Browsing by Author "Sippola, Perttu"
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Item 2D-materiaalien atomikerroskasvatus(2015-05-23) Saari, Aapo; Sippola, Perttu; Sähkötekniikan korkeakoulu; Turunen, MarkusItem Atomic layer deposition of AlN from AlCl3 using NH3 and Ar/NH3 plasma(2018-01) Rontu, Ville; Sippola, Perttu; Broas, Mikael; Ross, Glenn; Lipsanen, Harri; Paulasto-Kröckel, Mervi; Franssila, Sami; Department of Chemistry and Materials Science; Department of Electronics and Nanoengineering; Department of Electrical Engineering and Automation; Microfabrication; Harri Lipsanen Group; Electronics Integration and ReliabilityThe atomic layer deposition (ALD) of AlN from AlCl3 was investigated using a thermal process with NH3 and a plasma-enhanced (PE)ALD process with Ar/NH3 plasma. The growth was limited in the thermal process by the low reactivity of NH3, and impractically long pulses were required to reach saturation. Despite the plasma activation, the growth per cycle in the PEALD process was lower than that in the thermal process (0.4A ° vs 0.7A ° ). However, the plasma process resulted in a lower concentration of impurities in the films compared to the thermal process. Both the thermal and plasma processes yielded crystalline films; however, the degree of crystallinity was higher in the plasma process. The films had a preferential orientation of the hexagonal AlN [002] direction normal to the silicon (100) wafer surface. With the plasma process, film stress control was possible and tensile, compressive, or zero stress films were obtained by simply adjusting the plasma time.Item Comparison of mechanical properties and composition of magnetron sputter and plasma enhanced atomic layer deposition aluminum nitride films(2018-09-01) Sippola, Perttu; Pyymaki Perros, Alexander; Ylivaara, Oili M.E.; Ronkainen, Helena; Julin, Jaakko; Liu, Xuwen; Sajavaara, Timo; Etula, Jarkko; Lipsanen, Harri; Puurunen, Riikka L.; Department of Electronics and Nanoengineering; Department of Chemical and Metallurgical Engineering; Department of Chemistry and Materials Science; Physical Characteristics of Surfaces and Interfaces; Catalysis; Harri Lipsanen Group; VTT Technical Research Centre of Finland; University of JyväskyläA comparative study of mechanical properties and elemental and structural composition was made for aluminum nitride thin films deposited with reactive magnetron sputtering and plasma enhanced atomic layer deposition (PEALD). The sputtered films were deposited on Si (100), Mo (110), and Al (111) oriented substrates to study the effect of substrate texture on film properties. For the PEALD trimethylaluminum-ammonia films, the effects of process parameters, such as temperature, bias voltage, and plasma gas (ammonia versus N2/H2), on the AlN properties were studied. All the AlN films had a nominal thickness of 100 nm. Time-of-flight elastic recoil detection analysis showed the sputtered films to have lower impurity concentration with an Al/N ratio of 0.95, while the Al/N ratio for the PEALD films was 0.81-0.90. The mass densities were ∼3.10 and ∼2.70 g/cm3 for sputtered and PEALD AlN, respectively. The sputtered films were found to have higher degrees of preferential crystallinity, whereas the PEALD films were more polycrystalline as determined by x-ray diffraction. Nanoindentation experiments showed the elastic modulus and hardness to be 250 and 22 GPa, respectively, for sputtered AlN on the (110) substrate, whereas with PEALD AlN, values of 180 and 19 GPa, respectively, were obtained. The sputtered films were under tensile residual stress (61-421 MPa), whereas the PEALD films had a residual stress ranging from tensile to compressive (846 to −47 MPa), and high plasma bias resulted in compressive films. The adhesion of both films was good on Si, although sputtered films showed more inconsistent critical load behavior. Also, the substrate underneath the sputtered AlN did not withstand high wear forces as with the PEALD AlN. The coefficient of friction was determined to be ∼0.2 for both AlN types, and their wear characteristics were almost identical.Item Corrosion protection of steel with multilayer coatings: Improving the sealing properties of physical vapor deposition CrN coatings with Al2O3/ TiO2 atomic layer deposition nanolaminates(2017-04) Leppäniemi, Jarmo; Sippola, Perttu; Broas, Mikael; Aromaa, Jari; Lipsanen, Harri; Koskinen, Jari; Department of Electronics and Nanoengineering; Department