Thin film growth

The performance ofTi.3W.7 and Nb thin films as diffusion barriers for Au was investigated by Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES). The films were sputter deposited in Ar:N2 (70:30 vol%) or pure Ar on amorphous Si02. They were annealed in air at temperatures ranging from 250·C up to 750·C for several hours. In-depth profiles revealed an onset of oxidation of the barriers at 520·C for Nb and 600·C for TiW. Barrier oxidation and extensive diffusion could be correlated. Distinct diffusion behavior as a function of temperature was established between TiW and Nb. A Nb multilayer structure was found to provide the best reliability as the barrier and as the adhesion layer.

Sputter deposited molybdenum (Mo) thin films are used as back contact layer for Cu (In 1 À x Ga x )(Se 1 À y S y ) 2 based thin film solar cells. Desirable properties of Mo films include chemical and mechanical inertness during the deposition process, high conductivity, appropriate thermal expansion coefficient with contact layers and a low contact resistance with the absorber layer. Mo films were deposited over soda-lime glass substrates using DC-plasma magnetron sputtering technique. A 2 3 full factorial design was made to investigate the effect of applied power, chamber pressure, and substrate temperature on structural, morphological, and electrical properties of the films. All the films were of submicron thickness with growth rates in the range of 34-82 nm/min and either voided columnar or dense growth morphology. Atomic force microscope studies revealed very smooth surface topography with average surface roughness values of upto 17 nm. X-ray diffraction studies indicated, all the films to be monocrystalline with (001) orientation and crystallite size in the range of 4.6-21 nm. The films exhibited varying degrees of compressive or tensile residual stresses when produced at low or high chamber pressure. Low pressure synthesis resulted in film buckling and cracking due to poor interfacial strength as characterized by failure during the tape test. Measurement of electrical resistivity for all the films yielded a minimum v alue of 42 μΩ cm for Mo films deposited at 200 W DC power.

Using ion beam modification, films composed of synthesized
‘‘interphases’’ of ordered silica on OH-passivated (1 X 1) Si(100) underwent surface electro-chemical changes quantified by surface free energy via Sessile drop method and contact angle analysis using Young’s equation and Van Oss theory. IBMM caused the surface free energies initially ranging from 26.0 mJ/m2 to 57.3 mJ/m2 to converge to 43.1–45.4 mJ/m2 for various passivated and as-received wafer samples alike. Although TMAFM also identified topographic changes, these changes did not correlate to the change of surface free energies. Ion beam modification of the ordered silica film on Si(100) surface is analyzed using 3.045 MeV 16O(a, a)16O nuclear resonance scattering (NRS) in conjunction with channeling in (1 1 1) direction, which demonstrated the convergence of the partially ordered oxygen to amorphous at about 55 microCoulombs/mm2 He++ flux. Additionally, Si surface peak channeling in (1 0 0) and (1 1 1) directions also experienced an uptrend in areal density as incident ion flux increased, while the rotating random Si signal height remains stable, showing a disruption in the surface order during IBMM.

Dr. Herbots, Belgian-born, Ph.D. graduate in applied physics of Catholic University of Louvain and a microelectronics specialist, made progress in the course of three years as an Oak Ridge Re- search Associate and four years as an MIT professor (1987-1991). At MIT she developed new methods for synthesizing thin film layers on chips at low temperatures, and for creating films that can’t be grown using thermal processes.

