Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/60—Deposition of organic layers from vapour phase
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D4/00—Coating compositions, e.g. paints, varnishes or lacquers, based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; Coating compositions, based on monomers of macromolecular compounds of groups C09D183/00 - C09D183/16
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
  • B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
  • B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
  • B05D5/083—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface involving the use of fluoropolymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/50—Multilayers
  • B05D7/56—Three layers or more
  • B05D7/58—No clear coat specified
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2913—Rod, strand, filament or fiber
  • Y10T428/2929—Bicomponent, conjugate, composite or collateral fibers or filaments [i.e., coextruded sheath-core or side-by-side type]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2913—Rod, strand, filament or fiber
  • Y10T428/2929—Bicomponent, conjugate, composite or collateral fibers or filaments [i.e., coextruded sheath-core or side-by-side type]
  • Y10T428/2931—Fibers or filaments nonconcentric [e.g., side-by-side or eccentric, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2913—Rod, strand, filament or fiber
  • Y10T428/2933—Coated or with bond, impregnation or core
  • Y10T428/2936—Wound or wrapped core or coating [i.e., spiral or helical]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/3154—Of fluorinated addition polymer from unsaturated monomers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31652—Of asbestos
  • Y10T428/31663—As siloxane, silicone or silane
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/3188—Next to cellulosic
  • Y10T428/31895—Paper or wood
  • Y10T428/31906—Ester, halide or nitrile of addition polymer

Definitions

• Fluorocarbon and organosilicon thin films produced by chemical vapor deposition have a wide variety of applications, ranging from biocompatible coatings for medical implants, to low K dielectrics in integrated circuits.
• Fluorocarbon films have been found to be biocompatible and have low dielectric constants. However, they also have a high degree of roughness and do not adhere well to silicon substrates. Silicone films are biocompatible and offer the additional advantages of excellent adhesion to silicon substrates and superior thermal stability.
• a fluorocarbon- organosilicon copolymer film therefore has the potential to incorporate the desirable attributes of each class of material into a single film.
• the addition of fluorine to organosilicon films is anticipated to lower the dielectric constant, increase electrical resistivity, reduce surface energy, increase hydophobicity, and reduce permeability to water. All of these trends are favorable for biopassivation applications.
• the copolymer films can also retain the desirable adhesion characteristics and mechanical properties of the organosilicon homopolymer. Flexible copolymer films could also be used as biopassivation coatings on biomedical device components.
• Transparent, tough, hard, scratch resistant films having extreme hydrophobicity would make excellent protective and dirt resistant coatings on window glass, windshields, and eyewear. Since the substrate remains at low temperature during the process, temperature sensitive materials such as plastics and fabrics can also be coated. Potential applications include anti-fouling coatings on marine vessels and equipment, coatings for food containers, and biological and chemical laboratory equipment.
• the hybrid copolymer can also serve as an intermediate transition layer for graded coatings such as the stack substrate-organosilicon-copolymer-fluoropolymer. Such an arrangement can produce an adherent interface with a hydrophobic surface, or even a film in which one surface is hydrophobic and the other hydrophilic.
• Organosilicon or fluorocarbon homopolymers can be coated onto surfaces by a number of techniques such as spin-on coating, casting or chemical vapor deposition.
• An important advantage of chemical vapor deposition (CVD) is the ability to create copolymers that are difficult to synthesize by bulk or solution techniques, such as fluorocarbon- organosilicon copolymers. Fluorocarbon polymers are normally synthesized by free radical polymerization, whereas polysiloxanes are made by ionic polymerization techniques. Synthesis of a copolymer would thus require a transformation from ionic polymerization to free radical polymerization (or vice versa).
• hot-filament CVD also known as pyrolytic or hot-wire CVD
• HFCVD hot-filament CVD
• a precursor gas is thermally decomposed by a resistively heated filament.
• the resulting pyrolysis products adsorb onto a substrate maintained at around room temperature and react to form a film.
• HFCVD does not require the generation of a plasma, thereby avoiding defects in the growing film produced by UV irradiation and ion bombardment.
• films produced by HFCVD have a better-defined chemical structure because there are fewer reaction pathways than in the less selective plasma-enhanced CVD method.
• HFCVD provides films with a substantially lower density of dangling bonds, i.e. unpaired electrons. Further, HFCVD has been shown to produce films that have a low degree of crosslinking. Limb, S. J., Lau, K. K. S., Edell, D. J., Gleason, E. F., Gleason, K. K. Plasmas and Polymers 1999, 4, 21. HFCVD has been used to deposit fluorocarbon films that are spectroscopically similar to poly(tetrafluoroethylene) (PTFE) as well as organosilicon films that consist of linear and cyclic siloxane repeat units. Limb, S. J., Lau, K. K. S., Edell, D.
• PTFE poly(tetrafluoroethylene)
• Favia et al. investigated the plasma-enhanced CVD of a cyclic fluorinated siloxane, (3,3,3-trifluoropropyl)methylcyclotrisiloxane.
• the authors examined the effects of varying substrate temperature and substrate bias on the deposition rate and chemical composition of the films. Films deposited with substrate temperatures below 200 °C were determined to be structurally similar to the precursor. The carbon and hydrogen content of the films was found to decrease at higher substrate temperatures along with the deposition rate. Increasing the substrate bias resulted in greater crosslinking and higher deposition rate.
• the invention provides a method for forming a copolymer thin film on the surface of a structure.