of Electrical Engineering and Automation; Department of Chemistry and Materials Science; Department of Materials Science and Engineering; Department of Micro and Nanosciences; Department of Chemical and Metallurgical Engineering; Harri Lipsanen GroupAtomic Layer Deposition (ALD) of Al2O3/TiO2 nanolaminatewas applied to improve the sealing properties of CrN coating deposited with Physical Vapor Deposition (PVD) on high speed steel (HSS). The corrosion protection propertieswere explored with Linear Sweep Voltammetry and visual estimation. Nearly two orders of magnitude decrease in corrosion current density was obtained by applying plasma pre-treatment prior to ALD coating. Sealing of CrN pinholes was shown with Focused Ion Beam/Scanning Electron Microscope technique. The effect of the ALD deposition parameters to adhesion of the ALD coatings was investigated with Rockwell indentation and microscope analysis. Thickness and refractive index of the ALD coatings were measured with ellipsometry, and density and roughness of the ALD coatingswere investigatedwith X-Ray Reflectivity measurements. Neutral Salt Spray testing was used to investigate the corrosion resistance of PVD/ALD nanolaminates on HSS dental curettes.Item Effect of Surface Wear on Corrosion Protection of Steel by CrN Coatings Sealed with Atomic Layer Deposition(2018) Leppäniemi, Jarmo; Sippola, Perttu; Peltonen, Antti; Aromaa, Jari J.; Lipsanen, Harri; Koskinen, Jari; Department of Chemistry and Materials Science; Department of Electronics and Nanoengineering; Aalto Nanofab; Department of Chemical and Metallurgical Engineering; Physical Characteristics of Surfaces and Interfaces; Harri Lipsanen GroupCorrosion protection of steel obtained with physical vapor deposition (PVD) coatings can be further improved by sealing the intrinsic pinholes with atomic layer deposition (ALD) coatings. In this work, the effect of surface wear on corrosion protection obtained by a hybrid PVD CrN/ALD Al2O3/TiO2 nanolaminate coating was studied. The samples were investigated by alternating surface wear steps and exposure to salt solution and consecutively the progression of corrosion after each wear and each corrosion step was evaluated. Optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy showed that the rust spots were almost exclusively located on positions at which the wear steps had removed the top surface of the PVD CrN coating. Nevertheless, even after complete removal of the ALD nanolaminate from the top of the CrN surface by sandpaper grinding, the corrosion current density was less than half compared to the PVD CrN coating alone without surface wear. Cross-sectional SEM images obtained with focused ion beam milling showed not only the presence of the ALD coating at the CrN defects but also the opening of new pathways for the corrosion to attack the substrate. A mechanism for the effect of wear on the structure and corrosion protection of hybrid PVD/ALD coatings is proposed on the basis of this investigation.Item Influence of plasma parameters on the properties of ultrathin Al2O3 films prepared by plasma enhanced atomic layer deposition below 100 °c for moisture barrier applications(2018-12-01) Zhu, Zhen; Sippola, Perttu; Lipsanen, Harri; Savin, Hele; Merdes, Saoussen; Department of Electronics and Nanoengineering; School services, ELEC; Beneq OyWe report the effect of plasma parameters on the properties of ultrathin Al2O3 films prepared by plasma enhanced atomic layer deposition for moisture barrier applications. The Al2O3 films were grown at 90 °C using trimethylaluminum and O2 plasma as precursors. Plasma power, exposure time and O2 concentration are found to influence the growth behavior, composition and density of ultrathin Al2O3 films. Plasma power ≥ 100 W leads to lower impurity levels and higher mass densities of ∼2.85 g•cm-3. The optimum plasma parameters for our process, a plasma power of 100 W and an exposure time of 3 s, reveal a good water vapor transmission rate of 5 × 10-3 g•m-2•day-1 for polyethylene naphthalate substrates coated with 4 nm-thick Al2O3 films.Item Low-temperature atomic layer deposition of SiO2/Al2O3 multilayer structures constructed on self-standing films of cellulose nanofibrils(2018-02-13) Putkonen, Matti; Sippola, Perttu; Svärd, Laura; Sajavaara, Timo; Vartiainen, Jari; Buchanan, Iain; Forsström, Ulla; Simell, Pekka; Tammelin, Tekla; Department of Electronics and Nanoengineering; VTT Technical