HK1145301A - Plasma deposition apparatus - Google Patents

Description

Plasma deposition apparatus

Background

The present invention relates to an apparatus for nano-coating a surface of an article with a thin film polymer layer by plasma deposition.

Prior Art

Heretofore, plasma chambers have been known in particular for processing semiconductor wafers. Typically, the plasma chamber of this processing system is made of metal, such as stainless steel or aluminum. Internal capacitive plates are typically applied to generate the discharge in order to maximize the power delivered into the system, while minimizing losses and maximizing the amount of product that can be loaded at any one time. One such arrangement is disclosed in published international patent application WO-A-2005/089961.

US patent 5,647,913 describes a method of cleaning materials adhering to the inner wall of a plasma reactor using a capacitive plate arrangement. Another description, us patent application 2007/0034156, uses an ion guide (ion guide apparatus) which is surrounded by the deposition chamber and includes an aperture through the deposition vacuum chamber for introducing ionized molecules from a source.

Inductively coupled plasmas have also been used at low pressures in order to achieve some degree of surface modification, typically by etching, activation or deposition; such as described in U.S. patent No. 5,683,548. Other processes described in the literature include the formation of nanopowders (US patent application 2005/0258766), amorphous carbon films at high temperatures (US 6,423,384) and decomposition treatments of certain fluorocarbons as disclosed in japanese patent application JP 10028836.

Other examples describe systems capable of performing partial oxidation upgrading of carbon-containing compounds to produce fuels for energy production, as disclosed in published international patent application WO-A-2004/112447, and continuous production of carbon nanomaterials using high temperature inductively coupled plasmas as in WO-A-2005/007565. In processes where the workpiece is physically or chemically modified, then it is highly possible that the workpiece plane is combined to ensure that the homogenization process occurs in the required time frame.

The system described above does not address the rapid throughput (rapid throughput-put) of plasma modified articles such as fabrics or garments, footwear, medical devices, electronics, or automotive or aerospace parts in three dimensions. In addition, they do not describe the attachment of ultra-thin, well-adhered polymer layers to the surface of an article.

The plasma reactions required for semiconductor processing using induction coils are suitable for generating high levels of gas impact and fragmentation and operate at parameters unsuitable for tailoring complex 3D products with specific chemical groups functionalities that can be provided by the attachment of organic molecules in a controlled manner.

As the plasma system is scaled up to larger volumes to accommodate more product, the total amount of water vapor and/or degassed solvent delays the time to reach the desired operating pressure and conditions, resulting in longer throughput times per piece of equipment and lower speed annual production volumes. In addition, the total processing time may increase significantly depending on the proximity of the article to the source producing the active required to give the desired technical effect.

Summary of The Invention

According to the present invention there is provided an apparatus for coating a surface of an article with a thin film polymer layer by plasma deposition, the apparatus comprising:

at least one processing chamber into which one or more items can be placed;

means for providing a substance to the at least one process chamber, the substance capable of being formed into a plasma;

plasma forming means associated with the process chamber for establishing an electric field suitable for forming a plasma in said chamber, the plasma forming means being operable to establish an electric field within the associated process chamber for forming a plasma when said substance is supplied thereto such that the surface of said article can be coated with a thin film polymer layer by plasma deposition;

means for providing a time-varying current for providing the plasma forming apparatus with a time-varying current; and

pressure varying means (pressure varying means) for selectively controlling the pressure in the process chambers such that the pressure in any one or more of the chambers can be controlled independently of the pressure in another of the chambers.

Desirably, the plasma formation device comprises an induction device operable to induce an electric field within the process chamber.

Alternatively, or in addition to the induction means, the plasma forming means comprises capacitive means arranged to form an electric field within an associated process chamber so as to form a plasma.

Preferably, the coating is a thin layer, with a thickness of about a few or tens of nanometers, typically up to 100 and 200 nanometers thick. This coating is hereinafter referred to as nanocoating.

Other preferred and/or optional features of the invention are defined in the appended claims.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

brief Description of Drawings

FIG. 1 is a schematic illustration of an apparatus for nano-coating a surface of an article with a thin film polymer layer by plasma deposition;

FIG. 2 is a schematic view of a process chamber of the apparatus of FIG. 1;

FIG. 3 is a schematic illustration of another apparatus for nano-coating a surface of an article with a thin film polymer layer by plasma deposition; and

fig. 4 is a schematic view of yet another apparatus for coating a surface of an article with a nano-thin film polymer layer by plasma deposition.

Detailed description of illustrative embodiments

Referring to fig. 1 and 2, there is shown an apparatus 10 for coating a surface of an article with a thin film polymer layer by plasma deposition. The apparatus 10 includes a plurality of processing chambers 12(12a, 12b, 12c.. 12n), and one or more items 14 may be placed into each of the plurality of processing chambers 12.

Without limitation, these items may be fabrics or garments, footwear, medical devices, electronics, batteries, filters and filtration equipment (such as air filters), micro or nano devices or automotive or aerospace parts.

The nano-film polymer layer may produce any desired or advantageous technical effect, such as rendering the article hydrophobic or oleophobic.

