Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/28—Materials for coating prostheses
  • A61L27/34—Macromolecular materials
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L29/00—Materials for catheters, medical tubing, cannulae, or endoscopes or for coating catheters
  • A61L29/08—Materials for coatings
  • A61L29/085—Macromolecular materials
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L31/00—Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
  • A61L31/08—Materials for coatings
  • A61L31/10—Macromolecular materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y40/00—Manufacture or treatment of nanostructures
• • 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
  • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
  • Y10T428/261—In terms of molecular thickness or light wave length
• • 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
  • Y10T428/31667—Next to addition polymer from unsaturated monomers, or aldehyde or ketone condensation product

Definitions

• the present invention pertains to the surface treatment of implants and devices used in medical applications which require hydrophilic, biocompatible interfaces with bodily tissues and fluids.
• the ability of the implant to integrate into the location at which it is placed and to function in combination with surrounding tissues and fluids depends significantly on the hydrophilicity or hydrophobicity of the implant surface, and frequently depends on the presence or absence on the surface of the implant of chemical compounds having particular properties.
• the device With respect to a medical device surface used for chemical analysis, for example, the device must provide a functional surface which enables the particular analytical function.
• contact lenses For example, those skilled in the art have long recognized the need for rendering the surface of contact lenses hydrophilic in order to improve their biocompatibility or wettability by tear fluid in the eye. This is necessary to improve the wear comfort of contact lenses and/or to extend their resistance to bacterial infection, inflammation, and other adverse effects resulting from incompatibility of the lens with the human body and its functions.
• the lens surface In the case of contact lenses, in particular, the lens surface must be resistant to bacterial growth and infection, and must also be hydrophilic to allow for efficient binding of water by the lens and sufficient flow of oxygen to the surface of the eye.
• Carbohydrate type coatings are of particular interest, as they resemble the natural coating of a human cell and are less prone to inflammation and irritation of tissue due to chemical and biological incompatibility.
• surface structure and exterior coatings on that surface structure may be used for biotechnology applications where the surface wetting properties and functionality are useful for analytical purposes, for controlling fluid flow and sorting of fluid components, and for altering the composition of components which come into contact with the surface, for example.
• surface wetting properties and functionality are useful for analytical purposes, for controlling fluid flow and sorting of fluid components, and for altering the composition of components which come into contact with the surface, for example.
• a need has grown for improved methods of controlling the formation of the coating, including the formation of individual layers within a multi-layered coating, for example.
• coatings range in thickness from about 1 nm (10 A) to about 1 micron ( ⁇ ).
• organo silanes to form coatings which impart desired functional characteristics to an underlying oxide-containing surface.
• the organo silane is represented as R n SiX ( ⁇ n) where X is a hydrolyzable group, typically halogen, alkoxy, acyloxy, or amine.
• a reactive silanol group is said to be formed which can condense with other silanol groups, for example, those on the surface of siliceous fillers, to form siloxane linkages.
• Stable condensation products are said to be formed with other oxides in addition to silicon oxide, such as oxides of aluminum, zirconium, tin, titanium, and nickel.
• the R group is said to be a nonhydrolyzable organic radical that may possess functionality that imparts desired characteristics.
• the article also discusses reactive tetra- substituted silanes which can be fully substituted by hydrolyzable groups and how the silicic acid which is formed from such substituted silanes readily forms polymers such as .
• silica gel, quartz, or silicates by condensation of the silanol groups or reaction of silicate ions.
• Tetrachlorosilane is mentioned as being of commercial importance since it can be hydrolyzed in the vapor phase to form amorphous fumed silica.
• the article by Dr. Arkles shows how a substrate with hydroxyl groups on its surface can be reacted with a condensation product of an organosilane to provide chemical bonding to the substrate surface. The reactions are generally discussed and, with the exception of the formation of amorphous fumed silica, the reactions are between a liquid precursor and a substrate having hydroxyl groups on its surface. A number of different applications and potential applications are discussed.
• Patent No.5,002,794 to Ratner et al describes a method of controlling the chemical structure of polymeric films formed by plasma deposition.
• An important aspect of the method involves controlling the temperature of the substrate and the reactor to create a temperature differential between the substrate and reactor such that the precursor molecules are preferentially adsorbed or condensed onto the substrate either during plasma deposition or between plasma deposition steps.
• This reference discusses the immobilization of poly (ethylene glycol), also referred to as PEG or as polyethylene oxide (PEO).
• PEG-like thin films, grafted onto a wide variety of substrates is described as carried out using a plasma deposition apparatus. Substrates are said to be cleaned by etching with an argon plasma in some instances.
• An object to be treated is placed in a vacuum chamber, and reactant precursor is introduced into the chamber at a specified rate so as to maintain a constant pressure in the reactor.
• a power supply is used to maintain a plasma at a set power level during the deposition.
• the disclosure teaches that , depending on the length of time the plasma is maintained, the thickness of the deposited films may be controlled as desired.
• the precursor material is introduced into the reaction vessel and pressure and flow of the precursor material are stabilized, with the plasma deposition and condensation carried out simultaneously or alternately for any desired length of time.
• the coated specimens may be permitted to remain in the presence of the precursor "to permit the chemical reactions in the film to go to completion". This is referred to as a quench step.
• Monolayers containing mixtures of hydrophobic (methyl terminated) and hydrophilic [hydroxyl-, maltose-, and hexa(ethylene glycol)-terminated] alkanethiols are said to be tailored to select specific degrees of adsorption.
• the SAMS were prepared by the chemisorption of alkanethiols from 0.25 niM solutions in ethanol or methanol onto thin (200 ⁇ 20 run) gold films supported on silicon wafers.
• the hexa(ethylene glycol)-terminated SAMS are said to be the most effective in resisting protein adsorption. (Abstract)
• the subject matter of this article is hereby incorporated by reference in its entirety. [0019] hi June of 1991 , DJ. Ehrlich and J.
• the SAM molecules were reported as providing an [ideal] connection between the metal surface and the calcium phosphate coating.
• a trichlorosilane terminus of the SAM molecule was reported as insuring covalent attachment to the substrate, while a functionalized "tail" of the SAM molecule induced heterogeneous nucleation of the calcium phosphate coating from supersaturated solutions.
• the introduction of the article explains that bone and dental implant technology is currently inadequate.
• the bond between bone and implant materials (such as Ti and metal alloys) is said to fail, requiring additional surgery to remove and replace the implant after only a few years of use.
• hydroxyapatite (HAP) coatings are said to have shown exceptional promise as bioactive coatings for metallic implant devices.
• the silica primer layer is said to be preferably pyrolytically deposited, magnetron sputtered, or applied by a sol-gel condensation reaction (i.e. from alkyl silicates or chlorosilanes).
• a perfluoroalkyl alkyl silane combined with a fluorinated olefin telomer is said to produce a preferred surface treatment composition.
• the silane/olefm composition is employed as a solution, preferably in a fluorinated solvent. The solution is applied to a substrate surface by any conventional technique such as dipping, flowing, wiping, or spraying.
• a method of manufacturing a chemically adsorbed film is described.
• a chemically adsorbed film is said to be formed on any type of substrate in a short time by chemically adsorbing a chlorosilane based surface active-agent in a gas phase on the surface of a substrate having active hydrogen groups.
• the basic reaction by which a chlorosilane is attached to a surface with hydroxyl groups present on the surface is basically the same as described in other articles discussed above.
• a chlorosilane based adsorbent or an alkoxyl-silane based adsorbent is used as the silane-based surface adsorbent, where the silane-based adsorbent has a reactive silyl group at one end and a condensation reaction is initiated in the gas phase atmosphere.
• a dehydrochlorination reaction or a de-alcohol reaction is carried out as the condensation reaction.
• the unreacted chlorosilane-based adsorbent on the surface of the substrate is washed with a non-aqueous solution and then the adsorbed material is reacted with aqueous solution to form a monomolecular adsorbed film.
• Miqin Zhang et al. in an article entitled “Hemocompatible Polyethylene Glycol Films on silicon", published in Biomedical Microdevices, 1(1), pp.81 - 87 (1998), describe the functionalization of polyethylene glycol (PEG) by SiCl 3 groups on its chain ends, and the reaction of the PEG organosilicon derivatives with hydroxylated groups on silicon surfaces.
• the reactant preparations and the attachment of PEG film onto silicon surfaces were carried out in a glass apparatus which prevented exposure to the atmosphere. Nitrogen was used as the isolation gas, and the precursor formation reactions were carried out in solutions, with attachment of the precursor to the silicon surface by contact of a precursor solution with the silicon surface.
• silane “monolayers” which are typically formed on surfaces in organic solution, be vapor deposited instead, to reduce the formation of variable thickness films and the formation of submicron aggregates or islands on the silicon substrate surface.
• the vapor phase coating method is carried out at ambient pressure using nitrogen to flush out the system, and subsequently using nitrogen as a carrier gas for the reactants.
• an alternative strategy consists of (applying) coating silanes in high vacuum, but no process conditions were provided. Biomedical devices formed by the method are said to be useful in the formation of micro fabricated filters which regulate hydrophilicity of a surface and minimize unspecific protein absorption.
• PEG-3400 silane was dissolved in anhydrous toluene to form either a 1 % or a 2 % solution. Silicon and Pyrex® samples were placed in stirred PRG solution for varying times (24, 4 and 1.5 hours) to deposit a layer of PEG. Subsequently, all samples underwent 2 - 5 minute sonicating rinses in fresh anhydrous toluene before being cured for 14 hours at a temperature of 125 0 C in a vacuum under 30 in. Hg. [0029] In an article entitled "SiO 2 Chemical Vapor Deposition at Room Temperature Using SiCl 4 and H 2 O with an NH 3 Catalyst", by J. W. Klaus and S.M.
• the substrate over which the coating is applied is preferably glass.
• a silicon oxide anchor layer or hybrid organo-silicon oxide anchor layer is formed from a humidified reaction product of silicon tetrachloride or trichlorornethylsilane vapors at atmospheric pressure. Application of the oxide anchor layer is followed by the vapor-deposition of a chloroalkylsilane.
• the silicon oxide anchor layer is said to advantageously have a root mean square surface (RMS) roughness of less than about 6.0 nm, preferably less than about 5.0 nm and a low haze value of less than about 3.0 %.
• the RMS surface roughness of the silicon oxide layer is preferably said to be greater than about 4 nm, to improve adhesion.
• Too small an RMS surface is said to result in the surface being too smooth, that is to say an insufficient increase in the surface area/or insufficient depth of the surface peaks and valleys on the surface.
• too great an RMS surface area is said to result in large surface peaks, widely spaced apart, which begins to diminish the desirable surface area for subsequent reaction with the chloroalkylsilane by vapor deposition.
• Simultaneous vapor deposition of silicon tetrachloride and dimethyldichlorosilane onto a glass substrate is said to result in a hydrophobic coating comprised of cross-linked polydimethylsiloxane which may then be capped with a fluoroalkylsilane (to provide hydrophobicity).
• the substrate is said to be glass or a silicon oxide anchor layer deposited on a surface prior to deposition of the cross-linked polydimethylsiloxane.
• the substrates are cleaned thoroughly and rinsed prior to being placed in the reaction chamber.
• U.S. Patent 5,936,703 to Miyazaki et al, issued August 10, 1999 describes a specialized alkoxysilane compound or its acid-processed reaction product, which is used as a surface processing solution for a contact lense surface.
• the compound is said to be capable of providing hydrophilicity to the surface of various substrates which are treated with a surface processing solution of the compound.
