Pseudocubic SrRuO3 (100) epitaxial thin films were fabricated on Si (100) with a YBa2Cu3Ox / CeO2 / YSZ (yttria-stabilized-zirconia) triple buffer layer ∼ 14 nm thick by pulsed laser deposition (PLD). Reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) revealed that the first buffer layer of YSZ (100) was epitaxially grown on naturally oxidized Si (100) substrates with the process condition of PB (base pressure) = 1×10-Torr, PO2 (oxygen partial pressure) = 5×10- Torr, and Ts (substrate temperature) = 700 °C. Higher deposition rate of YSZ in the range of 0 ∼ 0.6 nm/min brought about better crystallinity with a smaller value of a full-width at half maximum (FWHM) in the YSZ (200) rocking curve. Subsequent deposition of CeO2, YBa2Cu3Ox, and SrRuO3 resulted in an SrRuO3 (100) epitaxial thin film exhibiting good crystallinity with FWHM = 1.7° in the SrRuO3 (200) rocking curve.

The interface behaviour during PE-MOCVD deposition of Y2O3 thin films on Si/SiO2 (8 Å) substrates has been investigated by XPS, TEM and OES analysis. The deposition process involves the sequential injection of MO precursors into the CVD chamber and is assisted by an O2 plasma. The injection frequency greatly influences the interface behaviour in terms of thickness and composition. The O2 plasma and the solvent also greatly affect substrate oxidation, and subsequently interface formation during deposition. Several mechanisms are discussed to account for substrate oxidation in view of a careful control of interface formation.

Water molecules and water-related species are present to a varying degree in SiO2 and other dielectrics and at Si-dielectric interfaces. Their presence, even in small concentrations, constitutes a critical reliability problem for present day ultrathin dielectrics. Here we present first-principles density functional calculations that probe the reactivity of water molecules at the Si-dielectric interface. We report results on different possible reaction pathways for water at the interface, including dissociation of water that can lead to the release of H+ ions. The released protons can migrate along the interface and depassivate dangling bonds. Results are also presented for the reaction of water with a hydrogen atom migrating laterally along the interface that lead to the creation of hydronium species. These atomic-scale mechanisms may account for at least some of the creation of interface traps and oxide trapped charge, the two features that give rise to negative bias temperature instability (NBTI), a well known reliability phenomenon that occurs in MOSFETs under normal operating and stress conditions.

The use of high-k materials as gate dielectric still meets a lot of unsolved problems such as thermal instability during post deposition anneals resulting in the formation of interfacial oxide layers or bad process compatibility. As long as these requirements are not accomplished alternative gate dielectrics have to be formed by oxynitrides or gate stacks built of oxynitrides and some high-k material. In order to achieve a low equivalent oxide thickness (EOT) it is necessary to grow homogeneously thin oxynitrides which are nitrogen-rich and which have a high interface quality. Therefore we have studied the growth of thin nitrides and oxynitrides (EOT = 1 – 2nm) formed by rapid thermal nitridation in NH3 and wet reoxidation. By varying the partial pressure of NH3 in the process gas ambient NH3/Ar the nitride quality could be optimized: it was found that an optimized ratio of NH3 and Ar during nitridation improves the electrical properties of the nitrides and oxynitrides significantly. Interface state densities as low as those of dry thermal oxides and leakage current densities reduced by four orders of magnitude compared to SiO2 of the same EOT have been obtained. Due to the high incorporation of nitrogen into the oxynitride by rapid thermal nitridation and following oxidation the leakage current densities are also lower than those of most oxynitrides reported in literature. In addition we present data concerning the suppression of boron diffusion from p+ poly-Si electrodes. In summary the developed oxynitrides are suitable to bridge the gap between common SiO2 and new alternative gate dielectrics or to form gate stacks in combination with high-k materials.

The bonding at interfaces of Si(100) with SrTiO3, LaAlO3 and HfO2 are considered using simple electron counting models.

