ICMCTF2009 Session H2-1: High Power Impulse Magnetron Sputtering

Thursday, April 30, 2009 8:00 AM in Room Sunset

Thursday Morning

Start	Invited?	Item
8:00 AM	Invited	H2-1-1 Target-Plasma-Film Interactions in High Power Pulsed Magnetron Sputtering K. Sarakinos (RWTH Aachen University, Germany) High power pulsed magnetron sputtering (HPPMS) provides high fluxes of ionized species to the growing film allowing for superior film properties in comparison to those obtained by conventional techniques, such as direct current magnetron sputtering (dcMS). In addition, in HPPMS lower film deposition rates (Rd) than the dcMS ones are commonly obtained. In order to elucidate the mechanisms responsible for these features, the investigation and the understanding of the target-plasma-film interactions in HPPMS are of key importance. Based on experimental studies of an Ar-Cr HPPMS discharge, the lower rates are primarily attributed to the re-direction of ionized sputtered species to the target (self-sputtering). It is shown that the self-sputtering occurs when high degree of ionization of the sputtered species and depletion of Ar species in front of the target (rarefaction) are simultaneously present. This notion is further supported by a semi-quantitative analysis that enables the estimation of the composition of the ion target current during HPPMS of C, Cr and Cu. In the case of reactive HPPMS it is shown that the deposition rate is mainly affected by the target coverage. Using a Zr target in an Ar-O2 ambient, it is demonstrated that HPPMS exhibits a stable transition sputtering zone, as opposed to dcMS. This facilitates growth of films with Rd values up to 2 times higher than in dcMS. Finally, HPPMS is employed for the growth of nitride (CrN) and oxide (TiO₂ and Al₂O₃) films allowing for effective tailoring of films’ morphology and phase composition. These findings are discussed in the light of the energetic bombardment provided at the various conditions.
8:40 AM		H2-1-3 Time Resolved Optical Imaging of HIPIMS Discharges: Selecting Pulse Parameters Based on Target Mass J.G. Jones, C. Muratore (Air Force Research Laboratory); A.N. Reed (Air Force Research Laboratory/University of Dayton Research Institute); A.R. Waite (Air Force Research Laboratory/UTC, Inc./University of Dayton); C.A. Cerbus (Air Force Research Laboratory/University of Dayton Research Institute); S.F. Noss, A.A. Voevodin (Air Force Research Laboratory) The highly ionized flux associated with high power impulse magnetron sputtering (HIPIMS) can yield unique and useful physical characteristics in thin film materials. Unfortunately, the deposition rate in HIPIMS tends to be lower than in standard magnetron sputtering when processes conducted with the same time-averaged power are compared. Dependence of deposition rate on target atom ionization energy and self-sputter yield have been reported for HIPIMS processes. Another property of the sputtered material that affects the deposition rate is the mass of the sputtered atoms, which dictates their transit time over characteristic lengths within the plasma chamber. The role of mass on the deposition rate of elemental metals with equivalent ionization energies but very different masses was investigated, and compared to the effects of ionization energy and self-sputter yield. Additionally, the effect of pulse parameters for targets of different masses on deposition rate was also examined. Two-dimensional optical images and plasma spectra were taken simultaneously during HIPIMS sputtering of several elemental targets, including hafnium and titanium with masses of 178 amu and 48 amu, respectively, and equivalent ionization energies of 6.8 eV. The characteristics of a density wave traveling perpendicular to the target surface at 5-8 km/s was observed in the images. Dependence on the mass of the target atoms was also observed. Spectroscopy techniques were used to observe temporal and spatial plasma chemistry. Time-resolved temperature measurements at the substrate surface were correlated to events occurring within the plasma, and compared to measurements of the time-averaged thermal load. The importance of flux composition and near surface temperature on growth phenomena are discussed in light of the results.