Research Centre of Finland; University of Jyväskylä; Air Products and Chemicals, Inc.In this paper, we have optimized a low-temperature atomic layer deposition (ALD) of SiO2 using AP-LTO® 330 and ozone (O3) as precursors, and demonstrated its suitability to surface-modify temperature-sensitive bio-based films of cellulose nanofibrils (CNFs). The lowest temperature for the thermal ALD process was 80°C when the silicon precursor residence time was increased by the stop-flow mode. The SiO2 film deposition rate was dependent on the temperature varying within 1.5–2.2 Å cycle−1 in the temperature range of 80–350°C, respectively. The low-temperature SiO2 process that resulted was combined with the conventional trimethyl aluminium + H2O process in order to prepare thin multilayer nanolaminates on self-standing CNF films. One to six stacks of SiO2/Al2O3 were deposited on the CNF films, with individual layer thicknesses of 3.7 nm and 2.6 nm, respectively, combined with a 5 nm protective SiO2 layer as the top layer. The performance of the multilayer hybrid nanolaminate structures was evaluated with respect to the oxygen and water vapour transmission rates. Six stacks of SiO2/Al2O with a total thickness of approximately 35 nm efficiently prevented oxygen and water molecules from interacting with the CNF film. The oxygen transmission rates analysed at 80% RH decreased from the value for plain CNF film of 130 ml m−2 d−1 to 0.15 ml m−2 d−1, whereas the water transmission rates lowered from 630 ± 50 g m−2 d−1 down to 90 ± 40 g m−2 d−1.Item Low-Temperature Plasma-Enhanced Atomic Layer Deposition of SiO 2 Using Carbon Dioxide(SPRINGER, 2019-02-12) Zhu, Zhen; Sippola, Perttu; Ylivaara, Oili M.E.; Modanese, Chiara; Di Sabatino, Marisa; Mizohata, Kenichiro; Merdes, Saoussen; Lipsanen, Harri; Savin, Hele; Department of Electronics and Nanoengineering; Hele Savin Group; Harri Lipsanen Group; Norwegian University of Science and Technology; University of Helsinki; Beneq Oy; VTT Technical Research Centre of FinlandIn this work, we report the successful growth of high-quality SiO2 films by low-temperature plasma-enhanced atomic layer deposition using an oxidant which is compatible with moisture/oxygen sensitive materials. The SiO2 films were grown at 90 degrees C using CO2 and Bis(tertiary-butylamino)silane as process precursors. Growth, chemical composition, density, optical properties, and residual stress of SiO2 films were investigated. SiO2 films having a saturated growth-per-cycle of similar to 1.15 angstrom/cycle showed a density of similar to 2.1g/cm(3), a refractive index of similar to 1.46 at a wavelength of 632nm, and a low tensile residual stress of similar to 30MPa. Furthermore, the films showed low impurity levels with bulk concentrations of similar to 2.4 and similar to 0.17at. % for hydrogen and nitrogen, respectively, whereas the carbon content was found to be below the measurement limit of time-of-flight elastic recoil detection analysis. These results demonstrate that CO2 is a promising oxidizing precursor for moisture/oxygen sensitive materials related plasma-enhanced atomic layer deposition processes.Item Metaanin optiset detektointimenetelmät ja kaupalliset sovellukset(2010) Sippola, Perttu; Suihkonen, Sami; Elektroniikan, tietoliikenteen ja automaation tiedekunta; Turunen, MarkusItem Nanometer-scale depth-resolved atomic layer deposited SiO2 thin films analysed by glow discharge optical emission spectroscopy(2018-03-21) Zhu, Zhen; Modanese, Chiara; Sippola, Perttu; Di Sabatino, Marisa; Savin, Hele; Department of Electronics and Nanoengineering; Hele Savin Group; Norwegian University of Science and TechnologyIn this contribution, pulsed radio frequency (rf) glow discharge optical emission spectroscopy (GDOES) is used to investigate the film properties of SiO2 deposited by plasma enhanced atomic layer deposition (PEALD), for example, the chemical composition, structural properties and film thickness. The total sputtering time until the interface between the SiO2 layer and the Si substrate is ≈13 s. The main impurities in the film, that is, H, C, and N, are detected. It is observed that both C and N intensities decrease with increasing plasma power during deposition of the thin film. The higher plasma power seems to increase the reactivity of the PEALD process and consequently, it might reduce the concentration of impurities in the deposited film. Moreover, the deviation of the GDOES sputtering