• U.S. Patent No. 6,200,626 to Grobe, III et al., issued March 13, 2001 describes an optically clear, hydrophilic coating produced on the surface of a silicone medical device by sequentially subj ecting the surface of a lens to plasma polymerization reaction in a hydrocarbon atmosphere, to produce a carbon layer, then graft polymerizing a mixture of monomers comprising hydrophilic monomers onto the carbon layer.
• the invention is said to be especially useful for forming a biocompatible coating on silicone hydrogen contact lenses.
• the invention is said to be directed toward treatment of silicone medical devices. (Col. 3, lines 17 - 19.)
• Various silicon-containing monomers and a silicone hydrogel material are described, which may be used to provide a substrate.
• the substrate surface is plasma oxidized, using a strong oxidizing plasma (Col. 8, lines 11 - 19), followed by plasma-polymerization deposition with a Cl to ClO saturated or unsaturated hydrocarbon to form a polymeric carbonaceous primary coating, followed by a grafting of a mixture of monomers (inclusive of macromers) onto the carbonaceous primary coating, to form a hydrophilic, biocompatible secondary coating.
• a strong oxidizing plasma Cold. 8, lines 11 - 19
• the grafting reaction may employ an initiator, or the carbonaceous layer may be activated to promote the covalent attachment of polymer to the surface.
• the grafting polymer may be formed by using an aqueous solution of an ethylenically unsaturated monomer or a mixture of monomers capable of undergoing graft addition polymerization. (Col. 9, lines 18 - 53.)
• U.S. Patent No. 6,213,604 to Valint, Jr. et al., issued April 10, 2001 describes plasma surface treatment of silicone hydrogel contact lenses.
• the surface of a contact lens is modified to increase its hydrophilicity by coating the lens with a carbon- containing layer made from a diolefinic compound having 4 to 8 carbon atoms.
• an optically clear, hydrophilic coating is provided upon the surface of a silicone hydrogel lens by sequentially subjecting the surface of the lens to: a plasma oxidation reaction, followed by a plasma polymerization reaction in the presence of a diolefm, in the absence of air (in the absence of oxygen or nitrogen, where "absence” is defined to mean at a concentration of less than 10 % by weight of oxygen or nitrogen, preferably less than two percent, and most preferably zero percent). Finally, the resulting carbon-containing layer is rendered hydrophilic by a further plasma oxidation reaction or by the attachment of a hydrophilic polymer chain. (Abstract and Col. 2, lines 44 - 53). Silicone lenses which are hydrogels can absorb and retain water in an equilibrium state.
• Hydrogels generally have a water content greater than about five weight percent and more commonly between about ten to about eighty weight percent. (Col. 1, lines 19 - 27.) [0037] D.M. Bubb et al., in an article entitled “Vapor deposition of intact polyethylene glycol thin films", published in Appl. Phys. A (2001) Digital Object Identified (DOI) 10.1 OO7/sOO3390100884, describe the deposition of polyethylene glycol (PEG) films of average molecular weight, 1400 amu, by both matrix assisted pulsed laser evaporation (MAPLE) and pulsed laser deposition (PLD). Films were deposited on NaCl plates, Si(111) wafers, and glass slides.
• MAPLE matrix assisted pulsed laser evaporation
• PLD pulsed laser deposition
• the MAPLE deposited films are said to have shown nearly identical resemblance to the starting material, while the PLD films did not.
• (Abstract) hi MAPLE the material to be deposited is dissolved in an appropriate solvent, typically at 0.1 to 2.0 wt. % concentration and is frozen solid. The composite is evaporated using a pulsed laser. The vaporized solvent is said not to form a film, and is pumped away by the vacuum system in the film deposition chamber.
• the precursors mentioned above are precursors for a cyclic version of a diethylene glycol structure.
• One of the methods described is the use of a self-assembled monolayer having an end group X available which provides chemisorption or physisorption of the monolayer onto the surface of a substrate.
• the substrate is a material such as silicon, silicon oxide, or a metal oxide
• X may be a monohalosilane, dihalosilane, trihalosilane, trialkoxysilane, dialkoxysilane, or a monoalkoxysilane.
• the other end group of the self-assembled monolayer, Y provides coupling with the protein readily under normal physiological conditions not detrimental to the activity of the protein.
• the functional group Y may either form a covalent linkage or a noncovalent linkage with the protein.
• Ketul C. Popat et al. in an article entitled "Characterization of vapor deposited ⁇ oly(ethylene glycol) films on silicon surfaces for surface modification of microfluidic systems", in the J. Vac. Sci. Technol. B 21(2), Mar/Apr 2003 at pages 645 - 654, discuss microfluidic systems which employ Poly (ethylene glycol) (PEG) as a surface coating to reduce protein adsorption on microfluidic surfaces. The PEG is said to reduce protein adsorption on the microfluidic surface.
• PEG Poly (ethylene glycol)
• the article focuses on the vapor deposition of silane and, subsequently, PEG on silicon surfaces in a moisture free nitrogen atmosphere.
• a basic starting molecule of ethylene oxide is used in combination with a gas catalyst.
• a substrate surface was a silicon wafer, p-type, boron doped, with (1,0,0) orientation.
• the silicon surface was treated with ammonium hydroxide and hydrogen peroxide in distilled water to attach an ⁇ OH group to the surface.
• Ethylene oxide in vapor phase was used to grow PEG on the silicon surface.
• the surface was first silanized with a reactive end group silane like 3-APTMS.
• Page 647 Boron trifluoride was used as a gaseous catalyst in combination with the ethylene oxide during formation of the PEG on the silicon surface.
• the boron trifluoride is said to be a weak Lewis acid which accepts a free pair of electrons of -NH 2 on APTMS, to make a reaction site available for a reactive ethylene oxide molecule to attach and then an additional polymerization reaction to form PEG on the substrate surface.
• the PEG composition is said to be controlled by the concentration of ethylene oxide and the polymerization time.
• the reaction is said to be terminated by flowing inert gas over the surface after an appropriate time. Nitrogen gas is used at specific flow rates through the PEG deposition chamber to maintain an inert atmosphere in the chamber.
• Silane is injected "in the flow loop" which is heated and maintained at a temperature a little above the boiling point of silane. Vapors of the silane are picked up by the running nitrogen.
• the methods include the use of vapor-phase alkylsilane-containing molecules to form a coating over a substrate surface.
• the alkylsilane-containing molecules are introduced into a reaction chamber containing the substrate by bubbling an anhydrous, inert gas through a liquid source of the alkylsilane- containing molecules, and transporting the molecules with the carrier gas into the reaction chamber.
• the formation of the coating is carried out on a substrate surface at a temperature ranging between about 15°C and 100°C, at a pressure in the reaction chamber which is said to be below atmospheric pressure, and yet sufficiently high for a suitable amount of alkylsilane-containing molecules to be present for expeditious formation of the coating.
• U.S. Patent Publication No. 2003/0180544 Al, published September 25, 2003, and entitled "anti-Reflective Hydrophobic Coatings and Methods describes substrates having anti-reflective hydrophobic surface coatings.
• the coatings are typically deposited on a glass substrate.
• a silicon oxide anchor layer is formed from a humidified reaction product of silicon tetrachloride, followed by the vapor deposition of a chloroalkylsilane.
• the thickness of the anchor layer and the overlay er are said to be such that the coating exhibits light reflectance of less than about 1.5 %.
• the coatings are said to be comprised of the reaction products of a vapor-deposited chlorosilyl group containing compound and a vapor-deposited alkylsilane.
• Preferred hydrogels are made using polyethylene glycol, polypropylene glycol or polysine, or a derivative (such as a branched or star molecule) or block co- ' polymer thereof.
• the immobilization or coupling of a hydrogel to a surface is typically carried out by contacting the hydrogel with a surface of interest to cause a physical or chemical reaction to occur between the hydrogel and the surface via one or more linkers.
• preferred surfaces include compositions containing oxides of silicon or tungsten.
• a silanized planar surface is also mentioned, where a surface having hydroxyl groups present is reacted with an organo-silane compound to create additional reactive groups for chemical coupling.
• one or more linkers comprising the hydrogel are contacted, with the surface by depositing an aqueous solution directly onto the surface, which optionally may contain an intermediate layer to facilitate binding.
• This reference is hereby incorporated by reference in its entirety.
• Other known related references pertaining to coatings deposited on a substrate surface from a vapor include the following, as examples and not by way of limitation.
• the coating may lack thickness uniformity and surface coverage, providing a rough surface.
• the coating may vary in chemical composition across the surface of the substrate.
• the coating may differ in structural composition across the surface of the substrate. Any one of these non-uniformities may result in functional discontinuities and defects on the coated substrate surface which are unacceptable for the intended application of the coated substrate.
• 10/759,857 of the present applicants describes processing apparatus which can provide specifically controlled, accurate delivery of precise quantities of reactants to the process chamber, as a means of improving control over a coating deposition process.
• the subject matter of the '857 application is hereby incorporated by reference in its entirety.
• the focus of the present application is the control of process conditions in the reaction chamber in a manner which, in combination with delivery of accurate quantities of reactive materials, provides a uniform, functional coating on a nanometer scale.
• the coating exhibits sufficient uniformity of thickness, chemical composition and structural composition over the substrate surface that such nanometer scale functionality is achieved.
• the coating formation method typically employs at least one stagnation reaction, and more typically a series of stagnation reactions. In each stagnation reaction all of the reactants which are to be consumed are charged to a vapor space over the substrate to be coated and are then permitted to react in a given process step, whether that step is one in a series of steps or is the sole step in a coating formation process.
• the coating formation process may include a number of individual steps where repetitive reactive processes are carried out in each individual step.
• the apparatus used to carry out the method provides for the addition of a precise amount of each of the reactants to be consumed in a single reaction step of the coating formation process.
• the apparatus may provide for precise addition of quantities of different combinations of reactants during each individual step when there are a series of different individual steps in the coating formation process.
• the present invention requires precise control over the cleanliness of the substrate, the order of reactant(s) introduction, the total pressure (which is typically less than atmospheric pressure) in the process chamber, the partial vapor pressure of each vaporous component present in the process chamber, and the temperature of the substrate and chamber walls.
• the control over this combination of variables determines the deposition rate and properties of the deposited layers.
• the coating deposition process is carried out in a vacuum chamber where the total pressure is lower than atmospheric pressure and the partial pressure of each vaporous component making up the reactive mixture is specifically controlled so that formation and attachment of molecules on a substrate surface are well controlled processes that can take place in a predictable manner, without starving the reaction from any of the precursors.
• the surface concentration and location of reactive species are controlled using total pressure in the processing chamber, the kind and number of vaporous components present in the process chamber, the partial pressure of each vaporous component in the chamber, temperature of the substrate, temperature of the process chamber walls, and the amount of time that a given set of conditions is maintained.
• more than one batch of reactants may be charged to the process chamber during formation of the coating.
• An important aspect of the present invention is the surface preparation of the substrate prior to initiation of any deposition reaction on the substrate surface.
• the hydrophobicity of a given substrate surface may be measured using a water droplet shape analysis method, for example.
• Silicon substrates when treated with oxygen-containing plasmas, can be freed from organic contaminants and typically exhibit a water contact angle below 10°, indicative of a hydrophilic property of the treated substrate.
• the deposition or creation of every thin oxide layer on the substrate surface may be used to alter the hydrophobicity of the substrate surface.
• An oxide layer may comprise aluminum oxide, titanium oxide, or silicon oxide, by way of example and not by way of limitation. When the oxide layer is aluminum or titanium oxide, an auxiliary process chamber (to the process chamber described herein) may be used to create this oxide layer.
• the silicon oxide layer may be applied by the method of the present invention, to provide a more hydrophilic substrate surface, or the silicon oxide may act as an oxide bonding layer.
