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Liljeholm, Lina
Alternative names
Publications (10 of 11) Show all publications
Mardani, S., Primetzhofer, D., Liljeholm, L., Vallin, Ö., Norström, H. & Olsson, J. (2014). Electrical properties of Ag/Ta and Ag/TaN thin-films. Paper presented at MAM 2013 - Materials for Advanced Metallization; 10-13 March 2013; Leuven, Belgium. Microelectronic Engineering, 120, 257-261
Open this publication in new window or tab >>Electrical properties of Ag/Ta and Ag/TaN thin-films
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2014 (English)In: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 120, p. 257-261Article in journal (Refereed) Published
Abstract [en]

Although wide band gap devices (WBG, e.g. GaN and SiC) are eminently suitable for high temperatures and harsh environments, these properties cannot be fully taken advantage of without an appropriate interconnect metallization. In this context, silver shows promise for interconnections at high temperatures. In this work, the thermal stability of Ag with two barrier metals – Ta and TaN – was therefore investigated. Metal stacks, consisting of 100 nm of silver on 45 nm of either Ta or TaN were sputter-deposited on the substrate. Each metal system was annealed in vacuum for one hour at temperatures up to 800 °C. Both systems showed stable performance up to 600 °C. The system with Ta as a barrier metal was found to be more stable than the TaN system. Above 700 °C, silver agglomeration led to degradation of electrical performance.

Keywords
Interconnect, Silver, Thermal stability, Ta and TaN diffusion barrier
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-215831 (URN)10.1016/j.mee.2013.06.002 (DOI)000336697300045 ()
Conference
MAM 2013 - Materials for Advanced Metallization; 10-13 March 2013; Leuven, Belgium
Funder
Swedish Foundation for Strategic Research
Available from: 2014-01-17 Created: 2014-01-17 Last updated: 2017-12-06Bibliographically approved
Mardani, S., Liljeholm, L., Primetzhofer, D. & Vallin, Ö. (2013). Thermal stability of Ag/Ta and Ag/TaN thin-films. In: : . Paper presented at MAM 2013 - Materials for Advanced Metallization; 10-13 March 2013; Leuven, Belgium (pp. 123-124).
Open this publication in new window or tab >>Thermal stability of Ag/Ta and Ag/TaN thin-films
2013 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-197281 (URN)
Conference
MAM 2013 - Materials for Advanced Metallization; 10-13 March 2013; Leuven, Belgium
Funder
Swedish Research CouncilSwedish Foundation for Strategic Research
Available from: 2013-03-21 Created: 2013-03-21 Last updated: 2016-04-21Bibliographically approved
Liljeholm, L. (2012). Reactive Sputter Deposition of Functional Thin Films. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Reactive Sputter Deposition of Functional Thin Films
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thin film technology is of great significance for a variety of products, such as electronics, anti-reflective or hard coatings, sensors, solar cells, etc. This thesis concerns the synthesis of thin functional films, reactive magnetron sputter deposition process as such and the physical and functional characterization of the thin films synthesized. Characteristic for reactive sputtering processes is the hysteresis due to the target poisoning. One particular finding in this work is the elimination of the hysteresis by means of a mixed nitrogen/oxygen processing environment for dual sputtering of Alumina-Zirconia thin films. For a constant moderate flow of nitrogen, the hysteresis could be eliminated without significant incorporation of nitrogen in the films. It is concluded that optimum processing conditions for films of a desired composition can readily be estimated by modeling. The work on reactively sputtered SiO2–TiO2 thin films provides guidelines as to the choice of process parameters in view of the application in mind, by demonstrating that it is possible to tune the refractive index by using single composite Six/TiO2 targets with the right composition and operating in a suitable oxygen flow range. The influence of the target composition on the sputter yield is studied for reactively sputtered titanium oxide films. It is shown that by using sub-stoichiometric targets with the right composition and operating in the proper oxygen flow range, it is possible to increase the sputter rate and still obtain stoichiometric coatings. Wurtzite aluminum nitride (w-AlN) thin films are of great interest for electro-acoustic applications and their properties have in recent years been extensively studied. One way to tailor material properties is to vary the composition by adding other elements. Within this thesis (Al,B)N films of the wurtzite structure and a strong c-axis texture have been grown by reactive sputter deposition. Nanoindentation experiments show that the films have nanoindentation hardness in excess of 30 GPa, which is as hard as commercially available hard coatings such as TiN. Electrical properties of w-(Al,B)N thin films were investigated. W-(Al,B)N thin films are found to have a dielectric strength of ~3×106 V/cm, a relatively high k-value around 12 and conduction mechanisms similar to those of AlN. These results serve as basis for further research and applications of w-(Al,B)N thin films. An AlN thin film bulk acoustic resonator (FBAR) and a solidly mounted resonator (SMR) together with a microfluidic transport system have been fabricated. The fabrication process is IC compatible and uses reactive sputtering to deposit piezoelectric AlN thin films with a non-zero mean inclination of the c-axis, which allows in-liquid operation through the excitation of the shear mode. The results on IC-compatibility, Q-values, operation frequency and resolution illustrate the potential of this technology for highly sensitive low-cost micro-biosensor systems for applications in, e.g. point-of-care testing.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. p. 52
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 945
Keywords
thin film, reactive sputtering, coating, resonator, sensor, FBAR, SMR, aluminum nitride, (Al, B)N
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-175666 (URN)978-91-554-8403-3 (ISBN)
Public defence
2012-09-21, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2012-08-17 Created: 2012-06-11 Last updated: 2013-01-22
Liljeholm, L. & Olsson, J. (2011). Electrical characterization of wurtzite (Al,B)N thin films. Vacuum, 86(4), 466-470
Open this publication in new window or tab >>Electrical characterization of wurtzite (Al,B)N thin films
2011 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 4, p. 466-470Article in journal (Refereed) Published
Abstract [en]

