Evaporation and Arc Technologies
Wednesday, April 12, 2000 1:30 PM in Room Golden West
B1-1-1 Missing - Sanders
D. Sanders ()
B1-1-3 The Hot Refractory Anode Vacuum Arc - A New Plasma Source for Metallic Film Deposition
I.I. Beilis, R.L. Boxman, S. Goldsmith (Tel-Aviv University, Israel)
The highly ionized, energetic, metal vapor plasma jet produced by cathode spots in vacuum arc is conventionally used to produce coatings. However, the presence of macroparticles (MP's) degrades the film quality. In this paper, a new form of vacuum arc, the Hot Refractory Anode Vacuum Arc (HRAVA), is presented as a plasma source with highly reduced MP contamination. @paragraph@Arcs were sustained between the parallel end surfaces of a pair of cylindrical electrodes. The cathode was water-cooled and constructed from Cu, while the anode was thermally isolated graphite or Mo. Arc currents of 175-340 A were sustained for periods of up to 120 s. Cu coatings were deposited on steel substrates placed 100 mm from the electrode axis along the inter-electrode gap mid-plane. A shutter controlled when the substrate was exposed to the plasma. The coating rates were measured by weighing, and the coating surface was examined by optical microscopy. @paragraph@The arcs started as conventional cathode spot vacuum arcs, and deposited material from the cathode spot jets onto the anode. The arc heated the anode to a sufficient temperature so that at a later stage, metal was re-evaporated from the hot refractory anode. In the steady-state, all of the material emitted from the cathode was eventually transported radially in the form of an expanding plasma jet. @paragraph@Films formed at the beginning of the arc, when it operated in the cathode spot mode, were heavily contaminated with MP's - in a 30 s exposure to a 175 A arc, the density of MP's with diameters of 3-50 µm was about 750 mm @super -2@. However, when a 30 s exposure began 30 s after arc initiation, by which time the arc was in the HRAVA mode, the MP density was reduced to about 1 mm @super -2@. The HRAVA deposition rate varied from 1.8 to 2.6 µm/min for arc currents of 175-340 A. Over this same current range, the ionization fraction increased from 31% to 45%, while the estimated extractable ion current to arc current fraction increased from 9.1% to 9.9%. These results indicate that the efficiency of the HRAVA in terms of mass of deposited material per unit charge transfer in the arc is comparable to conventional cathode spot vacuum arc deposition while having greatly reduced MP contamination, and several times greater than filtered vacuum arc deposition.
B1-1-4 Twist Filter for the Removal of Macroparticles from Cathodic Arc Plasmas
A. Anders, R.A. MacGill (Lawrence Berkeley National Laboratory)
Many approaches have been proposed and tested for the elimination of macroparticles from cathodic vacuum arc plasmas. Most successful are curved magnetic filters, originally introduced by Aksenov and co-workers in the late 1970s. Although high-quality metal, metal-compound, and diamond-like carbon films have been synthesized by filtered cathodic arc deposition, macroparticle filters suffer from two major drawbacks: (I) the plasma transport is inefficient, i.e. only a fraction of the original (unfiltered) plasma is actually useable for film deposition, and (II) the removal of macroparticles is not complete. The latter is particularly pronounced for solid macroparticles as observed with cathodic arc carbon plasmas. In the present work, a very compact and efficient version of a macroparticle filter is presented. The geometry is related to a previously described S-filter (in essence two 90° filters in series), with the twist that the second 90° filter is "twisted" out of plane. This has the advantage that it is less likely for a macroparticle to be transported: it takes more reflections from filter walls. Furthermore, the open architecture of the filter allowed us to remove "bouncing" macroparticles from the filter volume. The "Twist Filter" can be operated with very high magnetic field (B > 100 mT). Due to its compact structure and high field strength, plasma throughput is exceptionally high. For instance, we have obtained a filtered carbon ion current of 33 A for an arc current of 1 kA. In these experiments, the arc source was pulsed with a pulse duration of 300 µs and a repetition rate of up to 10 pulses per second. One of the possible applications of the Twist Filter is its incorporation into a cathodic arc deposition system for ultrathin (< 5 nm) diamondlike carbon coatings (a-C) on computer hard disks and read-write heads.