• the oxide surface hydrophobicity can be adjusted downward to be as low as 5 degrees, rendering the surface hydrophilic.
• Such oxide films can serve as a surface layer having controlled hydrophilic / hydrophobic characteristics, or may serve as a bonding, wetting, adhesion, or primer layer (subsequently referred to as a "bonding" layer herein for general purposes of ease in description) for subsequently deposited various molecular coatings, including, for example, silane-based silicon-containing coatings.
• a bonding layer By controlling the precise thickness, chemical, and structural composition of an oxide layer on a substrate, for example, we are able to tailor the oxide layer surface characteristics and thickness to a biological application. When the oxide serves as a bonding layer, we are able to direct the coverage and the functionality of a coating applied over the bonding oxide layer.
• the coverage and functionality of the coating can be controlled over the entire substrate surface on a nanometer scale.
• the degree of hydrophobicity of the substrate after deposition of an oxide bonding layer and after deposition of an overlying silane-based polymeric coating can be uniformly controlled over the substrate surface.
• Oxide films deposited according to the present method can be used as bonding layers for subsequently deposited biocompatible coating materials, such as (for example and not by way of limitation) polyethylene glycol (PEG).
• PEG polyethylene glycol
• Polyethylene glycol is available in a wide range of molecular weights. The molecular weight of the polyethylene glycol will determine its physical characteristics (e.g., as the molecular weight increases, viscosity and freezing point increase).
• Polyethylene glycol is also available with varying numbers of functional (i.e., binding) groups, such as monofunctional (one binding group), difunctional (two binding groups), and multi-functional (more than two binding groups).
• the molecular weight and functionality of the polyethylene glycol will in combination determine the particular applications in which it is most useful.
• Polyethylene glycols which are useful in the present method typically range from about 400 to about 2000 in molecular weight.
• Polyethylene glycol is commonly used in a wide range of industries, including electronics (e.g. , printed circuit board manufacturing), electron microscopy, paper coating, textiles, wood processing, the cosmetics and toiletry industry, and in the medical / pharmaceutical field.
• Polyethylene glycol (with a structural formula: -(CH 2 -CH 2 -O)-) is a well-known, non-toxic class of polymers useful in biotechnological and biomedical applications.
• PEG is widely used as a drug coating, and as a component of many medications (e.g. laxatives, ophthalmic solutions and others). It has been studied in blood and tissue engineering, as a material retarding bacterial growth and is widely used as a coating in analytical tools and in medical devices such as, for example, catheters or capillaries.
• PEG is known to be hydrophilic and to reduce adsorption of protein and lipid cells due to its highly hydrated surface.
• PEG is applied for surface treatment of substrates and devices which require hydrophilic, bio-compatible interfaces with body tissue and fluids or with biological reagents.
• Application of the PEG is by a molecular vapor deposition process performed in a vacuum.
• the application method steps include: a) subjecting a surface which is planar or a surface having any one of a variety of three-dimensional shapes to an oxygen-comprising plasma in a processing chamber which is at a subatmospheric pressure.
• the pressure typically ranges from about 0.01 Torr to about 1 Torr.
• the silicon chloride-containing vapor is preferably silicon tetrachloride.
• step c) subsequently, without exposure of the hydrophilic silicon oxide layer to ambient conditions which contaminate or react with the hydrophilic silicon oxide layer, exposing the oxide layer to a functionalized silane precursor vapor containing PEO/PEG groups, to react these groups with the hydrophilic silicon oxide layer, to form a layer selected from the group consisting of a monolayer, a self-aligned mono-layer, and a polymerized cross-linked layer.
• additional repetition of steps may be used, including a step: d) repeating steps a) through c); or repeating steps b) through c); or repeating step c) a nominal number of times without exposing the substrate to ambient contaminants.
• step c) can be repeated.
• the PEO/PEG precursor may be charged to the reactor chamber and then pumped down to remove byproduct and unreacted precursor material in a series of steps to increase deposited layer thickness.
• a series of the charge and pump down steps in the range of about 2 to about 10 is common, with a range of about 4 to about 8 being more common.
• Application of a series of add-on layers to increase the total thickness of the deposited PEO/PEG layer improves the uniformity of the deposited PEO/PEG layer over the surface of the substrate.
• a computer-driven process control system may be used to provide for a series of additions of reactants to the process chamber in which an individual layer or a coating is being formed.
• This process control system typically also controls other process variables, such as (for example and not by way of limitation), total process chamber pressure (typically less than atmospheric pressure), substrate temperature, temperature of process chamber walls, temperature of the vapor delivery manifolds, processing time for given process steps, and other process parameters if needed, i
• Oxide / polyethylene glycol coatings providing hydrophilicity can also be deposited, using the present method, over the surfaces of various medical devices and implants, which are intended for various time periods of use.
• Internal devices such as smart bio-chips, which may include internal diagnostic devices are excellent applications for coated structures.
• External devices such as contact lenses, external diagnostic devices (including microfluidic devices), and catheters, for example, provide excellent applications for coated structures.
• Coated structures which are intended for "permanent” ⁇ i.e., at least 5 to 10 years) implantation within the body may include devices such as intra-ocular lenses, synthetic blood vessels and heart valves, stents, joint (such as a hip or knee) or hard tissue ⁇ i.e., bone or cartilage) replacements, and breast implants, for example and without limitation.
• devices such as intra-ocular lenses, synthetic blood vessels and heart valves, stents, joint (such as a hip or knee) or hard tissue ⁇ i.e., bone or cartilage) replacements, and breast implants, for example and without limitation.
• the application of a hydrophilic oxide / PEG coating over surfaces of the medical device or implant improves both the hydrophilicity and biocompatibility of the device / implant.
• Figure 1 shows a cross-sectional schematic of one embodiment of the kind of an apparatus which can be used to carry out a vapor deposition of a coating in accordance with the method of the present invention.
• Figure 2 is a schematic which shows the reaction mechanism where tetrachlorosilane and water are reacted with a substrate which exhibits active hydroxyl groups on the substrate surface, to form a silicon oxide layer on the surface of the substrate.
• Figures 3A and 3B show schematics of atomic force microscope (AFM) images of silicon oxide bonding layers deposited on a silicon substrate.
• the initial silicon substrate surface RMS roughness measured less than about 0.1 nm.
• Figure 3 A shows the schematic for an AFM picture of a 4 nm thick silicon oxide bonding layer deposited from SiCl 4 precursor using the method of the present invention, where the RMS roughness is about 1.4 nm.
• Figure 3B shows the schematic for an AFM picture of a 30 nm thick silicon oxide bonding layer deposited from SiCl 4 precursor using the method of the present invention, where the RMS roughness is about 4.2 nm.
• Figure 4 shows a graph of the water contact angle (proportional to percentage of substrate surface coverage) as a function of time for a coating produced from a dimethyldichlorosilane precursor on the surface of a silicon substrate.
• Figure 5 shows a series of water contact angles measured for a coating surface where the coating was produced from a FOTS precursor on the surface of a silicon substrate. The higher the contact angle, the higher the hydrophobicity of the coating surface.
• Figure 6A shows a three dimensional schematic of film thickness of a silicon oxide bonding layer coating deposited on a silicon surface as a function of the partial pressure of silicon tetrachloride and the partial pressure of water vapor present in the process chamber during deposition of the silicon oxide coating, where the time period the silicon substrate was exposed to the coating precursors was four minutes after completion of addition of all precursor materials.
• Figure 6B shows a three dimensional schematic of film thickness of the silicon oxide bonding layer illustrated in Figure 6A as a function of the water vapor partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
• Figure 6C shows a three dimensional schematic of film thickness of the silicon oxide bonding layer illustrated in Figure 6 A as a function of the silicon tetrachloride partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
• Figure 7 A shows a three dimensional schematic of film roughness in RMS nm of a silicon oxide bonding layer coating deposited on a silicon surface as a function of the partial pressure of silicon tetrachloride and the partial pressure of water vapor present in the process chamber during deposition of the silicon oxide coating, where the time period the silicon substrate was exposed to the coating precursors was four minutes after completion of addition of all precursor materials.
• Figure 7B shows a three dimensional schematic of film roughness in RMS nm of the silicon oxide bonding layer illustrated in Figure 7 A as a function of the water vapor partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
• Figure 7C shows a three dimensional schematic of film roughness in RMS nm of the silicon oxide bonding layer illustrated in Figure 6 A as a function of the silicon tetrachloride partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
• Figure 8 A illustrates the change in hydrophilicity of the surface of the initial substrate as a function of the thickness of an oxide-based bonding layer generated over the initial substrate surface using an oxygen plasma, moisture, and carbon tetrachloride.
• the contact angle on the surface drops to about 5 degrees or less.
• Figure 8B illustrates the minimum thickness of oxide-based bonding layer which is required to provide adhesion of an organic-based layer, as a function of the initial substrate material, when the organic-based layer is one where the end or the organic-based layer which bonds to the oxide-based bonding layer is a silane and where the end of the organic-based layer which does not bond to the oxide-based bonding layer provides a hydrophobic surface.
• the oxide thickness is adequate to provide uniform attachment of the organic-based layer, the contact angle on the substrate surface increases to about 110 degrees or greater.
• Figure 9 shows stability in DI water for an organic-based self-aligning monolayer (S AM) generated from perfluorodecyltrichloro-silane (FDTS) applied over an acrylic substrate surface; and, applied over a 150 A (15 nm) thick oxide-based layer, or applied over a 400 A (40 nm) thick oxide-based layer, where the initial substrate surface is acrylic. Also shown is the improvement in long-term reliability and performance when a series of five pairs of oxide-based layer / organic-based layer are applied over the acrylic substrate surface.
• S AM organic-based self-aligning monolayer
• FDTS perfluorodecyltrichloro-silane
• Figure 1 OA illustrates the improvement in DI water stability of another multilayered coating, where the organic-based precursor was fiuoro- tetrahydrooctyldimethylchlorosilanes (FOTS).
• FOTS fiuoro- tetrahydrooctyldimethylchlorosilanes
• Figure 1OB shows the same kind of comparison as shown in Figure 1OA; however, the substrate is glass.
• Figure 1 IA shows a 1536-well micro-plate, which is typically polystyrene or polypropylene with 1536 wells present in the substrate surface. Each well is about 1.5 to 2.0 mm in diameter and 5.0 mm deep. Typical micro-plate well aspect ratios may range from about 1 : 1 to about 4 : 1. In Figure 1 IA, the hydrophobic polymeric surface of the polystyrene substrate does not permit a sample drop to enter the well.
• Figure 1 IB shows the same 1536-well micro-plate, where a two layer coating having an oxide bonding layer and a mono-functional PEG (mPEG) surface layer renders the hydrophobic micro-plate surface shown in Figure 1 IA hydrophilic, so that a fluid sample can more easily enter the well.
• mPEG mono-functional PEG
• Disclosed herein is a method of increasing the hydrophilicity of a biomedical device, where a surface of the device is vapor deposition coated with a material having a hydrophilicity which is related to the surface tension of a biological fluid which is present in or around the device. Fluids which are present in or around the implant or device are typically hydrophilic (typically, water-based fluids), and a surface of the device is coated with a coating which increases the hydrophilicity of the device surface.
• the most common vapor-deposited coating used to increase hydrophilicity include at least one oxide-based layer and at least one organic functional layer, where an organic functional layer provides the upper surface of the coating.
• the organic functional layer is a PEG-based layer
• the vapor deposited coating typically exhibits a deionized water wetting angle ranging from about 5° or less to about 60°; more typically, ranging from about 9° or less to about 50°; most typically, ranging from about 15° or less to about 45°.