• the copolymer is a fluorocarbon-organosilicon copolymer. This is accomplished by exposing the monomer gasses of a fluorocarbon precursor and organosilicon precursor to a source of heat having a temperature sufficient to pyrolyze the monomer gasses and produce a source of reactive CF 2 and siloxane species in the vicinity of the structure surface.
• the structure surface is maintained at a substantially lower temperature than that of the heat source to induce deposition and polymerization of the CF 2 and siloxane species on the structure surface.
• the gas mixture comprises hexafluoropropylene oxide and hexamethylcyclotrisiloxane
• the heat source preferably is a resistively-heated conducting filament suspended over the structure surface or a heated plate having a pyrolysis surface that faces the structure.
• the heat source temperature is preferably greater than about 400K and the structure surface is preferably maintained at a temperature less than about 300K.
• the structure on which surface the film is formed can be, for example only, a length of wire, a substrate, a neural probe, a razor blade, a ribbon cable, or a microstructure having multiple surfaces all maintained at a temperature substantially lower than that of the heat source.
• the invention provides a method for coating a non planar and flexible structure with a flexible fluorocarbon-organosilicon copolymer film.
• the coating is accomplished by exposing the structure to an environment in which monomer gasses are pyrolyzed to produce reactive CF 2 and organosilicon species.
• the invention also provides a method for substantially encapsulating a length of wire in a flexible fluorocarbon-organosilicon copolymer thin film.
• the wire length is supported on a wire holder such that surfaces of the wire length are substantially unmasked and portions of the wire length are out of contact with each other.
• the encapsulation process includes the step of exposing the monomer fluorocarbon and organosilicon gasses to a heat source to pyrolyze the monomer gasses and produce a source of reactive CF 2 and organosilicon species in the vicinity of the wire length, which is, e.g., between about 10 microns and 100 microns in diameter.
• the wire length is maintained at a temperature substantially lower than that of the heat source to induce deposition and polymerization of the CF 2 and organosilicon species on the wire length.
• a method for casting a flexile structure in a desired configuration This is accomplished by deforming the structure into the desired configuration and exposing the deformed structure to an environment in which monomer gasses of a fluorocarbon and organosilicon are pyrolyzed at high temperatures to form reactive monomeric species. Exposure of the deformed structure to the reactive monomeric species is maintained for a duration sufficient to produce on the deformed structure a fluorocarbon-organosilicon copolymer film having a thickness of more than about 5 microns.
• the invention also provides a length of twisted wire that includes a plurality of entwined wires and a flexible fluorocarbon-organosilicon copolymer thin film encapsulating the entwined wire plurality along at least a portion of the twisted wire length. Also provided by the invention is a length of tubing that includes a thin-walled, flexible polymeric cylinder and flexible fluorocarbon-organosilicon copolymer thin film on an outer surface of the cylinder along at least a portion of the tubing length.
• a neural probe in another aspect, there is provided by the invention a neural probe.
• the neural probe includes a substantially cylindrical shaft portion having a diameter less than about 100 microns and a tip portion connected to the shaft portion by a tapered shaft portion.
• the tip has a diameter less than about 15 microns.
• a flexible fluorocarbon-organosilicon copolymer film encapsulates the tapered shaft portion and cylindrical shaft portion of the probe.
• the invention additionally provides a substrate having a fluorocarbon-organosilicon copolymer thin film of less than 20 microns in thickness thereon; and further provides a microfabricated electronic circuit including at least one conducting layer having a fluorocarbon-organosilicon copolymer thin film of less than about 20 microns in thickness thereon.
• the polymer thin film on the substrate or conducting layer has a dangling bond density of less than about 10 18 spins/cm 3 .
• the invention is also drawn to a fluorocarbon-organosilicon copolymer coating prepared by HFCVD methods where monomeric fluorocarbon and organosilicon gasses are pyrolyzed to form reactive CF 2 and organosilicon species which copolymerize at ambient temperatures.
• the invention is also drawn to an apparatus for carrying out HFCVD of two or more monomeric gasses to form a copolymer film on a structure surface.
• Figure 1 depicts deposition rates of HFCVD films deposited from V 3 D and PFOSF as a function of filament temperature (T f ). Data points marked with circles are for films deposited from V 3 D 3 and PFOSF. The data point marked with a square represents a film deposited from V 3 D 3 alone.
• Figure 2 depicts TGA analysis of the HFCVD films deposited from V 3 D 3 and
• Figure 3 depicts environmental scanning electron micrographs of HFCVD wire coatings on 50 ⁇ m diameter platinum wires deposited from V 3 D and PFOSF at filament temperatures of (a) 540 °C, (b) 440 °C, and (c) 370 °C.
• Figure 4 depicts FTIR spectra of (a) copolymer film, (b) silicone film and (c) fluorocarbon film, all deposited by HFCVD under the same conditions.
• the fluorocarbon precursor is HFPO and the silicone precursor is D 3 .
• Figure 5 depicts the low wavenumber region from an FTIR spectrum of the fluorocarbon-organosilicon copolymer deposited from D 3 and HFPO.
• Figure 6 depicts FTIR spectrum of the HFCVD film deposited from V 3 D 3 and PFOSF at a filament temperature of 370 °C.
• Figure 7 depicts a carbon (Is) high-resolution x-ray photoelectron spectroscopic scan of the HFCVD copolymer film deposited from D 3 and HFPO, showing CF 2 and CH 3 peaks.
• Figure 8 depicts solid-state 19 F NMR spectrum of the HFCVD copolymer film deposited from D and HFPO. The feature at -72 ppm is a spectrometer artifact.
• Figure 9 depicts solid-state 13 C NMR spectra of the HFCVD copolymer film deposited from D 3 and HFPO, obtained with (a) ⁇ and (b) 19 F decoupling.