B1-1-5 Effect of Transverse Current Injection During Vacuum Arc Deposition of TiN
N. Parkansky, V.N. Zhitomirsky, B. Alterkop (Tel Aviv University, Israel); S. Goldsmith, R.L. Boxman (Tel-Aviv University, Israel); Y. Rosenberg, Z. Barkay (Tel Aviv University, Israel)
Transverse current injection (TCI) is a technique in which an electrical current is imposed parallel to the surface of a workpiece exposed to processing or to a service environment. In this work, TCI was applied during vacuum arc deposition of TiN film on WC cemented carbide substrates (90% WC, 8% Co, 2% TaNbC). The 5x8x22 mm bar samples were mounted on a holder that provided electrical contacts at their ends, and a thermocouple to measure sample temperature. Prior to deposition, the substrates were heated in vacuum up to 150@super o@ C by a current of 100 A. The TiN coatings were obtained by vacuum arc deposition of Ti plasma in 5 mTorr nitrogen background. Films with different thickness were obtained by controlling of the plasma flow density. The arc current was 250 A, and substrate temperature during deposition was in the range of 110-130@super o@ C. Two deposition rates: slow 2.3-3 nm/s and fast 20-23 nm/s were used. The injected dc transverse current was in the range of 0 - 40 A. Surface microhardness was measured by Vickers micro-indentation, using a 25 g load. Film structure was examined by X-ray diffractometry, scanning electron microscopy (SEM) using scattered electrons (SE), back scattered electrons (BSE), and energy dispersive spectroscopy (EDS). @paragraph@TiN coatings deposited at 110-130@super o@ C with TCI were uniform and did not contain delaminating fragments, whereas coating deposited using the same deposition parameters but without TCI contained delaminating fragments. XRD patterns indicated a cubic NaCl type TiN phase in thick films (4-4.5 µm), while the cubic TiN phase was absent in thinner films (~0.4 µm). EDS spectra indicated that approximately the same ratio of Ti and N atoms existed in both films. No X-ray diffraction lines of TiN were observed, and this sagest existence of nanocrystalline or amorphous structure of the thin films. In comparison with films deposited without TCI, the microhardness of thick TiN films (~4 µm) obtained with 10 A of transverse current was larger by a factor of 1.3, whereas the microhardness of thinner films (~0.4 µm) was up to a factor of 1.7 larger with 20 A of transverse current.
B1-1-6 Effects of Sintering in Ti-Al Targets on Microstructures of (Ti,Al)N Films
A. Kimura, T. Murakami (Keio University, Japan); K. Yamada (Sanyo Vacuum Industries Co., LTD., Japan); T. Suzuki (Keio University, Japan)
The arc ion plating (AIP) method is one of the PVD methods in which atoms or clusters ejected and ionized by discharging targets reach onto biased substrates. It is considered that microstructures of targets, such as density, grain size and surface morphology, would influence the properties of synthesized films. In this study, Ti and Al powder was mixed with identical atomic ratio and sintered at 650, 800 and 1100?, respectively and shaped for the use of targets. The density of targets monotonously increased with sintering temperature. The X-ray diffraction (XRD) pattern indicated the presence of Ti, Al, TiAl, Ti3Al and TiAl3. Next, Ti-Al targets were arc-discharged in nitrogen plasma and (Ti,Al)N films were synthesized onto mirror-polished cemented carbide and Si substrates. The target with low density, ~ 80 %, did not lead continuous discharge and was heavily eroded after a few minute. On the contrary, the target with high density, 99 %, led continuous discharge more than 1 hour. As a result, the growth rate for (Ti,Al)N films using the target with high density was 2 ~ 3 times larger than that by targets of the molting method.