rates on the film are related to the film density. The thickness of one-hundred-nanometer range SiO2 film is calculated from the GDOES silicon and oxygen emission profiles, and its difference from ellipsometry and X-ray reflectivity measurements highlights the challenges for the GDOES technique for transparent thin films.Item Pakkausprosessikehitys näkyvän alueen LED:eille(2014-03-31) Sippola, Perttu; Riuttanen, Lauri; Sähkötekniikan korkeakoulu; Sopanen, MarkkuValoa emittoivien diodien (LED) pakkausprosessi on suurin kuluerä koko tuotannossa. Tämä hidastaa korkean hyötysuhteen LED:ien laajaa omaksumista yleisvalaistukseen. Tässä diplomityössä kehitettiin pakkausprosessi optisen alueen LED:lle. Tutkimus ja kehitys suoritettiin Aalto-yliopiston Optoelektroniikan tutkimusryhmässä. Pakattujen LED:ien suorituskykyä tutkittiin elektroluminesenssi-mittauksilla ja pakkausepoksia optisella transmissiomittauksella. Kehitetty pakkausprosessi koostuu neljästä päävaiheesta. Ensin prosessoitu safiirikiekko sahataan yksittäisiksi LED-siruiksi kiekkosahalla. Seuraavaksi LEDsiru kiinnitetään metalliseen kahden pinnin TO-46 alustaan kiinnitysepoksilla. Tämän jälkeen sirun sähköiset kontaktit liitetään alumiinilangalla metallialustan kontakteihin. Lopulta LED-komponentti koteloidaan valamalla se läpinäkyvään pakkausepoksiin. Työn tuloksena valmistettiin sinisiä matalateho-LED:ejä tutkimustarkoituksiin. Mittausten tuloksena todettiin valitun kupuepoksin pystyvän korkeaan transmissioon sinisten LED:ien emissioaallonpituudella ja koko näkyvällä alueella. Elektroluminesenssimittausten tuloksena puolestaan havaittiin pakkausprosessoitujen LED:ien pystyvän tuottamaan 5,3 % ulkoisen kvanttihyötysuhteen (EQE, external quantum efficiency) ja 3,5 mW optisen tehon 20 mA ajovirralla. Optista suorituskykyä mittattiin ja vertailtiin myös prosessoidun kiekon kolmen eri alueen LEDsiruista ennen ja jälkeen epoksikoteloinnin. Mittaukset osoittivat LED-kiekolla esiintyvän eroja LED:ien optisessa tehossa ja EQE:ssä. Lisäksi epoksin todettiin laskevan emittoituvaa optista tehoa. Silti pakkausprosessin laadun todettiin täyttävän LED-pakkauksen vaatimukset riittävästi.Item Structural and chemical analysis of annealed plasma-enhanced atomic layer deposition aluminum nitride films(2016-07-01) Broas, Mikael; Sippola, Perttu; Sajavaara, Timo; Vuorinen, Vesa; Pyymaki Perros, Alexander; Lipsanen, Harri; Paulasto-Kröckel, Mervi; Department of Electrical Engineering and Automation; Department of Micro and Nanosciences; University of JyväskyläPlasma-enhanced atomic layer deposition was utilized to grow aluminum nitride (AlN) films on Si from trimethylaluminum and N2:H2 plasma at 200 °C. Thermal treatments were then applied on the films which caused changes in their chemical composition and nanostructure. These changes were observed to manifest in the refractive indices and densities of the films. The AlN films were identified to contain light element impurities, namely, H, C, and excess N due to nonideal precursor reactions. Oxygen contamination was also identified in the films. Many of the embedded impurities became volatile in the elevated annealing temperatures. Most notably, high amounts of H were observed to desorb from the AlN films. Furthermore, dinitrogen triple bonds were identified with infrared spectroscopy in the films. The triple bonds broke after annealing at 1000 °C for 1 h which likely caused enhanced hydrolysis of the films. The nanostructure of the films was identified to be amorphous in the as-deposited state and to become nanocrystalline after 1 h of annealing at 1000 °C.Item Study of Thermal and Plasma Enhanced Atomic Layer Deposition of AlN and Al2O3/TiO2 Films for Diverse Applications(Aalto University, 2019) Sippola, Perttu; Suihkonen, Sami, Dr., Aalto University, Department of Electronics and Nanoengineering, Finland; Elektroniikan ja nanotekniikan laitos; Department of Electronics and Nanoengineering; Nanoscience and Advanced Materials; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Lipsanen, Harri, Prof., Aalto University, Department of Electronics and Nanoengineering, FinlandAtomic layer deposition (ALD) has become widely utilized and researched technique for highly conformal and precise thickness controlled thin film fabrication. Due to these inherent advantages, ALD has been applied for diverse applications such as memories, logic and solar cells etc. This thesis presents research of certain plasma enhanced