Hexamethyldisiloxane Films Research Articles

Modification of polyethylene powder with an organic precursor in a spiral conveyor by hollow cathode glow discharge

Hexamethyldisiloxane (HMDSO) films were deposited on polyethylene (PE, (C2H4)n) powder by hollow cathode glow discharge. The reactive species in different HMDSO/Ar plasmas were studied by optical emission spectroscopy (OES). Increasing the HMDSO fraction in the gas mixture additional compounds like CHx, OH, SiC and SiO can be identified. After deposition the formed silicon and carbon containing groups (C–O, C=O, SiC and SiO) on the PE powder surface have been analyzed by X-ray photoemission spectroscopy (XPS). Changes in wettability depending on the HMDSO fraction were investigated by contact angle measurements (CAM). The free surface energy of the PE powder decreases with increasing HMDSO fraction in the process gas and encapsulation of the powder particles occurs. An aging effect of the plasma treated PE surface was observed depending on the process gas composition. The higher the HMDSO fraction the less is the aging effect of the plasma treated PE surface.

Studies of radiofrequency plasma deposition of hexamethyldisiloxane films and their thermal stability and corrosion resistance behavior

Hexamethyldisiloxane (HMDSO) films (thickness: 282–929 nm) are prepared by the radiofrequency plasma assisted chemical vapour deposition (RF-PACVD) method using an Ar/HMDSO/O 2 gas mixture. The deposition process is carried out in an RF reactor at a working pressure of 1.2 × 10 −1 mbar and an RF power range of 20–100 W. From the studies on Ar/O 2 and Ar/HMDSO/O 2 discharge characteristics using a self-compensated emissive probe, it is revealed that electrons play an important role in the plasma polymerization of HMDSO monomers. Optical emission spectroscopy (OES) and Fourier transform infrared (FT-IR) spectroscopy show that the plasma deposited HMDSO films tend to be more inorganic in nature at higher RF powers. A film prepared at an RF power of 100 W exhibits more thermal stability and corrosion resistance behavior in comparison to films deposited at lower powers (20–80 W). A correlation of the results obtained from OES and FT-IR analyses with the thermal stability and corrosion resistance behavior of the films has been attempted.

Low-energy electron-induced chemistry of condensed-phase hexamethyldisiloxane: Initiating dissociative process and subsequent reactions

Thin films of condensed hexamethyldisiloxane (HMDSO) have been exposed to electron irradiation at incident energies between 5 and 15 eV and analysed afterwards by thermal desorption spectrometry (TDS). Formation of products is observed at energies at and above 11 eV and quantified at 15 eV by comparison with reference samples of known composition. Gas-phase measurements aiming at detection of dissociative electron attachment (DEA) were, in addition, performed to obtain more insight into the dominant electron-induced dissociation channel expected to initiate further reactions in the condensed phase. Apart from CH 4 which is the most obvious product present in exposed films of HMDSO, tetramethylsilane (TMS) and smaller amounts of C 2H 6 have been detected. The quantity of the products is by one to two orders of magnitude smaller than the amount of decomposed HMDSO. In addition, signals ascribed to unquantified amounts of larger siloxanes have been observed. The present results together with previous gas-phase results from literature suggest that dissociative ionisation leading to Si–C bond rupture and release of a methyl radical is the most important electron-driven initial reaction step. Possible mechanisms of the subsequent reactions induced by the fragments of the initial dissociation reaction are reviewed and discussed in relation to the observed product quantities.

Effects of surface treatments using PECVD-grown hexamethyldisiloxane on the performance of organic thin-film transistor

Hexamethyldisiloxane (HMDSO) was deposited on a gate dielectric surface by plasma enhanced chemical vapor deposition for surface treatment, and its effects on the microstructure of pentacene and the transistor characteristics were examined. HMDSO films were deposited at room temperature at various RF powers (10 W to 120 W). Atomic force microscopy analysis of the pentacene films showed a significant increase in the grain size of the samples treated under the optimum RF power (10 W), which in turn led to a significant improvement in the electrical mobility. These results show that PECVD-grown HMDSO can be used as an effective surface treatment and warrants further investigation for process optimization.

Plasma polymerized hexamethyl disiloxane in adhesion applications

The plasma polymer of hexamethyl disiloxane (HMDSO) was investigated as an adhesive for the gluing of silicon-to-silicon for potential application in microelectronic device and sensor fabrication. The aim of this work was to determine whether nm-thick films of HMDSO deposited in excess oxygen could be used as an adhesion layer for the bonding of silicon or glass to itself or other materials. The adhesive should be stable at high temperature and it should not outgas. The chemical nature of the thin films was analysed using Fourier transform infra red spectroscopy (FTIR) and contact angle measurements. Thermal stability was investigated using gas chromatography combined with mass spectroscopy (GC/MS). Adhesive strength was determined using an Instron tensile testing apparatus. Results show that a combination of plasma surface modification and plasma deposition reactions allow for the fabrication of Si–Si sandwiches that show shear strength up to 6 MPa, which would be sufficient for bonding applications in many microelectronic devices. The deposited materials were temperature stable. Sources of errors and methods to overcome these are discussed.