9:00 AM		H2-1-4 Characterization of HIPIMS Discharge for Next Generation Semiconductor Fabrication A.N. Cloud, R.E. Flauta, M.J. Neumann, S.L. Rohde, D.N. Ruzic (University of Illinois at Urbana-Champaign) Thin films produced using High Power Impulse Magnetron Sputtering (HIPIMS) have attracted considerable attention in the coating industry due to their excellent adhesion, superior density, and other favorable tribological properties. The extreme high power pulse densities provide a high concentration of metal ions and produce high-quality, homogeneous coatings. The high ionization fraction allows for fine control of the sputtered species during deposition, a feature well suited to the needs of future semiconductor fabrication techniques. HIPIMS may provide a highly scalable means of depositing diffusion barrier coatings and metallic features in the high aspect ratio interconnect trenches required for future chip designs. HIPIMS discharges from a planar magnetron were characterized and evaluated for potential as a chip processing tool. A gridded energy analyzer and quartz crystal microbalance were used to measure a higher ionization fraction in the HIPIMS discharge than with conventional magnetron sputtering under a variety of deposition conditions. The energy spectrum and flux of these ions at the substrate location were also measured. Plasma electron temperature and density as a function of pressure and power were mapped over a 3D region between the sputter target and substrate level by Langmuir probe analysis. A triple probe was used to study plasma conditions during the pulse. Deposition rates and film quality were evaluated. Characterization of the resultant films’ structure, quality, and uniformity over the width of a 200 mm wafer and across surface features were performed.
9:20 AM		H2-1-5 Distance Dependent Plasma Composition and Ion Energy Distribution Functions in High Power Impulse Magnetron Sputtering of Ti and Cr A.P. Ehiasarian (Sheffield Hallam University, United Kingdom); J. Andersson (Ångstrom Laboratory, Sweden); A. Anders (Lawrence Berkeley National Laboratory) Research has shown that the target material in HIPIMS operation influences the total plasma density at the substrate, the metal ion–to–gas ion ratio, the speed of evolution of the discharge current and establishment of a self-sustained steady state. At the same time the ionization degree of metal vapor is constant with distance. However, the transport of particles from target to substrate is not well understood. We compare the diffusion of metal and gas ions to the substrate for Ti and Cr target materials with significant difference in sputter yield but similar mass. Ti and Cr HIPIMS plasmas operating at current density of ~0.5 Acm^-2 have been characterised with a HIDEN plasma-sampling energy-resolved mass spectrometer at distances from 50 to 300 mm from the sputtering target. Measurements of the argon and metal ion content as well as the ion energy distribution functions showed that: (1) single and doubly charged ions were present for argon and target metal , (2) the majority of ions were singly charged argon for both metals and all distances investigated, (3) the Cr ion density was maintained to further distances from the target than Ti. Gas rarefaction was identified as the main mechanism promoting transport of the metal ion vapor with stronger effect achieved for materials with higher sputter yield. In the Cr case, metal ions were found to displace significant proportion of the gas ions, whereas this was less evident in the Ti case. Electron temperature cooling through metal ionizing collisions was responsible to eliminate production of highly charged Ar²⁺ ions.
9:40 AM		H2-1-6 Mass/Energy Analysis of the Plasma During MPP and Conventional DC Sputter Deposition of Cr and CrN Films W.D. Sproul (Reactive Sputtering, Inc.); J. Lin, J.J. Moore (Colorado School of Mines); Z.L. Wu (Colorado School of Mines, and Dalian University of Technology, China); X. Zhang (Colorado School of Mines); R. Chistyakov (Zond, Inc.); B. Abraham (Zpulser, LLC); J.A. Rees (Hiden Analytical, Ltd.) An energy/mass analyzer was used to characterize the plasmas during modulated pulse power (MPP) and conventional DC power sputter deposition of Cr and reactive sputter deposition of CrN films in a two-cathode closed field unbalanced magnetron sputtering system. The inlet to the energy/mass analyzer was located midway between the two cathodes at the position where the substrates normally are located, which is about 14 cm from the target surfaces. Experiments were run with the different types of power applied to either just one of the cathodes or to both of the cathodes when the cathodes were set up in the closed field configuration or when one of the cathodes was removed. The mass analysis detected Cr plus one, Ar plus one, and Cr plus two ions. The intensity of the Cr plus one ions when the MPP power is used is significantly higher compared to when DC power is used. As the peak power and the average power of the MPP pulse was increased, the intensity of these ions also increased in the closed field condition as it did when DC power was used. When one of the cathodes was removed and the cathode magnetic field was not closed, the intensity of the ions decreased significantly. The energy analysis revealed that the average energy for the Cr and Ar plus one ions is about 2 eV and that the energy distribution is very small. There is a slight high energy tail to the ion energy distribution, and there is almost a mono-energetic source of ions in the MPP process.