• Figure 10 depicts solid-state 29 Si NMR spectra of the HFCVD copolymer film deposited from D 3 and HFPO, obtained with (a) ! H and (b) 19 F cross-polarization and decoupling.
• Figure 11 depicts a solid-state 19 F NMR spectrum of the HFCVD film deposited from V 3 D 3 and PFOSF at a filament temperature of 370 °C. The feature at -72 ppm is a spectrometer artifact.
• Figure 12 depicts solid-state I3 C NMR spectra of the HFCVD film deposited from V D 3 and PFOSF at a filament temperature of 370 °C obtained with (a) 19 F decoupling and (b) 1H decoupling.
• Figure 13 depicts 13 C NMR spectra of the HFCVD films deposited from V 3 D 3 and PFOSF at filament temperatures of (a) 370 °C, (b) 440 °C, and (c) 540°C.
• Figure 14 depicts 29 Si NMR spectra of the HFCVD films deposited from V 3 D 3 and PFOSF at filament temperatures of (a) 370 °C, (b) 440 °C, and (c) 540°C.
• Figure 15 depicts the basic structure of an exemplary neural probe that bears a coating of the present invention.
• Figure 16 depicts the "stud-pull" adhesion test used to quantify strength of the adhesion to a surface of a fluorocarbon-organosilicon copolymer film of the present invention.
• Figure 17 depicts a CVD reactor and a hot filament array used to deposit the copolymer films of the present invention on a surface.
• copolymer as used herein means a polymer of two or more different monomers.
• fluorocarbon as used herein means a halocarbon compound in which fluorine replaces some or all hydrogen atoms.
• organosilicon as used herein means a compound containing at least one Si-C bond.
• chemical vapor deposition means a process which transforms gaseous molecules or radicals into solid material in the form of thin film or powder on the surface of a substrate.
• carrier as used herein means a reactive intermediate that has the general formula R 2 C:, in which carbon has only a sextet of electrons.
• HFPO hexafluoropropylene oxide, an epoxide of the formula CF 3 CF(O)CF 2 and presented below.
• D units as used herein means a chemical unit of formula -OSi(CH 3 ) 2 -.
• D 3 as used herein means hexamethylcyclotrisiloxane, a cyclic compound of the formula (-OSi(CH 3 ) 2 -) 3 and presented below.
• D 4 as used herein means octamethylcyclotetrasiloxane, a cyclic compound of the formula (-OSi(CH 3 ) 2 -) 4 and presented below.
• PFOSF perfluorooctane sulfonyl fluoride
• biopassivation means the property of a structure surface that renders the structure impervious to its biological environment.
• the repeat units in the copolymer film consist of fluorocarbon units, siloxane units, and linkages between them. Spectroscopic data indicates that the fluorocarbon content of the films is almost entirely in the form of CF and that siloxane D units are present in both linear and cyclic form.
• copolymer linkages There are four distinct types of copolymer linkages.
• the Si-CF 2 Si linkage can be present between siloxane rings or between rings and linear siloxane groups.
• the (CH 3 ) 2 Si(CF 2 )(O) link is linear, and could act as a junction between linear siloxane segments and fluorocarbon units.
• (O) 2 Si(CF 2 ) 2 units are branch points, and can be present in siloxane rings or in linear chains.
• the (O) 3 Si(CF 2 ) unit which is present in low concentration, is a crosslinking group.
• siloxane rings in the film have some degree of CF 2 substitution, and hence these can also be considered as crosslinking groups and branch points. Since there is no evidence of tertiary carbon, crosslinking and branching occur entirely via these siloxane moieties.
• Chain termination takes place primarily with siloxane rings (Si-Si bonding between the repeat unit and the terminating ring). Termination could also occur by means of CF 3 CF 2 Si or CF CF 2 CF 2 , but the concentration of these linkages is small.
• films deposited via hot- filament CVD have well-defined compositions.
• PECVD-deposited fluorocarbon films comprise a variety of CF groups (e.g., CF 3 , tertiary C, and C-F, in addition to CF 2 ), while HFCVD-deposited fluorocarbon films consist almost entirely of CF 2 , along with a small amount of CF 3 moieties.
• the initiating and terminating groups in HFCVD are well-defined; whereas the precursors in PECVD processes undergo much greater fragmentation (these films have Si-F bonds, for instance, that result from total fragmentation of the fluorocarbon precursors).
• a consequence of the nature of the HFCVD process is that only the most thermally stable groups (e.g., CF 2 and siloxane rings) appear in the film, resulting in more thermally stable films.
• HFCVD films do not contain defects seen in PECVD films.
• HFCVD films do not have dangling bonds, which are always produced in PECVD processes. Dangling bonds are unpaired electrons left behind in the film. If such bonds are present, the film will undergo reactions with components of the ambient atmosphere (such as water, for instance, resulting in a large number of hydroxyl groups). Therefore, PECVD films are more susceptible to atmospheric ageing, and degradation of their optical, electrical and chemical properties.
• films produced by HFCVD processes are less dense than those produced by plasma- enhanced CVD processes. Due to the differences between the nucleation and growth mechanisms the two processes, it is possible to make porous films using HFCVD, but not using PECVD. Porosity is an important property for semiconductor applications because it allows further lowering of the dielectric constant of existing low- ⁇ materials by virtue of the low dielectric constant of air.
• the fluorocarbon radical subsequently combines with the propagating species, difluorocarbene (CF 2 ), which is generated by the pyrolysis of HFPO.