• Figure 1 shows a cross-sectional schematic of an apparatus 100 for vapor deposition of thin coatings.
• the apparatus 100 includes a process chamber 102 in which thin (typically 20 A (2 run) to 200 A (20 nm) coatings, or thicker coatings in the range of about 200 A (20 nm) to about 1 micron thick (1,000 nm) may be vapor deposited.
• a substrate 106 to be coated rests upon a temperature controlled substrate holder 104, typically within a recess 107 in the substrate holder 104. [0096] Depending on the chamber design, the substrate 106 may rest on the chamber bottom (not shown in this position in Figure 1).
• Attached to process chamber 102 is a remote plasma source 110, connected via a valve 108.
• Remote plasma source 110 may be used to provide a plasma which is used to clean and/or convert a substrate surface to a particular chemical state prior to application of a coating (which enables reaction of coating species and/or catalyst with the surface, thus improving adhesion and/or formation of the coating); or may be used to provide species helpful during formation of the coating (not shown) or modifications of the coating after deposition.
• the plasma may be generated using a microwave, DC, or inductive RF power source, or combinations thereof.
• the process chamber 102 makes use of an exhaust port 112 for the removal of reaction byproducts and is opened for pumping/purging the chamber 102.
• a shut-off valve or a control valve 114 is used to isolate the chamber or to control the amount of vacuum applied to the exhaust port.
• the vacuum source is not shown in Figure 1.
• the apparatus 100 shown in Figure 1 is illustrative of a vapor deposited coating which employs two precursor materials and a catalyst.
• a catalyst storage container 116 contains catalyst 154, which may be heated using heater 118 to provide a vapor, as necessary. It is understood that precursor and catalyst storage container walls, and transfer lines into process chamber 102 will be heated as necessary to maintain a precursor or catalyst in a vaporous state, minimizing or avoiding condensation. The same is true with respect to heating of the interior surfaces of process chamber 102 and the surface of substrate 106 to which the coating (not shown) is applied.
• a control valve 120 is present on transfer line 119 between catalyst storage container 116 and catalyst vapor reservoir 122, where the catalyst vapor is permitted to accumulate until a nominal, specified pressure is measured at pressure indicator 124.
• Control valve 120 is in a normally-closed position and returns to that position once the specified pressure is reached in catalyst vapor reservoir 122.
• valve 126 on transfer line 119 is opened to permit entrance of the catalyst present in vapor reservoir 122 into process chamber 102 which is at a lower pressure.
• Control valves 120 and 126 are controlled by a programmable process control system of the kind known in the art (which is not shown in Figure 1).
• a Precursor 1 storage container 128 contains coating reactant Precursor 1, which may be heated using heater 130 to provide a vapor, as necessary.
• Precursor 1 transfer line 129 and vapor reservoir 134 internal surfaces are heated as necessary to maintain a Precursor 1 in a vaporous state, minimizing and preferably avoiding condensation.
• a control valve 132 is present on transfer line 129 between Precursor 1 storage container 128 and Precursor 1 vapor reservoir 134, where the Precursor 1 vapor is permitted to accumulate until a nominal, specified pressure is measured at pressure indicator 136. Control valve 132 is in a normally closed position and returns to that position once the specified pressure is reached in Precursor 1 vapor reservoir 134.
• valve 138 on transfer line 129 is opened to permit entrance of the Precursor 1 vapor present in vapor reservoir 134 into process chamber 102, which is at a lower pressure.
• Control valves 132 and 138 are controlled by a programmable process control system of the kind known in the art (which is not shown in Figure 1).
• a Precursor 2 storage container 140 contains coating reactant Precursor 2, which may be heated using heater 142 to provide a vapor, as necessary.
• Precursor 2 transfer line 141 and vapor reservoir 146 internal surfaces are heated as necessary to maintain Precursor 2 in a vaporous state, minimizing, and preferably avoiding condensation.
• a control valve 144 is present on transfer line 141 between Precursor 2 storage container 146 and Precursor 2 vapor reservoir 146, where the Precursor 2 vapor is permitted to accumulate until a nominal, specified pressure is measured at pressure indicator 148.
• Control valve 141 is in a normally-closed position and returns to that position once the specified pressure is reached in Precursor 2 vapor reservoir 146.
• valve 150 on transfer line 141 is opened to permit entrance of the Precursor 2 vapor present in vapor reservoir 146 into process chamber 102, which is at a lower pressure.
• Control valves 144 and 150 are controlled by a programmable process control system of the kind known in the art (which is not shown in Figure 1).
• vapor reservoir 122 of the catalyst 154 may be added to process chamber 102.
• the total amount of vapor added is controlled by both the adjustable volume size of each of the expansion chambers (typically 50 cc up to 1,000 cc) and the number of vapor injections (doses) into the reaction chamber.
• the set pressure 124 for catalyst vapor reservoir 122, or the set pressure 136 for Precursor 1 vapor reservoir 134, or the set pressure 148 for Precursor 2 vapor reservoir 146 may be adjusted to control the amount (partial vapor pressure) of the catalyst or reactant added to any particular step during the coating formation process.
• This ability to control precise amounts of catalyst and vaporous precursors to be dosed (charged) to the process chamber 102 at a specified time provides not only accurate dosing of reactants and catalysts, but repeatability in the vapor charging sequence.
• This apparatus provides a relatively inexpensive, yet accurate method of adding vapor phase precursor reactants and catalyst to the coating formation process, despite the fact that many of the precursors and catalysts are typically relatively non- volatile materials.
• flow controllers were used to control the addition of various reactants; however, these flow controllers may not be able to handle some of the precursors used for vapor deposition of coatings, due to the low vapor pressure and chemical nature of the precursor materials.
• the rate at which vapor is generated from some of the precursors is generally too slow to function with a flow controller in a manner which provides availability of material in a timely manner for the vapor deposition process.
• the apparatus discussed above allows for accumulation of the specific quantity of vapor in the vapor reservoir which can be charged (dosed) to the reaction. In the event it is desired to make several doses during the coating process, the apparatus can be programmed to do so, as described above.
• a method of the invention provides for vapor-phase deposition of coatings, where at least one processing chamber (including an expansion volume and auxiliary valving and other apparatus) of the kind described above, or similar to the processing chamber described above is employed.
• a processing chamber of the kind described in detail herein permits precise charging of vaporous reactive species which react with a substrate surface under stagnated conditions.
• the kind of processing chamber which provides for stagnated reaction may be used in combination with other kinds of process chambers which permit a continuous flow of reactant components across a substrate surface during coating deposition (not shown in drawings herein).
• This latter kind of processing chamber is commonly used in the art for chemical vapor deposition (CVD) of thin films, for example.
• a multi-chambered coating deposition system which employs a combination of the stagnation reaction processing chamber of the present invention with processing chambers of the kind used in the art for CVD, where substrates are moved between various processing chambers while the substrates are under a controlled environment, is contemplated.
• Use of the stagnated reaction condition processing chamber of the kind described in detail herein permits precise charging of vaporous reactive species which react with a substrate surface under the stagnated conditions. This reaction under stagnated reaction conditions is employed during at least one individual deposition step to produce a given deposited layer, or is employed during deposition of at least one layer of a multilayered coating.
• Each coating precursor is transferred in vaporous form to a precursor vapor reservoir in which the precursor vapor accumulates.
• the vapor reservoir may be the processing chamber in which the coating is applied.
• a nominal amount of the precursor vapor which is the amount required for a coating layer deposition is accumulated in the precursor vapor reservoir.
• the at least one coating precursor is charged from the precursor vapor reservoir into the processing chamber in which a substrate to be coated resides.
• at least one catalyst vapor is added to the process chamber in addition to the at least one precursor vapor, where the relative quantities of catalyst and precursor vapors are based on the physical characteristics to be exhibited by the coating.
• a diluent gas is added to the process chamber in addition to the at least one precursor vapor (and optional catalyst vapor).
• the diluent gas is chemically inert and is used to increase a total desired processing pressure, while the partial pressure amounts of coating precursors and optionally catalyst components are varied.
• the example embodiments described below are with reference to formation of oxide coatings which exhibit a controlled degree of hydrophilicity; or, are with reference to use of a bonding oxide layer with an overlying silane-based polymeric layer or a bonding oxide with an overlying PEG polymeric layer to provide a hydrophobic surface on a substrate.
• the surface preparation of the substrate prior to application of the coating is very important.
• One method of preparing the substrate surface is to expose the surface to a uniform, non-physically-bonibarding plasma which is typically created from a plasma source gas containing oxygen.
• the plasma may be a remotely generated plasma which is fed into a processing chamber in which a substrate to be coated resides.
• the plasma treatment of the substrate surface may be carried out in the chamber in which the coating is to be applied.
• the substrate is easily maintained in a controlled environment between the time that the surface is treated and the time at which the coating is applied.
• a large system which includes several processing chambers and a centralized transfer chamber which allows substrate transfer from one chamber to another via a robot handling device, where the centralized handling chamber as well as the individual processing chambers are each under a controlled environment.
• the treatment may be a wet chemical clean, but is preferably a plasma treatment. Typically treatment with an oxygen plasma removes common surface contaminants.
• the oxide layer may be created using the well-known catalytic hydrolysis of a chlorosilane, such as a tetrachlorosilane, in the manner previously described. A subsequent attachment of an organo-chlorosilane, which may or may not include a functional moiety, may be made to impart a particular function to the finished coating.
• the hydrophobicity or hydrophilicity of the coating surface may be altered by the functional moiety present on a surface of an organo-chlorosilane which becomes the exterior surface of the coating.
• the oxide layer which may be silicon oxide or another oxide, may be formed using the method of the present invention by vapor phase hydrolysis of the chlorosilane, with subsequent attachment of the hydrolyzed silane to the substrate surface.
• the hydrolysis reaction may take place directly on the surface of the substrate, where moisture has been made available on the substrate surface to allow simultaneous hydrolyzation and attachment of the chlorosilane to the substrate surface.
• both density of film coverage over the substrate surface and structural composition over the substrate surface are more accurately controlled, enabling the formation of very smooth films, which typically range from about 0.1 nm to less than about 15 nm, and even more typically from about 1 nm to about 5 nm in surface RMS roughness.
• the thickness of the oxide film typically ranges from about 10 A (1 nm) to about 200 A (20 nm).
• the thickness of the layer may be greater, typically up to about 1,000 nm (1.0 ⁇ ), and more typically up to about 500 nm (0.5 ⁇ ).
• oxide films deposited according to the present method can be used as bonding layers for subsequently deposited biocompatible coating materials, such as (for example and not by way of limitation) polyethylene glycol (PEG).
• PEG polyethylene glycol
• the molecular weight of the polyethylene glycol will determine its physical characteristics (e.g., as the molecular weight increases, viscosity and freezing point increase).
• Polyethylene glycol is also available with varying numbers of functional (z.e., binding) groups, such as monofunctional (one binding group), difunctional (two binding groups), and multi-functional (more than two binding groups).
• the molecular weight and functionality of the polyethylene glycol will in combination determine the particular applications in which it is most useful.
• Polyethylene glycols which are useful in the present method typically range from about 400 to about 1000 in molecular weight.
• Polyethylene glycol (with a structural formula: -(CH 2 -CH 2 -O)-) is a well- known, non-toxic class of polymers useful in biotechnological and biomedical applications.
• PEG is widely used as a drug coating, and as a component of many medications (e.g.
• PEG polystyrene glycol
• Example One [0116] The vapor deposition techniques described previously herein were used to coat devices such as implantable (intraocular) lenses with a hydrophilic oxide / polyethylene glycol coating. Prior to deposition of the coating, the device surface was pre-treated by exposure to an oxygen plasma (150 - 200 seem O 2 at an RF power of about 200 W and a process chamber pressure of 0.3 Torr in an Applied MicroStructures' MVDTM process chamber) for 5 minutes in order to clean the surface and create hydroxyl availability on a substrate surface (by way of example and not by way of limitation).