B1-1-7 Copper Metallization in Microelectronics Using Filtered Vacuum Arc Deposition - Principles and Technological Development
P. Siemroth (Fraunhofer Institute for Material and Beam Technology Dresden, Germany); T. Schülke (Fraunhofer USA)
Continuous efforts to further increase the performance of microelectronic circuits challenge all of the involved process modules including thin film deposition, lithographic masking and etching. Specifically, the recent trend of introducing copper as the wiring material required a change of the conventional backend process sequence that is transferring the interconnect pattern. Whereas conventionally flat deposited aluminum is masked with and subsequently etched to generate metal lines, copper technology requires the filling of narrow vias and trenches etched into the dielectric interlayer. Established techniques such as thermal evaporation or sputtering have shown substantial difficulties in fully metallizing the prepared patterns. Typical failures are large voids in the volume of the resulting metal lines. In response to requirements for next generation devices, research on PVD processes continues to further improve film properties and reliability. In the last years, evaporation techniques that generate significantly higher ionized metal plasmas than conventional sputtering has shown its potential to suppress the formation of voids. Several pulsed magnetron-sputtering methods have been investigated as a possible alternative. So far vacuum arc plasma sources have not been considered as an alternative although they generate very effectively the highest plasma ionization. A major concern is the deposition of microscopic droplets of the cathode material that are inevitably generated during the arc discharge. Current demands, e.g. for ultra-thin and dense carbon coatings on computer hard discs or the copper metallization in CMOS structures have stimulated new developments of more compact and higher productive filtered arc sources. Focusing on copper metallization and barrier coatings (e. g. TaN) in microelectronics, the paper evaluates and summarizes the current stage of filtered arc technology gained by groups in the USA, East Asia and Europe.
B1-1-9 Filtered Cathodic Arc Deposition of Boron Carbide Coatings for Antenna Applications
O.R. Monteiro (Lawrence Berkeley National Laboratory); C.C.. Klepper (HY- Tech research Corp.)
Boron carbide based films have been prepared by filtered cathodic arc to be used as protective coatings for radio-frequency antennas used in magnetic fusion. The deposited films consisted of a mixture of B@sub 4@C and ta-C. The films were prepared using a single source system with a sintered B@sub 4@C cathode, and with a dual source system with a B@sub 4@C and a C cathode in order to achieve the desired microstructure. Control of the composition was achieved by means of adjusting the duration of the arc IN the individual plasma sources to achieve the desired ion flux at the substrate surface. The deposited films were characterized by Rutherford backscattering spectroscopy, X-ray diffraction and transmission electron microscopy. The effect of the process parameters on the film properties is discussed. Crystallinity is particularly desired in antenna application, in order to achieve good thermal conduction between the coated surface of the antenna and the water cooling channels inside the antenna structure. Preliminary analysis shows that substrate heating enhance the formation of the desired crystallinity. @footnote@ *Work supported by the U.S. Department of Energy through the STTR program (Award Number DE-FG02-98ER86078)
B1-1-10 Bias Voltage Effect on the Structure and Properties of Vacuum Arc Deposited TiN Coatings
V.N. Zhitomirsky (Tel-Aviv University, Israel); I. Grimberg (Technion - Israel Institute of Technology, Israel); L. Rapoport (Holon Center for Technological Education, Israel); R.L. Boxman, S. Goldsmith (Tel-Aviv University, Israel); B.Z. Weiss (Technion - Israel Institute of Technology, Israel)
TiN coatings were deposited on WC-Co bar substrates using a vacuum arc plasma gun connected to a cylindrical plasma duct in which an axial magnetic field was imposed. During deposition, the cathode arc current was 200 A, nitrogen pressure was 0.67 Pa, and the substrate temperature was 400@super o@ C. Substrate bias voltage (V) was varied in the range of -40 to -600 V. Coating structure and properties were studied both on the sample surface normal to the plasma flux, and on its side surfaces. Structure and phase composition were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Microhardness and coating adhesion to the substrate were studied using Vickers micro-indentation and scratch tests, respectively. @paragraph@ The TiN coatings consisted of oriented columnar grains, which had a single-phase cubic structure. The microstructure and preferred crystal orientation were the same on the front and side surfaces of the samples. The deposition rate to the front surface was to 2-4 times higher than that to the sides. The microstructure and grain orientation depended on the substrate bias voltage. At V=-40 V, the coating consisted of a mixture of (200) and (111) oriented grains, at V=-200 V and higher a strong (111) grain orientation was observed. At V=-40 V, equiaxed grains of 30-50 nm average size were observed near the coating-substrate interface, while the bulk of the coating consisted of columnar grains with 60-70 nm average size. With increasing the negative bias voltage, the average grain size increased up to 120-250 nm at V=-400 V. With increasing V from -40 to -600 V, the average deposition rate decreased from 22 to 12.5 nm/s on the face surface, and from 9 to 3 nm/s on the side surface, and the average superficial microhardness decreased from 27 to 20 GPa.
