Vratislav Peřina

Reactive magnetron sputtering of hard Si-B-C-N films with a high-temperature oxidation resistance

Based on the results obtained for C–N and Si–C–N films, a systematic investigation of reactive magnetron sputtering of hard quaternary Si–B–C–N materials has been carried out. The Si–B–C–N films were deposited on p-type Si(100) substrates by dc magnetron co-sputtering using a single C–Si–B target (at a fixed 20% boron fraction in the target erosion area) in nitrogen-argon gas mixtures. Elemental compositions of the films, their surface bonding structure and mechanical properties, together with their oxidation resistance in air, were controlled by the Si fraction (5–75%) in the magnetron target erosion area, the Ar fraction (0–75%) in the gas mixture, the rf induced negative substrate bias voltage (from a floating potential to −500V) and the substrate temperature (180–350°C). The total pressure and the discharge current on the magnetron target were held constant at 0.5Pa and 1A, respectively. The energy and flux of ions bombarding the growing films were determined on the basis of the discharge characterist...

Plasma modification of polycarbonates

Abstract We deposited protective coatings on polycarbonates from hexamethyldisiloxane (HMDSO) and HMDSO/O2 mixtures by the plasma enhanced CVD method. In particular, we studied deposition rate, optical constants in UV/VIS, film composition and mechanical properties dependent on rf power and oxygen to HMDSO flow rate ratio. Plasma polymer HMDSO films (PP-HMDSO) showed good transparency in the visible and increased absorption in UV region. The optical constants of HMDSO/O2 films were similar to the tabulated SiO2. In general, the films were characterised by a relatively high content of hydrogen (22–66%) and a carbon content below 20%. The films deposited at an oxygen-to-HMDSO flow rate ratio higher than 15 exhibited higher tensile stress and higher hardness than those prepared at ratios of 5–10. The nature of the internal stress changed to compressive for PP-HMDSO. Plasma pre-treatment of polycarbonate in argon significantly improved the film adherence, especially when low powers and short treatment times were used.

Study of nitrogen pressure effect on the laser-deposited amorphous carbon films

Abstract The series of amorphous carbon films (a-C) deposited at a vacuum of 2 ×10−3 Pa and nitrogenated amorphous carbon films (a-CN) deposited at different nitrogen pressures were grownby the pulsed laser deposition method. The influence of the molecular nitrogen pressure in the deposition chamber on the film properties was investigated. Electrical resistivity, intrinsic stress and UV-Vis transmission of the films were measured for this purpose. The optical bandgap was calculated from the absorption edge of the UV-Vis spectra. Changes of the structure, of the chemical bonding and of the stoichiometry were investigated usingRaman spectroscopy, X-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy respectively. Carbon nitride formation was indicated. The promotion of the sp2 bonding is indirectly indicated by Raman spectroscopy. A rapid enhancement of electrical resistivity of samples deposited at nitrogen pressure pN above 5 Pa was observed. We concluded that two contradictory effects result in non-monotonous dependence of the electrical resistivity and optical bandgap on the nitrogen pressure p N: graphitization and carbon nitride formation. The high compressive stress decreased with increasing nitrogen pressure pN and it even changed to tensile stress above 5 Pa. Formation of the voids in the structure is discussed.

Deposition of protective coatings in rf organosilicon discharges

The paper discusses the deposition of protective coatings ranging from organosilicon plasma polymers to SiO2-like films and hard diamond-like carbon/silicon oxide (DLC?:?SiOx) coatings in radio frequency capacitively coupled discharges using hexamethyldisiloxane (HMDSO). As a result of the optimization of the deposition conditions it was possible to obtain high performance protective coatings. In the HMDSO/O2 mixture, it was shown that rather than the SiO2-like film a hard cross-linked SiOxCyHz polymer film can be used as a protective coating for polycarbonate. The optimum conditions for the deposition of an almost stress-free film were 17% of HMDSO and dc bias voltage of ?240?V. The film hardness and elastic modulus were 10?GPa and 75?GPa, respectively. The refractive index at 600?nm was 1.5 and the extinction coefficient decreased from 0.02 at 240?nm down to zero at 600?nm.The films deposited from HMDSO/CH4 and HMDSO/CH4/H2 mixtures exhibited the attractive properties of DLC films with the partial elimination of some of their drawbacks, such as absorption in the visible and a high intrinsic stress. The optimum concentration of the HMDSO was approximately 21%. Under these conditions the concentration of SiOx in the films was approximately 9?at.%. The film hardness and elastic modulus were above 22?GPa and 120?GPa, respectively.

Influence of nitrogen-argon gas mixtures on reactive magnetron sputtering of hard Si-C-N films