• an oxygen plasma 150 - 200 seem O 2 at an RF power of about 200 W and a process chamber pressure of 0.3 Torr in an Applied MicroStructures' MVDTM process chamber
• SiCl 4 was charged to the process chamber from a SiCl 4 vapor reservoir, where the SiCl 4 vapor pressure in the vapor reservoir was 18 Torr, creating a partial pressure of 2.3 Torr in the coating process chamber.
• a first volume OfH 2 O vapor was charged to the process chamber from a H 2 O vapor reservoir, where the H 2 O vapor pressure in the vapor reservoir was 18 Torr.
• a total of five reservoir volumes of H 2 O were charged, creating a partial pressure of 5.0 Torr in the coating process chamber.
• the total pressure in the coating process chamber was 7.3 Torr.
• the substrate temperature and the temperature of the process chamber walls was about 35 0 C.
• the substrate was exposed for a time period of about 10 minutes after the final H 2 O addition.
• the silicon oxide coating thickness obtained was about 100 A.
• Four reservoir volumes of PEG were charged, creating a partial pressure of 250 mTorr in the coating process chamber. After charging of the reservoir volumes, the substrate was exposed to the PEG precursor vapor for a time period of 15 minutes.
• PEG precursor No charging of water vapor from a reservoir to the process chamber is necessary with this PEG precursor.
• An alternative precursor which may be used to form a PEG coating is methoxy(polyethyleneoxy)pro ⁇ yltrichlorosilane (Gelest P/N SIM6492.66).
• Gelest P/N SIM6492.66 methoxy(polyethyleneoxy)pro ⁇ yltrichlorosilane
• use of this PEG precursor requires the addition of water vapor.
• the temperature of the process chamber walls was within the range of about 25 0 C to about 60 0 C 5 and was most typically about 35°C.
• the PEG precursor source vessel and delivery line temperature was within the range of about 70 0 C to about 110 0 C, and was most typically about 100 0 C.
• the PEG coating thickness obtained was about 20 A (2nm).
• a chlorosilane or methoxysilane functionalized PEG-forming organosilicon derivative functionalized on either one or both PEG chain ends a poly(ethylene glycol) silane and bis-silane precursors
• Application of the PEG by a molecular vapor deposition process is performed in a vacuum.
• the application method steps include: a) subjecting a surface which is planar or a surface having any one of a variety of three-dimensional shapes to an oxygen-comprising plasma in a processing chamber which is at a subatmospheric pressure ranging from about 0.1 Torr to about 1.0 Torr; .
• steps a) through c) in a process chamber of the kind previously described having a volume of about 1.5 to about 2.0 liters used in combination with a reservoir having a volume of about 300 cc are as follows. It is understood that one skilled in the art could adjust (scale) the process conditions provided below to accommodate a larger or smaller process chamber or a larger or smaller reservoir. For manufacturing operations, the process chamber (and coordinated reservoirs) would typically be considerably larger.
• RF power to the plasma generation source is in the range of about 100 W to about 300 W, and the treatment time is about 1 minute to about 10 minutes, typically about 5 minutes.
• the PEG source and delivery line temperature typically ranges from about 70 0 C to about 110 0 C 3 preferably the temperature is about 100 °C.
• PEG-comprising precursor and other reactant vapors are injected from a vapor reservoir of approximately 300 cc. Typically about 4 injections of PEG-comprising precursor at 500 mTorr reservoir pressure are made. When water vapor is used, water vapor is typically injected at this time, by way of example and not by way of limitation.
• the reaction time period for the PEG-comprising precursor or the combination of reactants is in the range of about 5 minutes to 30 minutes, typically about 15 minutes.
• Oxide / polyethylene glycol coatings providing hydrophilicity can also be deposited, using the present method, over the surfaces of other medical devices and implants, including those which are intended for temporary use (such as contact lenses and catheters, for example and without limitation) and those which are intended for "permanent” (i.e., at least 5 to 10 years) implantation (such as intra-ocular lenses, synthetic blood vessels and heart valves, stents, joint (such as a hip or knee) or hard tissue (i. e. , bone or cartilage) replacements, and breast implants, for example and without limitation) within the body.
• other medical devices and implants including those which are intended for temporary use (such as contact lenses and catheters, for example and without limitation) and those which are intended for "permanent” (i.e., at least 5 to 10 years) implantation (such as intra-ocular lenses, synthetic blood vessels and heart valves, stents, joint (such as a hip or knee) or hard tissue (i. e. , bone or cartilage)
• a hydrophilic oxide / PEG coating over surfaces of the medical device or implant improves both the hydrophilicity and biocompatibility of the device / implant.
• oxygen plasma treatment activates dangling bonds on the substrate surface, which dangling bonds may be exposed to a controlled partial pressure of water vapor to create a new concentration of OH reactive sites on the substrate surface.
• the PEO/PEG coating deposition process may then be repeated, increasing the coating thickness.
• a computer-driven process control system may be used to provide for a series of additions of reactants to the process chamber in which the layer or coating is being formed.
• This process control system typically also controls other process variables, such as (for example and not by way of limitation), total process chamber pressure (typically less than atmospheric pressure), substrate temperature, temperature of process chamber walls, temperature of the vapor delivery manifolds, processing time for given process steps, and other process parameters if needed.
• the oxide-based layer for a thin film of an oxide-based layer, prepared on a silicon substrate, where the oxide-based layer exhibits a thickness ranging from about 2 nm to about 15 nm, typically the oxide-based layer exhibits a 1 - 5 nm RMS finish.
• the partial pressure of the silicon tetrachloride is in the range of about 0.5 to 4.0 Torr
• the partial pressure of the water vapor is in the range of about 2 to about 8 Torr
• the total process chamber pressure ranges from about 3 Torr to about 10 Torr
• the substrate temperature ranges from about 20°C to about 6O 0 C
• the process chamber walls are at a temperature ranging from about 30°C to about 60 0 C
• the time period over which the substrate is exposed to the combination of silicon tetrachloride and water vapor ranges from about 2 minutes to about 12 minutes.
• a multilayered coating process may include plasma treatment of the surface of one deposited layer prior to application of an overlying layer.
• the plasma used for such treatment is a low density plasma.
• This plasma may be a remotely generated plasma.
• the most important feature of the treatment plasma is that it is a "soft" plasma which affects the exposed surface enough to activate the surface of the layer being treated, but not enough to etch through the layer.
• the apparatus used to carry out the method provides for the addition of a precise amount of each of the reactants to be consumed in a single reaction step of the coating formation process.
• the apparatus may provide for precise addition of different combinations of reactants during each individual step when there are a series of different individual steps in the coating formation process. Some of the individual steps may be repetitive.
• One example of the application of the method described here is deposition of a multilayered coating including at least one oxide-based layer.
• the thickness of the oxide- based layer depends on the end-use application for the multilayered coating.
• the oxide- based layer (or a series of oxide-based layers alternated with organic-based layers) may be used to increase the overall thickness of the multilayered coating (which typically derives the majority of its thickness from the oxide-based layer), and depending on the mechanical properties to be obtained, the oxide-based layer content of the multilayered coating may be increased when more coating rigidity and abrasion resistance is required.
• the oxide-based layer is frequently used to provide a bonding surface for subsequently deposited various molecular organic-based coating layers.
• the organic-based coating layer typically includes, for example and not by way of limitation, a silane-based functionality which permits covalent bonding of the organic-based coating layer to -OH functional groups present on the surface of the oxide-based layer.
• the organic-based coating layer includes, for example, an -OH functional group, which permits covalent bonding of the organic-based coating layer to the oxide-based layer functional halogen group.
• an oxide-based layer on a substrate By controlling the precise thickness, chemical, and structural composition of an oxide-based layer on a substrate, for example, we are able to direct the coverage and the functionality of a coating applied over the bonding oxide layer. The coverage and functionality of the coating can be controlled over the entire substrate surface on a nm scale. Specific, different thicknesses of an oxide-based substrate bonding layer are required on different substrates. Some substrates require an alternating series of oxide- based/organic-based layers to provide surface stability for a coating structure. [0135] With respect to substrate surface properties, such as hydrophobicity or hydrophilicity, for example, a silicon wafer surface becomes hydrophilic, to provide a less than 5 degree water contact angle, after plasma treatment when there is some moisture present.
• a stainless steel surface requires formation of an overlying oxide- based layer having a thickness of about 30 A or more to obtain the same degree of hydrophilicity as that obtained by plasma treatment of a silicon surface. Glass and polystyrene materials become hydrophilic, to a 5 degree water contact angle, after the application of about 80 A or more of an oxide-based layer. An acrylic surface requires about 150 A or more of an oxide-based layer to provide a 5 degree water contact angle.
• oxide-based layer there is also a required thickness of oxide-based layer to provide a good bonding surface for reaction with a subsequently applied organic-based layer.
• a good bonding surface it is meant a surface which provides full, uniform surface coverage of the organic-based layer.
• about 80 A or more of a oxide-based substrate bonding layer over a silicon wafer substrate provides a uniform hydrophobic contact angle, about 112 degrees, upon application of a SAM organic-based layer deposited from an FDTS (perfluorodecyltrichlorosilanes) precursor.
• FDTS perfluorodecyltrichlorosilanes
• the organic-based layer precursor in addition to containing a functional group capable of reacting with the oxide-based layer to provide a covalent bond, may also contain a functional group at a location which will form the exterior surface of the attached organic-based layer. This functional group may subsequently be reacted with other organic-based precursors, or may be the final layer of the coating and be used to provide surface properties of the coating, such as to render the surface hydrophobic or hydrophilic, by way of example and not by way of limitation.
• the functionality of an attached organic-based layer may be affected by the chemical composition of the previous organic-based layer (or the chemical composition of the initial substrate) if the thickness of the oxide layer separating the attached organic-based layer from the previous organic- based layer (or other substrate) is inadequate.
• the required oxide-based layer thickness is a function of the chemical composition of the substrate surface underlying the oxide- based layer, as illustrated above. In some instances, to provide structural stability for the surface layer of the coating, it is necessary to apply several alternating layers of an oxide- based layer and an organic-based layer.
• the fluorine moiety at the other end of the organic molecule provides a hydrophobic coating surface.
• the degree of hydrophobicity and the uniformity of the hydrophobic surface at a given location across the coated surface may be controlled using the oxide-based layer which is applied over the substrate surface prior to application of the chlorosilane-comprising organic molecule. By controlling the oxide-based layer application, the organic-based layer is controlled indirectly.
• the initial substrate surface is a hydrophobic surface and it is desired to convert this surface to a hydrophilic surface
• a structure which comprises more than one oxide-based layer to obtain stability of the applied hydrophilic surface in water. It is not just the thickness of the oxide-based layer or the thickness of the organic-based layer which is controlling.
• the structural stability provided by a multilayered structure of repeated layers of oxide-based material interleaved with organic-based layers provides excellent results.
• This treatment activates reaction sites of the first organic-based layer and may be used as part of a process for generating an oxide-based layer or simply to activate dangling bonds on the substrate surface.
• the activated dangling bonds may be exploited to provide reactive sites on the substrate surface.
• an oxygen plasma treatment in combination with a controlled partial pressure of water vapor may be used to create a new concentration of OH reactive species on an exposed surface.
• the activated surface is then used to provide covalent bonding with the next layer of material applied.
• a deposition process may then be repeated, increasing the total coating thickness, and eventually providing a surface layer having the desired surface properties.
