ICMCTF2006 Session B1: Sputtering Coatings and Technologies

Thursday, May 4, 2006 8:30 AM in Room Royal Palm 1-3

Thursday Morning

Time Period ThM Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF2006 Schedule

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8:30 AM B1-1 Fundamental Understanding and Development of Nanostructured Ti-Al-Si-N and Zr-N-O Thin Films
L. Rebouta (Universidade do Minho, Portugal); K. Shein (Russian Academy of Sciences, Russia); P. Carvalho, F. Vaz, S. Carvalho (Universidade do Minho, Portugal)

Special attention will be dedicated to Ti-Si-N and Ti-Si-Al-N films prepared under conditions out of thermodynamic equilibrium, and the formation of mixed phases. In order to explain the influence of Si → Ti substitution in the bulk stoichiometric B1 TiN, calculations using first principles density functional theory were performed. A 16-atomic supercell Ti7SiN8, which corresponds to the nominal composition of Ti0.875Si0.125N was used as a model. A lattice compression in result of Si-Ti substitution was obtained.

These results suggest that the subsequent formation of the nanocomposite of the type nc-MeN/a-Si3N4 results from ion irradiation induced effects and a driven Si surface segregation, leading to continuous renucleation during film growth. This mechanism explains the formation of a multiphase system, where the crystalline TiN, (Ti,Al)N and (Ti,Al,Si)N phases were identified by X-ray diffraction, when the surface mobility is not enough to obtain a complete thermodynamically driven segregation. XPS measurements show the absence of Titanium silicide and the formation of the amorphous Silicon nitride phase.

Regarding the ZrOxNy, thin films, the evolution of film properties as a function of the reactive gas flow (a mixture of oxygen plus nitrogen), revealed the development of three distinct growth modes. These changes are particularly evident in the film’s structure evolution, which revealed a change from fcc ZrN-type growth at low gas flows, to a structure similar to that of Zr3N4, with oxygen inclusions, at intermediate gas flows, to oxide-type structures at the highest flows. These structural changes were also confirmed by resistivity measurements, whose values ranged from 250-400 Ωcm for low gas flows and up to 106 Ωcm for the highest flow rates. Color measurements in the films revealed a change from bright yellow at low reactive gas flows, to red-brownish at intermediate flows and dark blue for films prepared at the highest flows. Mechanical properties also tend to follow these different behaviors.

9:10 AM B1-3 Multi-Component Nitride Coatings Derived from Ti-Al-Cr-Si-V Target in RF Magnetron Sputter
C.-H. Lin (National Tsing Hua University, Taiwan); J.G. Duh (National Tsing Hua Univerisity, Taiwan)
The nitride coatings comprised of various constituent Ti, Al, Cr, Si, V were deposited on mild steel by RF magnetron sputtering process. The Ti-Al-Cr-Si-V multi-component target introduced in this study was fabricated by conventional metallurgical method with atomic ratio of each selected element maintained at 1:1:1:1:1. Different coatings were fabricated under various working pressure by adjusting nitrogen flux. After deposition process, composition and structure of the nitride coatings were analyzed by FE-EPMA and XRD, respectively. According to XRD patterns, only f.c.c. structure was revealed for all the coatings. In addition, microhardness of the nitride coatings was measured by nanoindentation, and hardness higher than 30 GPa was exhibited. The microhardness test showed and evidence that the multi-component nitride could be an potential candidate coating for tool steel.
9:30 AM B1-4 Influence of Nitrogen on the Microstructure and Nanomechanical Properties of TaSiN Thin Films by Magnetron Reactively Co-Sputtering
C.-K. Chung, T.-S. Chen, C.-C. Peng, B.-H. Wu (National Cheng Kung University, Taiwan)
This paper presents the relation between the process, microstructure and nano-hardness of the tantalum silicon nitride (TaSiN) nano-composite thin films by magnetron reactively co-sputtering at different nitrogen contents. The different N2 flow rates were controlled from 0% to 30% (N2% = N2 /(Ar+N2) x100%). The microstructure and nanomechanical properties were characterized by glancing-incident angle X-ray diffraction (GIAXRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and nanoindentation. GIAXRD results reveals that the microstructures of TaSiN nanocomposite film have nanocrystalline grain embedded in amorphous matrix (nc/±-TaSiN) at small N2 flow rates 2-10%. As N2 flow rates is up to 20% or more, it is transformed into the polycrystalline phase. Consequently, the grain size and nanomechanical properties have great changes with microstructures. The grain size of the films increases with increasing N2 flow rates. The polycrystalline TaSiN films with loose microstructure have larger grains at 20% N2 flow rates than that in nc/±-TaSiN film with denser microstructure obtained at 3% N2 flow rates. The topography and roughness of all TaSiN films were smooth, but the nc/±-microstructures have smaller roughness of about 3 nm. The nano-harnesses of TaSiN films were measured between 9.5 and 15.2 GPa by nanoindentation. It reveals that the maximum nano-hardness was found it at 3% N2, because the nanocrystalline grain (10- 20nm) embedded amorphous matrix of composite microstructure to enhance the hardness. As the grain size of TaSiN films increases with the increasing N2 flow rates, the nano-hardness decreases obviously at 20% N2. The microstructures and nano-hardness can be controlled by N2 flow rates. The nc/±-TaSiN film obtained at small N2 flow rate have the advantages of smoother morphology and higher nano-hardness than that at high N2 flow rate.
9:50 AM B1-5 Reactive Gas Effects in Pulsed Magnetron Sputtering: Time-Resolved Investigation
Th. Dunger, Th. Welzel, F. Richter (Chemnitz University of Technology, Germany)
A pulsed magnetron deposition discharge has been studied in argon with different admixtures of oxygen as reactive component. The target material used was magnesium and the pulsed discharge was operated in metal and oxide mode, resp.. The circular magnetron was asymmetrically bipolar pulsed with frequencies up to 200 kHz and at a fixed average power of 100 W. The discharge evolution during each pulse has been characterised by means of time-resolved Langmuir double probes, time-resolved optical emission spectroscopy and the waveform of the target voltage. These measurements show that - due to the characteristics of the Pinnacle Plus power supply unit used - the target voltage exhibits a strong overshoot in the on phase of the pulse. Contrary, both charge carrier density and optical emission exhibit two more or less strong peaks at the beginning of the on phase, the second of which being the most dominant. The temporal development of the discharge is clearly different for the two discharge modes: In the oxide mode, the structures in the on phase - except of the first maximum - significantly shift to shorter times compared to the metal mode. This is suggested to be due to the much higher secondary electron emission coefficient (γ) of MgO in comparison to Mg leading to increased ionisation starting with the second maximum. The first maximum, however, is believed to be due to residual electrons from the precedent pulse and is thus independent of the γ coefficient. A significant feedback from the discharge to the power supply is observed by changes in the voltage waveform: the more efficient discharge development is accompanied by a sharper and lower peak in the voltage. In the off phase where no electron generation at the target occurs, both discharge modes exhibit essentially the same behaviour.
10:10 AM B1-6 AC Powered Reactive Magnetron Deposition of Indium Tin Oxide (ITO) Films from a Metallic Target
H. Kupfer, R. Kleinhempel, Th. Welzel, Th. Dunger, F. Richter (Chemnitz University of Technology, Germany); W.-M. Gnehr, T. Kopte (Fraunhofer Institute for Electron Beam and Plasma Technology, Germany)