Hetero-epitaxy of crystalline perovskite SrTiO3 and BaTiO3 on GaAs(001) was achieved using molecular beam epitaxy. A number of surface and interface techniques were used to characterize the growth, structural, and chemical properties of epitaxial oxide films on GaAs. Reflection-high-energy-electron diffraction of SrTiO3 and BaTiO3 showed streaky diffraction features and low diffraction background through out growth, indicating that the epitaxial SrTiO3 and BaTiO3 films had good crystallinity. X-ray diffraction showed an epitaxial relationship between these perovskite oxides and GaAs(001) substrates. Transmission electron microscopy and scanning probe microscopy revealed an abrupt oxide/GaAs interface and smooth SrTiO3 and BaTiO3 surfaces. The success of growth of epitaxial perovskite oxides on GaAs enabled us to integrate a number of functional oxides such as piezoelectric and magnetic oxides epitaxially on GaAs substrates.

Thin HfAlOx films grown on SiON(0.9 nm)/Si by atomic layer deposition technique were characterized by using monoenergetic positron beams. The lifetimes of positrons in the HfAlOx film after post-deposition annealing (PDA) ranged between 412–403 ps. Since these lifetimes were longer than the lifetime of positrons trapped by point defects in metal oxides, such as LaCoO3, PbTiO3, and BaTiO3, the positrons in HfAlOx films were considered to annihilate from the trapped state by open spaces which exist intrinsically in their amorphous structure. The line-shape parameter S of the Doppler broadening spectrum corresponding to the annihilation of positrons in HfAlOx films decreased by PDA, and the S value decreased with increasing an O2-content in an atmosphere during PDA (0.004–1%). The observed behavior of the S value was attributed to the shrinkage of the open spaces due to the change in the matrix structure of HfAlOx. After P+- and B+-implantation into poly-Si films grown on the HfAlOx films, the diffusion of positrons in the Si substrates toward the HfAlOx film was suppressed. This fact was attributed to positive charges introduced near the HfAlOx films.

The growth and structural characterization of UHV-compatible LPCVD grown strained-Si layer on linearly graded relaxed SiGe layer and the electrical properties of the high-k ultrathin ZrO2 films deposited on strained-Si layer using microwave-plasma CVD at low temperature (150°C) are reported. The strained-Si layer has been characterized using AFM, TEM and Raman spectroscopy. The C-V and G-V characteristics of ZrO2 films have been used to calculate the interface trap density, Dit, near the midgap energy, and the fixed oxide charge density, Qf/q. These are found to be 2.24 × 1012 cm−2 eV−1 and 1.45 × 1011 cm−2, respectively. Poole-Frenkel (PF) conduction mechanism is found to dominate the current conduction at room temperature.

We have investigated ternary metal oxide films for high-k gate dielectrics by using a layer-by-layer deposition & annealing method so as to keep the dielectric constant of the film high with no crystallization. HfAlOx films have been prepared by alternating deposition of HfO2 and Al2O3 layers, where it is a key for the improvement of the film quality to understand the intermixing process between two layers by thermal treatments. So, we first discuss the atomic diffusion and structural change of the HfO2/Al2O3 “superlattice” film as a function of the annealing temperature by changing the Hf/Al ratio. In a typical case of the film with HfOx/AlOx=3Å/9Å cycle, a clear superlattice peak is observed below 750 °C by XRD. Above 850 °C, a different type of crystalline structure with no superlattice peaks is observed. These results indicate that the intermixing in HfO2/Al2O3 (3Å/9Å) films occurs between 750 and 850 °C. The intermixing onset temperature increases with increasing Al content in Hf/Al ratio.

To further increase the crystallization temperature, nitrogen incorporation into the film is considered, and effects of the nitrogen incorporation into HfAlOx films are studied from the structural and electrical viewpoints. The results indicate that there is a tradeoff between crystallization restriction and leakage current degradation for the nitrogen incorporation into HfAlOx films.

