Download History of Vacuum Deposition Using Energetic Ions of Condensable

History of Vacuum Deposition Using Energetic Ions
of Condensable Materials
Donald M. Mattox, Management Plus, Inc., Albuquerque, NM
Presented at the Third International Conference on Fundamentals and
Industrial Applications of HIPIMS, June 19 - 20, 2012, Sheffield, UK
Abstract
Historically the first important use of condensable ion deposition was
for the enrichment of uranium (235U) for the first atomic bomb using
magnetic sector ion sources (Calutrons). Many kilograms of uranium
ions were deposited. Pure and mixed energetic ion fluxes of condensable, reactive, and inert ions have been used for about 50 years to
deposit films and coatings as diverse as diamond-like-carbon (DLC)
and Ti-Al-C-N hard coatings. Continuous or periodic bombardment
effects on deposition include: in situ cleaning, modification of the
nucleation stage of film growth, interface formation, structure modification during growth (stress, crystallography, density, hardness, chemical
composition, etc.) chemical activation of reactive species, and bombardment enhanced chemical reactions on the surface. The sources of atoms
for ionization include: chemical vapor precursors, thermal vaporization, sputtering, arc vaporization, and pulsed laser ablation. A number
of sources of highly ionized fluxes have been developed including: arc
vaporization, HIPIMS, and those using post-vaporization ionization.
This paper will review some of the important milestones and developments for bringing energetic ion deposition into widespread industrial
application. These applications include: corrosion protection, low friction/wear, tools, hard/decorative/wear, erosion resistant, and optical
components. Often these coatings are deposited on temperature-sensitive substrates that make other techniques such as high-temperature
chemical vapor deposition (CVD) impractical.
Introduction
Film deposition in vacuum using condensable ions (“film ions”) is a more
energetic process than is film deposition just using atoms. When depositing ions both the energy of condensation and the ionization energy are
released in a localized region, when bombarding with non-condensable
ions the energy of ionization is released. This energy enhances chemical reaction and diffusion. If the ions have been accelerated to greater
than thermal energies the kinetic energy is also released and momentum
transfer can affect the atomic arrangement in the surface region.
In 1886 Eugen Goldstein observed rays in gas discharges at low
pressures that traveled away from the anode. Goldstein called these
positively charged anode rays “Kanalstrahen” or “canal rays.” Wilheim
Wien found that strong electric or magnetic fields deflected the “canal
rays” and in 1899 constructed a device that separated the positive rays
according to their charge-to-mass ratio. In 1918 A.J. Dempster created
the first magnetic sector mass spectrograph.
When the need developed to concentrate the radioactive isotope
235U from naturally occurring uranium Ernst O. Lawrence developed
a large-scale magnetic sector spectrograph for the separation [1]. The
device was called a Calutron and used a chemical vapor precursor
(UCl4) as the source of uranium ions. The ions were extracted from the
source at ~30keV at a current of about 100 mA. A bank of these sources
was used to deposit the 64 kilograms of weapons grade (~90%) 235U
used in the “Little Boy” atomic bomb*. There was no discussion of the
nature of the deposit thus formed but at 30 keV ion energy there would
be considerable sputtering and redeposition in the collector chamber.
The Calutron source has been used for the separation of stable isotopes
36 2013 Spring Bulletin
of a number of materials. The last Oak Ridge (USA) Calutron was
retired in 1999.
A number of different ion sources for condensable ions were developed after the Calutron [2]. In the 1980s a family of high-energy arc
sources termed MEVVA (Metal Vapor Vacuum Arc) was developed
for isotope separation and ion implantation [3]. A “filtered” version
of the MEVVA source was developed to remove the marcro-particles
(“macros”) generated during the arcing process [4].
High energy ions of both condensable and non-condensable species
may be used to advantage in modifying the surface region of a material in the process called “ion implantation”. Shockley first proposed
ion implantation for the doping of semiconductors [5]. The use of
surface modification by high-energy ion implantation prior to coating
formation as a hybrid deposition process was discussed in 1985 [6,7,8].
Bombardment with ions at lower energies (few eV to several hundred
eV) does not result in significant implantation but bombardment before
and/or during vacuum deposition may be used to control and tailor the
properties of deposited films and coatings.
Ion Bombardment Effects
In addition to thermal effects, ion bombardment on the surface and
during film growth affects the film deposition by momentum transfer
during the collision between the energetic ion and the “target” atoms.
