k dielectric materials have been studied extensively to replace current gate dielectric materials such as SiO2 and SiOxNy. Among the high-k dielectric materials, Hf-oxide is considered to be one of best choices for 45 nm technology and beyond. However, most of high-k oxides such as HfO2, ZrO2, Ta2O3, and TiO2 are transition metal oxides with the ionic nature and have poor interface quality and poor thermal stability with Si substrate. In addition, they exhibits high oxide traps and interface state densities, and large amount of oxygen vacancies, and are easily crystallized compared to SiO2. To overcome these drawbacks of high-k oxides, the technologies for growing high quality high-k oxides and improving the interface properties between high-k oxide and Si substrate are required. In this study, we chose HfO2 as high-k gate dielectrics and atomic layer deposition (ALD) as a deposition method. Among many deposition methods, ALD method is studied by many researchers because of its thin film deposition superiority. In our lab we applied both direct plasma ALD (DPALD) and remote plasma ALD (RPALD) methods to grow HfO2 thin films on Si substrates. These two different plasma methods exhibited the different thicknesses of silicate interlayer. We believe this interlayer is critical for the degradation of high-k dielectric materials. To investigate these interlayers we grew several different buffer layers before HfO2 growth. These buffer layers were formed by remote plasma oxidation (RPO) and nitridation (RPN) on Si substrates to monitor this interlayer, to suppress the initial formation of Hf silicate or interlayer and to improve the interlayer quality. The buffer layers were thin SiO2, SiOxNy, Al2O3, nitrided Al silicate and nitrided Hf silicate layers. The HfO2 films with buffer layers suppressed silicate formation or growth of an interlayer more effectively than those without buffer layers. The HfO2 films with buffer layers also showed lower effective oxide thickness (EOT), lower effective fixed oxide charge density (Qf,eff.), and lower leakage current density compared to those without buffer layers. The physical and electrical properties of HfO2 with buffer layers will be presented and discussed depending on the various buffer layers.