• treatment with the oxygen plasma and moisture provides a metal oxide-based layer containing -OH functional groups.
• a surface oxide layer can be used as a bonding layer for subsequent deposition of biocompatible coating materials, such as (for example and not by way of limitation) polyethylene glycol (PEG).
• PEG polyethylene glycol
• Polyethylene glycol can be deposited using molecular vapor deposition (MVDTM) to provide a surface layer over underling layers of other materials.
• Example Two [0142] Deposition of a Silicon Oxide Layer Having a Controlled Number of OH Reactive Sites Available On the Oxide Layer Surface
• a technique for adjusting the hydrophobicity/hydrophilicity of a substrate surface may also be viewed as adjusting the number of OH reactive sites available on the surface of the substrate.
• One such technique is to apply an oxide coating over the substrate surface while providing the desired concentration of OH reactive sites available on the oxide surface.
• a substrate 202 has OH groups 204 present on the substrate surface 203.
• a chlorosilane 208 such as the tetrachlorosilane shown, and water 206 are reacted with the OH groups 204, either simultaneously or in sequence, to produce the oxide layer 205 shown on surface 203 of substrate 202 and byproduct HCl 210.
• chlorosilane precursors chlorosiloxanes, fluorosilanes, and fluorosiloxanes may be used.
• the surface of the oxide layer 205 can be further reacted with water 216 to replace Cl atoms on the upper surface of oxide layer 205 with OH groups 217, to produce the hydroxylated layer 215 shown on surface 203 of substrate 202 and byproduct HCl 220.
• the frequency of OH reactive sites available on the oxide surface is controlled.
• Example Three [0147] In the preferred embodiment discussed below, the silicon oxide coating was applied over a glass substrate.
• the glass substrate was treated with an oxygen plasma in the presence of residual moisture which was present in the process chamber (after pump down of the chamber to about 20 mTorr) to provide a clean surface (free from organic contaminants) and to provide the initial OH groups on the glass surface.
• Various process conditions for the subsequent reaction of the OH groups on the glass surface with vaporous tetrachlorosilane and water are provided below in Table 2, along with data related to the thickness and roughness of the oxide coating obtained and the contact angle (indicating hydrophobicity/hydrophilicity) obtained under the respective process conditions.
• a lower contact angle indicates increased hydrophilicity and an increase in the number of available OH groups on the silicon oxide surface.
• Coating roughness is the RMS roughness measured by AFM (atomic force microscopy).
• the FOTS coating layer was a monolayer which added « 1 nm in thickness.
• the H 2 O was added to the process chamber 10 seconds before the SiCl 4 was added to the process chamber. 2.
• the SiCl 4 was added to the process chamber 10 seconds before the H 2 O was added to the process chamber.
• the FOTS was added to the process chamber 5 seconds before the H 2 O was added to the process chamber. 4.
• the substrate temperature and the chamber wall temperature were each 35 °C for both application of the SiO 2 bonding/bonding layer and for application of the FOTS organo- silane overlying monolayer (S AM) layer.
• chlorosilane precursors such as a trichlorosilanes, dichlorosilanes work well as a precursor for oxide formation.
• specific advantageous precursors include hexachlorodisilane (Si 2 Cl 6 ) and hexachlorodisiloxane (Si 2 Cl 6 O).
• chlorosiloxanes, fluorosilanes, and fluorosiloxanes may also be used as precursors.
• the vapor deposited silicon oxide coating from the SiCl 4 and H 2 O precursors was applied over glass, polycarbonate, acrylic, polyethylene and other plastic materials using the same process conditions as those described above with reference to the silicon substrate. Prior to application of the silicon oxide coating, the surface to be coated was treated with an oxygen plasma.
• a silicon oxide coating of the kind described above can be applied over a self aligned monolayer (SAM) coating formed from an organic precursor, for example and not by way of limitation from fluoro-tetrahydrooctyldimethylchforosilane (FOTS). Prior to application of the silicon oxide coating, the surface of the SAM should be treated with an oxygen plasma.
• SAM self aligned monolayer
• a FOTS coating surface requires a plasma treatment of about 10 - 30 seconds to enable adhesion of the silicon oxide coating.
• the plasma treatment creates reactive OH sites on the surface of the SAM layer, which sites can subsequently be reacted with SiCl 4 and water precursors, as illustrated in Figure 2, to create a silicon oxide coating.
• This approach allows for deposition of multi-layered molecular coatings, where all of the layers may be the same, or some of the layers may be different, to provide particular performance capabilities for the multi-layered coating.
• Functional properties designed to meet the end use application of the finalized product can be tailored by either sequentially adding an organo-silane precursor to the oxide coating precursors or by using an organo-silane precursor(s) for formation of the last, top layer coating.
• Organo-silane precursor materials may include functional groups such that the silane precursor includes an alkyl group, an alkoxyl group, an alkyl substituted group containing fluorine, an alkoxyl substituted group containing fluorine, a vinyl group, an ethynyl group, or a substituted group containing a silicon atom or an oxygen atom, by way of example and not by way of limitation.
• organic-containing precursor materials such as (and not by way of limitation) silanes, chlorosilanes, fluorosilanes, methoxy silanes, alkyl silanes, amino silanes, epoxy silanes, glycoxy silanes, and acrylosilanes are useful in general.
• FDTS perfluorodecyltrichlorosilanes
• UTS undecenyltrichlorosilanes
• VTS vinyl-trichlorosilanes
• DTS decyltrichlorosilanes
• OTS octadecyltrichlorosilanes
• DDMS dimethyldichlorosilanes
• DDTS dodecenyltricholrosilanes
• FTS fluoiO-tetrahydrooctyldimethylchlorosilanes
• ATMS aminopropylmethoxysilanes
• ATMS fluoropropylmethyldichlorosilanes
• perfluorodecyldimethylchlorosilanes aminopropylmethoxysilanes
• the OTS, DTS, UTS, VTS, DDTS, FOTS, and FDTS are all trichlorosilane precursors.
• the other end of the precursor chain is a saturated hydrocarbon with respect to OTS, DTS, and UTS; contains a vinyl functional group, with respect to VTS and DDTS; and contains fluorine atoms with respect to FDTS (which also has fluorine atoms along the majority of the chain length).
• Other useful precursors include 3-aminopropyltrimethoxysilane (APTMS), which provides amino functionality, and 3-glycidoxypropyltrimethoxysilane (GPTMS).
• silane-based precursors such as commonly used di- and tri- chlorosilanes, for example and not by way of limitation, tend to create agglomerates on the surface of the substrate during the coating formation. These agglomerates can cause structure malfunctioning or stiction. Such agglomerations are produced by partial hydrolysis and polycondensation of the polychlorosilanes.
• This agglomeration can be prevented by precise metering of moisture in the process ambient which is a source of the hydrolysis, and by carefully controlled metering of the availability of the chlorosilane precursors to the coating formation process.
• the carefully metered amounts of material and careful temperature control of the substrate and the process chamber walls can provide the partial vapor pressure and condensation surfaces necessary to control formation of the coating on the surface of the substrate rather than promoting undesired reactions in the vapor phase or on the process chamber walls.
• Example Four [0159] When the oxide-forming silane and the organo-silane which includes the functional moiety are deposited simultaneously (co-deposited), the reaction may be so rapid that the sequence of precursor addition to the process chamber becomes critical. For example, in a co-deposition process of SiCl 4 ZFOTSZH 2 O, if the FOTS is introduced first, it deposits on the glass substrate surface very rapidly in the form of islands, preventing the deposition of a homogeneous composite film. Examples of this are provided in Table 4, below.
• the oxide-forming silane is applied to the substrate surface first, to form the oxide layer with a controlled density of potential OH reactive sites available on the surface, the subsequent reaction of the oxide surface with a FOTS precursor provides a uniform film without the presence of agglomerated islands of polymeric material, examples of this are provided in Table 4 below.
• Step 1 Pump down the reactor and purge out the residual air and moisture to a final baseline pressure of about 30 mTorr or less.
• Step 2. Perform O 2 plasma clean of the substrate surface to eliminate residual surface contamination and to oxygenate/hydroxylate the substrate.
• the cleaning plasma is an oxygen-containing plasma.
• the plasma source is a remote plasma source, which may employ an inductive power source. However, other plasma generation apparatus may be used. In any case, the plasma treatment of the substrate is typically carried out in the coating application process chamber.
• Step 3 Inject SiC] 4 and within 10 seconds inject water vapor at a specific partial pressure ratio to the SiCl 4 , to form a silicon oxide base layer on the substrate.
• Step 5 Introduce the chlorosilane precursor and water vapor to form a hydrophobic coating.
• FOTS vapor was injected first to the charging reservoir, and then into the coating process chamber, to provide a FOTS partial pressure of 200 mTorr in the process chamber, then, within 10 seconds, H 2 O vapor (300 cc at 12 Torr) was injected to provide a partial pressure of about 800 mTorr, so that the total reaction pressure in the chamber was 1 Torr.
• H 2 O vapor 300 cc at 12 Torr
• the substrate was exposed to this mixture for 5 to 30 minutes, typically 15 minutes, where the substrate temperature was about 35 0 C. Again, the process chamber surface was also at about 35°C.
• Step 1 Pump down the reactor and purge out the residual air and moisture to a final baseline pressure of about 30 mTorr or less.
• Step 2. Perform remote O 2 plasma clean to eliminate residual surface contamination and to oxygenate/hydroxylatethe glass substrate. Process conditions for the plasma treatment were the same as described above with reference to Run No. 2.
• Step 3. Inject FOTS into the coating process chamber to produce a 200 mTorr partial pressure in the process chamber. Then, inject 1 volume (300 cc at 100 Torr) of SiQ from a vapor reservoir into the coating process chamber, to a partial pressure of 4 Torr in the process chamber.
• Step 4 Evacuate the process chamber to a pressure of about 30 mTorr to remove excess reactants.
• Figures 3A and 3B are schematics of AFM (atomic force microscope) images of surfaces of silicon oxide bonding coatings as applied over a silicon substrate.
• the initial silicon substrate surface RMS roughness was determined to be less than about 0.1 nm.
• Figure 3 A illustrates a deposition process in which the substrate was silicon. The surface of the silicon was exposed to an oxygen plasma in the manner previously described herein for purposes of cleaning the surface and creating hydroxyl availability on the silicon surface.
• SiCl 4 was charged to the process chamber from a SiCl 4 vapor reservoir, creating a partial pressure of 0.8 Torr in the coating process chamber.
• FIG. 3B illustrates a deposition process in which the substrate was silicon. The surface of the silicon was exposed to an oxygen plasma in the manner previously described herein for purposes of cleaning the surface and creating hydroxyl availability on the silicon surface.
• SiCl 4 was charged to the process chamber from a SiCl 4 vapor reservoir, creating a partial pressure of 4 Torr in the coating process chamber.
• HO vapor was charged to the process chamber from a H 2 O vapor reservoir, creating a partial pressure of 10 Torr in the coating process chamber.
• the total pressure in the coating process chamber was 14 Torr.
• the substrate temperature and the temperature of the process chamber walls was about 35°C.
• the substrate was exposed to the mixture of SiCl 4 and H 2 O for a time period of 10 minutes.
• the silicon oxide coating thickness obtained was about 30 nm.
• the coating roughness in RMS was 4.2 nm and Ra was 3.4 nm.
• FIG. 4 shows a graph 400 of the dependence of the water contact angle (an indication of hydrophobicity of a surface) as a function of the substrate exposure time for a silicon substrate coated directly with an organo-silane coating generated from a DDMS (dimethyldichlorosilane) precursor.
