ICMCTF2009 Session B1-3: Sputtering Coatings and Technologies

Thursday, April 30, 2009 8:00 AM in Room Golden West

Thursday Morning

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8:00 AM B1-3-1 Study of the Effect of Plasma Current Density on Nitrides and Oxynitrides Titanium Thin Films Prepared by Reactive DC Magnetron Sputtering
P.K. Barhai, N. Kumari, I. Banerjee (Birla Institute of Technology, India); S.K. Pabi (Indian Institute of Technology Kharagpur); S.K. Mahapatra (Birla Institute of Technology, India)
Nitrides and oxynitrides titanium films were deposited by varying the plasma current density from 10mA/cm2 to 40mA/cm2, using DC magnetron sputtering. Different colours of the films like golden, blue, pink and green were obtained at different current densities. At lower current density (~10mA/cm2), the film showed stoichiometric TiN, whereas, at higher current densities (~20, 30 and 40mA/cm2) the films showed non stoichiometric TixONy. Crystallinity and atomic concentration of the films have been characterized by GAXRD and XPS techniques. The average thickness of the films increased with plasma current from 775A0 to 996A0. The hardness, roughness and Young’s modulus of the films were analyzed by nano-indentation. Hardness of the films was found to increase from 7.054 Gpa to 17.49 Gpa and Young’s modulus from 209.774 Gpa to 257.586 Gpa with increasing plasma current density. AFM image of the films showed uniform nanostructured grains. The durability and the quality of the film colour have been characterized by colorimetric analysis. I-V characteristics of the films were also studied for their use in microelectronic applications.
8:20 AM B1-3-2 Chromium Containing Amorphous Hydrogenated Carbon Thin Films (a-c:H/Cr) as Selective Solar Absorber Coatings
H.Y. Cheng, W.Y. Wu, J.M. Ting (National Cheng Kung University, Taiwan)
Metal-containing amorphous hydrogenated carbon (a-c:H/Me) thin films are used as spectral solar selective absorber coatings. In this study, the obtained a-c:H/Cr thin films were deposited on silicon wafers or copper foils using a reactive magnetron sputter deposition method. The gases used were mixtures of methane and argon. The methane concentration was varied continuously from 0 to 40 % during the deposition. The obtained films were characterized using scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray absorption near edge spectroscopy, and extended X-ray absorption fine structure spectroscopy. The optical performance was examined using UV-Vis-NIR spectrophotometry and Fourier transform infrared spectrometry. The films were found to exhibit high absorptance greater than 95 % from 0.3 to 2.5 µm and low emittance less than 1 % from 2.5 to 10 µm. The dependence of the optical properties on the film microstruc ture, and the size distribution, concentration, and chemical state of the chromium will be presented and discussed.
8:40 AM B1-3-3 Investigation of the O- Ion Emission During Reactive Magnetron Sputtering
S. Mahieu, W.P. Leroy, D. Depla (Ghent University, Belgium)
One of the most used techniques to deposit thin films is magnetron sputtering. To deposit an oxide thin film, reactive magnetron sputtering, i.e. sputtering a metallic target in an Ar/O2 mixture, can be used. Since the target is at highly negative potential, negative oxygen ions formed at the target surface or within the cathode sheath will be accelerated away from the target, eventually towards the substrate. Hitting the growing film, the high energy negative ions will influence the film growth and eventually have a detrimental effect on the resulting film properties. Hence, characterizing the amount and energy of these negative ions is an important and challenging task. During planar magnetron sputtering, the energy distribution of negative O- ions has been measured by means of energy resolved mass spectrometry for 13 different target materials. For the same series of target materials the ion-induced secondary electron emission coefficient was determined in earlier published research. A correlation between this ion-induced secondary electron emission coefficient and the emission of the high energetic negative O- ions was observed. The influence of the cathode shape, i.e. a planar magnetron versus a rotating cylindrical magnetron, on the outward flux of negative ions has been investigated. Therefore, the amount, energy, and direction of the high energy negative ions have been measured, again by means of energy resolved mass spectrometry.
9:20 AM B1-3-5 A Satisfactory Explanation for the Discharge Voltage Behaviour During Reactive Magnetron Sputtering
D. Depla, S. Mahieu, R. De Gryse (Ghent University, Belgium)
The discharge voltage is perhaps the most accessible parameter of the magnetron sputter deposition process. As its value can be easily monitored, research reports generally contain its value. Nevertheless, the interpretation of the discharge voltage and/or its behavior, especially during reactive magnetron sputtering, is less straightforward. To understand its behavior, it is necessary to look into the details of the magnetron discharge, the processes occurring at the cathode or target and the influence of the important discharge parameters such as discharge current, magnet configuration, and discharge gas pressure. The influence of these parameters can be partially understood from a general formula. This formula, based on the original work of Thornton, shows that the discharge voltage behavior during reactive magnetron sputtering finds its origin in the formation of a compound layer on the target. The discharge voltage behavior depends strongly on the material properti es of the compound layer which is formed. Further research is of course still needed, but with this paper we hope to take away some frustration in the reactive sputter deposition community, as summarized by Westwood in his book on sputter deposition when discussing the material dependence of the discharge voltage on target material “A satisfactory explanation for these differences has not yet appeared”.