She joined Arizona State University in 1991,  to further develop a novel invention she had made at MIT. Called Combined Ion and Molecular Beam Deposition or CIMD, it is a  tech- nique for depositing materials on semiconductors that combines a so- phisticated evaporation system (molecular beam deposition) with an easily controlled ion beam.
But a life-threatening accident curtailed her research
After building a CIMD clean room at Arizona State University and getting research off to a good start, Nicole Herbot’s work, almost her life, came to an abrupt end in May 1994.  This is where the history of her research in ordered nanophases of SiO2 on Si(100) began. She had to rebuild her scientific understanding of matter,  interfaces, phase structures and nanophases after losing her short memory and developing "petit mal" (a milder form of epilepsy characterized by short or longer "absences" where the patient loses awareness of surroundings without loss of consciousness). The episodes increase with fatigue, mild illnesses and colds, to several a day.  They result in post-"absences" exhaustion, typical of epilepsy, where the patient needs to sleep for a period of time concomittant with the duration of the absences to recover.  The condition precludes driving.
The long hours spent on bed rest recovering from the petit mal absences gave her the time to reflect on the continuing mystery of SiO2/Si(100) extraordinary properties in microelectronics.  This is how her "Tsunami" model of structural collapse as Si(100) crystals oxidizes into an amorphous film came to be, and a new concept to prevent structure loss and thus grow heteroepitaxial SiO2 on Si(100) was conceived, and led to several patents (2003, 2010), PhD theses and papers.

This work investigates the use of ozone as a post-treatment of ALD-grown MnO and as a coreactant with bis-(ethylcyclopentadienyl)manganese (Mn(EtCp) 2) in ALD-like film growth. In situ quartz crystal microbalance measurements are used to monitor the mass changes during growth, which are coupled with ex situ materials characterization following deposition to evaluate the resulting film composition and structure. We determined that during O 3 post-treatment of ALD-grown MnO, O 3 oxidizes the near-surface region corresponding to a conversion of 22 Å of the MnO film to MnO 2. Following oxidation by O 3 , exposure of Mn(EtCp) 2 results in mass gains of over 300 ng/cm 2 , which exceeds the expected mass gain for reaction of the Mn(EtCp) 2 precursor with surface hydroxyls by over four times. We attribute this high mass gain to adsorbed Mn(EtCp) 2 shedding its EtCp ligands at the surface and releasing Mn(II) ions which subsequently diffuse into the bulk film and partially reduce the oxidized film back to MnO. These Mn(EtCp) 2 and O 3 reactions are combined in sequential steps with (a) Mn(EtCp) 2 reacting at the surface of an O-rich layer, shedding its two EtCp ligands and freeing Mn(II) to diffuse into the film followed by (b) O 3 oxidizing the film surface and withdrawing Mn from the subsurface to create an O-rich layer. This deposition process results in self-limiting multilayer deposition of crystalline Mn 5 O 8 films with a density of 4.7 g/cm 3 and an anomalously high growth rate of 5.7 Å/cycle. Mn 5 O 8 is a metastable phase of manganese oxide which possesses an intermediate composition between the alternating MnO and MnO 2 compositions of the near-surface during the Mn(EtCp) 2 and O 3 exposures.

We demonstrate alteration in diamond-like carbon (DLC) film structure, chemistry and adhesion on steel, related to variation in the argon plasma pretreatment stage of plasma enhanced chemical vapour deposition. We relate these changes to the alteration in substrate structure, crystallinity and chemistry due to application of an argon plasma process with negative self bias up to 600 V.

Extremely smooth (6 nm RMS roughness over 4 lm2), thin (100 nm), and continuous ultrananocrystalline diamond (UNCD) films
were synthesized by microwave plasma chemical vapor deposition using a 10 nm tungsten (W) interlayer between the silicon substrate and the diamond film. These UNCD films possess a high content of sp3-bonded carbon. The W interlayer significantly increased the initial diamond nucleation density, thereby lowering the surface roughness, eliminating interfacial voids, and allowing thinner UNCD films to be grown. This structural optimization enhances the films’ properties and enables its integration with a wide variety of substrate materials.

2006 Elsevier B.V. All rights reserved.

Nickel nanoparticles arrays, growth into hydro-genated amorphous carbon, were prepared by means of RF-plasma enhanced chemical vapor deposition and RF-sputtering co-deposition from acetylene and a nickel target. The resulting nanocomposite films were characterized by X-ray diffraction and atomic force microscopy, and their magnetic responses and magnetoresistance behavior were investigated as a function of the exciting magnetic field and the Ni nanoparticles content, which was conveniently controlled by adjusting the deposition time. These physical properties were explained by a combination of hopping and tunneling effects.

