Browsing by Author "Ylivaara, Oili M. E."

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  • Fracture properties of atomic layer deposited aluminum oxide free-standing membranes
    (2015) Berdova, Maria; Ylivaara, Oili M. E.; Rontu, Ville; Törmä, Pekka T.; Puurunen, Riikka; Franssila, Sami
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Microscratch testing method for systematic evaluation of the adhesion of atomic layer deposited thin films on silicon
    (2016-01-01) Kilpi, Lauri; Ylivaara, Oili M. E.; Vaajoki, Antti; Malm, Jari; Sintonen, Sakari; Tuominen, Marko; Puurunen, Riikka L.; Ronkainen, Helena
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The scratch test method is widely used for adhesion evaluation of thin films and coatings. Usual critical load criteria designed for scratch testing of coatings were not applicable to thin atomic layer deposition (ALD) films on silicon wafers. Thus, the bases for critical load evaluation were established and the critical loads suitable for ALD coating adhesion evaluation on silicon wafers were determined in this paper as LCSi1, LCSi2, LCALD1, and LCALD2, representing the failure points of the silicon substrate and the coating delamination points of the ALD coating. The adhesion performance of the ALD Al2O3, TiO2, TiN, and TaCN+Ru coatings with a thickness range between 20 and 600 nm and deposition temperature between 30 and 410°C on silicon wafers was investigated. In addition, the impact of the annealing process after deposition on adhesion was evaluated for selected cases. The tests carried out using scratch and Scotch tape test showed that the coating deposition and annealing temperature, thickness of the coating, and surface pretreatments of the Si wafer had an impact on the adhesion performance of the ALD coatings on the silicon wafer. There was also an improved load carrying capacity due to Al2O3, the magnitude of which depended on the coating thickness and the deposition temperature. The tape tests were carried out for selected coatings as a comparison. The results show that the scratch test is a useful and applicable tool for adhesion evaluation of ALD coatings, even when carried out for thin (20 nm thick) coatings.
  • On the reliability of nanoindentation hardness of Al2O3 films grown on Si-wafer by atomic layer deposition
    (2014) Liu, Xuwen; Haimi, Eero; Hannula, Simo-Pekka; Ylivaara, Oili M. E.; Puurunen, Riikka L.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • X-ray reflectivity characterization of atomic layer deposition Al2O3/TiO2 nanolaminates with ultrathin bilayers
    (2014) Sintonen, Sakari; Ali, Saima; Ylivaara, Oili M. E.; Puurunen, Riikka L.; Lipsanen, Harri
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Nanolaminate structures have many prospective uses in mechanical, electrical, and optical applications due to the wide selection of materials and precise control over layer thicknesses. In this work, ultrathin Al2O3/TiO2 nanolaminate structures deposited by atomic layer deposition from Me3Al, TiCl4, and H2O precursors with intended bilayer thicknesses ranging from 0.1 to 50 nm were characterized by x-ray reflectivity (XRR) measurements. The measurements were simulated to obtain values for thickness, density, and roughness of constituting layers. XRR analysis shows that the individual layers within the nanolaminate remain discrete for bilayers as thin as 0.8 nm. Further reduction in bilayer thickness produces a composite of the two materials.