Gas Sorption of Acetone, Diethyl Ether, Toluene, Acetic Acid, and Ammonia on Plasma-Polymerized Hexamethyldisiloxane Films Coated with Quartz Crystal Microbalance

Gas Sorption of Acetone, Diethyl Ether, Toluene, Acetic Acid, and Ammonia on Plasma-Polymerized Hexamethyldisiloxane Films Coated with Quartz Crystal Microbalance

Organic–inorganic behaviour of HMDSO films plasma-polymerized at atmospheric pressure

Abstract Recently, plasma-polymerization at atmospheric pressure has become a promising technology due to its reduced equipment costs and its possibility of in-line processing. This paper focuses on plasma deposition by an atmospheric pressure dielectric barrier discharge (DBD) using hexamethyldisiloxane (HMDSO) as gaseous precursor. HMDSO plasma-polymerized films are deposited onto polyethylene terephthalate (PET) films using argon and different argon/air mixtures as carrier gases. The chemical and physical properties of the obtained coatings are discussed using contact angle measurements, Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Contact angle and FTIR results show that the composition of the gas phase and the chemical structure of the obtained coatings are clearly correlated. When pure argon is used as working gas, the film is polymeric with a structure close to [(CH3)2–Si–O]n. However, with increasing air content, a gradual change is observed from organic polydimethylsiloxane-like coatings to inorganic, quartz-like deposits. AFM results clearly indicate that with increasing air content, the deposition rate decreases, while the surface of the deposited films becomes rougher. From this point of view, the capability of controlling both chemical and physical properties of the plasma-polymerized films by varying operation conditions opens interesting perspectives.

Low-energy electron-induced reactions in condensed HMDSO

Reactions induced by electrons at an incident energy of 15 eV in multilayer condensed films of hexamethyldisiloxane (HMDSO) serving as model for siloxane materials have been investigated by thermal desorption spectrometry (TDS). TDS of the non-exposed material as a function of coverage reveals the subsequent formation of two phases with different desorption temperature. The higher-temperature desorption peak, ascribed to an ordered phase, vanishes more rapidly under exposure to electrons than the low-temperature peak, ascribed to a disordered phase. Production of CH 4 is also more rapid during the initial depletion of the high-temperature desorption peak of HMDSO than at higher electron exposure. This gives evidence that two physically different phases with different reactivity under electron exposure must be present already at the deposition temperature. An estimate of the HMDSO depletion cross sections for the two phases is given and possible reasons for the different reactivity are discussed.

Thermal desorption spectrometry for identification of products formed by electron-induced reactions

Thermal desorption spectra of thin films of acetaldehyde and hexamethyldisiloxane were recorded before and after exposure to electrons with an energy of 15eV to monitor the formation of the products CO, propionaldehyde, and methane. While the identification of the products in previous work reported in literature has relied on a comparison with desorption temperatures of pure multilayer films, it is proposed here to compare with reference samples containing specific amounts of the anticipated product. It is shown that this approach is more accurate because the desorption temperatures can be modified considerably by a molecular matrix or by coadsorbates. Also trapping of the products within a molecular film can occur and lead to a delayed desorption as exemplified by the production of methane in thin films of hexamethyldisiloxane.

Synthesis and Characterization of Plasma-Polymerized HMDSO Films Using an Ion Gun Inverse Magnetron Source

Plasma-polymerized hexamethyldisiloxane (PPHMDSO) films have been deposited using an ion gun inverse magnetron source at low pressure with Ar/O2/N2/HMDSO plasmas. Deposition rates and structures of the highly cross-linked PPHMDSO layers have been determined. Surface mechanical properties were studied using the nanoindentation technique, and wettability was measured by contact angle method and modifications induced on optical properties were studied at different wavelengths. Results showed remarkable differences in hardness and contact angles of distilled water depending on the plasma conditions. In addition, plasma parameters also had a very significant effect on the background fluorescence.

