High Power Impulse Magnetron Sputtering

High Power Impulse Magnetron Sputtering (HIPIMS, also known as High Power Pulsed Magnetron Sputtering, HPPMS) is a method for physical vapor deposition of thin films which is based on magnetron sputter deposition. HIPIMS utilises extremely high power densities of the order of kWcm−2 in short pulses (impulses) of tens of microseconds at low duty cycle (on/off time ratio) of < 10%. A distinguishing feature of HIPIMS is its high degree of ionisation of the sputtered metal and high rate of molecular gas dissociation.

HIPIMS is used for:

The first US patent on HIPIMS was filed by Vladimir Kouznetsov (priority date 9 Dec 1997), Kouznetsov US 6296742 B1.

Contents

HIPIMS Plasma Discharge

HIPIMS plasma is generated by a glow discharge where the discharge current density can reach up to 6 Acm−2, whilst the discharge voltage is maintained at several hundred volts.[1] The discharge is homogeneously distributed across the surface of the cathode of the chamber. HIPIMS generates a high density plasma of the order of 1013 ions cm−3[1] containing high fractions of target metal ions. The main ionisation mechanism is electron impact, which is balanced by charge exchange and diffusion. The ionisation rates depend on the plasma density.
The ionisation degree of the metal vapour is a strong function of the peak current density of the discharge. At high current densities, sputtered ions with charge 2+ and higher - up to 5+ for V - can be generated. The appearance of target ions with charge states higher than 1+ is responsible for a potential secondary electron emission process that has a higher emission coefficient than the kinetic secondary emission found in conventional glow discharges. The establishment of a potential secondary electron emission may enhance the current of the discharge.
HIPIMS is typically operated in short pulse (impulse) mode with a low duty cycle in order to avoid overheating of the target and other system components. In every pulse the discharge goes through several stages[1]:

The discharge that maintains HIPIMS is a high-current glow discharge, which is transient or quasistationary. Each pulse remains a glow up to a critical duration after which it transits to an arc discharge. If pulse length is kept below the critical, the discharge operates in a stable fashion infinitely.

Substrate pretreatement by HIPIMS

Substrate pretreatment in a plasma environment is required prior to deposition of thin films on mechanical components such as automotive parts, metal cutting tools and decorative fittings. The substrates are immersed in a plasma and biased to a high voltage of a few hundred volts. This causes high energy ion bombardment that sputters away any contamination. In cases when the plasma contains metal ions, they can be implanted into the substrate to a depth of a few nm. HIPIMS is used to generate a plasma with a high density and high proportion of metal ions. When looking at the film-substrate interface in cross-section, one can see a clean interface. Epitaxy or atomic registry is typical between the crystal of a nitride film and the crystal of a metal substrate when HIPIMS is used for pretreatment.[2] HIPIMS has been used for the pretreatment of steel substrates for the first time in February 2001 by A.P. Ehiasarian.[3]
Substrate biasing during pretreatment utilises high voltages, which require purpose-designed arc detection and suppression technology. Dedicated DC substrate biasing units provide the most versatile option as they maximize substrate etch rates, minimise substrate damage, and can operate in systems with multiple cathodes. An alternative way is the use of two HIPIMS power supplies synchronised in a master–slave configuration: one to establish the discharge and one to produce a pulsed substrate bias [4]

Thin Film Deposition by HIPIMS

Thin films deposited by HIPIMS at discharge current density > 0.5 Acm−2 have a dense columnar structure with no voids.
The deposition of copper films by HIPIMS was reported for the first time by V. Kouznetsov for the application of filling 1 µm vias with aspect ratio of 1:1.2[5]

Transition metal nitride (CrN) thin films were deposited by HIPIMS for the first time in February 2001 by A.P. Ehiasarian. The first thorough investigation of films deposited by HIPIMS by TEM demonstrated a dense microstructure, free of large scale defects.[3] The films had a high hardness, good corrosion resistance and low sliding wear coefficient.[3] This research paved the way to the first industrial upscaling of the technology in January 2004 at Sheffield Hallam University, UK in collaboration with Advanced Converters, Warsaw, Poland (present day Hüttinger Electronics, Poland).[6] The commercialisation of HIPIMS hardware that followed from this made the technology accessible to the wider scientific community and triggered developments in a wide range of areas.

