Organosilicon Films Research Articles

Mass density determination of thin organosilicon films by X-ray reflectometry

The mass density of thin organosilicon films deposited by chemical vapour deposition on silicon (0 0 1) surfaces has been determined by X-ray reflectometry. This method does not give a unique mass density value, but instead a bandwidth of possible values and compositions that are compatible with the experimental data if the layer thickness is not larger than about 350 nm. For thicker films thickness values obtained from ellipsometry data are used. The possible composition ranges are compared with data obtained by X-ray photo electron spectroscopy.

Gadolinium-doped organosilicon films grown by plasma chemical vapor deposition

Thin organosilicon films doped with gadolinium were prepared by plasma chemical vapor co-deposition (13.56 MHz) using hexamethyldisiloxane as a precursor for the light-guide matrix, and tris(2,2,6,6-tetramethyl-3-5-heptanedionato)gadolinium(III) as a source of luminescent centers. The chemical composition of such films was investigated by Fourier transform infrared spectroscopy and quantitative microanalysis. Measurements of optical (ultraviolet–visible) absorption and photoluminescence were also performed. It was found that the optically active centers are created by Gd3+ ions bonded to the matrix via oxygen atoms. The center excitation consists of a non-radiative transfer of energy absorbed in the matrix (200–230 nm) to the ion. The emission light observed at 312 nm is attributed to the 6P7/2→8S7/2 transition in Gd3+.

Experimental investigation of the respective roles of oxygen atoms and electrons in the deposition of SiO2 in O2/TEOS helicon plasmas

The respective roles of electrons and oxygen atoms in the plasma enhanced chemical vapor deposition of SiO2-like films are investigated in a low-pressure radio-frequency helicon oxygen/tetraethoxysilane (TEOS) plasma. The plasma and film growth are monitored by optical emission spectroscopy and in situ spectroscopic ellipsometry, respectively. The variations of the atomic oxygen density [O] (measured by actinometry) and the deposition rate are studied as a function of the organosilicon fraction in the O2/TEOS plasma. First, on the basis of these measurements and the data available in the literature, it is established that electrons have the key role in TEOS fragmentation while the contribution of O is shown to be very weak. Second, it is shown that organosilicon films deposited in a TEOS rich plasma are etched by O atoms when exposed to a pure oxygen plasma. The etching rate is proportional to [O] and is of the same order of magnitude than the deposition rate, which demonstrates that deposition and etching really compete in O2/TEOS plasma.

Conductive Circuit Formation on Organosilicon Films by Patterning with UV

Abstract This paper concerns a novel method for the preparation of silver metal from AgBF4 by reduction with polysilanes, and an application of the method to the direct formation of conducting pattern on the surface of organosilicon polymers in combination with UV light lithography without any other promoters, reductants and photoresists.

表面制御された超はっ水性皮膜のマイクロ波プラズマＣＶＤ法による作製

Polymerized organosilicon films containing fluorine were fabricated using microwave plasma-enhanced chemical vapor deposition (MW PECVD). Chemical and physical surface properties were controlled by changing PECVD reaction conditions. Water-repellent films having water contact angles exceeding 150 degrees were obtained at Ts=70°C and total pressure exceeding 40Pa.Films were prepared from a mixed source gas of tetramethylsilane (TMS) or hexamethyldisilane (HMDS), containing no oxygen atoms, and a (heptadecafluoro-1, 1, 2, 2, tetrahydro-decyl)-1-trimethoxysilane (FAS-17). FAS-17 was introduced into a reactor using Ar carrier gas. Water contact angles of these films increased from 115 to 160 degrees as total pressure increased from 25 to 50Pa. Their surface roughnesses increased from Rrms=11.3 to 60.8nm. The film structure became more granular when prepared at a higher pressure. With an increase in the substrate temperature, however, film surfaces became smooth and perfluoro-alkyl groups peeled from films, markedly decreasing in water-contact angles.Films were then prepared from hexamethyldisiloxane (HMDSO), which contains oxygen atoms, and FAS-17 with Ar. Rrms ranged from 10 to 12nm and contact angles remained constant at 110 degrees in the total 25∼50Pa. Oxygen atoms in the source material, i. e., HMDSO, promoted film surface smoothing and reduced water repellency.