9:40 AM B1-3-6 Ion Energy Distributions in AZO Magnetron Sputtering from Planar and Rotatable Magnetrons
F. Richter, T. Welzel (TU Chemnitz, Germany); R. Kleinhempel (Southwall Europe GmbH, Germany); T. Dunger (TU Chemnitz, Germany); T. Knoth, M. Dimer, F. Milde (von Ardenne Anlagentechnik GmbH, Germany)
Ion energy distribution functions (IEDFs) have been measured at the substrate position in magnetron sputtering of an aluminium doped zinc oxide (AZO) target in inert and reactive atmosphere. The IEDFs have been obtained against ground potential with an in-line energy dispersive ion mass spectrometer (plasma monitor) which was facing the target surface. Two different magnetron configurations have been investigated: a circular planar magnetron on laboratory scale and an industrial scale rotatable magnetron. The magnetrons were operated with asymmetric-bipolar pulsed d.c., the planar magnetron also in d.c. mode. Positive ions of the working gas as well as Al+, Zn+, and AlO+ were observed, which show a low energy peak in their IEDF from the ‘on’ phase and a high energy peak of several 10 eV from the ‘off’ phase of the pulsed d.c. Negative ions, being mainly O- from the target, exhibit a strong peak in their IEDF at several 100 eV correspo nding to the negative target voltage. With strongly varying target voltage in the ‘on’ phase the IEDF may extend to very high energies. Maximum and average energy of both positive and negative ions depend on the discharge power as the voltage in the ‘on’ and ‘off’ phase governing the high energy ions changes with power. The changes in the negative ions have consequences even on floating substrates whereas the changes in positive ions may only affect grounded substrates. The differently sized planar and rotatable magnetron exhibit very similar IEDFs for positive as well as negative ions proving that basic physical processes are essentially the same. Significant differences were observed for both sources when the connection between the anode of the power supply and the magnetron source was altered.
10:00 AM B1-3-7 Investigation of the Role of Hydrogen in Silicon Deposition Using an Energy-Resolve Mass Spectrometer in an Ar/H2 Radio Frequency Magnetron Discharge
S.L. Mensah (University of Arkansas); H.H. Abu-Safe (Lebanese American University, Lebanon); H.A Naseem, M.H. Gordon (University of Arkansas)
Ion energy distributions of sputtered Si particles have been measured by an energy-resolved mass spectrometer, and we correlate the results with measured thin film properties. The plasmas have been generated in a simple magnetron chamber powered with 30-180W at 13.56MHz at pressures ranging from 5-30mTorr. Various Hx+, SiHy+, fragments (with x,y = 1,2,3) together with Ar+ and ArH+ species were detected in the discharge. The most important species for the film deposition appear to be SiHy+ with y =1,2, and the H+ fragments seem to play the most important role to the hydrogen content in the material. In a pure argon discharge, the Ar+ flux increases with power and pressure, and decreases as hydrogen is introduced into the discharge. The flux of Ar+ decreases in this case as that of ArH+ increases with increase in power and pressure. Plasma parameters, such as plasma potential and electron density and energy, measured with the Langmuir probe and are in good agreement with literature. The ion energy of SiHy+ radicals becomes bimodal with increasing pressure.
10:20 AM B1-3-8 Simulation of Layer Sequence in Multilayer Coatings Prepared by Sputtering
M. Panjan (Jozef Stefan Institute, Slovenia); T. Peterman (University of Ljubljana, Slovenia); P. Panjan, M. Cekada (Jozef Stefan Institute, Slovenia)
Multilayer coatings are commonly prepared by PVD processes. Multilayer structure with specific layer sequence is obtained when substrates rotate around targets of different materials. In order to deposit coating on all parts of the substrate with complicated geometry (e.g. a tool), substrates need to rotate around two, three or even four axes (e.g. planetary rotation). Trajectories of substrates are therefore rather complex and layer sequence depends on the number of rotations and initial positions of the substrate. In some applications, sequence and thickness of layers significantly influences physical properties of the coating. For example, optical properties or hardness of superlattices are both strongly affected by the thickness and sequence of layers. Therefore, when depositing multilayer coatings it is important to have control over these parameters. The most convenient approach to predict the multilayer structure is to use a computer simulation. We developed such simulation for sputtering in industrial deposition system with four magnetron sources arranged in the corners of rectangle where substrates can rotate around three axes. In the simulation we can calculate growth rate in dependence of rotation and determine the sequence and the thickness of layers. Simulation results were compared to layer sequence of TiAlN/CrN and TiAlN/VN multilayer coatings prepared in industrial magnetron sputtering system CC800/9 (CemeCon). Samples were investigated by transmission electron microscope. TEM micrographs and simulated multilayer structure agree well for all types of rotation and any initial position of substrate. Our simulation therefore offers precise information of multilayer structure for all coatings prepared in the single batch.