• the use of PFOSF resulted in higher deposition rates, more efficient utilization of HFPO, and endcapping by CF groups.
• PFOSF can be used as an initiator in the HFCVD of polymeric films from a cyclic vinylmethylsiloxane, l,3,5-trivinyl-l,3,5-trimethylcyclotrisiloxane (V 3 D 3 ).
• V 3 D 3 cyclic vinylmethylsiloxane
• use of PFOSF allows rapid deposition of films at relatively low filament temperatures.
• Spectroscopic characterization shows that chain propagation occurs by polymerization across the vinyl bonds of V 3 D 3 .
• This HFCVD process thus resembles classical free radical polymerization of vinyl monomers driven by an initiator. Odian, G. Principles of Polymerization, Wiley-Interscience: New York, 1991. The synthetic approach described in this work can be applied to other vinyl monomers.
• V 3 D 3 in this HFCVD process is initiated by reactions between fluorocarbon radicals and vinyl groups in the V 3 D 3 molecules. Radical species generated by these reactions can react with other V 3 D 3 molecules to propagate chains along vinyl bonds. These chains consist of hydrocarbon backbones with siloxane rings as pendant groups. Cross-linking between chains occurs if more than one vinyl group on any V 3 D 3 molecule undergoes initiation and propagation reactions. Chain termination occurs when these propagating chains react with fluorocarbon radicals, sulfonyl fluoride radicals or with other propagating chains. As the filament temperature is increased, vinyl abstraction from the silicon atoms becomes more prevalent, as does breakdown of the siloxane rings to vinylmethylsilanone. As a result, the concentration of siloxane rings decreases and the films consist of polymer chains with siloxane backbones. Furthermore, these siloxane chains have a high degree of crosslinking via T groups. Tliermal Analysis
• Figure 2 shows the TGA results for films deposited at 370 °C, 440 °C, and 540 °C.
• the six-membered cyclic siloxane, hexamethylcyclotrisiloxane, is known to be more thermally stable than linear poly(dimethylsiloxane) (PDMS).
• PDMS linear poly(dimethylsiloxane)
• the siloxane rings are the repeat units, and the structure takes advantage of the superior thermal stability of the siloxane rings relative to linear PDMS.
• the HFCVD f lm deposited using a filament temperature of 370 °C is similar to this type of architecture since the structure consists of carbon backbone chains with siloxane ring pendant groups. Individual siloxane rings can be connected to more than one carbon chain since more than one vinyl group on a ring can undergo polymerization.
• the HFCVD film deposited at 540 °C is almost completely devoid of ring structures, and would therefore have lower thermal stability relative to the 370 °C film.
• the onset of thermal decomposition of the 370 °C film occurs at a higher temperature compared to the 540 °C film ( Figure 2).
• the film deposited at 440 °C lies in-between, consistent with a mixture of rings and linear units in the film structure.
• the chemical structure of fluorocarbon-organosilicon films synthesized from V 3 D 3 and PFOSF by HFCVD is dependent on filament temperature.
• the films are comprised of carbon-oackbone polymer chains with siloxane rings as pendant groups, whereas at higher filament temperatures the films consist of linear siloxane chains crosslinked via T groups.
• the retention of the siloxane ring structure confers greater thermal stability on the low filament temperature films.
• the high concentration of T groups in the high filament temperature films is manifest in the form of brittleness observed in wire coatings. Overall, the 370 °C film appears to be the best candidate for biomedical applications based on its flexibility and thermal stability. J-Ptre Coatings
• Figure 3 shows micrographs of wire coatings made from V 3 D 3 and PFOSF at the same set of filament temperatures.
• the wires were tied into loops to examine the flexibility of the copolymer coating.
• the difference in chemical composition manifests itself in the form of brittleness, which increases as filament temperature is increased.
• the film deposited with a filament temperature of 540 °C cracks extensively when the wire is bent and peels off almost completely.
• the 440 °C coating is marginally better, and the 370 °C coating shows no apparent cracking. This trend is consistent with the brittleness observed with increasing T group concentration in organosilicon films deposited by plasma CVD by Cech et al.
• Fluorocarbon coatings with a high degree of crosslinking were found to be more brittle than those comprised of mostly linear chains.
• Figure 4 shows the FTIR spectrum of a copolymer film compared with the spectra of homopolymeric fluorocarbon and silicone films obtained from HFPO and D 3 respectively.
• Table 1 gives the absorption band assignments from the literature. All of the bands associated with the pure fluorocarbon and the pure silicone film appear in the hybrid film, although slight shifts in position occur in some of the bands.
• Table 1 Absorption Band Assignments for FTIR Spectra
• FTIR bands in all three HFCVD films in Fig. 4 are relatively narrow (FWHM of ⁇ 60 cm “1 or less), aiding in the resolution of specific chemical environments.
• FWHM ⁇ 60 cm "1 or less
• the symmetric (1155 cm “1 ) and asymmetric (1223 cm “1 ) CF 2 stretches can be clearly resolved in Fig. 4(c).
• the narrowness of the FTIR bands thus indicates the structural simplicity of the HFCVD copolymer films.
• the asymmetric stretching mode (ASM) of the siloxane (Si-O-Si) group is also easily resolvable.
• the region around these bands in the copolymer spectrum is expanded for detail in Figure 5.
• the ASM appears as a doublet, as in the case of polydimethylsiloxane chains with three or more siloxane units, or ring structures of more than eight siloxane units.
• Si-C stretching bands appear at 808 and 848 cm “1 .
• the copolymer spectrum contains both of these bands and a third band at 899 cm “1 .