• the silicon substrate was cleaned and functionalized to provide surface hydroxyl groups by an oxygen plasma treatment of the kind previously described herein.
• DDMS was then applied at a partial pressure of 1 Torr, followed within 10 seconds by H 2 O applied at a partial pressure of 2 Torr, to produce a total pressure within the process chamber of 3 Torr.
• graph 400 the substrate exposure period with respect to the DDMS and H 2 O precursor combination is shown in minutes on axis 402, with the contact angle shown in degrees on axis 404.
• Curve 406 illustrates that it is possible to obtain a wide range of hydrophobic surfaces by controlling the process variables in the manner of the present invention. The typical standard deviation of the contact angle was less than 2 degrees across the substrate surface. Both wafer-to wafer and day-to day repeatability of the water contact angle were within the measurement error of ⁇ 2° for a series of silicon samples.
• Figure 5 illustrates contact angles for a series of surfaces exposed to water, where the surfaces exhibited different hydrophobicity, with an increase in contact angle representing increased hydrophobicity. This data is provided as an illustration to make the contact angle data presented in tables herein more meaningful.
• FIG. 6A shows a three dimensional schematic 600 of film thickness of a silicon oxide bonding layer coating deposited on a silicon surface as a function of the partial pressure of silicon tetrachloride and the partial pressure of water vapor present in the process chamber during deposition of the silicon oxide coating, where the temperature of the substrate and of the coating process chamber walls was about 35 °C, and the time period the silicon substrate was exposed to the coating precursors was four minutes after completion of addition of all precursor materials.
• the precursor SiCl 1 vapor was added to the process chamber first, with the precursor H 2 O vapor added within 10 seconds thereafter.
• the partial pressure of the IpD in the coating process chamber is shown on axis 602, with the partial pressure of the SiCl 4 shown on axis 604.
• the film thickness is shown on axis 606 in Angstroms.
• the film deposition time after addition of the precursors was 4 minutes.
• the thinner coatings exhibited a smoother surface, with the RMS roughness of a coating at point 608 on Graph 600 being in the range of 1 nm (10 A).
• the thicker coatings exhibited a rougher surface, which was still smooth relative to -coatings generally known in the art.
• the RMS roughness of the coating was in the range of 4nm (40 ⁇ ).
• Figure 7 A shows a three dimensional schematic 700 of the film roughness in RMS, nm which corresponds with the coated substrate for which the coating thickness is illustrated in Figure 6A.
• the partial pressure of the H 2 O in the coating process chamber is shown on axis 702, with the partial pressure of the SiCl 4 shown on axis 704.
• the film roughness in RMS, nm is shown on axis 706.
• the film deposition time after addition of all of the precursors was 7 minutes.
• the thinner coatings exhibited a smoother surface, with the RMS roughness of a coating at point 708 being in the range of lnm (10 A) and the roughness at point 710 being in the range of 4 nm (40 A) .
• Figure 6B shows a three dimensional schematic 620 of film thickness of the silicon oxide bonding layer illustrated in Figure 6A as a function of the water vapor partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
• the time period of exposure of the substrate is shown on axis 622 in minutes, with the H 2 O partial pressure shown on axis 624 in Torr, and the oxide coating thickness shown on axis 626 in Angstroms.
• the partial pressure OfSiCl 4 in the silicon oxide coating deposition chamber was 0.8 Torr.
• Figure 6C shows a three dimensional schematic 640 of film thickness of the silicon oxide bonding layer illustrated in Figure 6A as a function of the silicon tetrachloride partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
• the time period of exposure is shown on axis 642 in minutes, with the SiCl 4 partial pressure shown on axis 646 in Torr, and the oxide thickness shown on axis 646 in Angstroms.
• the H 2 O partial pressure in the silicon oxide coating deposition chamber was 4 Torr.
• a comparison of Figures 6A - 6C makes it clear that it is the partial pressure of the H 2 O which must be more carefully controlled in order to ensure that the desired coating thickness is obtained.
• Figure 7B shows a three dimensional schematic 720 of film roughness of the silicon oxide bonding layer illustrated in Figure 6B as a function of the water vapor partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
• the time period of exposure of the substrate is shown on axis 722 in minutes, with the H 2 O partial pressure shown on axis 724 in Torr, and the surface roughness of the silicon oxide layer shown on axis 726 in RMS, nm.
• the partial pressure of the SiCl 4 in the silicon oxide coating deposition chamber was 2.4 Torr.
• Figure 7C shows a three dimensional schematic 740 of film roughness thickness of the silicon oxide bonding layer illustrated in Figure 6 A as a function of the silicon tetrachloride partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
• the time period of exposure is shown on axis 642 in minutes, with the SiCl 4 partial pressure shown on axis 646 in Torr, and the surface roughness of the silicon oxide layer shown on axis 746 in RMS, nm.
• the partial pressure of the H 2 O in the silicon oxide coating deposition chamber was 7.0 Torr.
• Figure 8 A is a graph 800 which shows the hydrophilicity of an oxide-based layer on different substrate materials, as a function of the thickness of the oxide-based layer. The data presented in Figure 8 A indicates that to obtain full surface coverage by the oxide-based layer, it is necessary to apply a different thickness of oxide-based layer depending on the underlying substrate material.
• the oxide-based layer was a silicon-oxide-based layer prepared in general in the manner described above, with respect to Run No.
• the graph 800 shows the contact angle for a deionized (DI) water droplet, in degrees, on axis 804, as measured for a given oxide-based layer surface, as a function of the thickness of the oxide-based layer in Angstroms shown on axis 802.
• Curve 806 illustrates a silicon-oxide- based layer deposited over a single crystal silicon wafer surface.
• Curve 808 represents a silicon-oxide-based layer deposited over a soda lime glass surface.
• Curve 810 illustrates a silicon-oxide-based layer deposited over a stainless steel surface.
• Curve 812 shows a silicon- oxide-based layer deposited over apolystyrene surface.
• Curve 814 illustrates a silicon-oxide- based layer deposited over an acrylic surface.
• Graph 800 shows that a single crystal silicon substrate required only about a 30 A thick coating of a silicon oxide-based layerto provide a DI water droplet contact angle of about 5 degrees, indicating the maximum hydrophilicity typically obtained using a silicon o oxide-based layer.
• the glass substrate required about 80 A of the silicon oxide-based layer to provide a contact angle of about 5 degrees.
• the stainless steel substrate required a silicon oxide-based layer thickness of about 80 A to provide the contact angle of 5 degrees.
• FIG. 8B shows a graph 820, which illustrates the relationship between the hydrophobicity obtained on the surface of a SAM layer deposited from perfluorodecyltrichlorosilane (FDTS), as a function of the thickness of an oxide-based layer over which the FDTS layer was deposited.
• FDTS perfluorodecyltrichlorosilane
• the oxide layer was deposited in the manner described above, using tetrachlorosilane precursor, with sufficient moisture that a silicon oxide surface having sufficient hydroxyl groups present to provide a surface contact angle (with a DI water droplet) of 5 degrees was produced.
• the oxide-based layer and the organic-based layer generated from an FDTS precursor were deposited as follows: The process chamber was vented and the substrate was loaded into the chamber. Prior to deposition of the oxide-based layer, the surface of the substrate was plasma cleaned to eliminate residual surface contamination and to oxygenate / hydroxylate the substrate. The chamber was pumped down to a pressure in the range of about 30 mTorr or less.
• the substrate surface was then plasma treated using a low density, non-physically-bombarding plasma which was created externally from a plasma source gas containing oxygen.
• the plasma was created in an external chamber which is a high efficiency inductively coupled plasma generator, and was fed into the substrate processing chamber.
• the plasma treatment was in the manner previously described herein, where the processing chamber pressure during plasma treatment was in the range of about 0.5 Torr, the temperature in the processing chamber was about 35 °C, and the duration of substrate exposure to the plasma was about 5 minutes. [0193] After plasma treatment, the processing chamber was pumped down to a pressure in the range of about 30 mTorr or less to evacuate remaining oxygen species.
• processing chamber may be purged with nitrogen up to a pressure of about 10 Torr to about 20 Torr and then pumped down to the pressure in the range of about 30 mTorr.
• An adhering oxide-based layer was then deposited on the substrate surface. The thickness of the oxide- based layer depended on the substrate material, as previously discussed.
• SiCl 4 vapor was injected into the process chamber at a partial pressure to provide a desired nominal oxide- based layer thickness.
• the partial pressure in the process chamber of the SiCl 4 vapor ranges from about 0.5 Torr to about 4 Torr, more typically from about 1 Torr to about 3 Torr.
• the reaction time to produce the oxide layer may range from about 5 minutes to about 15 minutes, depending on the processing temperature, and in the exemplary embodiments described herein the reaction time used was about 10 minutes at about 35°C.
• the chamber was once again pumped down to a pressure in the range of about 30 mTorr or less.
• the processing chamber may be purged with nitrogen up to a pressure of about 10 Torr to about 20 Torr and then pumped down to the pressure in the range of about 30 mTorr, as previously described.
• the organic-based layer deposited from an FDTS precursor was then produced by injecting FDTS into the process chamber to provide a partial pressure ranging from about 30 mTorr to about 1500 mTorr, more typically ranging from about 100 mTorr to about 300 mTorr.
• the exemplary embodiments described herein were typically carried out using an FDTS partial pressure of about 150 mTorr.
• water vapor was injected into the process chamber to provide a partial pressure of water vapor ranging from about 300 mTorr to about 1000 mTorr, more typically ranging from about 400 mTorr to about 800 mTorr.
• the exemplary embodiments described herein were typically carried out using a water vapor partial pressure of about 600 mTorr.
• the reaction time for formation of the organic-based layer ranged from about 5 minutes to about 30 minutes, depending on the processing temperature, more typically from about 10 minutes to about 20 minutes, and in the exemplary embodiments described herein the reaction time used was about 15 minutes at about 35 0 C.
• the oxide-based layer was a silicon-oxide-based layer prepared in the manner described above, with respect to Figure 8A.
• the graph 820 shows the contact angle of a DI water droplet, in degrees, on axis 824, as measured for an oxide-based layer surface over different substrates, as a function of the thickness of the oxide-based layer in Angstroms shown on axis 822.
• Curve 826 illustrates a silicon-oxide-based layer deposited over a single crystal silicon wafer surface described with reference to Figure 8 A.
• Curve 828 represents a silicon-oxide-based layer deposited over a glass surface as described with reference to Figure 8A.
• Curve 830 illustrates a silicon-oxide-based layer deposited over a stainless steel surface, as described with reference to Figure 8 A.
• Curve 832 shows a silicon- oxide-based layer deposited over a polystyrene surface, as described with reference to Figure 8 A.
• Curve 834 illustrates a silicon-oxide-based layer deposited over an acrylic surface described with reference to Figure 8 A.
• the FDTS-generated SAM layer provides an upper surface containing fluorine atoms, which is generally hydrophobic in nature. The maximum contact angle provided by this fluorine-containing upper surface is about 117 degrees.
• this maximum contact angle indicating an FDTS layer covering the entire substrate surface is only obtained when the underlying oxide-based layer also covers the entire substrate surface at a particular minimum thickness.
• oxide-based layer thickness There appears to be another factor which requires a further increase in the oxide-based layer thickness, over and above the thickness required to fully cover the substrate, with respect to some substrates. It appears this additional increase in oxide-layer thickness is necessary to fully isolate the surface organic-based layer, a self-aligned-monolayer (SAM), from the effects of the underlying substrate. It is important to keep in mind that the thickness of the SAM deposited from the FDTS layer is only about 10 ⁇ to about 20 A.