Transparent highly conductive indium tin oxide (ITO) films for low cost applications were deposited by a reactive dual-magnetron sputter process using metallic targets. The magnetrons were equipped with rectangular (130 x 400 mm2) In/Sn targets (90 wt.-% In / 10 wt.-% Sn). A sine wave power supply was used at a frequency of about 70 kHz. All experiments were done in the transition mode at a constant argon flow of 40 sccm. The oxygen flow rate was varied between 35 and 70 sccm. The total pressure was kept constant at 0.4 Pa.

The films were deposited onto silicon and float glass substrates which were either moved in an oscillatory manner (dynamic deposition) or fixed in front of the targets (static mode) during deposition. A dynamic deposition rate of about 96 nmxm/min was obtained at an averaged power of 2 kW per cathode. The film thickness was adjusted to 500 nm. At an optimised Ar/O2 gas flow ratio of 0.6 we found an electrical resistivity as low as 1x10-3 Ωcm. The refractive index of these films was about 2.05 indicating a dense film structure. The optical absorption of k = 10-2 is comparable to typical results of other groups. Moreover, the film texture and the mechanical stress were investigated by XRD methods.

Applying a static deposition we have achieved a lower electrical resistivity with a minimum value of 5x10-4 Ωcm. In this case, the resistivity was not constant over the substrate but depends on the lateral position in front of the target. In order to explain this inhomogeneity we have performed spatially resolved Langmuir probe and OES measurements and related their results to film structure and properties. In order to improve the film properties at dynamic deposition the growth conditions have to be homogenised at all substrate positions.

10:30 AM B1-7 The Effect of Pulsed Magnetron Sputtering on the Structure and Mechanical Properties of CrB2 Coatings
M. Audronis, A. Leyland (The University of Sheffield, United Kingdom); P.J. Kelly (Manchester Metropolitan University, United Kingdom); A. Matthews (The University of Sheffield, United Kingdom)

Chromium diboride PVD coatings possess desirable combinations of properties (high hardness, wear resistance, chemical inertness, high thermal and electrical conductivity), which are attractive for a wide range of potential applications.

Pulsed magnetron sputtering (at 100 kHz frequency) of loosely-packed powder targets allowed deposition of stoichiometric CrB2 coatings at low substrate temperatures (110-150°C). The structure, composition and mechanical properties of these coatings were found to be strongly dependent on the deposition process parameters. Investigation of the coating structure could explain certain differences between them, indicating directions for improvement and giving important information about the characteristics of the deposition process.