In this report, we present the detailed analysis of the interstitial oxygen (O2+, O0, O2-) diffusion in monoclinic HfO2 (hafnia) using the first principles calculations. The interstitial oxygen atom kicks out the oxygen atom at the 3-fold-site and occupies the 3-fold-site. And then the newly kicked-out interstitial oxygen atom jumps to the nearest neighbor site and couples again with the atoms at the crystal sites. This kick-out- mechanism is valid for all charge states of the interstitial oxygen in monoclinic HfO2. In hafnia, the interstitial oxygen atom can take 3 charge states (+2, 0, -2) depending on the chemical potential (Ef), whereas the oxygen-vacancy in hafnia can get +2 or 0 charge state being dependent on Ef. In the lower range of Ef, O2+ and O0 might contribute. In the middle range of Ef, the O2- does not contribute to the diffusion process in hafnia because of the pair annihilation process between O2- and oxygen vacancy (V2+) defect pair. We can simulate such a pair annihilation process in hafnia. In the higher range, O2- might contribute the diffusion process.

Hafnium dioxide HfO2 is a candidate with promising properties for semiconductor industries as well as for optical and sensorial applications under harsh environments. The material can be deposited using various techniques such as CVD or PVD in different thickness ranges. The chemical inertness of HfO2 and the high band gap draw the attention of this paper towards application in optics as active and protective layer at the same time, chemical and physical sensors, such as moisture sensors and thin film capacities. In order to improve the layer properties with the sensorial application in mind, the deposition process and the post-processing need to be tightly controlled.

Layers with thicknesses between 100 and 150nm have been deposited by r.f. sputtering of a high purity HfO2 target onto bare or oxidized silicon wafers under Ar- or Ar/O2-athmospheres. Initially the HfO2 has a mainly amorphous structure. Subsequent annealing controls the growth of recrystallized areas characterized by grain size and ratio between crystals and amorphous bodies. High heating rates of about 50K/s and annealing temperatures ranging 800 to 1000°C in a rapid thermal annealing (RTA) chamber seem to be advantageous for the properties desired. The layer's structure such as grain size, crystal type and orientation was investigated using AFM, TEM and XRD. Layer tension was evaluated using laser deflection. The differences in structure found have been correlated to the chemical inertness obtained in measurements for layer applications.

As gate oxide thickness decreases, the capacitance associated with the depleted layer in polysilicon gate becomes significant, making it necessary to consider alternative gate electrodes. Titanium nitride (TiN) films elaborated with TiCl4 precursor is widely studied as metal gate in semi-conductor technology. In this work, a study of TiN metal gate deposited by MOCVD using TDMAT (Tetrakisdimethylamino titanium) precursor is proposed. N2, H2 plasma application and SiH4 treatment after TiN thin film growth modify composition and microstructure. Consequently, they alter the physical properties of films. Such treatments may be a way to modulate work function and thus to control threshold voltage.

Metallic layers were deposited in a chamber using a commercial 8 inch wafer deposition tool. In this study, structural and compositional properties of TiN were correlated with work function measurements. Firstly, the composition evolution (carbon content) was studied by AES and SIMS as a function of plasma and SiH4 treatments; XRD gave details on the microstructure. Secondly, MOS structures were processed on uniformly p-type doped wafers. C-V curves of capacitors were used to estimate the flat band voltage (VFB) and gave access to the work function, the effect of oxide fixed charges and the density of interface states. It is shown that as-deposited amorphous films exhibit a work function of 4.4 eV. Exposure to SiH4 is shown to increase this work function of about 150 meV. Thin films properties are not impacted by anneal treatments. Work function stability was tested at 425 °C, 900 °C and 1050 °C. Thermodynamic compatibility with gate oxide was verified thanks to experimental results and calculations.

A study of metal-insulator-semiconductor (MIS) structures based on atomic layer deposited HfO2, Ta2O5 and Nb2O5−Ta2O5−Nb2O5 thin films is presented. Our attention was focussed on interface quality and defect density in the dielectric. Interface states as well as defects inside the insulator bulk were measured by using capacitance-voltage (C-V), deep level transient spectroscopy (DLTS) and conductance transient (G-t) techniques. Nb2O5−Ta2O5−Nb2O5 based capacitors exhibit the highest interface state density, whereas the minimum is obtained for HfO2. Conductance transients are not observed in Al/HfO2/SiO2/Si stacks, thus indicating that disordered induced gap states (DIGS) are not present in these structures. We also observed that post-metallization annealing in forming gas diminishes the trap interface density at the expense of increasing DIGS in the Al/HfO2/Si cases.

