Comparative Study of , , and BeO Ultrathin Interfacial Barrier Layers in Si Metal-Oxide-Semiconductor Devices

In a previous study, we have demonstrated that beryllium oxide (BeO) film grown by atomic layer deposition (ALD) on Si and III-V MOS devices has excellent electrical and physical characteristics. In this paper, we compare the electrical characteristics of inserting an ultrathin interfacial barrier layer such as SiO2, Al2O3, or BeO between the HfO2 gate dielectric and Si substrate in metal oxide semiconductor capacitors (MOSCAPs) and n-channel inversion type metal oxide semiconductor field effect transistors (MOSFETs). Si MOSCAPs and MOSFETs with a BeO/HfO2 gate stack exhibited high performance and reliability characteristics, including a 34% improvement in drive current, slightly better reduction in subthreshold swing, 42% increase in effective electron mobility at an electric field of 1？MV/cm, slightly low equivalent oxide thickness, less stress-induced flat-band voltage shift, less stress induced leakage current, and less interface charge. 1. Introduction The CMOS scaling is bringing the SiO2 thickness below 1.5？nm. For these very thin oxides, the leakage current becomes unacceptably large. One way to reduce the leakage current is the substitution of the SiO2 by a material with a higher dielectric constant. The main advantage of high-k dielectrics is the low gale leakage achieved due to its high physical thickness. That also makes it attractive for low power applications. Because of these requirements, over the past 10 years, hafnium oxide (HfO2) has gained considerable interest as a high dielectric constant material for fabricating complementary metal oxide semiconductor (CMOS) devices. It has several attractive properties such as a high dielectric constant, good thermodynamic stability with Si, and good electrical properties [1]. Unfortunately, some of the other physical properties like mobility reduction, charge trapping, and threshold voltage ( ) instability are a major drawback for the performance of metal oxide semiconductor field effect transistors (MOSFETs) [2]. Especially HfO2 high-k dielectric stacked MOSFETs were reported with low carrier mobility [3]. The main cause for the low mobility is still unknown, but has been attributed to remote Coulomb scattering caused by charges in the high-k dielectric [4] or optical phonon scattering [5]. Many researchers have believed that it is inevitable for all high-k dielectrics to have low energy bandgap and high scattering, compared to SiO2. Therefore, if high-k dielectric with high energy bandgap and low scattering can be found, it will be the true solution for the above problems. An alternative