10:00 AM		H2-1-7 Stress in TiN Coatings Grown by HIPIMS R. Machunze (Delft University of Technology,, Netherlands); A.P. Ehiasarian (Sheffield Hallam University, United Kingdom); G.C.A.M. Janssen (Delft University of Technology, Netherlands) Titanium nitride coatings (TiN) are used amongst other applications as wear-protective coatings or as diffusion barriers in IC technology. In these applications the biaxial stress is a key factor determining the performance of the coating. High power impulse magnetron sputtering (HIPIMS) leads to a high degree of ionization of 20-30% of the metal flux towards the growing film, which allows film growth at high ad-atom mobility and yet, a low incident ion energy of < 6 eV average. The ad-atom mobility is an important parameter influencing the film growth. The microstructure of HIPIMS grown TiN coatings is significantly denser compared to films grown by unbalanced magnetron sputtering (UBM). The crystallographic texture of HIPIMS coatings tends towards (001) in contrast to (111) for UBM coatings [J.Paulitsch et al., TSF (2008), doi:10.1016/j.tsf.2008.06.080]. In previous work we related the film stress and the stress gradient in UBM grown TiN coatings to their microstructure and texture. We proposed a model for increased compressive stress generation in crystals with a (001) orientation with respect to crystals with (111) orientation [R.Machunze and G.C.A.M.Janssen, submitted for publication to JAP]. In the present contribution we will compare film stress, microstructure and texture in UBM and HIPIMS grown TiN coatings. The influence of increased ad-atom mobility on the development of crystallographic texture and stress with film thickness will be discussed.
10:20 AM		H2-1-8 Cutting Performance Improvement of PVD Tialn-Based Coatings, Produced by HPPMS Technology K.-D. Bouzakis, G. Skordaris, S. Gerardis, G. Katirtzoglou, S. Makrimallakis, M. Pappa (Aristoteles University of Thessaloniki, Greece); R. Cremer, H.-G. Fuss, W. Koelker, J. Dukwen (CemeCon A.G., Germany) Recently High Power Pulsed Magnetron Sputtering technology (HPPMS) has been identified as a most powerful tool in the production of hard coatings. The enormous increase in metal atom ionization in HPPMS-generated plasmas gives to the PVD films’ development of new possibilities. HPPMS technology affects significantly many physical properties of hard coatings like crystallographic, topographic and mechanical ones. In turn the properties result in higher cutting tools performance. In the investigations described in the paper, TiAlN and TiAlCrN PVD coatings have been produced using an industrial CemeCon CC800/9 HPPMS coating unit. Nanoindentations were conducted in all examined films and the corresponding results were evaluated with the aid of a FEM based algorithm, to determine the films’ stress strain characteristics. Additionally, perpendicular as well as inclined impact tests were performed. By FEM-based simulations of these procedures, the fatigue properties and th e film adhesion were quantified. Moreover the wear behavior of coated cemented carbide inserts was investigated in milling of hardened steel. Appropriate FEM calculations of the developed temperature and stress fields in the cutting wedge region were conducted, to enable insights in the cutting process during milling. The results revealed the effect of the applied HPPMS technology during PVD films’ deposition on the fatigue strength and film’s adhesion as well as on the wear behaviour of coated tools.