The influence of polarization on hole transport in plasma-polymerized organosilicon films

The influence of polarization procedure on charge carrier transport in plasma polymerized organosilicon films was investigated. Mobility of holes was determined using the time-of-flight method. It was found that frozen-in polarization of the plasma polymerized hexamethyldisilazane films increases the value of drift mobility. This process is fully reversible and after depolarization the value of drift mobility returns to the one before polarization. >

Field-induced water sorption in plasma polymers

Abstract The field-induced water sorption in plasma-polymerized organosilicon films is presented. It was found that this effect occurs in samples which were cooled below 270 K and then heated up with an applied electrical field. Based on the results, a molecular model for the observed field-induced water sorption is proposed.

Quantitative electron-probe microanalysis of light elements: Determination ofa-Si?C?N?O?H insulating films

Amorphous Si∶C∶N∶O∶H films (1–3 μm) are studied by EPMA after deposition of gold (1–5 nm) as a conductive coating. Its influence on thek-ratios (X-ray intensity relative to an uncoated standard) of silicon, carbon, nitrogen and oxygen is described as a linear function of the simultaneously determinedk-ratio of gold. Thek-ratios representing the uncoated specimen are obtained by extrapolation and, in combination with the PAP matrix correction model, quantitative EPMA can be performed with an analytical error of 2–5%, as it is demonstrated by samples of SiC, Si3N4 and SiO2. No systematic shift of the concentrations is observed for layers ofa-Si∶C∶N∶O∶H determined at various electron energies of 5–12.5 keV. Hydrogen is calculated by difference and the concentrations prove to be a useful estimate in agreement with the results of chemical analysis. Si-Kβ/Si-Kβ′ spectra recorded on organo-silicon films and binary silicon compounds point out significant differences concerning the formation of Si-C, Si-N and Si-O chemical bonds.

Water in plasma-polymerized organosilicon films: Dielectric properties

Abstract In earlier publications it has been reported that plasmapolymerized organosilicon films may contain up to 6.8 wt% water. A distinction has been made between “weakly” and “strongly” bound water in the polymer matrix, the strongly bound water being incorporated into the film in the form of network aggregates connected with the glass by means of hydrogen bonds. The observation in those materials of a phase transition is due to the changed inner structure of the aggregates in question. The goal of this study is the determination of the effect of absorbed water on the dielectric properties of plasma-polymerized organosilicon films. It is shown that the weakly bound water activates a relaxation process whose frequency at room temperature is above 0.5 MHz. In contrast, the strongly bound water reveals its presence by two relaxation processes of very low frequency, with activation energies of 0.65 eV and 0.87 eV. It was found that the absorbed molecules of strongly bound water may also inhibit the rotati...

Phase transition effects in plasma-polymerized organosilicon films

Abstract Some detailed investigations recently carried out on plasma-polymerized organosilicon films have revealed a number of phenomena which may be related to a phase transition taking place at ca. 270 K. The existence of this effect is confirmed by measurements of the temperature dependence of the thermal expansion coefficient of these films, by DSC measurements, and by measurements of the temperature dependence of the dielectric constant. It was found that the observed phase transition effect appears to be related to the presence of water molecules in the film volume. The water molecules form aggregates strongly bound to the film structure and stay there even under vacuum and at high temperature (to ca. 450 K).

Photoinjection into plasma-polymerised thin organosilicon films. II. The structure of energy levels

For pt.I see ibid., vol.14, p.1877 (1981). Studies of the photoinjection of carriers from metal into plasma-polymerised organosilicon films, optical investigations and the results of conductivity measurements, are used to describe the energy band structures of the bulk and surface of these films. Also discussed is the structure of the organosilicon glass-metal contact. The parameters determined include transport gap Eg (=6.3 eV), optical gap Egopt (=3.1 eV for aged and untreated films), electron affinity X (=0.7 eV), ionisation potential J(=7.0 eV), bulk worn-function Wi(=6.35 eV) and surface work-function Ws (=4.1 eV for the case of high surface state density). The results obtained indicate that the basic molecular structure of organosilicon films is of the types SixCy:H in spite of differences in the chemical constitution of the compounds used in plasma polymerisation. It is found that in the transport gap there are localised states which are inhomogeneously distributed in the film thickness. These states are probably connected with free spins.

