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Plasma Characterization & Thin Film Growth and Analysis in Highly Ionized Magnetron Sputtering
Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis addresses two research areas related to film growth in a highly ionized magnetron sputtering system: plasma characterization, and thin film growth and analysis. The deposition technique used is called high power pulsed magnetron sputtering (HPPMS). Characteristic for this technique are high energy pulses (a few Joules) of length 50-100 µs that are applied to the target (cathode) with a duty time of less than 1 % of the total pulse time. This results in a high electron density in the discharge (>1x1019 m-3) and leads to an increase of the ionization fraction of the sputtered material reaching up to 70 % for Cu.

In this work the spatial and temporal evolution of the plasma parameters, including the electron energy distribution function (EEDF), the electron density and the electron temperature are determined using electrostatic Langmuir probes. Electron temperature measurements reveal a low effective temperature of 2-3 eV. The degree of ionization in the HPPMS discharge is explained in light of the self-sputtering yield of the target material. A simple model is therefore provided in order to compare the sputtering yield in HPPMS and that in dc magnetron sputtering (dcMS) for the same average power.

Thin Ta films are grown using HPPMS and dcMS and their properties are studied. It is shown that enhanced microstructure and morphology of the deposited films is achieved by HPPMS. The Ta films are also deposited at a number of substrate inclination angles ranging from 0o (i.e., facing the target surface) up to 180 o (i.e., facing away from the target). Deposition rate measurements performed at all inclination angles for both techniques, reveal that growth made using HPPMS resulted in an improved film thickness at higher inclination. Furthermore, the high ionization of the Ta atoms in HPPMS discharge is found to allow for phase tailoring of the deposited films at all inclination angles by applying a bias voltage to the substrate. Finally, highly ionized magnetron sputtering of a compound MAX-phase material (Ti3SiC2) is performed, demonstrating that the HPPMS discharge could also be used to tailor the composition of the growing Ti-Si-C films.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi , 2005.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 948
Keyword [en]
Highly ionized pulsed magnetron sputtering, HPPMS, HPPIMS, thin film, plasma analysis, Langmuir probe
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-4147ISBN: 91-85299-40-5 (print)OAI: oai:DiVA.org:liu-4147DiVA: diva2:20537
Public defence
2005-06-03, 10:15 (English)
Opponent
Supervisors
Note
On the day of the public defence of the doctoral thesis, the status of articles III and IV was Submitted. The titles of papers VI and VII changed between their manuscript forms and when they were published.Available from: 2005-10-25 Created: 2005-10-25 Last updated: 2013-10-30
List of papers
1. Evolution of the electron energy distribution and plasma parameters in a pulsed magnetron discharge
Open this publication in new window or tab >>Evolution of the electron energy distribution and plasma parameters in a pulsed magnetron discharge
2001 (English)In: Applied Physics Letters, ISSN 0003-6951, Vol. 78, no 22, 3427- p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate the creation of high-density plasma in a pulsed magnetron discharge. A 2.4 MW pulse, 100 µs wide, with a repetition frequency of 50 Hz is applied to a planar magnetron discharge to study the temporal behavior of the plasma parameters: the electron energy distribution function, the electron density, and the average electron energy. The electron density in the vicinity of the substrate, 20 cm below the cathode target, peaks at 8×1017 m–3, 127 µs after initiating the pulse. Towards the end of the pulse two energy groups of electrons are present with a corresponding peak in average electron energy. With the disapperance of the high-energy electron group, the electron density peaks, and the electron energy distribution appears to be Maxwellian like. Following the electron density peak, the plasma becomes more Druyvesteyn like with a higher average electron energy.

