Atomic layer deposition of Ru films from bis(2,5-dimethylpyrrolyl)ruthenium and oxygen

Ru thin films were grown on hydrogen terminated Si, SiO₂, Al₂O₃, HfO₂, and TiO₂ surfaces by atomic layer deposition from bis(2,5-dimethylpyrrolyl)ruthenium precursor and oxygen. The 4-20 nm thick films on these surfaces consisted of nanocrystalline hexagonal metallic ruthenium, regardless of the deposition temperature. At the lowest temperatures examined, 250-255 °C, the growth of the Ru films was favored on silicon, compared to the growth on Al₂O₃, TiO₂ and HfO₂. At higher temperatures the nucleation and growth of Ru became enhanced in particular on HfO₂, compared to the process on silicon. At 320-325 °C, no growth occurred on Si-H and SiO₂-covered silicon. Resistivity values down to 18 μΩ·cm were obtained for ca. 10 nm thick Ru films.     

Physical properties of high pressure reactively sputtered hafnium oxide

Hafnium oxide films were deposited on silicon by High Pressure Reactive Sputtering (HPRS) at pressures between 0.8 and 1.6 mbar. Growth, composition and morphology were investigated using Transmission Electron Microscopy (TEM), Heavy Ion Elastic Recoil Detection Analysis (HI-ERDA), Fourier Transform Infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD). The growth rate was found to decrease exponentially with deposition pressure. The films showed a monoclinic polycrystalline structure, with higher grain size for intermediate pressures. All the films were slightly oxygen rich with respect to stoichiometric HfO₂, which is attributed to the oxygen plasma. Additionally, it was observed the formation of an interfacial silicon oxide layer, with a minimum thickness for deposition pressures around 1.2 mbar. These results are explained by the oxidation action of the oxygen plasma and the diffusion of oxygen through the grain boundaries of the HfO₂ film.     

Aerosol assisted chemical vapour deposition of germanium thin films using organogermanium carboxylates as precursors and formation of germania films

Diethyl germanium bis-picolinate, [Et₂Ge(O₂CC₅H₄N)₂], and trimethyl germanium quinaldate, [Me₃Ge(O₂CC₉H₆N)], have been used as precursors for deposition of thin films of germanium by aerosol assisted chemical vapour deposition (AACVD). The thermogravimetric analysis revealed complete volatilization of complexes under nitrogen atmosphere. Germanium thin films were deposited on silicon wafers at 700°C employing AACVD method. These films on oxidation under an oxygen atmosphere at 600°C yield GeO₂. Both Ge and GeO₂ films were characterized by XRD, SEM and EDS measurements. Their electrical properties were assessed by current?Cvoltage (I?CV) characterization.     

Modelization of hafnium silicate chemical vapor deposition using tetrakis-diethyl-amino-hafnium and tetrakis-dimethyl-amino-silane

The Chemical Vapor Deposition growth mechanism of a hafnium silicate film deposited by means of the co-flow of two precursors, TDEAH (tetrakis-diethyl-amino-hafnium) and 4DMAS (tetrakis-dimethyl-amino-silane), is characterized. Typical growth kinetics demand that the deposition rate increases and the silicon concentration remain stable with increasing reactor pressure. Though the deposition rate follows the expected growth kinetics, the silicon concentration in the silicate does not and exhibits an abnormal increase with increasing reactor pressure. To understand this atypical behavior the formation of pure HfO₂ from TDEAH and pure SiO_x from 4DMAS is first studied. Experimental results show that whereas the HfO₂ deposition is well behaved and fits a diffusion-based model defined by assuming diffusion of TDEAH through a boundary layer, the deposition of SiO_x with 4DMAS requires Hf-O nucleation sites and self-saturates after a single Si―O monolayer is formed. Based on these observations, a model is developed for hafnium silicate formation. The Atomic Layer Deposition like behavior of 4DMAS decomposition results in a deposition rate and film stoichiometry that are weakly sensitive to the 4DMAS partial pressure, and instead are driven by the TDEAH reaction. Since TDEAH operates within a transport-limited regime, the deposition rate is insensitive to substrate temperature, and is only controlled by the TDEAH partial pressure and the gas phase kinematics, rendering the process robust and easily controllable with excellent reproducibility.     