• the Si-C stretching mode is dependent on the vibrations of the substituents on the silicon atom. Matsurra, H., Ohno, K., Sato, T., Murata, H. J. Mol. Struct. 1979, 52, 13. Hence it is likely that the band at 899 cm “1 is due to the Si-C stretching mode of a siloxane moiety that has both methyl and CF 2 substituents bonded to silicon.
• the bands at 2913 and 2967 cm “1 represent the symmetric and asymmetric stretching modes of the CH bond in sp 3 CH 3 respectively.
• the absence of sp 3 CH 2 bands indicates that there is no crosslinking through methylene bridges.
• Figure 6 shows the FTIR spectrum of the film deposited from V 3 D 3 and PFOSF at a filament temperature of 370 °C.
• the asymmetric stretching mode (ASM) of the siloxane (Si-O-Si) group appears as a doublet with the low wavenumber band more intense than the high wavenumber band.
• Table 2 summarizes atomic composition data obtained from a survey scan.
• the Si:0 ratio is approximately 1:1.13.
• the high-resolution Si (2p) scan (not shown) contains a single peak with no apparent shoulders.
• the line width of this peak is slightly larger than that obtained from a film deposited under the same conditions using D 3 only.
• the line width of the Si (2p) peak indicates the possibility of a small concentration of different oxidation states.
• a C Is high-resolution scan ( Figure 7) indicates the presence of only two types of carbon moieties, CF 2 and CH 3 .
• the respective assignments at 290.0 eV and 282.8 eV were made using data obtained from a pure fluorocarbon and a pure silicone film.
• Figure 9 shows the 13 C NMR spectra obtained with ! H and 19 F decoupling. Chemical shift assignments for these spectra are summarized in Table 4. Assignments for peaks (i)-(i ⁇ ) are taken from the literature. Ovenall, D. W., Chang, J. J. J. Magn. Reson. 1977, 25, 361 ; Kaplan, S., Dilks, A. J. Appl. Polym. Sci. : Appl. Polym. Symp. 1984, 38, 105; Mallouk, T., Hawkins, B. L., Conrad, M. P., Zilm, K., Maciel, G. E., Bartlett, N. Phil. Trans. R. Soc. Lond.
• the peak at -6.4 ppm is assigned to the ⁇ -R 3 environment in the copolymer film.
• the o-R 3 represents a ring structure of three siloxane units that is bound to the film structure by Si-Si bonds. The presence of these groups is attributed to a reaction pathway involving abstraction of one or more methyl groups in D 3 with retention of the ring structure.
• the absence of peaks at -9 and -19 ppm suggests that all of the siloxane ring structures have some degree of fluorocarbon substitution.
• the peak at 0 ppm is assigned to linear siloxane units with two methyl groups and one CF 2 unit bonded to each silicon atom.
• Figure 11 shows the 19 F NMR spectrum of a film deposited from V 3 D and PFOSF at a filament temperature of 370 °C.
• Chemical shift assignments are given in Table 6. The peaks in this spectrum can be divided into three groups. The peaks between -140 and -100 ppm are due to fluorine atoms in CF 2 groups. The peaks between -100 and -50 ppm are due to fluorine atoms in CF 3 groups. The single peak at 55.6 ppm is due to fluorine atoms in S0 2 F groups. Table 6. Chemical Shift Assignments for the 19 F Spectrum.
• Equation 3 The appearance of the CF 3 CF 2 CH 2 group and the CF 3 CH 2 group suggest that some of the perfluorooctane radicals generated by the pyrolysis of PFOSF are capable of further breakdown as shown in Equation 3. These reactions could proceed by separation of CF 2 units from the perfluorooctane chains in the form of difluorocarbene. Alternatively, the CF 2 units could leave the chains in pairs, as tetrafluoroethylene. The radicals generated in these reactions could then react with V 3 D 3 molecules by pathways analogous to Equation 2.
• the chemical shift of fluorine atoms in SO 2 F groups is between 40 and 70 ppm and depends on the nature of atoms bonded to the sulfur atom. Banks, R. E. Fluorocarbons and their Derivatives, 2nd ed.; MacDonald Technical and Scientific: London, 1970; p 237. For instance, the chemical shift of CF 2 SO 2 F* is around 45 ppm, and that of CH 2 SO 2 F* is approximately 53 ppm. Hollitzer, E.; Sartori, P. J. Fluor. Chem. 1987, 35, 329. The peak at 55.6 ppm is assigned to a moiety similar to the latter, CH(Si)S0 2 F*.
• the 13 C NMR spectra indicate that the ratio of CF 2 groups to CF groups is much smaller (approximately 2:1), providing support for further breakdown of these chains as given by Equation 3.
• the CF 2 /CF 3 ratio calculated from the 13 C spectra is in quantitative agreement with that calculated from the 19 F spectrum. The latter ratio is given by (sum of all CF 2 * peak areas/2)/(sum of all CF 3 * peak areas/3). This calculation indicates that the 13 C spectra are consistent with the 19 F spectrum.
• the chemical shifts of CH 2 groups and CH groups can vary significantly with position on a carbon backbone.
• the chemical shifts of the first CH 2 group (CH 3 CH 2 CH 2 CH 2 CH 3 ) and the second CH 2 group (CH 3 CH 2 CH 2 CH 3 ) are 22.8 ppm and 34.8 ppm respectively.
• the width of the 12-41 ppm peak is thus consistent with carbon-backbone polymer chains of varying lengths.