Plasma-polymerized organosilicones as engineered interlayers in glass fiber/polyester composites

The plasma polymerization technique was used to surface modify glass fibers in order to form a strong but tough link between the glass fiber and the polyester matrix, and enable an efficient stress transfer from the polymer matrix to the fiber. Plasma polymer films of hexamethyldisiloxane, vinyltriethoxysilane, and tetravinylsilane in a mixture with oxygen gas were engineered as compatible interlayers for the glass fiber/polyester composite. The interlayers of controlled physico-chemical properties were tailored using the deposition conditions with regard to the elemental composition, chemical structure, and Young's modulus in order to improve adhesion bonding at the interlayer/glass and polyester/interlayer interfaces and tune the cross-linking of the plasma polymer. The optimized interlayer enabled a 6.5-fold increase of the short-beam strength compared to the untreated fibers. The short-beam strength of GF/polyester composite with the pp-TVS/O2 interlayer was 32% higher than that with industrial sizing developed for fiber-reinforced composites with a polyester matrix.

Morphology and Patterning Processes of Thin Organosilicon and Perfluorinated Bi‐Layer Plasma Polymer Films

AbstractSummary: An audio‐frequency plasma polymerization set‐up with a planar plasma source was used to deposit thin bi‐layer plasma polymer films using heptadecafluoro‐1‐decene (HDFD) and hexamethyldisiloxane (HMDSO) as monomers. HDFD was used to deposit a thin Teflon‐like plasma polymer film with low surface energy. HMDSO was used to coat this layer with a highly cross‐linked SiCxOyHz film. The growth of the HMDSO plasma polymer illustrates the aspects of island formation at small film thickness (d < 10 nm) as a result of the low surface energy of the HDFD plasma polymer film surface and the buckling‐induced patterning by the compressive stress of the HMDSO plasma polymer film at higher film thickness (d > 10 nm). The film thickness was controlled by quartz crystal microbalance (QCM) and spectroscopic ellipsometry. The chemical structure of the films was measured by means of FT‐IR and XPS. The information about the surface morphology was provided by atomic force microscopy (AFM) measurements.AFM image (50 × 50 µm2) of anisotropic patterning of bi‐layer plasma polymer films (30 nm HMDSO film on top of a 100 nm HDFD film) on Si wafers at a point defect (dust particle).magnified imageAFM image (50 × 50 µm2) of anisotropic patterning of bi‐layer plasma polymer films (30 nm HMDSO film on top of a 100 nm HDFD film) on Si wafers at a point defect (dust particle).

X-Ray and Neutron Reflectometry Study of Glow-Discharge Plasma Polymer Films

Radio-frequency glow-discharge plasma polymer thin films of allylamine (AA) and hexamethyldisiloxane (HMDSO) were prepared on silicon wafers and analyzed by a combination of X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray reflectometry (XRR), and neutron reflectometry (NR). AFM and XRR measurements revealed uniform, smooth, defect-free films of 20-30 nm thickness. XPS measurements gave compositional data on all elements in the films with the exception of hydrogen. In combination with XRR and NR, the film composition and mass densities (1.46 and 1.09 g cm(-)(3) for AA and HMDSO, respectively) were estimated. Further NR measurements were conducted with the AA and HMDSO films in contact with water at neutral pH. Three different H(2)O/D(2)O mixtures were used to vary the contrast between the aqueous phase and the polymer. The amount of water penetrating the film, as well as the number of labile protons present, was determined. The AA film in contact with water was found to swell by approximately 5%, contain approximately 3% water, and have approximately 24% labile protons. The HDMSO polymer was found to have approximately 6% labile protons, no thickness increase when in contact with water, and essentially no solvent penetration into the film. The difference in the degree of proton exchange within the films was attributed to the substantially different surface and bulk chemistries of the two films.

Synthesis and characterization of plasma-polymerized hexamethyldisiloxane films

The deposition rates of plasma-polymerized (pp-) films from hexamethyldisiloxane (HMDSO) monomer were determined by the quartz crystal microbalance technique. Using the several polymerization conditions for HMDSO, these were found that the deposition rates were proportional to the polymerization time. The deposition rate of the pp-HMDSO films increased with the increasing RF power. But for vapor pressure, the deposition rates increased with increasing the vapor pressure until 100 Pa; above it, deposition rates tended to decrease gradually. The maximum deposition rate of pp-HMDSO film was obtained 4.577 μg/min on 150 W of RF power at 100 Pa of monomer pressure.

Surface structures tailoring of hexamethyldisiloxane films by pulse rf plasma polymerization

The surface structures of hexamethyldisiloxane (HMDSO) films prepared by rf plasma polymerization are investigated by Fourier transform infrared, solid-state 29Si CP/MAS nuclear magnetic resonance and scanning electron microscope. The reactive species in HMDSO plasma and the mechanism of HMDSO plasma synthesis are studied by optic emission spectrum. The effect of continuous wave discharge and different pulse discharge parameters especially plasma “high power” time on chemical structure and physical morphology modifications of HMDSO polymer film is compared elaborately. The results show that HMDSO-continuous-wave polymer is an organic film without Si O group. Its surface consists of several microscale islands with many clustered rods. While HMDSO-pulse-polymer is a network of interconnected primary methylsiloxane units and minor hydroxyl, oxymethylene, hydrogen and carbonyl groups. The ratio of Si O Si to Si (CH 3) n and new functional groups of OH, C O and C O are effectively “tailored” by changing plasma “high power” time. Moreover, HMDSO-pulse-polymer is a continuous, regular and compact film with a few asteroid protuberances. This deposited film becomes more regular after increasing plasma “high power” time and gradually presents perfect “straw-mat” morphology. It is indicated that pulse plasma polymerization is an effective way to tailor the surface structures of plasma polymer films through controlling plasma “high power” time.

