Coating processes – Coating by vapor – gas – or smoke
Reexamination Certificate
1999-04-22
2001-07-24
Meeks, Timothy (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
C427S255230, C427S255250, C427S255280
Reexamination Certificate
active
06265026
ABSTRACT:
BACKGROUND
The present invention relates to vapor phase deposition, and more particularly to vapor phase deposition of coatings.
Uniform and monolayer coatings, such as silanes, on silicon based surfaces are desired for a number of applications. In the micromachining of microelectromechanical system (MEMS), a final hydrophobic coating on the device is needed to prevent adhesion of adjacent surfaces due to capillary forces in water.
In contrast, a hydrophillic coating is desired for silicon based medical devices, such as filters or capsules, that are in contact with protein solutions to regulate hydrophilicity and minimize unspecific protein adsorption.
Currently, the coating methods most often used typically involve the assembly of a silane “monolayer” onto a silicon surface in an organic solution. It is known that alcohol groups, being hydrophilic and neutral, can drastically reduce protein adsorption on the surface of contact lenses, glass membranes, and porous silica. To assemble a monolayer of alcohol groups onto a silicon filter surface for protein ultrafiltration, one step is to coat silicon with vinyltrichlorosilane (VTS) or &ggr;-glycidoxy-propyltrimethoxysilane (GPTMS), then convert the vinyl or epoxide resulting from the initial coating step to alcohol groups. Typical precursor molecules are alkyltrichlorosilanes (denoted as RSiCl
3
) or alkyltrimethoxysilanes (denoted as RSi(OCH
3
)
3
), where R is any desired functional group to be introduced into the coating. However, trichlorosilanes and trimethoxysilanes are very sensitive to moisture. Even trace amounts of water in the organic solution could lead to polymerization. This causes the formation of multilayers with variable thicknesses, and submicron aggregates or islands on the silicon surface. To avoid this polymerization problem, an alternative method involves the use of monochlorosilane, which is incapable of polymerization. However, monochlorosilanes form a less stable coating than alkyltrichlorosilanes or alkyltrimethoxysilanes.
Another method calls for coating the silanes in a high vacuum. This approach, however, is more expensive than solution coating.
SUMMARY
One aspect of the invention is directed to an apparatus for forming a coating on an article. The apparatus includes a process chamber in which the article is supported; a storage region to contain a liquid coating reagent; an inflow assembly to flow a carrier gas through the storage region to produce a gas mixture including a vaporized coating reagent and the carrier gas, and to direct the gas mixture into the process chamber and onto the article to deposit the vaporized coating reagent on the article; and an outflow assembly to remove the gas mixture from the process chamber.
In another aspect, the invention is directed to a method of forming a coating on a surface of an article placed in a process chamber. The method includes providing a liquid coating reagent in a flow passageway extending into the process chamber; flowing a carrier gas through the flow passageway to produce a gas mixture including a vaporized coating reagent and the carrier gas; directing the gas mixture into the process chamber; and depositing the vaporized coating reagent on the surface of the article to form a coating thereon.
In yet another aspect, the invention is directed to a method of forming a coating on a surface of an article wherein, the method includes placing a porous article between an upper housing portion and a lower housing portion of a process chamber. The article spans a cross-section of the process chamber and the upper housing portion is sealed to the lower housing portion. A liquid coating reagent is introduced into a flow passageway extending into the process chamber, and a carrier gas is flowed through the flow passageway to produce a gas mixture including a vaporized coating reagent and the carrier gas. This gas mixture is directed into the process chamber to contact the article and form a coating thereon. The gas mixture is then exhausted from the process chamber.
Features of the just described method include the following. The carrier gas is flowed through the flow passageway before introducing the liquid coating reagent in the flow passageway. The flow rate of the carrier gas is measured to provide a first flow rate. After the gas mixture has been exhausted from the process chamber, the flow rate of the carrier gas is measured again to provide a second flow rate. The first flow rate is compared to the second flow rate to determine if the coating procedure has been performed successfully.
Advantages of the invention include the following. The coating has a surface that is extremely smooth and without any detectable submicron aggregates. A uniform coating of about 1 nanometer (nm) in thickness can be consistently achieved. Use of the invention is particularly advantageous whenever it is necessary to coat irregular shapes or channels in microdevices. No solvent is needed in the coating step. The invention is applicable to a wide range of surfaces, including silicon based surfaces, glass based surfaces and metal oxide based surfaces.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the invention will be apparent from the description and drawings, and from the claims.
REFERENCES:
patent: 5090985 (1992-02-01), Soubeyrand et al.
patent: 5108792 (1992-04-01), Anderson et al.
patent: 5419924 (1995-05-01), Nagashima et al.
patent: 5651900 (1997-07-01), Keller et al.
patent: 5916359 (1999-06-01), Baum et al.
patent: 5925189 (1999-07-01), Nguyen et al.
Sekoguchi et al, Han'guk Pyomyon Konghak Hoechi, 29(6) P. 781-787 (Abstract), 1996.*
Chang et al., “Use of Oxiranes in the Preparation of Bonded Phase Supports,” Chromatography, 120, 321-333, 1976.
Jorgenson et al., “Capillary Zone Electrophoresis,” Science, vol.222, 266-272, 1983.
Schnabel et al., “Review: Controlled-pore Glass as a Stationary Phase in Chromatography,” J. Chromatography, 544, 137-146, 1991.
Gray et al., “Ellipsometric and Interferometric Characterization of DNA Probes Immobilized on a Combinatorial Array,” Langmuir, 13, 2833-2842, 1997.
Kittilsland et al., “A Sub-micron Particle Filter in Silicon,” Sensors and Actuators, A21-A23, 904-907, 1990.
Tu et al., “Characterization of bulk-micromachined, direct-bonded silicon nanofilters,” SPIE Bios '98 Conference, vol.3258, pp. 148-155, 1998.
Brody et al., “Biotechnology at Low Reynolds Numbers,” Biophysical Journal, 71, 3430-3441, 1996.
Wilding et al., “Manipulation and Flow of Biological Fluids in Straight channels Micromachined in Silicon,” Clinical Chemistry, 40. 43-47, 1994.
Wasserman et al., “Structure and Reactivity of Alkylsiloxane Monolayers Formed by Reaction of Alkyltrichlorosilanes on Silicon Substrates,” Langmiur, 5, 1074-1087, 1989.
Ulman, “Formation and Structure of Self-Assembled Monolayers,” Chemical Reviews, 96, 1553-1554, 1996.
Maboudian et al., “Critical Review: Adhesion in surface micromechanical structures,” J. Vacuum Science and Technology B 15, 1-20, 1997.
Jonsson, et al., “Chemical Vapor Deposition of Silanes,” Thin Solid Film, 124, 117-123, 1985.
Hoffmann et al., “Vapor Phase Self-Assembly of Fluorinated Monlayers on Silicon and German Oxide,” Langmuir, 13, 1877-1880, 1997.
Duchet et al., “Influence of the Deposition Process on the Structure of Grafted Alkylsilane Layers,” Langmuir, 13, 2271-2278, 1997.
Yuchun Wang, “Surface Modification of Pollymeric Membranes and Silicon Filters,” Disertation work, UC Berkeley, Fall 1998, 109 pp.
Wang et al., “Vapor phase deposition of uniform and ultrathin silanes”, Proceedings of SPIE vol. 3258, SPIE Bios'98, 1998, San Jose, CA, 9 pp.
Fish & Richardson P.C.
Meeks Timothy
The Regents of the University of California
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