• Figure 13 shows the 13 C NMR spectra of the V 3 D 3 films produced at three different filament temperatures. Chemical shift assignments for these spectra are given in Table 7. In our prior investigation of the chemical structure of films deposited at a filament temperature of 370 °C, 9 the peak between 12 and 41 ppm was shown to be evidence of carbon-backbone chains formed by polymerization across the vinyl bonds of V 3 D 3 (Equation 4).
• "I” represents a fluorocarbon initiator fragment produced by the thermal decomposition of PFOSF. S. K. Murthy, B. D. Olsen, K. K. Gleason Langmuir 18, 6424 (2002).
• Figure 14 shows 29 Si NMR spectra of the same set of films, with peak assignments listed in Table 8.
• T group formation Another requirement for T group formation is the creation of a third Si-O bond.
• the six-membered siloxane rings would either have to open or break down. It is known that scission of the Si-O bond in cyclic siloxanes to produce diradicals of the form • Si(CH 3 ) 2 (OSi[CH 3 ] 2 ) n O- is unlikely. L. E. Guselnikov, N. S. Nametkin Chem. Rev. 19, 529 (1979); and M. G. VoronkovJ. Organomet. Chem. 557, 143 (1998). It is therefore postulated that the first step in T group formation is the breakdown of the six-membered ring to yield a dimer and monomer as illustrated in Equation 6.
• the second step in the formation of T groups would then be reaction of vinylmethylsilanone with a vinyl-abstracted siloxane group, as shown in Equation 7.
• the radical species produced by this reaction could undergo propagation reactions with other dimethylsilanone molecules, or termination reactions with fluorocarbon radicals.
• the 29 Si NMR spectrum of the precursor V 3 D 3 contains only one peak at -22 ppm. This peak appears in the spectrum of the film deposited at the lowest filament temperature
• Figure 14a is assigned to the vinylmethylsiloxane group in a ring structure of three siloxane units. Also present in Figure 14a is a peak at -10.9 ppm, which is assigned to the siloxane group in a pendant ring that is directly bonded to a carbon-backbone chain (peak i in Table 8; see reaction 4). Since both of the carbon atoms attached to the silicon atom of interest in this moiety are sp 3 hybridized, its chemical shift is close to the -10 ppm shift reported for the dimethylsiloxane groups in hexamethylcyclotrisiloxane. Pryce Lewis, H. G.; Casserly, T. B.; Gleason, K. K. J.
• the concentration of vinyl groups is highest in Figure 14a (as evidenced by the presence of the -22 ppm peak and the intensity of the -33.7 ppm peak), a result that is consistent with the 13 C NMR data.
• the peaks between -10 and -34 ppm indicate that the siloxane groups in the films are primarily in the form of rings when the filament temperature is low. At higher filament temperatures, these groups are mainly in linear chains.
• the proposed mechanism for the conversion of six-membered siloxane rings into linear chains is via equation 6 and subsequent reaction of the vinylmethylsilanone molecules to form linear siloxane chains as shown in Equation 8. These chains could also undergo vinyl-abstraction reactions and form cross-links via T groups in pathways analogous to Equations 5 and 7.
• Biopassivating coatings i.e., coatings that insulate an article and render it impervious to its biological environment, are generating an increased amount of attention as many biomedical and other applications are not optimally addressed by available coatings in the art such as polytetrafluoroethylene, also known as PTFE, (CF 2 ) n , and Teflon TM, for example.
• PTFE polytetrafluoroethylene
• Teflon TM Teflon TM
• Biologically-implantable devices such as neural probes, catheter inserts, implantable tubing, and other such devices, all of which are becoming increasingly complicated in geometry, are preferably encapsulated with a film to render the devices impervious to a biological environment, rather than being housed in a bulky PTFE package structure.
• Such implantable devices typically require of an encapsulating film not only the desired biological compatibility, but due to complex topology and connections to lead wires and associated circuitry, also inherently require an encapsulating film to be conformal and thin, as well as electrically insulating, tough, and flexible. Such a film should further be a good permeation barrier against the implantation environment.
• the fluorocarbon- organosilicon copolymer coatings of the present invention show improved biopassivation properties over the organosilicon polymers alone in saline soaking tests. Additionally, the fluorocarbon-organosilicon copolymer coatings have lower dielectric constants and increased hydrophobicity relative to organosilicon coatings alone. All of which favors increased biopassivation. Rigidity/Flexibility as a factor of crosslinking
• the flexibility of the copolymer coatings of the present invention makes them ideally suited for the many applications listed below. For instance it would not be desirable to have coated wires in biomedical applications that are brittle and flake under strain. In this area, organosilicon coatings have been lacking, but fluorocarbon coatings have performed well. By copolymerizing the organosilicon and fluorocarbon active species, the coatings of the present invention improve upon the flexibility of organosilicon coatings alone.
• Coating rigidity/flexibility is a function of the amount of crosslinking between the polymer chains.
• HFCVD is advantageous over plasma enhanced chemical vapor deposition (PECVD) in this regard as fewer number of side reactive species capable of forming crosslinking bonds are formed during HFCVD.
• PECVD plasma enhanced chemical vapor deposition
• lower filament temperature results in less crosslinking and therefore less rigidity and brittleness.
• the present invention offers a way of tuning the degree of flexibility according to the application by adjusting the filament temperature.
• Various techniques may be used to quantify the degree of crosslinking in a coating of the present invention. For example, peak area calculations using 29 Si NMR data may be used. However, the 9 Si NMR spectra must have been acquired without cross-polarization in order for the data to useful for quantification of crosslinking.