Extremely smooth (6 nm RMS roughness over 4 lm 2 ), thin (100 nm), and continuous ultrananocrystalline diamond (UNCD) films were synthesized by microwave plasma chemical vapor deposition using a 10 nm tungsten (W) interlayer between the silicon substrate and the diamond film. These UNCD films possess a high content of sp 3 -bonded carbon. The W interlayer significantly increased the initial diamond nucleation density, thereby lowering the surface roughness, eliminating interfacial voids, and allowing thinner UNCD films to be grown. This structural optimization enhances the films' properties and enables its integration with a wide variety of substrate materials.

Si1-x-y ,GexCy is a novel group IV semiconductor alloy with interesting possibilities for strain modification and bandgap
engineering. To investigate the growth kinetics of this new semiconductor, heteroepitaxial Si1-x-y ,GexCy films were grown
on 4 in. Si(100) wafers by combined ion and molecular beam deposition at temperatures between 450 and 560°C.
Transmission electron microscopy (TEM) combined with diffraction show that the films, 1000 ± 220 A thick, are single
phase heteroepitaxial cubic diamond solid solutions. For films with a Si : Ge ratio of 7 : 3 the defect density is low for carbon
concentrations less than I%. The (Xmin) minimum yield increases from 0.13 to 0.89 as the carbon concentration increases
from 0.5 to 3%. For low C concentrations, the channeling yield increases with depth indicating that the defect density
increases near the film substrate interface, which is characteristic of partial film relaxation. For C concentrations of 2% and
higher the defect density is uniformly high throughout the films indicating that defects are uniformly nucleated throughout
the film during growth. Infrared spectroscopy measurements show that the Si-C bond length distribution broadens as the
carbon concentration increases and also shows that carbon exhibits a higher substitutionality for a growth temperature of
450°C than for 560°C. A possible interpretation of these results is that the high local strain associated with the Si-C bonds
deteriorates the elastic properties of Si1-x-y ,GexCy, making it more susceptible to relaxation and defect nucleation than
Si1-x-y ,GexCy I under similar strain and growth temperatures.

The transformation of C49 phaseTiSi2 to the low resistivity C54 phase is necessary for many microelectronic applications. Here, we report on attempts to decrease this transformation temperature by low-energy ion bombardment at elevated temperature. Ion irradiation was performed using a broad beam Kaufman ion source operated in N2 or Ar gas between 0.1 and 2 keV beam energy,with ion doses ranging from 2.0 X 10E16 to 1.9X 10E18 ions/cm2, and sample temperatures from 480°C to 735°C. For comparison, room-temperature Ar + implantation at higher energy (105-210 keV) was performed with a dose of 10E16 ions/cm2 with projected ranges within and beyond the TiS2 layer thickness. Resistivity measurements as a function of temperature, X-ray diffraction, and Rutherford Backscattering Spectrometry were used to determine the composition and phases. Results show that low - energy ion bombardment does not promote the C49-C54 transformation at the temperatures studied, while ion implantation actually raises the temperature for the transformation.
In addition, bombardment of C54 TiSi2, does not cause it to revert to the C49 phase,indicating that both phases appear to be surprisingly stable under ion bombardment. Simulations of defect production using the TRIM code indicate the formation of a higher number of displaced atoms than are usually required to initiate a transformation. We conclude that the defects introduced into C49 TiSi2, by ion bombardment at energies up to 2 keV are either not sufficient to nucleate the C54 phase or they are annealed out too quickly at the temperature needed for C54 phase growth.

