M.-C. Hugon

Study of a HPPMS discharge in Ar/O2 mixture: I. Discharge characteristics with Ru cathode

High power pulsed magnetron sputtering discharges have been actively studied during the last ten years in order to achieve high ionization fraction of sputtered species. These sputtering discharges begin to be well understood in non-reactive mode. However, very few works have been devoted to studying reactive conditions. We report results obtained for these discharges working in an Ar/O2 mixture, with a preionization system to accelerate the current pulse rising. A Ru target was used for deposition of RuO2 conductive oxide. This paper discusses the role played by the presence of oxygen on both the preionization phase and the high current discharge characteristics. A comparison is made of results obtained in an Ar/O2 mixture with those obtained in pure argon. Emphasis is laid on the influence of the O2 flow rate and of the total Ar/O2 mixture pressure. It is observed that the O2 content in the inlet gas mixture strongly affects the preionization phase by the electron attachment to O2 as well as the high current discharge development.

Study of a HPPMS discharge in Ar/O2 mixture: II. Plasma optical emission and deposited RuOx film properties

A high power pulsed magnetron sputtering discharge was used in reactive gas conditions for the deposition of conductive ruthenium oxide. In a previous paper (paper I), the physical characterization of the discharge in the case of Ar/O2 mixtures was studied. This companion paper is devoted to the study of the transition from a metallic working regime to an oxide one. The plasma phase was analyzed with time resolved optical emission spectroscopy. Characteristic Ar?I, Ar?II and O?I emission lines of buffer gas atoms together with Ru?I and Ru?II ones of sputtered species were followed during the discharge pulse for different pressure values and flow rate composition of Ar/O2 gas mixture. Conjectures on specific kinetic processes such as Penning ionization and excitation and charge transfer are emphasized in order to interpret the temporal behavior of line emissions. The transition from metallic to oxide regimes, as observed by optical emission, is well correlated with the film stoichiometry and it is rather sharp. This transition was found to be intrinsically free of the hysteresis effect. However, the important modifications of the current and voltage discharge pulses at this transition region makes it difficult to precisely control deposited film stoichiometry.

Atomic Transport in LaAlO3 Films on Si Induced by Thermal Annealing

LaAlO 3 films sputter-deposited on Si were submitted to rapid thermal annealing at 800 and 1000°C. Atomic transport and chemical changes were investigated using ion beam analysis and X-ray photoelectron spectroscopy. Annealing induced La and Al losses or their migration into a newly formed interracial layer and Si migration into the film. The mechanism of Si incorporation into the film is influenced by the annealing atmosphere. These instabilities were hampered by a thermal nitridation in NH 3 at 700°C performed prior to rapid thermal annealing, indicating a possible route for producing a thermally stable La-based high-K gate dielectric.

Narrow resonance profiling study of the oxidation of reactively sputtered Ti1−xAlxN thin films

Abstract The bottom electrode structure used with ferroelectric (FE) and high dielectric constant (HDC) materials requires a material to promote FE or HDC cristallisation (Pt or IrO2) and a material with diffusion barrier properties; this last material being between Pt (or IrO2) film and Si substrate. TiN, TiAlN and TaSiN have been proposed for diffusion applications. Ti1−xAlxN films have drawn much attention as alternatives to TiN diffusion barriers. In this paper we have investigated the effect of Al content on the oxidation resistance of Ti1−xAlxN films prepared by radio frequency reactive sputtering in a mixed Ar+N2 discharge. The concentration depth profiles of both 18O and 27Al were measured before and after the rapid thermal annealing of samples at 750°C for 30 s in 18O2, via the narrow resonances of 18O(p,α)15N at 151 keV (fwhm=100 eV) and 27Al(p,γ)28Si at 992 keV (fwhm=100 eV). It was found that Al incorporation in the films reduces oxide growth. The Al excitation curves indicate a uniform Al content for as deposited Ti1−xAlxN, and reveal Al diffusion to the surface during oxidation, which indicates the formation of an Al rich oxide layer at the Ti1−xAlxN surface. The results suggest that Ti1−xAlxN films with x>0.39 are promising candidates as electrically conductive diffusion barrier layers.

Thermally Induced Atomic Transport in Nanometric LaAlON Films on Si

The thermal stability of nanometric lanthanum aluminum oxynitride films on silicon was investigated in vacuum and oxygen. Isotopic enrichment of the films with 15 N and of the annealing atmosphere with 18 O combined with nuclear reaction analysis and Rutherford backscattering spectrometry provides direct evidence of atomic transport starting at 600°C. Oxygen exchange and nitrogen replacement are identified. Interfacial silicon oxide growth takes place as the interfacial N concentration falls below 5 X 10 21 cm -3 . Complementary X-ray photoelectron spectroscopy shows changes in chemical bonding as a function of annealing temperature and ambient.