Keyword
sputter deposition
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-13372 (URN)10.1063/1.1376150 (DOI)
Available from: 2005-10-25 Created: 2005-10-25 Last updated: 2013-10-30
2. Spatial and temporal behavior of the plasma parameters in a pulsed magnetron discharge
Open this publication in new window or tab >>Spatial and temporal behavior of the plasma parameters in a pulsed magnetron discharge
2002 (English)In: Surface and Coatings Technology, Vol. 161, no 2-3, 249-256 p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate the evolution of the electron, energy distribution and the plasma parameters in a high-density plasma in a pulsed magnetron discharge. The high-density plasma is created by applying a high power pulse (1–2.4 MW) with pulse length 100 μs and repetition frequency of 50 Hz to a planar magnetron discharge. The spatial and temporal behavior of the plasma parameters are investigated using a Langmuir probe; the electron energy distribution function, the electron density and the average electron energy. The electron energy distribution function during and shortly after the pulse can be represented by a bi-Maxwellian distribution indicating two energy groups of electrons. Furthermore, we report on the variation of the plasma parameters and electron energy distribution function with gas pressure in the pressure range 0.5–20 mtorr. We report electron density as high as 4×1018 m−3 at 10 mtorr and 9 cm below the target in a pulsed discharge with average power 300 W. We estimate the traveling speed of the electron density peak along the axis of the discharge. The traveling speed decreases with increased gas pressure from 4×105 cm/s at 0.5 mtorr to 0.87×105 cm s−1 at 10 mtorr. The effective electron temperature peaks at the same time independent of position in the discharge, which indicates a burst of high energy electrons at the end of the pulse.

Keyword
Pulsed magnetron sputtering, Time evolution, Ionized sputtering, High density plasma, Ionized metal plasma
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-13373 (URN)10.1016/S0257-8972(02)00518-2 (DOI)
Available from: 2005-10-25 Created: 2005-10-25 Last updated: 2013-10-30
3. Plasma dynamics in a highly ionized pulsed magnetron discharge
Open this publication in new window or tab >>Plasma dynamics in a highly ionized pulsed magnetron discharge
Show others...
2005 (English)In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 14, no 3, 525-531 p.Article in journal (Refereed) Published
Abstract [en]

We report on electrostatic probe measurements of a high-power pulsed magnetron discharge. Space- and time-dependent characteristics of the plasma parameters are obtained as functions of the process parameters. By applying high-power pulses (peak power of ~0.5 MW), with a pulse-on time of ~100 µs and a repetition frequency of 20 ms, peak electron densities of the order of ~1019 m− 3, i.e. three orders of magnitude higher than for a conventional dc magnetron discharge, are achieved soon after the pulse is switched on. At high sputtering gas pressures (>5 mTorr), a second peak occurs in the electron density curve, hundreds of microseconds after the pulse is switched off. This second peak is mainly due to an ion acoustic wave in the plasma, reflecting off the chamber walls. This is concluded from the time delay between the two peaks in the electron and ion saturation currents, which is shown to be dependent on the chamber dimensions and the sputtering gas composition. Finally, the electron temperature is determined, initially very high but decreasing rapidly as the pulse is turned off. The reduction seen in the electron temperature, close to the etched area of the cathode, is due to cooling by the sputtered metal atoms.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-13374 (URN)10.1088/0963-0252/14/3/015 (DOI)
Available from: 2005-10-25 Created: 2005-10-25 Last updated: 2017-12-13
4. Ion-accoustic solitary waves in a high power pulsed magnetron sputtering discharge
Open this publication in new window or tab >>Ion-accoustic solitary waves in a high power pulsed magnetron sputtering discharge
2005 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 38, no 18, 3417-3421 p.Article in journal (Refereed) Published
Abstract [en]

We report on the creation and propagation of ion-acoustic solitary waves in a high power pulsed magnetron sputtering discharge. A dense localized plasma is created by applying high energy pulses (4–12 J) of length 70 µs, at a repetition frequency of 50 pulses per second, to a planar magnetron sputtering source. The temporal behaviour of the electron density, measured by a Langmuir probe, shows solitary waves travelling away from the magnetron target. The velocity of the waves depends on the gas pressure but is roughly independent of the pulse energy.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-13375 (URN)10.1088/0022-3727/38/18/015 (DOI)
Available from: 2005-10-25 Created: 2005-10-25 Last updated: 2017-12-13
5. Ion-assisted Physical Vapor Deposition for enhanced film properties on non-flat surfaces
Open this publication in new window or tab >>Ion-assisted Physical Vapor Deposition for enhanced film properties on non-flat surfaces
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2005 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 23, no 2, 278-280 p.Article in journal (Refereed) Published
Abstract [en]

We have synthesized Ta thin films on Si substrates placed along a wall of a 2-cm-deep and 1-cm-wide trench, using both a mostly neutral Ta flux by conventional dc magnetron sputtering (dcMS) and a mostly ionized Ta flux by high-power pulsed magnetron sputtering (HPPMS). Structure of the grown films was evaluated by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The Ta thin film grown by HPPMS has a smooth surface and a dense crystalline structure with grains oriented perpendicular to the substrate surface, whereas the film grown by dcMS exhibits a rough surface, pores between the grains, and an inclined columnar structure. The improved homogeneity achieved by HPPMS is a direct consequence of the high ion fraction of sputtered species.