Synthesis and characterization of HfO2 and ZrO2 thin films deposited by plasma assisted reactive pulsed laser deposition at low temperature

A plasma assisted reactive pulsed laser deposition process was demonstrated for low-temperature deposition of thin hafnia (HfO₂) and zirconia (ZrO₂) films from metallic hafnium or zirconium with assistance of an oxygen plasma generated by electron cyclotron resonance microwave discharge. The structure and the interface of the deposited films on silicon were characterized by means of Fourier transform infrared spectroscopy, which reveals the monoclinic phases of HfO₂ and ZrO₂ in the films with no interfacial SiO_x layer between the oxide film and the Si substrate. The optical properties of the deposited films were investigated by measuring the refractive indexes and extinction coefficients with the aid of spectroscopic ellipsometry technique. The films deposited on fused silica plates show excellent transparency from the ultraviolet to near infrared with sharp ultraviolet absorption edges corresponding to direct band gap.     

Atomic layer deposition of HfO2 on self-assembled monolayer-passivated Ge surfaces

HfO₂ films are not easily deposited on hydrophobic self-assembled monolayer (SAM)-passivated surfaces. However, in this study, we deposited HfO₂ films on a tetradecyl-modified SAM with a Ge surface using atomic layer deposition at 350 °C. A slightly thinner HfO₂ film thickness was obtained on the tetradecyl-modified SAM passivated samples than that typically obtained on GeO_x-passivated samples. The resulting electrical properties are explained by the physical thickness and stoichiometry of the interfacial layer.     

Investigation of crystallographic properties of thin germanium crystals grown on silicon substrates by chemical vapor deposition

The quality of germanium crystals deposited from the gas phase by chemical vapor deposition using pyrolytic decomposition of GeH₄ in a helium atmosphere at various growth temperatures on silicon substrates was determined.X-ray diffraction and rocking curve measurements proved to be very useful in determining the degree of preferred orientation of the germanium deposit, since they distinguish clearly between the reflections of the thin germanium deposited layer and those of the thick silicon substrate. Therefore they permit fairly accurate calculations. Laue measurements, in this case, proved to be unsatisfactory because of inadequately low resolution. The results show that a preferred orientation of germanium crystallites in the layer of up to 99.9% was reached.     

Optische und mechanische Eigenschaften von RLVIP HfO2‐Schichten

Optical and mechanical properties of RLVIP HfO₂ films In this paper HfO₂‐films were deposited on unheated fused silica, borosilicate glass, and silicon wafer substrates by reactive low voltage ion plating (RLVIP). Optical film properties, i. e. refractive index and absorption as well as mechanical properties, particularly film stress, were investigated. Their dependence on deposition parameters, i. e. arc current and oxygen partial pressure was studied. The film refractive index was calculated from spectrophotometric measurements. The low absorption was determined by photothermal deflection spectrometry. Stress measurements were performed by bending disc method with uncoated and coated silicon wafer substrates.     

Surface treatment for high-quality Al2O3 and HfO2 layers deposited on HF-dipped surface by atomic layer deposition

Al₂O₃ and HfO₂ thin layers were deposited on either 0.7-nm chemical SiO₂ surface layers, HF-dipped Si surfaces or on HF-dipped Si surfaces with an innovative Cl₂ surface treatment. This chemical treatment leads to the formation of one mono-layer of –OH groups on the silicon surface without any SiO _x growth. Thicknesses, composition, and structure of the high-k layers as well as the nature of their interfaces with silicon were studied using spectrometric ellipsometry, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). While deposition on a HF-dipped Si surface led to a nucleation retardation and to a 3-dimensional growth mode, high-quality, uniform Al₂O₃ layers were obtained on a Cl₂-treated Si surface. XPS and ATR analyses showed a very small SiO _x regrowth, less than 0.26 nm during deposition.     

Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

Investigations of bilayer and trilayer Al₂O₃/SiO₂ and Al₂O₃/HfO₂/SiO₂ antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10^?3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al₂O₃, 0.6 nm ? 0.8 nm/s for HfO₂ and 0.6 nm/s for SiO₂. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al₂O₃/SiO₂ and 78 nm/156 nm/78 nm for Al₂O₃/HfO₂/SiO₂. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.     