The maximum momentum is transferred when the atomic masses are
the same. Some important aspects of momentum transfer by energetic
bombardment on film deposition are: masses of the bombarding ions,
energy (or energy distribution) of the bombarding ions, flux of the
bombarding ions, the mass of the atoms in the surface being bombarded, and the flux of the condensing (and possibly reacting) species.
In film growth under bombardment conditions the surface of the growing film is continually being buried by subsequent deposited material.
Bombardment may cause: ejection of a surface atom by momentum
transfer processes (“sputtering”), compaction and densification of
the atomic structure, introduction of structural defects and stresses,
enhanced chemical reactions on the surface, preferential removal of
weakly bonded material, diffusion into the surface, and introduction
and trapping of species in the near-surface region (“subplantation”).
The stages of film formation are: nucleation, interface formation and
film growth [9]. Ion bombardment may affect each of these stages.
In situ (sputter) cleaning of surfaces
In 1955 it was demonstrated that sputtering of a surface in a good
vacuum using inert gas ions could produce an atomically clean surface (“sputter cleaning”) [10]. In the early 1960s it was shown that by
combining sputter cleaning with thermal evaporation deposition that
started while the sputter cleaning was in progress that a highly adherent
coating could be produced if the deposition rate was greater than the
sputtering rate (“ion plating”) [11,12]. The use of sputter cleaning using
energetic metal ions was commercialized in the “arc bond sputtering”
(ABS) process using an arc moving in a planar magnetron track [13].
Film formation - nucleation
Energetic bombardment can increase the nucleation density of
“adatoms” on the surface thus increasing the surface coverage and film
adhesion [9]. Very low energy bombardment can increase the adatom
mobility on the surface and enhance the epitaxial growth (“oriented
overgrowth”) of the film on a crystal surface [14,15].
Film formation - interface formation
Interfacial regions may be categorized as: 1) abrupt, 2) mechanical interlocking, 3) diffusion, 4) compound, and/or 5) “pseudodiffusion” [9]. Ion
bombardment before and during deposition provides a clean surface
and good atom-to-atom contact by having a high nucleation density.
Bombardment also provides energy for chemical reaction and diffusion as
well as penetrating the first few atomic layers to give “subplantation” [16].
Film formation - film growth
Ion bombardment during film deposition densifies the deposit by
compaction and/or sputtering/redeposition by momentum transfer [17,18,19]. These processes also affect the intrinsic film stress.
Subplantation may be an important factor in film growth and the incorporation of foreign species in the growing film [16]. Bombardment
also enhances chemical reaction of reactive species on the surfaces and
promotes the removal of un-reacted or poorly bonded species [20].
These bombardment effects are important in depositing stoichiometric
compounds and such unique materials as amorphous “diamond-likecarbon” (DLC) films, which have a high degree of sp3 bonding between
the carbon atoms.
Ion Sources
Ion sources of “film ions” may be in the form of unconfined sources or
may involve extraction of ions from confined sources [e.g. 2].
Cathodic arc vaporization source
Arc plasmas and arc vaporization has a long history preceding even the
invention of the voltaic pile by Volta (1800) [21]. Bradley used an arc
between two carbon rod electrodes in vacuum to deposit thin carbon
films in 1954 [22]. In Russia, stable long-lived cathodic continuous arc
vaporization from a planar surface was developed by Sablev [23] and was
used for film deposition by Romanov and Andreev in the early 1970s.
The process is called Condensation - Ion Bombardment (CIB) [24,25].
The first commercial batch coater (BULAT 3) was available in Russia
in 1977. Pulsed arcs traveling over the surface have been used to vaporize the surface of long rods with the cathode spot made to move over
the surface either due to the magnetic field caused by the arc current in
the rod [26] or by an externally formed axial magnetic field [27]. Lowvoltage, high-current cathodic arcs produce a high percentage of ions in
the vapor plume [28].
The use of magnetic fields to deflect the plasma and eliminate the
deposition of droplets (“macros”) formed by the arc began with the work
of Aksenov [29] and resulted in various forms of “filtered arc” sources
[30,31]. An extraction type arc ion source was developed by Aisenberg
in the early 1970s and used to deposit amorphous (a-C) diamond-likecarbon (DLC) films. [32]. DLC was also being deposited in Russia at
about the same time using CIB technology [24].