Wurtzite aluminum nitride (w-AlN) thin films are of great interest for electro-acoustic applications and their material properties have in recent years been extensively studied. One way to tailor material properties is to vary the composition by adding other elements. Boron is an element that can take the place of aluminum in the crystal lattice of w-AlN. In the present study, polycrystalline w-(AI,B)N thin films were grown on p-Si(100) and Al/p-Si(100) substrates by pulsed DC reactive magnetron sputtering from a single Al/B target. MIS and MIM structures were fabricated to investigate the electrical properties of w-(AI,B)N thin films. Important dielectric thin film properties for microelectronics applications are the breakdown field, the permittivity (K) and leakage current through the film. The (AI,B)N thin film is found to have a dielectric strength of similar to 3 x 10(6) V cm(-1) and a kappa close to 12. The measured leakage current through the film is assumed to be mainly due to Frenkel-Poole emission with a trap energy at 0.71 eV below the conduction band edge.

Place, publisher, year, edition, pages
Elsevier, 2011
Keywords
w-AlBN, Reactive sputtering, Permittivity, Breakdown field, Leakage current
National Category
Natural Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-161821 (URN)10.1016/j.vacuum.2011.10.002 (DOI)000298212000021 ()
Available from: 2011-11-18 Created: 2011-11-18 Last updated: 2017-12-08Bibliographically approved
Liljeholm, L., Junaid, M., Kubart, T., Birch, J., Hultman, L. & Katardjiev, I. (2011). Synthesis and characterization of (0001)-textured wurtzite Al(1-x)B(x)N thin films. Surface & Coatings Technology, 206(6), 1033-1036
Open this publication in new window or tab >>Synthesis and characterization of (0001)-textured wurtzite Al(1-x)B(x)N thin films
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2011 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 6, p. 1033-1036Article in journal (Refereed) Published
Abstract [en]

Al(1-x)B(x)N films of the wurtzite structure and a strong c-axis texture have been grown at room temperature by reactive sputter deposition with B concentrations of up to 10 at.%. The crystallographic structure of the films has been studied with XRD and HRTEM/SAED with stoichiometry and chemical bonding determined by XPS. Nanoindentation experiments show that the films have a hardness in excess of 30 GPa, which is retained after annealing for 1 h at 1000 degrees C. An amorphous phase is observed at the interface, the thickness of which increases with the B concentration in the film, while the film crystallinity is seen to improve with film thickness.