Keyword
tantalum, ion beam assisted deposition, sputter deposition, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, surface structure, surface roughness, porosity, metallic thin films
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-13376 (URN)10.1116/1.1861049 (DOI)
Available from: 2005-10-25 Created: 2005-10-25 Last updated: 2017-12-13
6. Phase tailoring of Ta thin films by highly ionized pulsed magnetron sputtering
Open this publication in new window or tab >>Phase tailoring of Ta thin films by highly ionized pulsed magnetron sputtering
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2007 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 7-8, 3434-3438 p.Article in journal (Refereed) Published
Abstract [en]

Ta thin films were grown on Si substrates at different inclination angles with respect to the sputter source using high power impulse magnetron sputtering (HIPIMS), an ionized physical vapor deposition technique. The ionization allowed for better control of the energy and directionality of the sputtered species, and consequently for improved properties of the deposited films. Depositions were made on Si substrates with the native oxide intact. The structure of the as deposited films was investigated using X-ray diffraction, while a four-point probe setup was used to measure the resistivity. A substrate bias process-window for growth of bcc-Ta was observed. However, the process-window position changed with changing inclination angles of the substrate. The formation of this low-resistivity bcc-phase could be understood in light of the high ion flux from the HIPIMS discharge.

Place, publisher, year, edition, pages
Elsevier, 2007
Keyword
HPPMS, Ionized PVD, IPVD, Pulsed sputtering
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-10442 (URN)10.1016/j.tsf.2006.10.013 (DOI)
Note
Original publication: J. Alamia, P. Eklunda, J.M. Anderssona, M. Lattemanna, E. Wallina, J. Bohlmarka, P. Perssona, and U. Helmersson, Phase tailoring of Ta thin films by highly ionized pulsed magnetron sputtering, 2007, Thin Solid Films, (515), 7-8, 3434-3438. http://dx.doi.org/10.1016/j.tsf.2006.10.013. Copyright: Elsevier B.V., http://www.elsevier.com/Available from: 2007-12-14 Created: 2007-12-14 Last updated: 2017-12-14Bibliographically approved
7. High-power impulse magnetron sputtering of Ti-Si-C thin films from a Ti3SiC2 compound target
Open this publication in new window or tab >>High-power impulse magnetron sputtering of Ti-Si-C thin films from a Ti3SiC2 compound target
Show others...
2006 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 4, 1731-1736 p.Article in journal (Refereed) Published
Abstract [en]

We have deposited Ti-Si-C thin films using high-power impulse magnetron sputtering (HIPIMS) from a Ti3SiC2 compound target. The as-deposited films were composite materials with TiC as the main crystalline constituent. X-ray diffraction and photoelectron spectroscopy indicated that they also contained amorphous SiC, and for films deposited on inclined substrates, crystalline Ti5Si3Cx. The film morphology was dense and flat, while films deposited with dc magnetron sputtering under comparable conditions were rough and porous. Due to the high degree of ionization of the sputtered species obtained in HIPIMS, it is possible to control the film composition, in particular the C content, by tuning the substrate inclination angle, the Ar process pressure, and the bias voltage.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2006
Keyword
HIPIMS, Titanium silicon carbide
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-10437 (URN)10.1016/j.tsf.2006.06.015 (DOI)000242931900079 ()
Note

Original publication: J. Alami, P. Eklund, J. Emmerlich, O. Wilhelmsson, U. Jansson, H. Högberg, L. Hultman, & U. Helmersson, High-power impulse magnetron sputtering of Ti-Si-C thin films from a Ti3SiC2 compound target, 2006, Thin Solid Films, (515), 4, 1731-1736. http://dx.doi.org/10.1016/j.tsf.2006.06.015. Copyright: Elsevier B.V., http://www.elsevier.com/.

Available from: 2007-12-14 Created: 2007-12-14 Last updated: 2017-12-14Bibliographically approved

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