High power impulse magnetron sputtering (HIPIMS) source
The HIPIMS plasma discharge used for magnetron sputtering from a
conventional planar magnetron source is formed by a current/voltage
pulse that forms a high-current glow discharge, which transients into
an arc discharge before it is terminated. If pulse length is kept below a
critical value, the discharge may be operated in a stable fashion infinitely
and target heating is manageable. This type of plasma discharge was first
proposed for sputtering in 1997 (patent priority date) [33]. A high percentage of the vaporized material is ionized [34] along with some of the
gaseous species present. HIPIMS has been used for deposition of metals
(Cu) [35] and, by reactive deposition, for the deposition of compounds
[36].
Post-vaporization ionization sources
Vaporization of atoms into a gaseous equilibrium plasma whose atomic
density is too low to cause appreciable vapor phase nucleation of the
atomic species results in very little ionization of the atomic flux [37].
Appreciable ionization can be achieved by vaporization through or dissociation in a dense, energetic (10s to 100s eV) electron “cloud.” Such
regions may be generated above a vaporizing source using “spotless”
arc discharges (SAD) using high intensity thermionic electron emission
[38,39] or by using a hollow cathode arc discharge (HAD) [40].
Summary
Energetic vacuum deposition using “film ions” has several advantages.
These include: 1) the momentum transfer on bombardment is maximized, 2) effects of subplantation on interface formation and film
growth may be enhanced, and 3) incorporation of unwanted gaseous
species in the surface and growing film is minimized. Energetic deposition processes have led to increasing use of PVD processes for functionally demanding coatings such as hard coatings, tribological coatings,
decorative/wear coatings, optical coatings, and adherent coatings of all
types.
* Calutron enrichment raised the uranium purity from about 20%
to about 90% 235U so there was about 3 times as many 238U ions
formed as 235U ions formed and ~250 kg of uranium ions (~1026 ions)
deposited.
235U
References
1. Ernst O. Lawrence, USP 2,709,222, “Method of and apparatus for separating materials,”
(filed Oct. 9, 1944) issued May 24, 1955; USP 2,847,576, “Calutron System,” (filed Jan.16,
1946) issued Aug. 12, 1958; “Calutron receivers,” USP 2,850,639 (filed Feb. 21, 1946)
issued Sept. 2, 1958.
2. “Ion Sources,” Ch. 3 in Atom and Ion Sources, L. Valyi, John Wiley and Sons (1978)
3. I.G. Brown, J.E. Galvin, and R.A. MacGill, “High Current Ion Source,” Appl. Phys. Lett. 47
358 (1985).
4. S. Anders, A. Anders, I.G. Brown, R.A. MacGill, and M.R. Dickinson, “Vacuum Arc Ion
Source with Filtered Plasma for Macroparticle-free Implantation,” Rev. Sci. Instrum. 65,
1319 (1994)
5. “Forming semiconducting devices by ionic bombardment,” W. Shockley, USP
#2,787,564 issued April 2, 1957
6. R.J. Alder and S.T. Picraux, “Repetitively Pulsed Metal Ion Beams for Ion Implantation,”
Nucl. Instrum. Meth. Phys. Res. B691-2) 123 (1985)
7. I.G. Brown, X. Godechot, and K.M. Yu, Appl. Phys. Lett. 58, 1392 (1991)
8. S. T. Picraux, “Ion Implantation Metallurgy,” Physics Today 37(11) 38, 1984
9. “Thin Film Adhesion and Adhesive Failure - A Perspective,” Donald M. Mattox p. 54
in ASTM Proc. of Conf. on Adhesion Measurement of Thin Films, Thick Films and Bulk
Coatings, ASTM-STP640 (Code 04-640000-25), 1978
10. H.E. Farnsworth, R.E. Schlier, T.H. George, and R.M. Burger, “Application of the Ion
Bombardment Cleaning Method to Titanium, Germanium, Silicon, and Nickel as
Determined by Low‐Energy Electron Diffraction,” J. Appl. Phys., 26, 252 (1955)
11. D.M. Mattox, “Film Deposition Using Accelerated Ions,” Electrochem. Technology 2, 295,
1964
12. “Apparatus for coating a cathodically biased substrate from plasma of ionized coating
material,” D.M. Mattox, USP # 3,329,601 issued July 4,1967; B. Berghaus, British Patent
#510,993 (1938)
13. W.D. Muntz, D. Schulze, and F.J.M. Hauser, Surf. Coat. Technol. 50 169 (1992)
14. “Growth of solid layers on substrates which are kept under bombardment before and
during deposition,” G. Wehner, USP #3,021,271, issued Feb. 13, 1962
15. T. Ohmi and T. Shibata, “Advanced Scientific Semiconductor Processing Based on
High-precision Controlled Low-energy Ion Bombardment,” Thin Solid Films, 241, 159
(1993)
16. Y. Lifshitz, S.R. Kasi, and J.W. Pabalais, “Subplantation Model for Film Growth from
Hyperthermal Species,” Phys. Rev. B41, 10468 (1990)
17. K.H. Guenther, B. Loo, D. Burns, J. Edgell, D. Windham, and K.-H. Müller, “Microstructure
Analysis of Thin Films Deposited by Reactive Evaporation and Reactive Ion Plating,”
