Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
1998-11-05
2001-01-30
Beck, Shrive (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C427S578000, C427S237000, C427S238000
Reexamination Certificate
active
06180191
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to plasma processing and in particular to a method and apparatus for plasma enhanced chemical vapor deposition of a thin film onto the interior surface of a container.
BACKGROUND OF THE INVENTION
Traditionally, containers for chemically sensitive materials have been made from inorganic materials such as glass. Glass containers offer the advantage that they are substantially impenetrable by atmospheric gases and thus provide a product with a long shelf life. Glass containers are also readily recyclable. However, glass containers are heavy and expensive to manufacture.
More recently, lighter and less expensive containers made of polymeric materials are being used in applications where traditionally glass containers were used. These polymeric containers are less suspectable to breakage, are less expensive to manufacture, are lighter and less expensive to ship than glass containers. Further, polymeric containers can be made transparent thus allowing the contents of the container to be readily viewed by a consumer before the product is purchased.
However, polymeric containers are not without disadvantages. One significant disadvantage is that polymeric containers are ordinarily highly permeable to gases. This high permeability to gases allows atmospheric gases to pass through the polymeric container to the packaged product and also allows gases in the packaged product to escape through the polymeric container, both of which undesirably degrade the quality and shelf life of the packaged product.
One approach to decrease the gas permeability of polymeric containers is to form a multilayered polymeric container which includes at least one low gas permeable polymeric layer along with at least one other polymeric layer. However, such an approach is relatively complicated, costly and often produces a container which is difficult to recycle.
Another approach to decrease the gas permeability of polymeric containers is to deposit a barrier coating, i.e. a coating having a substantial resistance to the permeation of gaseous or volatile material, on the polymeric container. To date however, there are several obstacles which have prevented barrier coated polymeric containers from gaining wide acceptance.
One obstacle which has inhibited the use of barrier coated polymeric containers is that conventional barrier coating deposition techniques are not well suited for mass production. To illustrate, in Thomas et al., U.S. Pat. No. 5,378,510 a method and apparatus for depositing barrier coatings on the interior surface of a polymeric container is presented. However, in Thomas et al., a tubular plasma chamber
46
with downstream extension
52
, adaptor
50
, tube
54
and coaxial conduit are employed to convert an oxidizing gas into a plasma and to deliver the activated oxidizing gas species separately from organosilicon vapor to the vicinity of the article to be coated (see col. 6, lines 46-67 and FIG.
1
). Thus, although Thomas et al. demonstrates the feasibility of depositing a barrier coating on an article, the tubular plasma chamber and associated equipment are relatively expensive and complex and thus are not well suited to the production environment.
Another obstacle which has inhibited the use of barrier coated polymeric containers is the difficulty associated with depositing a uniform barrier coating. Generally, it is preferable to deposit a uniform barrier coating on the polymeric container to ensure that the entire polymeric container provides an effective gas permeation barrier.
One conventional technique to improve the uniformity of the deposited barrier coating is to rotate the container during processing. To illustrate, in Thomas et al. at col. 9, lines 14-20 the polymeric container is rotated during the deposition of the barrier coating to promote the even distribution of the barrier coating on the interior surface of the polymeric container. However, as rotation of the polymeric container is accomplished using an additional motor which rotates a shaft extending into the chamber through an air to vacuum feedthrough, rotation of the polymeric container further increases the cost and decreases the reliability of the barrier coating deposition process.
Accordingly, the art needs a simple, inexpensive and reliable process for depositing a barrier coating on a polymeric container. The process should have a fast cycle time to accommodate production demands. Further, the barrier coating deposited should have good uniformity without the necessity of rotating the polymeric container and the barrier coated polymeric container should be readily recyclable.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method and apparatus for depositing a thin film onto a surface of a container is presented.
The apparatus includes a chamber made of an electrically insulating material. Located adjacent an exterior surface of the chamber is a main electrode. Extending into the chamber is a counter electrode which is a hollow tube that also serves as a gas inlet.
The chamber is sealed on a first end with a chamber door and on a second end with a face plate. The face plate is fitted with a vent port capable of being connected to a vent valve and with a pressure port capable of being connected to a pressure measuring device.
The apparatus further includes a pumping plenum attached on a first end to the face plate and a T-coupler attached on a first end to a second end of the pumping plenum. The counter electrode extends through the pumping plenum and through the T-coupler. A vacuum seal is formed between the counter electrode and a second end of the T-coupler. The T-coupler is made of an electrically insulating material thus electrically isolating the counter electrode from the pumping plenum, the face plate and the chamber.
Also coupled to the T-coupler is a vacuum pump which is capable of creating a vacuum inside of the chamber.
The face plate also has a gas inlet port connected to a first process gas source. A first flow controller is coupled between the gas inlet port and the first process gas source. The first flow controller has the capability of controlling the flow of gas from the first process gas source to the chamber.
Connected to the counter electrode is a second process gas source. The second process gas source includes a first gas component source and a second gas component source. To control the flow of gas from the first gas component source to the counter electrode, a second flow controller is coupled between the counter electrode and the first gas component source.
The second gas component source is a container of organosilicon liquid. A vaporizer/flowcontroller system (VF system) is provided to vaporize the organosilicon liquid into organosilicon vapor and to control the flowrate of the organosilicon vapor generated. The VF system includes a first valve, a second valve and a capillary tube coupled on a first end to the first valve and on a second end to the second valve. The capillary tube has an inside diameter typically in the range of 0.001 inches to 0.010 inches. The first valve is also coupled to the counter electrode and the second valve is also coupled to a liquid line which is inserted into the container of organosilicon liquid.
Also connected to the counter electrode is a pressurized gas source. By opening an ejection shutoff valve connected between the pressurized gas source and the counter electrode, the counter electrode is flushed with compressed gas.
The main electrode and counter electrode are powered by an alternating current (AC) power supply which preferably has an output frequency of 13.56 megahertz (MHz).
To allow a container to be readily mounted in the chamber, a mandrel is mounted on the counter electrode. The mandrel has a lip on to which the container can be mounted. Extending through the mandrel are one or more gas outlet ports which allow process gas to flow from the interior to the exterior of the container.
Mounted on a first end of the counter electrode is a gas nozzle. The gas no
Beck Shrive
Chen Bret
Gunnison McKay & Hodgson, L.L.P.
Hodgson Serge J.
Nano Scale Surface Systems, Inc.
LandOfFree
Method for plasma deposition of a thin film onto a surface... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for plasma deposition of a thin film onto a surface..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for plasma deposition of a thin film onto a surface... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2479597