10:40 AM B1-3-9 Improving the Oxidation Resistance of AlCrn Coatings by Tailoring Chromium Out-Diffusion
R. Escobar Galindo (Universidad Autonoma de Madrid, Spain); J. Endrino (Instituto de Ciencia de Materiales de Madrid, Spain); G. Fox-Rabinovich (McMaster University, Canada); J.M. Albella (Instituto de Ciencia de Materiales de Madrid, Spain)
In this work, we have studied the influence on the oxidation resistance of AlCrN-based coatings of the deposition of an additional subsurface titanium nitride barrier layer. Since oxidation is interrelated with the inward diffusion of oxygen into the surface of AlxCr(1-x)N (x=0.70) coatings and the outward diffusion of Cr to the surface, it is believed that the oxidation behaviour of the aluminium-rich AlCrN coatings can be tuned by the design and composition of the coating. The buried depth of the barrier layer and the oxidation time were varied and changes in the AlCrN/TiN depth composition profiles and surface oxidation states were analyzed by means of Glow Discharge Optical Emission Spectroscopy (GDOES) and Cross Sectional SEM (X-SEM) maps. It was observed that when the TiN barrier was deposited near the top surface (500 nm) the formation of beneficial alumina surface layers was promoted. This is explained in terms of a limited surplus of chromium from the coating t o the surface and corroborated after performing experiments using CrN as barrier layers. The oxidation kinetics of the multilayer CrAlN/TiN was followed using GDOES depth profiles of samples by fixing the barrier buried depth and varying the oxidation time.
11:00 AM B1-3-10 Phase Transformation, Thermal Stability, Morphological and Mechanical Characteristics of the Ni- Al and Ni-P-Al Alloy Coating Systems
C.C. Wu, F.B. Wu (National United University, Taiwan)
In this study, binary Ni-Al and ternary Ni-P-Al alloy films were fabricated by magnetron sputtering technique for comparison. Through X-ray diffraction technique, the as-deposited Ni-Al films revealed noticeable crystallization peaks. On the other hand, a broadened peak with relatively low intensity, implying an amorphous microstructure, was found for the Ni-P-Al coating. It was believed that the co-deposition of P element could induce the amorphous feature of the Ni-Al-based coatings. After annealing from 350 to 600°C, the Ni-Al films showed a well-crystallized microstructure similar to that observed for the as-deposited films. The Ni-P-Al coatings maintained amorphous feature below a high annealing temperature of 550°C. As the annealing temperature was increased to 600°C, the Ni-P-Al coating transformed to Ni crystalline matrix with precipitations of NixPy and NipAlq intermetallic compounds. The surface morphology evaluatio n was carried out by atomic force microscopy. It was found the Ni-Al coatings exhibited a surface roughness around 2.7 nm in both as-deposited and heat-treated states. On the contrary, the surface roughness of the Ni-P-Al coatings increased with phase transformation phenomenon due to post annealing. Nevertheless, the Ra was kept at a low value of approximately 3.2 nm for the Ni-P-Al alloy coating under 600°C annealing. In addition, the evolution of phase transformation related mechanical properties of these alloy coatings were also discussed.
11:20 AM B1-3-11 Oxidation Study of Mo-Ru Hard Coatings
Y.-I. Chen (National Taiwan Ocean University, Taiwan)
Mo-Ru coating, a high melting point metal alloy coating, has been used as a protective coating on the top surface of the glass molding die to prolong the lifetime of the die material. In a realistic molding environment, the atmosphere was consisted of steadily purged nitrogen and residual oxygen. The oxidation resistance of the coating under the cyclic thermal history in mass production is a critical issue. In this study, the diffusion of oxygen into the Mo38.1Ru61.9 deposits annealed at 600°C in the molding atmosphere were investigated by EPMA and Auger depth profile, which revealed an apparent oxygen content in the near surface region. An atomic percentage of 5 % was observed in a depth of 0.04 and 0.27 µm of the Mo38.1Ru61.9 deposits annealed for 4 and 16 hours, respectively. The microstructure evolution of Mo-Ru coating was studied by XRD, SEM and TEM, which revealed a columnar structure with a major axis perpendicular to the su bstrate either before or after annealed in the molding environment. The oxygen diffusion did not transform the Mo5Ru3 phase but strengthen the surface hardness of the Mo38.1Ru61.9 deposits from 13GPa to 19GPa after 4 hours annealing and sustain a level of 18GPa till 16 hours. ESCA analysis was performed to confirm the phase stability at the near surface region of the Mo-Ru coatings.
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