J. Vac. Sci. Technol. A7 1436 (1989)
18. C. Weissmantel, “Ion Beam Deposition of Special Film Structures,” J. Vac. Sci. Technol.
18(2) 179 (1981)
19. I. Petrov, P.B. Barna, L. Hultman, and J.E. Greene, “Microstructural Evolution During Film
Growth,” J. Vac. Sci. Technol. A21(6) S117 (2003)
continued on page 38
2013 Spring Bulletin 37
History of Vacuum Deposition Using Energetic Ions
of Condensable Materials
continued from page 37
20. H.T.G. Hentzell, J.M.E. Harper, and J.J. Cuomo, “Synthesis of Compound Thin Films by
Dual Ion Beam Deposition II: Properties of Aluminum-nitrogen Films,” J. Appl. Phys. 58,
556 (1985)
21. André Anders, “Tracking Down the Origin of Arc Plasmas Physics: I Early Pulsed and
Oscillating Discharges,” IEEE Trans. Plasma Sci., 31, 1052 (2003): Tracking Down the
Origin of Arc Plasma Physics: II Early Continuous Discharges,” IEEE Trans. Plasma Sci. 31,
1060 (2003)
22. D.E. Bradley, Brit. J. Appl. Phys., 5,65 (1954)
23. L. P. Sablev, USP #3,783,231 issued Jan. 1, 1974; USP #3,793,179 issued Feb. 1, 1974
24. I.I. Aksenov, V.A. Belous, and V.E. Strel’nitskij, “Vacuum-arc surface modification and
coating deposition methods in KIPT, Ukraine (Historical Review),” Proceedings of the
55th Annual Technical Conference (2012), Society of Vacuum Coaters (in preparation)
33. “Method and apparatus for magnetically enhanced sputtering,” Vladimir Kouznetsov,
USP #6296742 B1, filed Sept. 10, 1999, issued Oct. 2, 2001 (priority date 9 Dec 1997)
34. A.P. Ehiasarian, R. New, K.M. Macak, W.-D. Muntz, L. Hultman, U. Helmersson, and
V. Kouznetsov, “Influence of High Power Densities on the Composition of Pulsed
Magnetron Plasmas,” Vacuum 65, 147 (2002); J. Bolmark, M. Lattemann, J.T. Gud
mundsson, A.P. Ehiasarian, Y. Arnada Gonsalva, N. Benning, and U. Helmersson, “The
Ion Energy Distributions and Ion Flux Composition From a High Power Impulse
Magnetron Sputtering Discharge,” Thin Solid Films 515(4) 1522 (2006)
35. V. Kouznetsov, K. Macak, J.M. Schneider, U. Helmersson, and I. Petrov, “A Novel Pulsed
Magnetron Sputter Technique Utilizing Very High Target Power Technique,” Surf. Coat.