Abstract Si–C–N films were deposited on p-type Si(100) substrates by dc magnetron co-sputtering of silicon and carbon using a single sputter target with variable Si/C area ratios in nitrogen–argon mixtures. The film characteristics were primarily controlled by the argon concentration (0–75%) in the gas mixture at a fixed 40% silicon fraction in the magnetron erosion track area. The total pressure and the discharge current on the magnetron target were held constant at P =0.5 Pa and I m =1 A, the substrate temperature was adjusted at T s =600 °C by an ohmic heater and the rf-induced negative substrate bias voltage, U b was −500 V. Mass spectroscopy was used to explain differences between sputtering of carbon and silicon in nitrogen–argon discharges. The films, typically 1.0–1.5 μm thick, were found to be amorphous with a very smooth surface ( R a ≤0.8 nm). It was shown that the nitrogen–argon gas mixture composition is an important process parameter in a reproducible production of Si–C–N compounds with controlled properties by dc magnetron co-sputtering using a composed C–Si target with variable Si/C area ratios. With a rising argon concentration in the gas mixture, the Si content in the films rapidly increases (from 19 to 34 at.% for a 40% Si fraction in the erosion target area), while the C content decreases (from 34 to 19 at.%) at an almost constant (39–43 at.%) N concentration. An intensified bombardment of growing films by argon leads to its subplantation into the films (up to 5 at.%) and to a decrease in a volume concentration of hydrogen (from 5 to 1 at.%). As a result, the NSi and SiN bonds dominate over the respective NC and SiO bonds, preferred in a pure nitrogen discharge, and the film hardness increases up to 40 GPa. The effect of the negative substrate bias voltage (from a floating potential of −18 to −500 V) on characteristics of the films prepared in a 50% N 2 +50% Ar gas mixture is not too marked at T s =600 °C. A decrease in the T s values to 135–210 °C leads to a higher incorporation of hydrogen into the films (up to 6 at. %) and to a stronger influence of the negative substrate bias voltage.

Deposition of hard thin films from HMDSO in atmospheric pressure dielectric barrier discharge

An atmospheric pressure dielectric barrier discharge burning in nitrogen with a small admixture of hexamethyldisiloxane (HMDSO) was used for the deposition of thin organosilicon films. The thin films were deposited on glass, silicon and polycarbonate substrates, and the substrate temperature during the deposition process was increased up to values within the range 25 - 150 C in order to obtain hard SiOx-like thin films.

Characterization of silicon oxide thin films deposited by plasma enhanced chemical vapour deposition from octamethylcyclotetrasiloxane/oxygen feeds

Abstract Plasma enhanced chemical vapour deposition (PECVD) of thin oxide films was investigated, changing electrical potential conditions at the substrate electrode (dc, rf coupled or positive biased). Rf discharge at the frequency of 13.56 MHz was generated in a planar reactor with two internal electrodes. Silicon substrates were placed on the powered electrode. The octamethylcyclotetrasiloxane (OMTS) was chosen as a source of OSiO groups in order to test new possibilities in the silicon oxide depositions. The reflectance in the visible, the transmittance in the infrared region, X-ray photoelectron spectra (XPS) and Rutherford backscattering method (RBS) analyses were applied to describe the deposition rate, the optical properties, the composition and the structure of the deposited films. The comparison among these four methods concerning the film composition and structure is discussed. The pronounced changes in the deposition rate with rf power or dc bias typical of every electrical potential condition were observed. However, other film characteristics seemed to be very similar. The film optical parameters and the atomic composition were close to those of amorphous silicon dioxide.

Germanium nitride layers prepared by supersonic r.f. plasma jet

Abstract Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS) have been used to characterize GexNy films grown on Si substrates. The films were deposited in a plasma chemical reactor by a radio frequency (r.f.)-generated supersonic plasma jet. The Ge nozzle of the r.f. electrode was reactively sputtered in the plasma jet generated in the nitrogen and the germanium nitride films were created in the reactor. The RBS method showed that the ratio Ge:N in the layer was close to the expected stoichiometric ratio 3:4 (for example, 0.73, which is within experimental error) when traces of oxygen were suppressed. The chemical bonding state of GeN, as found by XPS analysis, showed that, close to the thin film surface, the Ge:N ratio was also near 3:4. The impurities present, although in small amount, were preferentially bonded into the film.

Correlation between SiOx content and properties of DLC:SiOx films prepared by PECVD

Hard diamond like carbon (DLC) films with an addition of SiOx were deposited in capacitively coupled rf discharges from a mixture of methane and hexamethyldisiloxane (HMDSO). The flow rate of HMDSO was changed in order to vary the SiOx content in the films. Complete atomic composition of the films was determined by Rutherford backscattering spectroscopy combined with elastic recoil detection analysis. The thickness and the optical properties were obtained from the ellipsometric measurements. The mechanical properties were studied by a depth sensing indentation technique using Fischerscope H100 tester. The O/Si ratio in DLC:SiOx films was 0.286 and the content of SiOx increased with the HMDSO-to-methane flow rate ratio q. The DLC:SiOx films were close to DLC films as concerning the optical properties in the uv/visible and the high hardness if q was maximum 0.25. However, the compressive stress in the films was reduced, the film fracture toughness was improved and the deposition rate increased.

Magnetron sputtered Si–B–C–N films with high oxidation resistance and thermal stability in air at temperatures above 1500 °C

Novel quaternary Si–B–C–N materials are becoming increasingly attractive because of their possible high-temperature and harsh-environment applications. In the present work, amorphous Si–B–C–N films were deposited on Si and SiC substrates by reactive dc magnetron cosputtering using a single C–Si–B or B4C–Si target in nitrogen-argon gas mixtures. A fixed 75% Si fraction in the target erosion areas, a rf induced negative substrate bias voltage of −100 V, a substrate temperature of 350 °C, and a total pressure of 0.5 Pa were used in the depositions. The corresponding discharge and deposition characteristics (such as the ion-to-film-forming particle flux ratio, ion energy per deposited atom, and deposition rate) are presented to understand complex relationships between process parameters and film characteristics. Films deposited under optimized conditions (B4C–Si target, 50% N2+50% Ar gas mixture), possessing a composition (in at. %) Si32–34B9–10C2–4N49–51 with a low (less than 5 at. %) total content of hydrog...