An upper temperature limit of 450 degrees C has been established for growth of heteroepitaxial Si1-x-yGexCy solid solutions with substitutional C on Si(100) by combined ion and molecular beam deposition (CIMD). At 450 degrees C infrared absorption spectroscopy shows that C is on substitutional sites and no SiC precipitates are detected, whereas at 560 degrees C the substitutional C signal is much smaller but SiC precipitates are still not detected. High resolution transmission electron microscopy shows that Si1-x-yGexCy films deposited at 560 degrees C exhibit Ge deficient, coherent, secondary phase clusters in the cubic diamond matrix, which are not seen in films deposited at 450 degrees C. These observations suggest that the clusters are C-rich, Ge-deficient precursors to SiC, with a lattice which is distorted but free of extended defects. Ion channeling results indicate that the Si1-x-yGexCy films might have a distribution of different bond lengths. (C) 1996

Molybdenum thin¯lms were sputter deposited under di®erent conditions of DC power and chamber pressure. The structure and topography of the¯lms were investigated using AFM, SEM and XRD techniques. Van der Pauw method and tape test were employed to determine electrical resistivity and interfacial strength to the substrate, respectively. All the¯lms are of sub-micron thickness with maximum growth rate of 78 nm/min and crystallite size in the range of 4 to 21 nm. The¯lms produced at high power and low pressure exhibit compressive residual strains, low electrical resistivity and poor adhesion to the glass substrate, whereas the converse is true for¯lms produced at high pressure.

Stress is inevitable during thin film growth. It is demonstrated here that the growth stress has a significant effect on the dielectric constant of high-k thin films. ZrO2 thin films were deposited on Ge by reactive direct current sputtering. Stress in these films was measured using in-situ curvature measurement tool. The growth stress was tuned from -2.8 to 0.1 GPa by controlling deposition rate. Dielectric permittivity of ZrO2 depends on temperature, phase, and stress. The correct combination of parameters—phase, texture, and stress—is shown to yield films with an equivalent oxide
thickness of 8 Å. Growth stresses are shown to affect the dielectric constant both directly by affecting lattice parameter and indirectly through the effect on phase stability of ZrO2.

"En este trabajo se prepararon películas delgadas de trióxido de molibdeno (MoO3) por la técnica de atomización pirolítica. Las películas fueron depositadas sobre sustratos de vidrio y obtenidas a partir de una solución precursora de Heptamolibdato de Amonio Tetrahidratado ((NH3) 6Mo7O24.4H2O) 0.1 M. La temperatura del sustrato se mantuvo constante en 400 oC y se varió el volumen de la solución precursora. Las muestras se caracterizaron por difracción de Rayos X (XRD), espectroscopía infrarroja, Microscopía Electrónica de Barrido (SEM) y eléctricamente a través de medidas de resistividad eléctrica en función de la temperatura. Las muestras crecen con estructura cristalina correspondiente a la fase alfa del MoO3 con dirección preferencial de crecimiento a lo largo de los planos (0k0). Al aumentar el volumen de la solución precursora la superficie de las muestras se vuelve porosa. La resistividad en estas muestras cambia en un orden de magnitud cuando son expuestas a la atmosfera de CO"

Sputter deposited molybdenum (Mo) thin films are used as back contact layer for Cu (In 1 À x Ga x )(Se 1 À y S y ) 2 based thin film solar cells. Desirable properties of Mo films include chemical and mechanical inertness during the deposition process, high conductivity, appropriate thermal expansion coefficient with contact layers and a low contact resistance with the absorber layer. Mo films were deposited over soda-lime glass substrates using DC-plasma magnetron sputtering technique. A 2 3 full factorial design was made to investigate the effect of applied power, chamber pressure, and substrate temperature on structural, morphological, and electrical properties of the films. All the films were of submicron thickness with growth rates in the range of 34-82 nm/min and either voided columnar or dense growth morphology. Atomic force microscope studies revealed very smooth surface topography with average surface roughness values of upto 17 nm. X-ray diffraction studies indicated, all the films to be monocrystalline with (001) orientation and crystallite size in the range of 4.6-21 nm. The films exhibited varying degrees of compressive or tensile residual stresses when produced at low or high chamber pressure. Low pressure synthesis resulted in film buckling and cracking due to poor interfacial strength as characterized by failure during the tape test. Measurement of electrical resistivity for all the films yielded a minimum v alue of 42 μΩ cm for Mo films deposited at 200 W DC power.