• Graph 820 shows that a SAM surface layer deposited from FDTS over a single crystal silicon substrate exhibits the maximum contact angle of about 117 degrees when the oxide-based layer overlying the single crystal silicon has a thickness of about 30 A or greater.
• the surface layer deposited from FDTS over a glass substrate exhibits the maximum contact angle of about 117 degrees when the oxide-based layer overlying the glass substrate has a thickness of about 150 ⁇ or greater.
• the surface layer deposited from FDTS over the stainless steel substrate exhibits the maximum contact angle of about 117 degrees when the oxide-based layer overlying the stainless steel substrate has a thickness of between 80 A and 150 A or greater.
• FIG. 9 illustrates the stability of the hydrophobic surface provided by the SAM surface layer deposited from FDTS, when the coated substrate is immersed in deionized (DI) water for a specified time period.
• DI deionized
• FIG. 9 shows a graph 980 which illustrates the stability of an approximately 15 A thick layer of a SAM deposited from FDTS over an acrylic substrate without and with various oxide coatings applied over the acrylic substrate surface. Curve 986 shows the contact angle when the SAM was applied directly over the acrylic substrate.
• Curve 988 shows the contact angle for a test specimen where a 150 ⁇ thick silicon oxide layer was applied over the acrylic substrate surface prior to application of the SAM layer.
• Curve 990 shows the contact angle for a test specimen where a 400 A thick silicon oxide layer was applied over the acrylic substrate surface prior to application of the SAM layer. While increasing the thickness of the oxide layer helped to increase the initial hydrophobic properties of the substrate surface (indicating improved bonding of the SAM layer or improved surface coverage by the SAM layer), the structure was not stable, as indicated by the change in contact angle over time.
• the number of sets of oxide-based layer/organic-based layer may be fewer; however, use of at least two sets of layers helps provide a more mechanically stable structure.
• the stability of the deposited SAM organic-based layers can be increased by baking for about one half hour at 11O 0 C, to crosslink the organic-based layers. Baking of a single pair of layers is not adequate to provide the stability which is observed for the multilayered structure, but baking can even further improve the performance of the multilayered structure.
• the integrated method for creating a multilayered structure of the kind described above includes: Treatment of the substrate surface to remove contaminants and to provide either -OH or halogen moieties on the substrate surface, typically the contaminants are removed using a low density oxygen plasma, or ozone, or ultra violet (UV) treatment of the substrate surface.
• the -OH or halogen moieties are commonly provided by deposition of an oxide-based layer in the manner previously described herein.
• a first SAM layer is then vapor deposited over the oxide-based layer surface.
• the surface of the first SAM layer is then treated using a low density isotropic oxygen plasma, where the treatment is limited to just the upper surface of the SAM layer, with a goal of activating the surface of the first SAM. layer.
• the surface treatment is similar to a substrate pretreatment, where the surface is treated with the low density isotropic oxygen plasma for a time period ranging from about 25 seconds to about 60 seconds, and typically for about 30 seconds.
• the pretreatment is carried out by pumping the process chamber to a pressure ranging from about 15 mTorr to about 20 mTorr, followed by flowing an externally-generated oxygen-based plasma into the chamber at a plasma precursor oxygen flow rate of about 50 seem to 200 seem, typically at about 150 seem in the apparatus described herein, to create about 0.4 Torr in the substrate processing chamber.
• a second oxide-based layer is vapor deposited over the first sam layer.
• a second SAM layer is then vapor deposited over the second oxide-based layer.
• the second SAM layer is then plasma treated to activate the surface of the second SAM layer.
• the process of deposition of oxide-based layer followed by deposition of S AM layer, followed by activation of the SAM surface may be repeated a nominal number of times to produce a multilayered structure which provides the desired mechanical strength and surface properties.
• the surface properties desired are those of the final organic- based layer.
• the final organic-based layer may be different from other organic-based layers in the structure, so that the desired mechanical properties for the structure may be obtained, while the surface properties of the final organic-based layer are achieved.
• the final surface layer is typically a SAM layer, but may also be an oxide- based layer.
• the thickness and roughness of the initial oxide- based layer can be varied over wide ranges by choosing the partial pressure of precursors, the temperature during vapor deposition, and the duration time of the deposition. Subsequent oxide-based layer thicknesses may also be varied, where the roughness of the surface may be adjusted to meet end use requirements.
• the thickness of an organic-based layer which is applied over the oxide-based layer will depend on the precursor molecular length of the organic-based layer. In the instance where the organic-based layer is a SAM, such as FOTS, for example, the thickness of an individual SAM layer will be in the range of about 15 A.
• the thicknesses for a variety of SAM layers are known in the art.
• organic-based layer thicknesses will depend on the polymeric structure which is deposited using polymer vapor deposition techniques.
• the organic-based layers deposited may be different from each other, and may present hydrophilic or hydrophobic surface properties of varying degrees.
• the organic-based layers may be formed from a ' mixture of more than one precursor.
• the organic-based layer may be vapor deposited simultaneously with an oxide-based structure to provide crosslinking of organic and inorganic materials and the formation of a dense, essentially pinhole-free structure.
• FIGS 1 OA and 1 OB provide comparative examples which further illustrate the improvement in structure stability and surface properties for a SAM which is deposited from a FOTS precursor over a multilayered structure of the kind described above (with respect to a SAM deposited from FDTS).
• Figure 1OA shows a graph 1000 which illustrates the improvement in DI water stability of a SAM when the organic-based precursor was fluoro- tetrahydrooctyldimethylchlorosilanes (FOTS) and the multilayered structure described was present beneath the FOTS based SAM layer.
• FOTS fluoro- tetrahydrooctyldimethylchlorosilanes
• Curve 1008 shows physical property data (contact angle with a DI water droplet) for an approximately 800 A thick layer of a SAM deposited from FOTS directly upon a single crystal silicon substrate which was oxygen plasma pre-treated in the manner previously described herein.
• the DI water droplet contact angle is shown on axis 1004 in degrees; the number of days of immersion of the substrate (with overlying oxide and SAM layer in place) is shown on axis 1002 in days.
• the stability of the organic-based SAM layer decreases gradually from an initial contact angle of about 108° to a contact angle of less than about 90° after a 14 day time period, as illustrated by curve 1006.
• This decrease in contact angle compares with a decrease in contact angle from about 110° to about 105 ° over the 14 day time period, when the structure is a series of five pairs of silicon oxide / FOTS SAM layers, with a SAM surface layer, as illustrated by curve 1008.
• Figure 1OB shows a graph 1020 illustrating stability in DI water for the same FOTS organic-based SAM layer applied directly over the substrate or applied over a series of five pairs of silicon oxide / FOTS SAM layers, when the substrate is soda lime glass.
• the DI water droplet contact angle is shown on axis 1024 in degrees; the number of days of immersion of the substrate (with overlying oxide and SAM layer in place) is shown on axis 1022 in days.
• the stability of the organic-based SAM layer decreased gradually from an initial contact angle of about 98° to a contact angle of less than about 88° after a 14 day time period, as illustrated by curve 1026. This compares with a decrease in contact angle from about 108° to about 107° overthe 14 day time period, when the structure is a series of five pairs of silicon oxide / FOTS SAM layers, as illustrated by curve 1028.
• FIGS HA and HB show schematic views of the top surfaces of high throughput screening (HTS) micro-plates, where water droplets were applied to small wells in the plates.
• Figure 1 IA illustrates the ability of the water droplet to flow into the wells in the plate with no coating on the polystyrene substrate of the screening plate.
• Figure 1 IB illustrates the ability of the water drop to flow into the wells in the plate when a 150 A thick oxide layer was applied by molecular vapor deposition (MVDTM, Applied MicroStructures, Inc., San Jose, California) over the polystyrene surface, followed by MVDTM of a layer of biocompatible, mono functional PEG (mPEG) at a thickness of about 20 A.
• MVDTM molecular vapor deposition
• mPEG mono functional PEG
• a 1536-well screening micro-plate typically measures about 130 mm x 85 mm x 10 mm (L x W x H) and contains 1536 small wells.
• a well typically has a volume of about 12 ⁇ l.
• a micro-plate well normally has a diameter ranging from about 1.0 mm to about 2.0 mm and extends to a depth ranging from about 1.0 mm deep to about 5.0 mm deep.
• the aspect ratio (the depth of the well divided by the diameter of the well) of a well ranges from about 0.5 : 1 to about 5 : 1.
• an aspect ratio ranges from about 2 : 1 to about 4 : 1.
• micro-plates are made of very hydrophobic materials, such as polystyrene or polypropylene, each of which has a water contact angle of around 100°. Water readily beads up on these materials, making it difficult to fill narrow wells formed within micro- plates made from such hydrophobic materials. The difficulty in filling these wells will become more severe in future micro-plates with higher well density.
• the droplet size of a droplet of water-based material applied to each well often ranges from about 1 mm to about 3 mm. Allowing for even small amounts of imprecision in application of a droplet of water-based material, it is apparent why a droplet may trap air in the well and sit at the top of the well.
• Figure 1 IA shows how the water-based material flowed into the wells in the micro-plate 1110, to provide a relatively flush upper surface 1112 of the water-based material on the upper surface 1113 of micro-plate 1110 at each well 1114.
• the droplets of water-based material were comprised of deionized water.
• the micro-plate polystyrene substrates were at 25°C, and the length of time permitted for the water-based material to flow into the wells was about 2 - 3 seconds with respect to the test results illustrated above.
• the oxide / PEG-coated micro-plates were prepared as follows: The surface of the polystyrene plate was exposed to an oxygen plasma (150 seem O 2 at an RF power of about 200 W in an Applied MicroStructures' MVDTM process chamber) for 5 minutes in order to clean the surface and create hydroxyl availability on the polystyrene surface.
• SiCl 4 was charged to the process chamber from a SiCl 4 vapor reservoir, where the SiCl 4 vapor pressure in the vapor reservoir was 18 Torr, creating a partial pressure of 2.4 Torr in the coating process chamber.
• a first volume of IJO vapor was charged to the process chamber from a H 2 O vapor reservoir, where the H 2 O vapor pressure in the vapor reservoir was 18 Torr.
• a total of five chamber volumes of H 2 O were charged, creating a partial pressure of 6.0 Torr in the coating process chamber.
• the total pressure in the coating process chamber was 9 Torr.
• the substrate temperature and the temperature of the process chamber walls was about 35 0 C. The substrate was exposed for a time period of about 10 minutes after each H 2 O addition.
• the silicon oxide coating thickness obtained was about 150 A.
• the HTS micro-plate embodiment illustrates the use of a hydrophilic coating to draw a water-based substance into wells in an HTS micro-plate which is formed from plastic
• the interior of the wells has been coated to provide a hydrophilic surface, while the exterior surface of the plate remains hydrophobic because it has not been coated. This may be accomplished using a masking material over the plastic surface exterior of the wells during application of a coating which provides a hydrophilic surface over the interior of the wells.
• the hydrophobic surface surrounding a well helps force the water-based droplet into the hydrophilic interior of the well, and reduces the possibility of well-to-well contamination of samples being tested.

Applications Claiming Priority (2)

Publications (1)

Family

ID=37394322

Family Applications (1)

Country Status (2)

Cited By (8)

Families Citing this family (56)

Family Cites Families (34)

• 2005
  • 2005-05-05 US US11/123,487 patent/US20060251795A1/en not_active Abandoned
• 2006
  • 2006-04-12 WO PCT/US2006/014071 patent/WO2006121573A1/en active Application Filing
• 2009
  • 2009-11-03 US US12/611,639 patent/US7955704B2/en active Active
• 2011
  • 2011-05-13 US US13/107,243 patent/US8323723B2/en active Active

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events