The decreasing feature sizes in complementary metal-oxide semiconductor (CMOS) transistor technology will require the replacement of SiO2 with gate dielectrics that have a high dielectric constant (high-k) because as the SiO2 gate thickness is reduced below 1.4 nm, electron tunnelling effects and high leakage currents occur in SiO2, which present serious obstacles to future device reliability. In recent years significant progress has been made on the screening and selection of high-k gate dielectrics, understanding their physical properties, and their integration into CMOS technology. Now the family of hafnium oxide-based materials has emerged as the leading candidate for high-k gate dielectrics due to their excellent physical properties. It is also realized that the high-k oxides must be implemented in conjunction with metal gate electrodes to get suffcient potential for CMOS continue scaling. In the advanced nanoscale Si-based CMOS devices, the composition and thickness of interfacial layers in the gate stacks determine the critical performance of devices. Therefore, detailed atomic-scale understandings of the microstructures and interfacial structures built in the advanced CMOS gate stacks, are highly required. In this paper, several high-resolution electron, ion, and photon-based techniques currently used to characterize the high-k gate dielectrics and interfaces at atomic-scale, are reviewed. Particularly, we critically review the research progress on the characterization of interface behavior and structural evolution in the high-k gate dielectrics by high-resolution transmission electron microscopy (HRTEM) and the related techniques based on scanning transmission electron microscopy (STEM), including high-angle annular dark-field (HAADF) imaging (also known as Z-contrast imaging), electron energy-loss spectroscopy (EELS), and energy dispersive X-ray spectroscopy (EDS), due to that HRTEM and STEM have become essential metrology tools for characterizing the dielectric gate stacks in the present and future gen
Xinhua Zhu Jian-min Zhu Aidong Li Zhiguo Liu Naiben Ming
N-doped ZnO films were prepared in nitrogen plasma by pulsed laser deposition.Clear room temperature ferro-magnetism has been observed in the film prepared at a substrate temperature of 500 C.The structural characterizations of X-ray diffraction,Raman,and X-ray photoelectron spectroscopy confirm the substitution of O by N in ZnO,which has been considered to be the origin of the observed ferromagnetism.Furthermore,ferroelectricity has been observed at room temperature by piezoelectric force microscopy,indicating the potential multiferroic applications.
0.67BiFeO_(3)-0.33BaTiO_(3)multiferroic ceramics doped with x mol%MnO_(2)(x=2-10)were synthesized by solid-state reaction.The formation of a perovskite phase with rhombohedral symmetry was confirmed by X-ray diffraction(XRD).The average grain sizes were reduced from 0.80mm to 0.50mm as increasing the Mn-doped levels.Single crystalline nature of the grains was revealed by high-resolution transmission electron microscopy(HRTEM)images and electron diffraction patterns.Polar nano-sized ferroelectric domains with an average size of 9 nm randomly distributed in the ceramic samples were revealed by TEM images.Ferroelectric domain lamellae(71°ferroelectric domains)with an average width of 5 nm were also observed.Vibrational modes were examined by Raman spectra,where only four Raman peaks at 272 cm^(-1)(E-4 mode),496 cm^(-1)(A_(1)-4 mode),639 cm^(-1),and 1338 cm^(-1)were observed.The blue shifts in the E-4 and A_(1)-4 Raman mode frequencies were interpreted by a spring oscillator model.The dieletric constants of the present ceramics as a function of the Mn-doped levels exhibited a V-typed curve.They were in the range of 350-700 measured at 10^(3)Hz,and the corresponding dielectric losses were in range of 0.43-0.96,approaching to 0.09 at 10^(6)Hz.