B1-1-11 High Rate Arc Evaporation of Ceramic Coatings for Tools and Components
H.M. Gabriel (PVT Plasma und Vakuum Technik GmbH, Germany); G. Ebersbach (GFE e.V. - IMPT, Germany); J. Freund (Gunther & Co. GmbH, Germany)
Hard coatings such as TiN, Ti(C,N), TiAlN and others are deposited by most different ion assisted PVD - processes. These coatings are widely used on cutting tools to reduce wear to improve lifetime and to boost productivity when applied at higher feed and speed. Their application on components still lags significantly behind the cutting tools. @paragraph@Independent from the PVD - process used for the application of the coatings the cycles for the deposition of such coatings last many hours. @paragarph@For this reason the development of a high rate arc evaporation process was initiated to increase the deposition rates and to significantly reduce the deposition time. At the same time the established qualities of the coatings had to be maintained.@paragraph@This development is not limited to the arc evaporation source concerning its: 1) design, 2) geometry and 3) control, but all other relevant peripheral elements of the vacuum coating systems were taken into consideration such as: 1) multiaxis rotatable substrate carrier, 2) arc evaporation power supply, 3) bias power supply and 4) control software. The goals of this development are: 1) to reduce the deposition time, 2) to reduce the cost of production, 3) to reduce the cost per coated part and 4) to engineer an improved plasma surface treatment process.
B1-1-12 Comparison of Substrate Temperature and Deposition Rate Between Modified Pulsed Arc Process and D.C. Arc Process
B. Engers (AWS Achslagerwerk Staßfurt GmbH, Germany); H. Fuchs (Otto-von-Guericke-University of Magdeburg, Germany); J. Schultz (AWS Achslagerwerk Staßfurt GmbH, Germany); E. Hettkamp, H. Mecke (Otto-von-Guericke-University of Magdeburg, Germany)
The cathodic arc process is widely used in industry for the deposition of hard coatings of metal nitrides, carbides and oxides as well as of DLC too in the latest time. In particular, the high ion energy in an almost completely ionized plasma combined with the outstanding layer properties are advantageous. In the coating process, a thermal load of the substrates caused by an intense ion bombardment is unavoidable. However, for specific applications (e.g. plastics, films, tempered substrates), the deposition temperature is strongly limited. Due to the fact that the deposition rate and the substrate temperature are connected by the number of metal ions hitting the substrate it has to be found a compromise between economic process control and thermal load of the substrates. The contribution reports on work to this range of problems. Both the conventional d.c. arc process and the modified pulsed arc process (superposition of an basic evaporation current with current impulses) were used. The modified pulsed arc process is characterized by some positive physical effects, for example the accelerated movement of the cathode spots, the increase of ion energy, and the modification of the spatial plasma extension. This results in effects on the technological process (improved target exploitation, reduced droplet emission, increased deposition rate). Dependences on the electric parameters of the arc current (such as the time behavior of the ion current density) could have been proved by the evolution and use of numerous pulsed power supplies. In comparison of both processes it should be shown how known effects of the pulsation of the arc current take effect on the substrate temperature, the deposition rate and its interaction. The investigations were carried out in different deposition systems both for industry as well as for laboratory application distinguished in shape and volume of the recipient. Metal substrates of different hardness were coated. The temperature was measured by a pyrometer as well as by thermocouples. For the determination of the layer thickness, a Calo-Tester was used.