AlON thin films formed by the electron cyclotron resonance (ECR) plasma oxidation of the AlN thin films deposited on p/p+−Si(100) by the ECR sputtering method were investigated for high-k gate insulator application. The leakage current density was found to be decreased with the ECR plasma oxidation of the AlN thin films. Furthermore, the equivalent oxide thickness (EOT) of 1.5 nm with the leakage current density of 5.1×10−4 A/cm2 (@Vfb−1 V) was obtained after the 1000°C rapid thermal annealing (RTA) because of the high quality interfacial layer formation.

Electronic structure of Mn/ZnO system has been investigated by synchrotron radiation photoemission. Manganese vacuum deposition was done at room temperature onto a ZnO(0001) single crystal for coverage ΘMn < 4 ML. Photoemission spectra taken near Mn3p-Mn3d absorption edge after each deposition step show resonant enhancement of Mn3d states within 10 eV of the Fermi level. The experimentally deduced partial Mn3d density of states for Θ > 1.2 ML shows at least three features: a major Mn3d structure at 3.8–4.5 eV below the Fermi energy, a valence structure at lower binding energy (1–3 eV) and a broad satellite in the 5.5 – 9 eV range. The branching ratio of satellite/main structure increases with deposition from 0.33 for 0.4 ML to 0.65 for 4 ML. After annealing up to 500 C the satellite/main ratio decreases to 0.43 indicating a high degree of hybridization between the Mn3d states and valence band of ZnO. After annealing no manganese cap layer was found at the crystal surface as was confirmed by the lack of metallic Fermi edge in photoemission spectra and by scanning Auger spectroscopy experiment. The photoemission Mn3p core level spectra taken after annealing consist of two components separated by about 4eV. It is evidence that at least two manganese states are observed in the Mn-ZnO interface region.

We investigate the use of the complex band structure of high-k gate dielectrics to estimate their charge neutrality levels, and compute band offsets to Si. Results of these model calculations are then compared to those obtained with direct electronic structure methods and available experiment. It appears that charge neutrality levels thus obtained indeed provide a consistent picture. However, the uncertainty in the conduction band position inherent in the local density approximation may render the theory inadequate for the engineering support. Despite this limitation, linear re-scaling of the charge neutrality levels based on the experimental band gaps has shown excellent agreement with experimental data.

High-quality substrates with thin uniform oxide layers are critical to the development of low-power epitaxy-based GaSb electronic and electro-optic devices. In this material system, the thickness and elemental composition of the oxide layers are a strong function of the surface preparation method. Here, a figure of merit for quantifying the thickness and thickness variations of an oxide layer on GaSb has been developed using bromine ion beam assisted etching (Br-IBAE). Furthermore, the overall thickness and composition of the oxide determines the etch depth for a fixed set of Br-IBAE parameters. The etch rate in GaSb was determined to be ∼395nm/min and that of its surface oxides was measured to be between 1.86 to 4.2nm/min. Hence, due to the difference in etch rates, nano fluctuations of the oxide thickness at the oxide surface and at the substrate/oxide interface, result in amplified roughness fluctuations in the etched GaSb substrate. The average roughness of Br-IBAE etched surfaces is used as figures of merit to quantify the uniformity and smoothness of the oxide layer. To demonstrate this, GaSb surfaces with various oxide layers and thicknesses were identically etched and their surface roughness measured using atomic force microscopy (AFM). This novel technique can generally be extended to a number of material systems.

Aluminum and copper are widely used for microelectronic interconnect applications. Interfacial oxides can cause device performance degradation and failure by significantly increasing electrical resistance. Interfacial oxide layers found in Al/Ta and Ta/Cu metal stacks were studied using Transmission Electron Microscopy (TEM) combined with Energy Dispersive Spectroscopy (EDS) and Parallel Electron Energy Loss Spectroscopy (PEELS). The analysis indicates that the observed interfacial oxide layers, Al2O3 and mainly Ta2O5, result from spontaneous reductions of Ta oxide and Cu oxide, respectively. Thermodynamics enables interpretation of the results.