Keywords
Aluminum boron nitride, Wurtzite, Single phase, Hardness, c-texture
National Category
Natural Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-165603 (URN)10.1016/j.surfcoat.2011.07.028 (DOI)000297825600001 ()
Available from: 2012-01-16 Created: 2012-01-09 Last updated: 2017-12-08Bibliographically approved
Sharma, G., Liljeholm, L., Enlund, J., Bjurström, J., Katardjiev, I. & Hjort, K. (2010). Fabrication and characterization of a shear mode AlN solidly mounted resonator-silicone microfluidic system for in-liquid applications. Sensors and Actuators A-Physical, 159(1), 111-116
Open this publication in new window or tab >>Fabrication and characterization of a shear mode AlN solidly mounted resonator-silicone microfluidic system for in-liquid applications
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2010 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 159, no 1, p. 111-116Article in journal (Refereed) Published
Abstract [en]

A shear mode AlN solidly mounted resonator (SMR) microfluidic sensor system was fabricated and characterized. The AlN SMR fabrication process is fully IC compatible and uses reactive sputtering to deposit piezoelectric AlN thin films with a non-zero mean inclination of the c-axis, which allows in-liquid operation through the excitation of the shear mode. Silicone encapsulation bonded on top of the Si sensor chip includes a microfluidic system to transport the analyte and confine the flow to the active area of the sensor chip. The sensor operation in air, water, glycerol and acetone was characterized. The resonator had a resonance frequency of around 1.2 GHz and a Q value in water of around 100. Results concerning the stability and resolution are also presented. The results indicate a potential of highly sensitive low-cost microfluidic sensor systems for applications in, e.g. point-of-care testing.

Keywords
surface mounted resonator, pdms, microfluidic system
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-100394 (URN)10.1016/j.sna.2010.02.009 (DOI)000277661800016 ()
Projects
WISENET
Available from: 2009-03-31 Created: 2009-03-31 Last updated: 2017-12-13Bibliographically approved
Liljeholm, L., Nyberg, T., Kubart, T., Roos, A. & Berg, S. (2010). Reactive sputtering of SiO2–TiO2 thin film from composite Six/TiO2 targets. Vacuum, 85(2), 317-321
Open this publication in new window or tab >>Reactive sputtering of SiO2–TiO2 thin film from composite Six/TiO2 targets
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2010 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 85, no 2, p. 317-321Article in journal (Refereed) Published
Abstract [en]

Coatings of SiO2–TiO2 films are frequently used in a number of optical thin film applications. In this work we present results from depositing films with variable Si/Ti ratios prepared by reactive sputtering. The different Si/Ti ratios were obtained by varying the target composition of composite single targets. Compared to co-sputtering this facilitates process control and composition uniformity of the films. Varying the oxygen supply during sputter deposition can result in films ranging from metallic/substoichiometric to stoichiometric oxides. Transmittance spectra of the different films are presented and the optical constants are determined from these spectra. Furthermore, the deposition process, films structure and composition of the films are discussed. The study shows that by choosing the right composition and working in the proper oxygen flow range, it is possible to tune the refractive index.