Design of a tri-layer bottom anti-reflective coating for KrF, ArF and F2 lithographies

We report a novel tri-layer bottom antireflective coating (BARC) design based on hexamethyldisiloxane (HMDSO) films working simultaneously at 157, 193 and 248 nm wavelengths. The required optical constant for each layer can be tuned by varying the gas flow rate ratio of oxygen to HMDSO in an electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) process. The swing effect in the resist is experimentally shown to be reduced significantly by adding this tri-layer BARC structure.

Design of a tri-layer bottom anti-reflective coating for KrF, ArF and F 2 lithographies

We report a novel tri-layer bottom antireflective coating (BARC) design based on hexamethyldisiloxane (HMDSO) films working simultaneously at 157, 193 and 248 nm wavelengths. The required optical constant for each layer can be tuned by varying the gas flow rate ratio of oxygen to HMDSO in an electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) process. The swing effect in the resist is experimentally shown to be reduced significantly by adding this tri-layer BARC structure.

Characterization and protein-adsorption behavior of deposited organic thin film onto titanium by plasma polymerization with hexamethyldisiloxane

Plasma polymerized hexamethyldisiloxane (HMDSO) thin film was deposited onto titanium using a radio-frequency apparatus for the surface modification of titanium. A titanium disk was first polished using colloidal silica at pH=9.8. Plasma-polymerized HMDSO films were firmly attached to the titanium by heating the titanium to a temperature of approximately 250°C. The thickness of the deposited film was 0.07–0.35 μm after 10–60 min of plasma polymerization. The contact angle with respect to double distilled water significantly increased after HMDSO coating. X-ray photoelectron spectroscopy revealed that the deposited thin film consisted of Si, C, and O atoms. No Ti peaks were observed on the deposited surface. The deposited HMDSO film was stable during 2-weeks immersion in phosphate buffer saline solution. Fourier transform reflection–absorption spectroscopy showed the formation of Si–H, Si–C, C–H, and CO bonds in addition to Si–O–Si bonds. Quartz crystal microbalance-dissipation measurement demonstrated that the deposition of HMDSO thin films on titanium has a benefit for fibronectin adsorption at the early stage. In conclusion, plasma polymerization is a promising technique for the surface modification of titanium. HMDSO-coated titanium has potential application as a dental implant material.

XPS study of siloxane plasma polymer films

Plasma polymer films were deposited from hexamethyldisiloxane (HMDSO), dichloro(methyl)phenylsilane (DCMPS) and vinyltriethoxysilane (VTEO) on polished silicon wafers using a RF helical coupling deposition system. The composition of elements in the surface region (top 6–8 nm) of the deposited films was studied by X-ray-induced photoelectron spectroscopy (XPS) on an ADES 400 VG Scientific photoelectron spectrometer using MgK α (1253.6 eV) or AlK α (1486.6 eV) photon beams at the normal emission angle. Aging effects of plasma-polymerized (PP) HMDSO and DCMPS films stored under standard laboratory conditions were investigated by employing XPS. Post-deposition contamination and oxidation of pp-DCMPS and pp-HMDSO film was carefully observed. An increase in oxygen atoms on the film surface over time is accompanied by changes in bulk atomic concentrations. Sequential sputtering with an Ar ion-beam, together with XPS analysis, was used to measure concentration depth profiles in pp-HMDSO and pp-DCMPS films.

Feasibility of utilizing hexamethyldisiloxane film as a bottom antireflective coating for 157 nm lithography

The feasibility of utilizing a bottom antireflective coating (BARC) layer composed of hexamethyldisiloxane (HMDSO) film for 157 nm lithography is studied. The vaporized liquid HMDSO is used as a coating material in a conventional electron cyclotron resonance-plasma enhanced chemical vapor deposition process. The required optical constants of suitable HMDSO films can easily be tuned by adjusting the gas flow rate ratio of O2 to HMDSO. The swing effect is experimentally shown to be reduced significantly on Si substrates by applying either a single layer BARC or a bilayer BARC. Additionally, the bilayer BARC is shown by simulation to be capable of providing larger thickness-controlled tolerances than a single layer BARC.