A comparative study on negative ion formation in the scattering of a proton beam from both a clean and one monolayer of barium-covered Ag͑111͒ surface is presented. The angular and energy dependence of the backscattered negative hydrogen ions as a function of incoming and azimuthal angles has been determined for a beam energy of 750 eV. The backscattered negative particles emerge from the surface as well as from deeper layers of the crystal. The angular dependence of the outgoing particles shows a very rich structure, which is explained by shadowing and blocking of the incoming and outgoing particles. In addition, the angular dependence of the outgoing neutral particles is determined. The essential features appear the same, but distinct differences can be observed. These are due to changes in the probability for negative ion formation as a function of outgoing angle. The energy distributions of the outgoing particles suggest a large penetration depth along the crystal channels. We have performed classical trajectory calculations that simulate the angular distributions of the backscattered particles very well. These calculations also show considerable penetration of particles into the bulk of the crystal and complicated zigzag trajectories through the bulk before leaving the crystal. The ͑electronic͒ stopping inside the Ag solid is at least one or two orders of magnitude smaller ͑Ͻ0.3 eV/Å at Eϭ700 eV͒ than the values found in the literature. Comparing the Ag͑111͒ data and the data of Ag͑111͒ covered by one monolayer barium, we conclude that the barium atoms occupy lattice positions of the crystal. The overlayer must contain vacancies to accommodate the large size mismatch between the barium atoms and those of the substrate.

Extremely smooth (6 nm RMS roughness over 4 lm 2 ), thin (100 nm), and continuous ultrananocrystalline diamond (UNCD) films were synthesized by microwave plasma chemical vapor deposition using a 10 nm tungsten (W) interlayer between the silicon substrate and the diamond film. These UNCD films possess a high content of sp 3 -bonded carbon. The W interlayer significantly increased the initial diamond nucleation density, thereby lowering the surface roughness, eliminating interfacial voids, and allowing thinner UNCD films to be grown. This structural optimization enhances the films' properties and enables its integration with a wide variety of substrate materials.

. Ž . Electron paramagnetic resonance EPR measurements have been made of defects in amorphous hydrogenated carbon a-C:H thin films. The films were grown on silicon substrates on the earthed electrode of an rf-powered plasma enhanced chemical vapour deposition reactor and were subsequently implanted with a range of doses of boron, carbon or nitrogen ions with energies Ž . from 20 keV to 32.5 keV. Two paramagnetic centres are observed, the carbon defect in the film with gs 2.0028 1 and a silicon Ž . defect in the substrate with gs 2.0058 6 . The volume concentration of the carbon defect increases approximately linearly with dose, from approximately 3 = 10 17 cm y3 for unimplanted samples to 2.7= 10 20 cm y3 at the highest implantation of 2 = 10 16 B q y2 Ž . ions cm . The increase in dose over this range also causes a narrowing of the EPR line from 0.83 mT to 0.13 mT and a Ž y5 y8 . significant decrease in the spin-lattice relaxation time from 3 = 10 s to 6 = 10 s which approaches the spin᎐spin relaxation time at the highest dose. The narrowing is attributed to motional averaging produced by either exchange or hopping. We also report the effects of annealing samples implanted with a range of boron doses. The prime novelty of this paper is that it is the first EPR study of defects produced by the implantation of a range of ions into polymer-like amorphous hydrogenated carbon. ᮊ

A 2D phase-field model was applied to simulate the phase-transition kinetics and the thermal field distribution during the lateral crystallization of a-Si induced by single pulse excimer laser. The higher tilt of solidyliquid interface increases the supercooling temperature in the melt due to the fast latent heat extraction at the solidyliquid interface. The lateral growth velocity is in average four times faster than the vertical one. When the lateral growth velocity exceeds the critical value of 19 mys, amorphization of Si can be initiated because of unstable growth front. Therefore, thickness of Si film and the thermal properties of underlying layer play a crucial role not only in ultra-large grain fabrication but also in defect-free crystal growth. ᮊ

Molybdenum thin¯lms were sputter deposited under di®erent conditions of DC power and chamber pressure. The structure and topography of the¯lms were investigated using AFM, SEM and XRD techniques. Van der Pauw method and tape test were employed to determine electrical resistivity and interfacial strength to the substrate, respectively. All the¯lms are of sub-micron thickness with maximum growth rate of 78 nm/min and crystallite size in the range of 4 to 21 nm. The¯lms produced at high power and low pressure exhibit compressive residual strains, low electrical resistivity and poor adhesion to the glass substrate, whereas the converse is true for¯lms produced at high pressure.