EFFECTS OF NITROGEN INCORPORATION IN LANTHANUM-BASED DIELECTRIC FILMS

ABSTRACT Thermal stability, electrical and structural properties induced by nitrogen incorporation in lanthanum-based high-k dielectrics were investigated. Thermal growth of a thin silicon oxynitride previously to LaAlO3 deposition induced higher dielectric constant, lower equivalent oxide thickness, and better interfacial stability during post-deposition annealing of MOS structures. But it also degraded others electrical and structural properties such as leakage current and charges densities, and interfacial roughness. Deposition of LaAlON films, either by reactive sputtering in Ar/N2 plasma, or by thermal nitridation in ammonia of LaAlO3, reduced partially several thermal instabilities after post-deposition annealing in 18O2, such as metallic losses, silicon diffusion and substrate oxidation.

Recent Developments on Ionized Physical Vapour Deposition: Concepts, Determination of the Ionisation Efficiency and Improvement of Deposited Films

While most of the IPVD reactors use radio-frequency (RF) coils to create additional ionization, we developed an alternative technique consisting of a home made magnetron sputtering device in which the ionization of the emitted sputtered vapor is achieved by two microwave antennas. Langmuir probe measurements were used to determine electronic density and temperature. Emission optical spectroscopy has been performed and argon and titanium line intensities have been measured, showing an increase of Ti+* to Ti* line intensity ratio. Optical absorption spectroscopy using a titanium hollow cathode lamp powered with a pulsed power supply has also been performed to determine the ionized fraction of the sputtered vapor. Preliminary results are also given for a conventional IPVD system (with RF loops) used for the deposition of Ti-based biomaterials.

Electrical Properties and Interfacial Characteristics of RuO[sub 2]∕HfAlO[sub x]∕SiON∕Si and RuO[sub 2]∕LaAlO[sub 3]∕SiON∕Si Capacitors

Electrical and structural properties of metal-oxide-semiconductor capacitors having as dielectric nanoscopic LaAlO 3 or HfAlO x films deposited on nitrided or nonnitrided Si substrates were investigated. The electrical superiority of RuO 2 /HfAlO x /SiON/Si stacks was evidenced by a dielectric constant of 19 and a leakage current density of 67 mA/cm 2 at a gate voltage of - 1 V, for a capacitance equivalent to silicon oxide thickness of 1.1 nm. Morphology, composition, and structure of the stacks were accessed by X-ray diffraction and reflectometry, spectroscopic ellipsometry, X-ray photoelectron spectroscopy, and narrow resonant nuclear reaction profiling with isotopic substitution. In spite of presenting crystalline phases associated with HfO 2 , the HfAlO x dielectric layers led to a smoother and thinner interfacial layer, improved by the thermal nitridation of the Si substrate prior to high-K deposition. This SiON-like interlayer thickness is self-limited even after postdeposition annealing owing to the formation of an effective diffusion barrier by the strong N-Si-N and N-Si-O-N bonds, which is also effective in preventing substrate oxidation.

Electrical properties and interfacial characteristics of RuO2/HfAlOx/SiON/Si and RuO2/LaAlO3/SiON/Si capacitors

Electrical and structural properties of metal-oxide-semiconductor capacitors having as dielectric nanoscopic LaAlO 3 or HfAlO x films deposited on nitrided or nonnitrided Si substrates were investigated. The electrical superiority of RuO 2 /HfAlO x /SiON/Si stacks was evidenced by a dielectric constant of 19 and a leakage current density of 67 mA/cm 2 at a gate voltage of - 1 V, for a capacitance equivalent to silicon oxide thickness of 1.1 nm. Morphology, composition, and structure of the stacks were accessed by X-ray diffraction and reflectometry, spectroscopic ellipsometry, X-ray photoelectron spectroscopy, and narrow resonant nuclear reaction profiling with isotopic substitution. In spite of presenting crystalline phases associated with HfO 2 , the HfAlO x dielectric layers led to a smoother and thinner interfacial layer, improved by the thermal nitridation of the Si substrate prior to high-K deposition. This SiON-like interlayer thickness is self-limited even after postdeposition annealing owing to the formation of an effective diffusion barrier by the strong N-Si-N and N-Si-O-N bonds, which is also effective in preventing substrate oxidation.

Electrical Properties and Interfacial Characteristics of RuO2 ∕ HfAlO x ∕ SiON ∕ Si and RuO2 ∕ LaAlO3 ∕ SiON ∕ Si Capacitors

Electrical and structural properties of metal-oxide-semiconductor capacitors having as dielectric nanoscopic LaAlO 3 or HfAlO x films deposited on nitrided or nonnitrided Si substrates were investigated. The electrical superiority of RuO 2 /HfAlO x /SiON/Si stacks was evidenced by a dielectric constant of 19 and a leakage current density of 67 mA/cm 2 at a gate voltage of - 1 V, for a capacitance equivalent to silicon oxide thickness of 1.1 nm. Morphology, composition, and structure of the stacks were accessed by X-ray diffraction and reflectometry, spectroscopic ellipsometry, X-ray photoelectron spectroscopy, and narrow resonant nuclear reaction profiling with isotopic substitution. In spite of presenting crystalline phases associated with HfO 2 , the HfAlO x dielectric layers led to a smoother and thinner interfacial layer, improved by the thermal nitridation of the Si substrate prior to high-K deposition. This SiON-like interlayer thickness is self-limited even after postdeposition annealing owing to the formation of an effective diffusion barrier by the strong N-Si-N and N-Si-O-N bonds, which is also effective in preventing substrate oxidation.