Keywords
Reactive sputtering; Optical properties; SixTiO2 films; AR coating
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-133323 (URN)10.1016/j.vacuum.2010.07.003 (DOI)000282548700036 ()
Available from: 2010-11-08 Created: 2010-11-08 Last updated: 2017-12-12Bibliographically approved
Kubart, T., Jensen, J., Nyberg, T., Liljeholm, L., Depla, D. & Berg, S. (2009). Influence of the target composition on reactively sputtered titanium oxide films. Vacuum, 83(10), 1295-1298
Open this publication in new window or tab >>Influence of the target composition on reactively sputtered titanium oxide films
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2009 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 83, no 10, p. 1295-1298Article in journal (Refereed) Published
Abstract [en]

Titanium dioxide thin films have many interesting properties and are used in various applications. High refractive index of titania makes it attractive for the glass coating industry, where it is used in low-emissivity and antireflective coatings. Magnetron sputtering is the most common deposition technique for large area coatings and a high deposition rate is therefore of obvious interest. It has been shown previously that high rate can be achieved using substoichiometric targets. This work deals with reactive magnetron sputtering of titanium oxide films from TiOx targets with different oxygen contents. The deposition rate and hysteresis behaviour are disclosed. Films were prepared at various oxygen flows and all films were deposited onto glass and silicon substrates with no external heating. The elemental compositions and structures of deposited films were evaluated by means of X-ray photoelectron spectroscopy, elastic recoil detection analysis and X-ray diffraction. All deposited films were X-ray amorphous. No significant effect of the target composition on the optical properties of coatings was observed. However, the residual atmosphere is shown to contribute to the oxidation of growing films.

Keywords
magnetron sputtering, titanium dioxide, high rate deposition, sputtering, tio2, tio2 films, refractive-index, thin-films, dc, ion, deposition, dioxide, time
National Category
Physical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-110289 (URN)10.1016/j.vacuum.2009.03.026 (DOI)000267505100022 ()0042-207X (ISBN)
Note

Sp. Iss. SI 464KZ Times Cited:0 Cited References Count:19

Available from: 2009-11-09 Created: 2009-11-09 Last updated: 2017-12-12Bibliographically approved
Kubart, T., Trinh, D. H., Liljeholm, L., Hultman, L., Hogberg, H., Nyberg, T. & Berg, S. (2008). Experiments and modeling of dual reactive magnetron sputtering using two reactive gases. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 26(4), 565-570
Open this publication in new window or tab >>Experiments and modeling of dual reactive magnetron sputtering using two reactive gases
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2008 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 26, no 4, p. 565-570Article in journal (Refereed) Published
Abstract [en]

Reactive sputtering from two elemental targets, aluminum and zirconium, with the addition of two reactive gases, oxygen and nitrogen, is studied experimentally as well as theoretically. The complex behavior of this process is observed and explained. It is shown that the addition of oxygen to a constant supply of nitrogen significantly changes the relative content of aluminum with respect to zirconium in the film. Moreover, it is concluded that there is substantially more oxygen than nitrogen in the films even when the oxygen supply is significantly lower than the nitrogen supply. It is further shown that the addition of a certain minimum constant flow of nitrogen reduces, and eventually eliminates, the hysteresis with respect to the oxygen supply. It is concluded that the presented theoretical model for the involved reactions and mass balance during reactive sputtering of two targets in two reactive gases is in qualitative agreement with the experimental results and can be used to find optimum processing conditions for deposition of films of a desired composition.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-109141 (URN)10.1116/1.2913582 (DOI)000257424200002 ()
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
Kubart, T., Trinh, D. H., Liljeholm, L., Hultman, L., Högberg, H., Nyberg, T. & Berg, S. (2007). Experiments and modelling of reactive sputtering using two reactive gases and two targets. In: : . Paper presented at AEPSE 2007, Nagasaki, Japan, September 24-28.
Open this publication in new window or tab >>Experiments and modelling of reactive sputtering using two reactive gases and two targets
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2007 (English)Conference paper, Published paper (Refereed)
National Category
Physical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-12925 (URN)
Conference
AEPSE 2007, Nagasaki, Japan, September 24-28
Available from: 2008-01-18 Created: 2008-01-18 Last updated: 2016-04-11Bibliographically approved
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