Using ion beam modification, films composed of synthesized ''interphases'' of ordered silica on OH-passivated (1 Â 1)Si(100) underwent surface electro-chemical changes quantified by surface free energy via Sessile drop method and contact angle analysis using Young's equation and Van Oss theory. IBMM caused the surface free energies initially ranging from 26.0 mJ/m 2 to 57.3 mJ/m 2 to converge to 43.1-45.4 mJ/m 2 for various passivated and as-received wafer samples alike. Although TMAFM also identified topographic changes, these changes did not correlate to the change of surface free energies. Ion beam modification of the ordered silica film on Si(100) surface is analyzed using 3.045 MeV 16 O(a, a) 16 O nuclear resonance scattering (NRS) in conjunction with channeling in h111i direction, which demonstrated the convergence of the partially ordered oxygen to amorphous at about 55 lC/mm 2 He ++ flux. Additionally, Si surface peak channeling in h100i and h111i directions also experienced an uptrend in areal density as incident ion flux increased, while the rotating random Si signal height remains stable, showing a disruption in the surface order during IBMM.

. Ž . Electron paramagnetic resonance EPR measurements have been made of defects in amorphous hydrogenated carbon a-C:H thin films. The films were grown on silicon substrates on the earthed electrode of an rf-powered plasma enhanced chemical vapour deposition reactor and were subsequently implanted with a range of doses of boron, carbon or nitrogen ions with energies Ž . from 20 keV to 32.5 keV. Two paramagnetic centres are observed, the carbon defect in the film with gs 2.0028 1 and a silicon Ž . defect in the substrate with gs 2.0058 6 . The volume concentration of the carbon defect increases approximately linearly with dose, from approximately 3 = 10 17 cm y3 for unimplanted samples to 2.7= 10 20 cm y3 at the highest implantation of 2 = 10 16 B q y2 Ž . ions cm . The increase in dose over this range also causes a narrowing of the EPR line from 0.83 mT to 0.13 mT and a Ž y5 y8 . significant decrease in the spin-lattice relaxation time from 3 = 10 s to 6 = 10 s which approaches the spin᎐spin relaxation time at the highest dose. The narrowing is attributed to motional averaging produced by either exchange or hopping. We also report the effects of annealing samples implanted with a range of boron doses. The prime novelty of this paper is that it is the first EPR study of defects produced by the implantation of a range of ions into polymer-like amorphous hydrogenated carbon. ᮊ

Electron paramagnetic resonance (EPR) measurements have been made at X-band (f9.5 GHz) and W-band (f95 GHz) of a-C:H films on (1 0 0) silicon substrates; the sample temperature was varied in the range 5-300 K. Two types of film were examined. The first type are amorphous hydrogenated carbon (a-C:H) films grown by plasma enhanced chemical vapour deposition (PECVD) with negative self bias voltages in the approximate range 100-500 V. The second type were initially highly polymeric-like a-C:H films grown on Si placed on the earthed electrode of a PECVD system but were subsequently implanted with either 6=10 cm B or 2=10 cm B ions. At both X-and W-band and throughout the temperature range 5-300 K 15 y2 q 16 y2 q the EPR signal of the carbon unpaired electrons consists of a single symmetric line with gs2.0026"0.0002. As the temperature is lowered, several samples develop a dependence on sample orientation of the external field required for resonance. This anisotropy is explained in terms of the demagnetising fields more usually encountered in ferromagnetic resonance. ᮊ