Characterization of the films was performed by cross-sectional and plan-view transmission electron microscopy techniques (electron diffraction and bright-field/dark-field imaging). Some results from XRD, RBS and nanoindentation studies of these films are also presented. The structures of coatings deposited with different parameters are investigated and compared; the reasons for the structural differences observed are discussed.

All coatings studied exhibited extremely fine, dense and uniform structure and morphology. For example, films deposited at 80% duty cycle (100 kHz frequency) onto negatively biased substrates (-30V DC) resulted in a crystalline, nanocolumnar structure (column width ~ 4-6 nm), which exhibits very strong preferred (001) orientation. Such coatings were also found to have highest hardness and better corrosion resistance. However, significant structural differences between these coatings were also evident. The structure of CrB2 coatings, and changes that resulted from variation of deposition parameters (such as target voltage pulse regime, duty cycle and substrate biasing conditions), are discussed in detail.

10:50 AM B1-9 Preparation and Characterization of Non-Evaporable Porous Ti-Zr-V Getter Films
C.-C. Li, J.-L. Huang (National Cheng-Kung University, Taiwan); R.-J. Lin (Intellectual Property Exchange Limited, Taiwan)
The non-evaporable getter (NEG) materials, such as titanium or titanium alloys, have been widely used in vacuum-type devices to upgrade and sustain the vacuum environment inside the cavity of the device by the chemical interaction between getters and gases. With the progress of microelectromechanical system (MEMS) technologies, the development of the minimizing vacuum devices, such as high Q mechanical resonators, infrared detectors of focal plane array and tunneling sensors, etc., have largely increased. Nevertheless, the conventional bulk or thick-film getters can not be used in these MEMS-type devices due to the restricted space. Therefore, the development of non-evaporable porous thin-film-type getters is strongly required for improving the capability to absorb the residual gases inside these minimizing vacuum devices. The highly porous TiZrV film getters on (100) silicon substrates have been successfully grown by the glancing angle deposition of dc magnetron sputtering method. The glancing angle is defined as the angle between the surface normal of the substrate and the surface normal of the target. The main deposition parameters that produce the porous TiZrV films are the pressure of sputtering gas Ar and glancing angle at the condition of room substrate temperature. The porous films are composed of isolated nano-columnar crystalline crystals with (002) preferred orientation. The typical size and inter-distance between the columnar crystals of porous TiZrV films are 120 and 15 nm, respectively. The detailed results will be presented in the areas of (1) the relationship between the film composition, surface morphologies, microstructure, crystal structure, specific surface area of the porous TiZrV film, activation temperature and the deposition parameters, and (2) the performance characterization of gettering capability of the TiZrV films.
11:10 AM B1-10 An Analysis of Target Processees in Reactive Magnetron Sputtering
A. Billard (Ecole des Mines, France)
Reactive magnetron sputtering is a powerful technique for deposition of ceramic coatings from metallic targets which however often presents the drawback of an unstable behaviour of the sputtering mode, in particular in industrial plants. The so-called related hysteresis phenomenon is due to both the significant decrease of the average sputtering yield proceeding from the target poisoning and to the getter occurring at the surface of the chamber walls. In this context, the processes at the surface of the target significantly contribute to the instability of the sputtering mode. In this paper, we present the influence of several parameters directly conditioning the target processes, in turn involving the stability of the sputtering mode. We first describe the influence of the sputtered metal flow, respectively by increasing the discharge current or the discharge voltage, which can allow the deposition of stoichiometric ceramic coatings in the so-called elemental sputtering mode due to the increase of the sputtering wind already described by Rossnagel. Hence, we describe the influence of the target temperature in the case of targets presenting or not an allotropic transition. We then show that increasing the target temperature is susceptible to stabilise the sputtering mode. This stabilisation of the sputtering mode is discussed in relation with the structure of the target which, in particular, conditions the diffusion rate of metalloid species into the bulk target. Finally, we present the main trends of a new model taking into account the diffusion into the bulk target which comforts the influence of this phenomenon owing to the stability of the sputtering mode and can also simulate the transient sputtering stages, used for example when modulating at low frequency either the discharge current or the reactive flow rate.
11:50 AM B1-11 Monitoring and Control During Deposition of AlN Films by a PVD Process
J. Acosta, A. Rojo, O Salas (ITESM, Mexico); J. Oseguera (ITESM-CEM, Mexico)
Consumed nitrogen and deposition rate of AlN films deposited by non-balanced magnetrons during reactive magnetron sputtering, were monitored by optical emission spectroscopy (OES) and a Langmuir probe. The depositions were carried out at different pressures and gas mixtures. The microstructure of the resulting AlN films was characterized by SEM and XRD. OES allowed the identification and the evolution of some spectral lines, while the Langmuir probe provided the electron temperatures and densities in the reactive system. This information together with the microstructural characterization provide means to control the characteristics of the deposited films.
Time Period ThM Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF2006 Schedule