ALD (PEALD) and thermal ALD thin films with a focus on the effect of process parameters on the material properties. Mechanical properties of PEALD aluminum nitride films (mainly trimethylaluminum (TMA) and ammonia processes) were studied and supported with structural and compositional analysis. The study showed that higher deposition temperature and capacitively coupled plasma bias voltage improved density and impurity incorporation of the films, consequently positively influencing coating hardness and elastic modulus. Also, tensile stress magnitude was found to increase with temperature and high bias voltage lead to slightly compressive film. Moreover, adhesion and tribological behavior were determined but no marked correlation to process conditions were established. PEALD AlN was also studied with an inductively coupled plasma source and TMA/N2:H2 precursor chemistry with a focus on structural and compositional annealing (400–1000 °C) behavior of the films. Results showed outgassing of hydrogen, slight oxidation despite the vacuum environment and likely hydrolysis of the AlN films due to annealing. The films maintained their amorphous structure and their thickness reduced. The third studied AlN PEALD chemistry of AlCl3/NH3 employed a high process temperature (~500 °C). The developed process produced (002) preferential crystallinity, very low impurity concentration and high mass density films. In addition, the residual stresses of the films were found controllable by plasma exposure time and varied from slightly tensile to strongly compressive. ALD of consecutive bilayers of Al2O3/TiO2 (aka a nanolaminate) was investigated together with a physical vapor deposition (PVD) hard coating for wear resistant anticorrosive protection of steel. First, the corrosion resistance capability of the ALD nanolaminate improved with increased thickness and with plasma pretreatments which increased coating adhesion. Endurance against detrimental corrosion current was increased with two orders of magnitude with these hybrid films in comparison to the bare steel. In the follow-up study, the hybrid film samples were exposed to subsequent wear-corrosion environments showing that the anticorrosion protection was maintained at a high level despite the top-most ALD nanolaminate was completely removed. It can be concluded that the ALD nanolaminate encapsulates conformally the PVD coatings pinholes and defects which act as the main pathways for corrosion currents.Item X-ray reflectance and infrared spectroscopy study of plasma enhanced atomic layer deposited Al2O3 and SiO2(2017-05-08) Ostrovskaia, Elena; Sippola, Perttu; Sähkötekniikan korkeakoulu; Lipsanen, HarriIn this thesis, Al2O3 and SiO2 thin films produced by plasma enhanced atomic layer deposition were studied using X-ray reflectance (XRR) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Structural characterization of thin films such as thickness, roughness and density was obtained with the XRR technique. Qualitative chemical constitution of the samples was studied with infrared spectra. The samples were deposited using different plasma powers at low temperature ALD. The characteristic difference between as-deposited vs. 400 celsius annealed Al2O3 thin films were investigated. In case of SiO2, the effect of plasma time and ALD cycle number to thin film properties were analyzed. It was found that thickness does not show any dependence on plasma power, but density is increasing with plasma power for Al2O3, while for SiO2 no apparent dependence was revealed. Analysis of roughness showed that it increases with plasma power for Al2O3 and thin SiO2 samples, while for thicker SiO2 samples it does not change significantly. Analysis of ATR-FTIR spectra showed that there was no significant thin film composition dependence on the different plasma powers. ATR-FTIR results revealed that the structure of Al2O3 includes stretching and bending modes of Al-O bonds and also have sharp valley of Si-O bond due to the presence of native oxide between the Al2O3 thin film and Si substrate. SiO2 infrared spectra comprises Si-O bending and stretching bands and also bands connected with the presence of O-H groups. Also detectable traces of CH3 impurities was found, especially in case of thicker SiO2 thin films. On the basis of the performed analysis the dependence of SiO2 and Al2O3 thin film density, roughness, thickness and molecular constitution on plasma parameters was reported.