Hole transport in polyorganosilicon thin films

Hole transport in plasma — polymerized organosilicon films has been investigated. Measurements of the stationary conductivity dependence on temperature and applied electrical field and mobility determination by time of flight method were carried out. It was shown that holes can be transported either by states laying near or in the valence band, or by states near the Fermi level. The first transport mechanism dominates at about room temperature and above and the second one was found only in polysilazane at low temperature. Nitrogen containing structures are proposed as transport states near the Fermi level.

Photoinjection into plasma-polymerised organosilicon thin films. I. Surface states

Investigations into photoinjection of carriers from metal (Au, Al) into thin (0.65 mu m) plasma-polymerised organosilicon films have been made. The presence of two photoinjection threshold energies is indicated; the lower threshold is ascribed to holes, the upper one to electrons. The existence of a significant density of surface states at the metal-polymer contact is proved. A chemical nature is attributed to these states. It is shown that thermal treatment of films causes a rapid decrease of the density of these states. Adsorption of oxygen gas at the metal-polymer contact introduces only a small number of additional charged surface states.

A scanning electron microscope study of plasma‐polymerized organosilicon films suitable for use as lightguides. A determination of the cause of signal attenuation

AbstractThe scanning electron microscope was used to evaluate the optical quality of a plasma‐deposited organic film. A major source of signal attenuation in lightguide films results from scattering by microscopic embedded spheres. The spheres are produced in the gas phase, and their size and population density are a function of the substrate surface and the rate of film formation. For all systems studied, the number of spheres increase with increasing rate. High‐quality films were deposited more easily on silicon, silicon dioxide, tungsten, and glass than on Nichrome or β‐tantalum. Gold, copper, and titanium surfaces proved more difficult, while aluminum was the most intractable material encountered. The rate of film growth usually increased with an increase in power input for any ratio of total pressure‐partial pressure of monomer. Spheres were essentially eliminated or their number reduced to a tolerable level by a proper choice of reaction conditions.

Organosilicon Films Formed by an RF Plasma Polymerization Process

The purpose of this research was to develop a plasma polymerization process for producing polymeric films and to achieve an understanding of the chemistry involved. A technique for the production of polymer coatings from a capacitively coupled RF plasma is presented. The resulting films contain trapped free radical sites which can react with oxygen and nitric oxide. The rate of polymer formation is a complicated function of power input, total system pressure, and partial pressure of monomer. The rates of reaction differ for different monomers under identical reaction conditions. The stoichiometry and infrared spectra of the polymers indicate that considerable fragmentation and bond reorganization of the monomeric starting material occurs during the polymerization process. A mechanism is proposed to account for conversion of monomer to polymer by formation and fragmentation of ionic species in the discharge. Neutralization of the ionic fragments at the walls yields radicals which can react with adsorbed species and be cross‐linked to form polymer.

Thin Organosilicon Films for Integrated Optics

The continued development of integrated optics is heavily dependent upon the availability of materials that are suitable for the construction of thin-film optical circuitry and devices. We report here an investigation of new films made by an rf discharge polymerization process of organic chemical monomers. We concentrate our discussion on films prepared from vinyltrimethylsilane and hexamethyldisilbxane. These films are smooth, tough, pinhole-free, transparent from 0.4 microm to 0.75 microm, and exhibit very low loss (<0.04 dB/cm) for light-wave propagation. More importantly, experiments demonstrate the possibility of controlling the refractive index of the films either by the mixing of the two monomers before deposition or by chemical treatment after the film is deposited. The use of the prism-film coupler for studying the refractive index of each material is discussed in detail.

The dielectric properties of organosilicon films and the effect of γ-radiation on their structure

The aim of the work reported here was to study the polymerization conditions and heating temperature of the samples on the dielectric properties of the films, and also the effect of γ-radiation on their structure.

Organosilicon films on glass surfaces, Part I

Organosilicon films on glass surfaces, Part I