Formation of Nickel Silicide Films from Nickel Acetylacetonate and Organosilicon Compounds

Nickel films were deposited from nickel acetylacetonate vapor on silicon, gallium arsenide, and germanium wafers and SiO₂/Si structures, and their composition and properties were studied. Annealing in dimethyldichlorosilane or hexamethyldisilazane vapor exerts a considerable effect on the composition and properties of Ni/Si structures. Films deposited from the gas phase containing nickel acetylacetonate and an organosilicon compound (OSC) were examined. As found by Auger electron spectroscopy with Ar⁺ion profiling of the surface, nickel silicide films can be obtained by Ni(AcAc)₂vapor deposition followed by annealing the resulting nickel film in OSC vapor and by OSC + Ni(AcAc)₂vapor deposition.     

Study of electrical and micro-structural properties of high-κ gate dielectric stacks deposited using pulse laser deposition for MOS capacitor applications

The electrical properties of hafnium oxide (HfO₂) gate dielectric as a metal–oxide–semiconductor (MOS) capacitor structure deposited using pulse laser deposition (PLD) technique at optimum substrate temperatures in an oxygen ambient gas are investigated. The film thickness and microstructure are examined using ellipsometer and atomic force microscope (AFM), respectively to see the effect of substrate temperatures on the device properties. The electrical J–V, C–V characteristics of the dielectric films are investigated employing Al–HfO₂–Si MOS capacitor structure. The important parameters like leakage current density, flat-band voltage (V_fb) and oxide-charge density (Q_ox) for MOS capacitors are extracted and investigated for optimum substrate temperature. Further, electrical studies of these MOS capacitors have been carried out by incorporating La₂O₃ into HfO₂ to fabricate HfO₂/La₂O₃ dielectric stacks at an optimized substrate temperature of 800 °C using a PLD deposition technique under oxygen ambient. These Al–HfO₂–La₂O₃–Si dielectric stacks MOS capacitor structure are found to possess better electrical properties than that of HfO₂ based MOS capacitors using the PLD deposition technique.     

Contactless transfer of image via the gas phase in a thermoactivated process

The formation of hafnium oxide (HfO₂) layers in slit structures by pulsed metalorganic chemicalvapor deposition (MOCVD) method with discrete dosage of reactants has been studied. The MOCVD process employed hafnium tetrakisdipivaloylmethanate as a precursor and oxygen as a gaseous reactant. The slit structure was formed by a silicon plate and a glass substrate with a chromium-film pattern. The slit width was varied within 0.1–2.0 mm, so that the aspect ratio changed from 150 to 30. The deposited layers were studied by the scanning ellipsometry technique. The phenomenon of image transfer from the glass substrate to the opposite plate in the form of a nanosized HfO₂ film relief, which reproduces the chromium-film pattern, is discovered. The in-plane resolution of the obtained image in these experiments reached 0.025 mm. This effect can be used for nonlithographic formation of images of film structures.     

Modulation of the structural and optical properties of sputtering-derived HfO2 films by deposition power

High-k gate dielectric HfO₂ thin films have been deposited on Si and quartz substrate by radio frequency magnetron sputtering. The structural and optical properties of HfO₂ thin films related to deposition power are investigated by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), ultraviolet–visible spectroscopy (UV–Vis), and spectroscopic ellipsometry (SE). Results confirmed by XRD have shown that the as-deposited HfO₂ thin films are not amorphous state but in monoclinic phase, regardless of deposition power. Analysis from FTIR indicates that an interfacial layer has been formed between the Si substrate and the HfO₂ thin film during deposition. AFM measurements illustrate that the root mean square (RMS) of the as-deposited HfO₂ thin films’ surface demonstrates an apparent reduction with the increase of deposition. Combined with UV–Vis and SE measurements, it can be noted reduction in band gap with an increase in power has been observed. Additionally, increase in refractive index (n) has been confirmed by SE.     