Technol., 122(2-3) 290, 1999
36. A.P. Ehiasarian, W.-D. Muntz, L.Hultman, and I. Petrov, “High Power Pulsed Magnetron
Sputtered CrN Films,” Surf. Coat. Technol. 163/164, 267 (2003)
37. C. Christou and Z.H. Barber, “Ionization of Sputtered Material in a Planar Magnetron
Discharge,” J. Vac. Sci. Technol. A18, 2897 (2000)
38. K. Goedicke, B. Schellel, and S. Schiller, “Plasma-activated High Rate Electron Beam
Evaporation Using a Spotless Cathodic Arc,” Surf. Coat. Technol. 69-69, 799 (1994)
25. “A brief history of cathodic arc coating,” André Anders, Ch. 16, p. 120 in 50 Years of
Vacuum Coating Technology and the Growth of the Society of Vacuum Coaters,
edited by Donald M. Mattox and Vivienne Harwood Mattox, Society of Vacuum
Coaters (2007)
39. C. Metzner, B. Scheffel, H. Morgner, and O. Zywitzki, “Functional and decorative
coatings onto metal strips deposited by plasma-activated high-rate electron beam
physical vapor deposition (EBPVD),” Proceedings of the 55th Annual Technical
Conference (2012), Society of Vacuum Coaters (in preparation)
26. “Method of coating a metal gas-pressure bottle or tank,” Eduard Pinkhasov, USP
#4,859,489, filed Jul 18, 1988, issued Aug. 22, 1989; also “Electric arc vapor deposition
device,” G.E. Vergason, USP #5,037,522, filed Jul. 24, 1990, issued 1991
40. H. Morgner, M. Neumann, S. Straach, and M. Krug, “The Hollow-cathode: A High
Performance Tool for Plasma-activated Deposition,” Surf. Coat. Technol. 108/109, 513
(1998).
27. “Apparatus and method for coating a substrate using vacuum arc evaporation,”
Richard P. Welty, USP #5,269,898, filed Dec. 17, 1991, issued Dec. 14, 1993
28. J.E. Daalder, “Experimental Observations of Cathode-spot Surface Phenomena in the
Transition from a Vacuum Metal-vapor Arc to a Nitrogen Arc,” J. Phys. D8, 1647 (1975)
29. I.I. Aksenov, V.A. Belous, V.G. Padalka, and V.M. Khoroshikh, “Apparatus to Rid the
Plasma of a Vacuum Arc of Microparticles,” Instrum. Exp. Tech. 21, 1416 (1978)
30. “Macroparticle Filters,” Ch. 7 in Cathodic Arcs: From Fractal Spots to Energetic
Condensation, André Anders, Springer (2008)
31. I.I. Aksenov, V.A. Belous, and V.E. Strel’nitskij, “Nanostructured carbon and TiN
based coatings deposited by filtered vacuum-arc apparatus in NSC KIPT, Ukraine,”
Proceedings of the 55th Annual Technical Conference (2012), Society of Vacuum
Coaters (in preparation)
32. S. Aisenberg and R. Cabot, “Ion-beam Deposition of Thin Films of Diamondlike
Carbon,” J. Appl. Phys. 42, 2953 (1971)
38 2013 Spring Bulletin
Donald M. Mattox became a Staff Member
at Sandia Corporation, now Sandia National
Laboratories (SNL) in 1961. He retired from SNL
in 1989 after 28 years as a Member of the Technical
Staff and then as Technical Supervisor. At retirement he was Supervisor of SNL’s Surface and
Interface Technology Division. Don has had more
than 50 years experience in research, development, application, and production of thin films
and coatings prepared by PVD processes and other
techniques. He has published more than 100 papers Donald M. Mattox
and book chapters on the subject of PVD processing. Don was President of the American Vacuum Society (now AVS – The Science
and Technology Society) in 1985. At the 9th International Conference on Vacuum
Metallurgy (ICVM) Don received an award “In Recognition of Contributions Made
to Metallurgical Coating Technology (1961 to 1988).” In 1995 he was the recipient
of the AVS Albert Nerken Award for his work in the development of the ion plating
process, which uses bombardment by energetic atomic-sized particles to improve
adhesion and modify the morphology and properties of vacuum deposited coatings. Don received the Nathaniel Sugerman Memorial Award from the SVC in 2007.
In 1985 he and his wife Vivienne founded Management Plus, Inc., (MPI), where,
after his retirement from SNL, he provided consulting services on PVD processing,
technology transfer, and patent litigation. From 1989 through 2006 Don served as
the Technical Director of the Society of Vacuum Coaters. He is the author of the
Handbook of Physical Vapor Deposition (PVD) Processing, 2nd edition, published
by Elsevier (2010) and The Foundations of Vacuum Coating Technologies published
by Noyes Publications (2003). He is also the author of the Education Guides to
Vacuum Coating Processing published by the SVC (2009) and co-editor of 50 Years
of Vacuum Coating Technology and the Growth of the Society of Vacuum Coaters
published by the SVC (2007).