• crosslinking can be made by comparing peak areas within a spectrum. For example, if a film has a large number of crosslinking groups, e.g., (0) 3 Si(CF 2 ), relative to other groups, then significant crosslinking can be inferred.
• the flexibility of the coatings of the present invention may be quantified using the technique of nano-indentation. This technique enables the measurement of the modulus and toughness of thin films. Adhesion
• a useful film has to have good adherence to the surface upon which it is coated.
• organosilicon films have performed well but fluorocarbon films have been lacking. It is therefore expected that a copolymer film between fluorocarbons and organosilicons will improve adherence over fluorocarbon films alone. Indeed, this is what is observed.
• 2 micron films were deposited on silicon wafers via HFCVD.
• Copolymer films of two compositions were analyzed: fluorocarbon-rich and organosilicon-rich. The results are presented in Table 9 below. Table 9. - Adhesion values for various polymers and copolymers.
• Performance enhancement is possible with SCF CO 2 due to the unique properties of the supercritical phase, including low viscosity, negligible surface tension, high diffusivity relative to the gas phase, and a density similar to that of the liquid phase.
• the solvating capability of SCF CO 2 towards the fluorocarbon-organosilicon copolymer films can be fine-tuned by temperature and pressure control.
• SCF CO 2 suitable as a developer for HFCVD fluorocarbon-organosilicon system, as well as for fluorinated resists patterned with small and high aspect ratio features that may otherwise experience pattern collapse due to surface tension from aqueous developers.
• HFCVD film formation and dry development present a unique processing combination with impressive environmental and safety advantages over current solvent-based spin-on coating and aqueous development.
• Solvent -based technologies typically generate large quantities of liquid waste that is hazardous and costly to dispose of.
• HFCVD techniques generate only gaseous effluent and CVD chemistries can be designed to minimize the toxicity of this effluent.
• CO 2 is non-toxic, non-flammable, recyclable material that is typically collected from waste-streams of other synthetic processes and is available at a low cost with no waste generation.
• the advantage of HFCVD deposition of a fluorocarbon and organosilicon to form a fluorocarbon-organosilicon copolymer upon a structure surface is that the fluorocarbon- organosilicon copolymer combines the desirable properties of the fluorocarbon with the desirable properties of the organosilicon.
• those properties include low dielectric constants, high resistivity, low surface energy, high hydrophobicity, and flexibility.
• the desirable properties include superior thermal stability, better adhesion to silicon substrates, smooth films, and they are suitable for implantations. However, both individual coatings also possess undesirable properties.
• Fluorocarbons have high degrees of roughness and poor adhesion to silicon substrates.
• Organosilicons have lower resistivity and higher dielectric constants.
• a multilayer approach would not only be able to exploit the advantageous properties of both types of coatings more effectively, but is also particularly well suited to CVD techniques.
• only one gaseous monomer would initially be fed into the HFCVD chamber depositing a first layer upon a structure surface.
• a pure organosilicon layer would be deposited upon a surface to take advantage of its superior adhesion properties.
• the composition of the feed gas would be varied to include a fluorocarbon so that the next layer is a fluorocarbon-organosilicon copolymer.
• the composition of the feed gas would then be varied again resulting in an outer layer of just the fluorocarbon polymer to take advantage of its high resistivity, low surface energy, and high hydrophobicity.
• the hybrid interlayer is for compatibility between the outer organosilicon and fluorocarbon layers.
• Compositional changes can be made by varying the feed gas and process conditions in real time offering the potential for a wide range of coating properties.
• an organosilicon monomer used in a method of the present invention may be selected from the group of suitable organosilicons.
• the organosilicon monomer used may be hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, 1,3,5- trivmyl-l,3,5-trimethylcyclot ⁇ isiloxane, l,3,5,7-tetravinyl-l,3,5,7- tetramethylcyclotrisiloxane, 3 -(N-allylamino)propyltrimethoxysilane, allyldichlorosilane, allyldimethoxysilane, allyldimethylsilane, allyltrichlorosilane, allyltrimethoxysilane, allyltrimethylsilane, bis(dimethylamino)vinylmethylsilane, para-(t- butyldimethylsiloxy)styrene
• a halocarbon monomer used in a method of the present invention may be selected from the group of suitable halocarbons.
• the halocarbon monomer used may be hexafluoropropylene oxide, tetrafluoroethylene, hexafluorocyclopropane, octafluorocyclobutane, perfluorooctanesulfonyl fluoride, octafluoropropane, trifluoromethane, difluoromethane, difluorodichloromethane, difluorodibromomethane, difluorobromomethane, difluorochloromethane, trifluorochloromethane, tetrafluorocyclopropane, tetrachlorodifluorocyclopropane, trichlorotrifluoroethane, or dichlorotetrafluorocyclopropane.
• Jet Engine Components Turbo Pump Components, Chemical Processing Equipment, Dairy Process Equipment, Marine Components, Power Tool Components, Photocopier Parts, Printing Equipment Pump Components, Web Press Parts, Automotive Components
• FTIR Fourier-transform infrared
• 29 Si NMR was performed with proton cross-polarization (CP) and proton decoupling to enhance the signal and resolution from the low natural abundance 29 Si nuclei.
• the ⁇ - ⁇ Si CP time was 5ms and the 90° pulse width was 1.3 ⁇ s.
• 29 Si spectra were also obtained with fluorine cross-polarization and fluorine decoupling. The purpose of this was to determine which silicon atoms were in close proximity ( ⁇ 10 A) to fluorine-containing moieties. Contact time experiments indicated that a CP time of 5 ms was sufficient to maximize signal intensity.