Structural and electrical properties of HfO2/Dy2O3 gate stacks on Ge substrates

In the present work we report on the structural and electrical properties of metal-oxide-semiconductor (MOS) devices with HfO₂/Dy₂O₃ gate stack dielectrics, deposited by molecular beam deposition on p-type germanium (Ge) substrates. Structural characterization by means of high-resolution Transmission Electron Microscopy (TEM) and X-ray diffraction measurements demonstrate the nanocrystalline nature of the films. Moreover, the interpretation of the X-ray reflectivity measurements reveals the spontaneous growth of an ultrathin germanium oxide interfacial layer which was also confirmed by TEM. Subsequent electrical characterization measurements on Pt/HfO₂/Dy₂O₃/p-Ge MOS diodes show that a combination of a thin Dy₂O₃ buffer layer with a thicker HfO₂ on top can give very good results, such as equivalent oxide thickness values as low as 1.9 nm, low density of interfacial defects (2-5 × 10¹² eV^− 1 cm^− 2) and leakage currents with typical current density values around 15 nA/cm² at V_g = V_FB − 1V.     

Evolution of SiO2/Ge/HfO2(Ge) multilayer structure during high temperature annealing

Use of germanium as a storage medium combined with a high-k dielectric tunneling oxide is of interest for non-volatile memory applications. The device structure consists of a thin HfO₂ tunneling oxide with a Ge layer either in the form of continuous layer or discrete nanocrystals and relatively thicker SiO₂ layer functioning as a control oxide. In this work, we studied interface properties and formation kinetics in SiO₂/Ge/HfO₂(Ge) multilayer structure during deposition and annealing. This material structure was fabricated by magnetron sputtering and studied by depth profiling with XPS and by Raman spectroscopy. It was observed that Ge atoms penetrate into HfO₂ layer during the deposition and segregate out with annealing. This is related to the low solubility of Ge in HfO₂ which is observed in other oxides as well. Therefore, Ge out diffusion might be an advantage in forming well controlled floating gate on top of HfO₂. In addition we observed the Ge oxidation at the interfaces, where HfSiO_x formation is also detected.     

Influence of deposition temperature on the structure and optical properties of HfO2 thin films

Hafnium oxide (HfO₂) thin films were deposited on Si (001) substrates by electron beam evaporation at various growth temperatures. It was found that the film was amorphous when deposited at temperatures lower than 200°C. It was polycrystalline when deposited at 250°C and 300°C. At temperatures above 400°C, it was grown preferably along the [111] direction. The influence of growth temperature on the surface morphology and optical property was also investigated.     

Polycrystalline silicon film growth in a SiF4/SiH4/H2 plasma

The growth of polycrystalline silicon (polysilicon) films from SiF₄/SiH₄/H₂ gas mixtures is reported. The polysilicon films have been deposited in a multi process reactor by a PECVD process. The effect of r.f. power, chamber temperature and gas flow ratios on grain size and deposition rate have been determined. The fluorine concentration and the grain sizes of the films have been determined by SIMS and atomic force microscopy (AFM), respectively. Grain sizes in excess of 900 Å are reported for layers deposited at 300°C.     

Effects of annealing temperature on the characteristics of ALD-deposited HfO2 in MIM capacitors

We have investigated the annealing effects of HfO₂ films deposited by an atomic layer deposition (ALD) method on the electrical and physical properties in the Si/SiO₂/Pt/ALD-HfO₂/Pd metal-insulator-metal (MIM) capacitors. If the annealing temperature for HfO₂ films was restricted below 500 °C, an annealing step using a rapid thermal processor (RTP) improves the electrical properties such as the dissipation factor and the dielectric constant. On the other hand, annealing at 700 °C degrades the electrical characteristics in general; the dissipation factor increases over the frequency range of 1∼4 MHz, and the leakage current increases up to 2 orders at the low electric field regions. We found that the degradation of electrical properties is due to the grain growth in the HfO₂ film (i.e., poly-crystallization of the film) by the high temperature annealing processing. We suggested that the annealing temperature must be restricted below 500 °C to obtain the high quality high-k film for the MIM capacitors.     

Introducing densification mechanisms into the modelling of HfO2 atomic layer deposition

Density functional theory calculations are used to highlight some basics of the densification mechanisms arising during atomic layer deposition of HfO₂ onto silicon dioxide. The obtained results are discussed at the light of a multi-model approach that enables process simulation at the atomic scale via Kinetic Monte Carlo simulations. The impact of the proposed densification mechanisms on the growth is demonstrated. We show that a complete coverage is possible thanks to these mechanisms at a slow rate after that all surface reactive sites (OH sites) have been consumed by precursor molecules.