The following materials have, amongst others, been deposited successfully by HIPIMS:

Industrial application

HIPIMS has been successfully applied for the deposition of thin films in industry. The first HIPIMS coating units appeared on the market in 2006 and were supplied by SVS Vacuum Coating Technologies GmbH.

References

  1. ^ a b c Ehiasarian, Arutiun P.; New, R.; Munz, W.-D.; Hultman, L.; Helmersson, U.; Kouznetsov, V. (2002). "Influence of High Power Densities on the Composition of Pulsed Magnetron Plasmas". Vacuum 65 (2): 147–154. doi:10.1016/S0042-207X(01)00475-4 .
  2. ^ Ehiasarian, Arutiun P.; Wen, J.G.; Petrov, I. (2007). "Interface microstructure engineering by high power impulse magnetron sputtering for the enhancement of adhesion". Journal of Applied Physics 101 (5): item 054301, 10 pp.. doi:10.1063/1.2697052 .
  3. ^ a b c Ehiasarian, Arutiun P.; Munz, W.-D.; Hultman, L.; Helmersson, U.; Petrov, I. (2003). "High Power Pulsed Magnetron Sputtered CrNx Films". Surface and Coatings Technology 163-164: 267–272. doi:10.1016/S0257-8972(02)00479-6 .
  4. ^ a b Broitman, E.; Czigány, Zs.; Greczynski, Greczynski, G; Böhlmark, J; Cremer, R.; Hultman, L..; (2010). "Industrial-scale deposition of highly adherent CNx films on steel substrates". Surface and Coatings Technology (Elsevier) 204 (21-22): 3349–33576. doi:10.1016/j.surfcoat.2010.03.038 .
  5. ^ Kouznetsov, V.; Macak, K.; Schneider, J.; Helmersson, U.; Petrov, I. (1999). "A novel pulsed magnetron sputter technique utilizing very high target power densities". Surface and Coatings Technology 163-164 (2-3): 290–293. doi:10.1016/S0257-8972(99)00292-3 
  6. ^ Ehiasarian, A.P.; Bugyi, R. (2004). "Industrial size high power impulse magnetron sputtering". 47th Ann. Techn. Conf. Proc. Society of Vacuum Coaters. April (Dallas, TX: Society of Vacuum Coaters) 2004: 486–490. ISSN 0737-5921. 
  7. ^ Purandare, Y.P.; Ehiasarian, A..; Hovsepian, P.Eh.; (2008). "Deposition of nanoscale multilayer CrN/NbN physical vapor deposition coatings by high power impulse magnetron sputtering". J. Vacuum Sci. Technol. A (AVS) 26 (2): 288–296. doi:10.1116/1.2839855. 
  8. ^ Hovsepian, P. Eh; Reinhard, C.;Ehiasarian, A. P.; (2006). "CrAlYN/CrN superlattice coatings deposited by the combined high power impulse magnetron sputtering/unbalanced magnetron sputtering technique". Surf. Coat. Technol. (Elsevier) 201 (7): 4105–10. doi:10.1016/j.surfcoat.2006.08.027. 
  9. ^ Konstantinidis, S.; Dauchot, J.P.; Hecq, M. (2006). "Titanium oxide thin films deposited by high-power impulse magnetron sputtering". Thin Solid Films 515 (3): 1182–1186. doi:10.1016/j.tsf.2006.07.089 
  10. ^ Konstantinidis, S.; Hemberg, A.; Dauchot, J.P.; Hecq, M. (2007). "Deposition of zinc oxide layers by high-power impulse magnetron sputtering". J. Vac. Sci. Technol. B 25 (3): L19–L21. doi:10.1116/1.2735968 
  11. ^ Sittinger, V.; Ruske, F.; Werner, W.; Jacobs, C.; Szyszka, B.; Christie, D.J. (2008). "High power pulsed magnetron sputtering of transparent conducting oxides". Thin Solid Films 516 (17): 5847–5859. doi:10.1016/j.tsf.2007.10.031 
  12. ^ J. Alami, P. Eklund, J. Emmerlich, O. Wilhelmsson, U. Jansson, H. Högberg, L. Hultman, and U. Helmersson (2006-12-05). "High-power impulse magnetron sputtering of Ti–Si–C thin films from a Ti3SiC2 compound target". Thin Solid Films (Elsevier B.V.) 515 (4): 1731–1736. doi:10.1016/j.tsf.2006.06.015. 

Further reading

External links