• the 90° pulse width for these measurements was 1.2 ⁇ s. 29 Si chemical shifts were externally referenced to tetramethylsilane.
• 19 F NMR spectra were obtained by direct polarization with a 90° pulse width of 1.2 ⁇ s. Chemical shifts were externally referenced to trichlorofluoromethane. 13 C spectra were obtained by direct polarization with proton decoupling as well as direct polarization with fluorine decoupling. The 90° pulse width was 1.8 ⁇ s for both types of spectra. C chemical shifts were externally referenced to tetramethylsilane. Deposition Methods Start up Procedure
• the interior of the deposition chamber was cleaned thoroughly with paper towels and Scotch Brite soaked in acetone or isopropanol.
• the filament wire was then strung onto the holder, and the holder was placed inside the reactor and connected to the power supply.
• the chamber was then evacuated.
• the filament voltage was then raised to 86.5V over a 5 min span.
• HFPO was then flowed into the chamber at a rate of 30 seem with the chamber pressure maintained at 1 Torr for 20 min.
• the chamber was then evacuated, and the filament power was turned down over a 5 min span. After turning off the power the filament completely, the chamber was pumped up to atmospheric pressure. The filament holder was removed, and the interior of the chamber was cleaned as described above.
• the substrate and filament holder were then placed on the stage.
• the filament holder was then connected to the power supply and the chamber was pumped down to vacuum. Filament power was raised to 86.5V over a 5 min span.
• the valve on the D3 line was opened to the appropriate setting, followed by the valve on the HFPO line.
• the chamber pressure was then set to 1 Torr.
• Depositing the Copolymer Film Depositions were performed in a custom-built vacuum chamber on to silicon wafer substrates. Pressure within the chamber was controlled by a butterfly valve connected to a PI controller.
• Substrates were placed on a stage maintained at a low temperature (15 + 5 °C) by the circulation of chilled water through internal coils.
• Precursor breakdown was achieved by means of a resistively heated nichrome (80% nickel, 20% chromium; Omega Engineering) wire 0.038 cm in diameter.
• the frame holding the filament wire was equipped with springs to compensate for thermal expansion of the wire upon heating.
• the distance between the filament wire and the substrate was 1.4 cm.
• Filament temperature was measured by a 2.2 ⁇ m infrared pyrometer. The spectral emissivity was estimated to be 0.85 based on direct contact thermocouple experiments.
• the flow of fluorocarbon precursor, hexafluoropropylene oxide gas (HFPO), into the chamber was controlled by an MKS Model 1295C Mass Flow Controller (MFC).
• MFC Mass Flow Controller
• the silicone precursor, hexamethylcyclotrisiloxane (D 3 ) was vaporized in a stainless steel vessel that was heated to 90 + 5°C.
• the lines leading from the vessel to the vacuum chamber were maintained at 130 + 5 °C.
• Flow of vapor from the vessel into the chamber was regulated by a needle valve.
• Depositions were performed at a filament temperature of 620°C and a chamber pressure of 1 Torr. Precursor flow rates were 20 seem for HFPO and 28 seem for D 3 . The duration of these depositions ranged between 10 min and 30 min. The deposition rate, determined by profilometry, was approximately 250 A/min.
• V3D3 Polymerization Film depositions were carried out in a custom-built vacuum chamber described previously. Precursor breakdown was achieved by use of a resistively heated 0.038-cm- diameter Nichrome wire (80% nickel, 20% chromium; Omega Engineering). The filament temperature was measured using a 2.2 ⁇ m infrared pyrometer with a spectral emissivity of 0.85. V 3 D 3 (Gelest) was vaporized in a stainless steel vessel that was heated to 110 + 5 °C and fed to the reactor through a line maintained at 140 + 5 °C.
• V 3 D and PFOSF (Aldrich) was vaporized in a glass container held at 60 ⁇ 5 °C and fed through a line held at 90 ⁇ 5 °C.
• the flow of both V 3 D and PFOSF into the reactor was regulated by needle valves. Depositions were carried out at a range of filament temperatures between 350 and 540 °C with a chamber pressure of 0.5 Torr. For all depositions, the flow rates of V 3 D 3 and PFOSF were 23 seem and 12 seem respectively.
• the stage supporting the substrate was maintained at 25 ⁇ 2 °C. Film thickness was measured by profilometry, using a Tencor P-10 Surface Profiler.
• thermogravimetric analysis films were deposited on silicon wafers at filament temperatures of 370, 440, and 540 °C.
• NMR nuclear magnetic resonance
• TGA thermogravimetric analysis
• longer duration depositions approximately 60 minutes long were carried out to prepare 14-16 mg samples for each of the three filament temperatures.
• Sample preparation for TGA was done by scraping films off wafers and loading into a platinum pan covered with aluminum foil.
• TGA was performed on a Perkin Elmer TGA 7 analyzer using nitrogen as the purge gas with a flow rate of 20 ml/min. Samples were held at 40 °C for 3 min and then heated to approximately 450 °C at a rate of 10 °C/min.
• the instrument used is a Sebastian I Adherence Tester made by Quad Group, and the procedure is as follows.
• the samples being analyzed were typically cut into 2 cm 2 pieces.
• 2.7 mm epoxy coated aluminum pull studs also supplied by Quad Group) were secured onto the test surface by means of clips.
• the sample was then placed in an oven to cure the epoxy at a temperature of 150 degrees C for about 1 hour.
• the sample was then allowed to cool to room temperature.
• the sample was then mounted onto the adherence tester. The device clamped the stud and pulled it with a measured force until the stud was pulled off the sample surface.

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