As shown in more detail in fig. 2, the article 14 is placed on a fixture 16 in the chamber 12 such that the article can be positioned within the chamber such that efficient deposition can occur on the article or such that the article can be moved into multiple orientations during processing to effectively nano-coat all of its surfaces. The lid for each chamber is shown in phantom in the figure.

The apparatus 10 comprises means for supplying reactive species to the process chamber to form a plasma in the chamber. The active material is typically a monomer that is stored in a monomer tube 18 and undergoes polymerization on the surface of the article as the monomer decomposes and forms a plasma. The monomer is gaseous and stored under pressure in the tube 18 so that on operation of the valve 20, the monomer passes along the conduit 22 and into the process chamber 12. The valve 21 is operable to selectively provide gas to any one or more of the process chambers 12. The carrier gas is stored in a tube 19 to deliver the monomer to the process chamber.

A plurality of induction devices 24 are associated with respective processing chambers 12, each induction device being operable to induce an electric field within the associated processing chamber to form a plasma when reactive species are provided to the processing chamber such that the surface of the article may be coated with a thin film polymer layer by plasma deposition.

The control device 26 controls the operation of the sensing device. The control means 26 comprise means for providing a time-varying current in the induction means 24. Preferably, the control means 26 also includes an L-C or suitable matching unit and a power meter for coupling the output of the 13.56MHz RF generator connected to the power supply. This arrangement ensures that the Standing Wave Ratio (SWR) of the transmitted power to the partially ionized gas within the process chamber can be minimized. For pulsed plasma deposition, a pulsed signal generator may be used.

In the arrangement shown in fig. 1, each inductive device 24 comprises a coil of electrically conductive material, such as copper in the form of a wire or tube. The ends of the copper are connected to a control device 26 as shown by the arrows in the figure. In an advantageous arrangement, the sensing devices may each have a wireless connection to the control device 26.

The walls of the process chamber may be made of a dielectric material. Quartz or borosilicate glass is a suitable and inexpensive dielectric material. The coil may be formed outside the process chamber 12 by winding a copper conductor around the chamber. In one variation, the coil may be embedded in a wall of the process chamber or disposed inside the chamber, but the latter configuration is not currently preferred because it interferes with cleaning. The process chamber may be made of a metallic material, in which case the induction coil arrangement is substantially internal to the chamber and is configured such that, in use, it provides a magnetic field within the main volume of the chamber. The induction coils may be single, such as solenoids, paired, such as in a helmholtz configuration, or have an odd or even number of higher multiples. The coil may be circular or rectangular in cross-section, with the cross-section being either vertical or horizontal as appropriate to the shape of the chamber.

The apparatus 10 further includes a pressure control device 28 for selectively controlling the pressure in the process chambers 12 such that the pressure in any one or more of the chambers can be controlled independently of the pressure in any other of the chambers. Thus, the apparatus can be controlled such that, for example, the pressure in chamber 12a is at atmospheric pressure, while the pressure in chamber 12b is at the process pressure, and the pressure in chamber 12c is reduced from atmospheric pressure to the process pressure. The pressure control device 28 may also control the pressure within the chamber so that process steps requiring different pressures may be performed in different chambers.

Typically, the pressure required for plasma deposition is 1X 10^-5To 1 torr (approximately 1 x 10)^-8Bar to 1X 10^-3Bar), however, pressures outside this typical range may be required.

The pressure control means 28 preferably comprises a vacuum pumping means 30, which vacuum pumping means 30 can be selectively placed in fluid communication with said process chambers, so that the chambers 12 can be evacuated independently of each other. Although a single pumping unit may be selected to achieve a typical processing pressure, preferably the vacuum pumping arrangement 30 comprises a high pressure pumping or backing unit 32 for reducing the pressure from atmospheric to a first or intermediate pressure and a low pressure pumping unit 34 for reducing the pressure from the first pressure to the processing pressure.

The high pressure pumping unit 32 may suitably be a roots pump. The low pressure pumping unit 34 may suitably be a turbo-molecular pump. The outlet of this low pressure pumping unit is generally not capable of venting to atmosphere and so the outlet is connected to the inlet of the high pressure pumping unit. Thus, typically the low pressure pumping unit 34 is not actuated until the pressure in the low pressure pumping unit has been reduced to an intermediate pressure by the high pressure pumping unit 32.

The pressure control device 28 may include a pre-evacuation chamber or pressure tank 36 connected in series with the vacuum pumping device 30 and the process chamber 12. The pre-evacuation chamber may therefore be maintained at a pressure below atmospheric pressure, and preferably below the process pressure, by the vacuum pumping means, such that the pressure within the process chamber or chambers is reduced whilst there is fluid communication between the pre-evacuation chamber and any one or more of the process chambers.

In more detail, the internal volume of the pre-evacuation chamber 36 is preferably greater than the internal volume of any of the process chambers 12. When the pre-evacuation chamber has been evacuated to a low pressure and a fluid flow path is opened between the process chamber 12 and the pre-evacuation chamber, a pressure gradient causes evacuation within the process chamber. Because the volume of the pre-evacuation chamber is relatively large, the rate at which the pressure within the processing chamber decreases is relatively greater than the rate at which the pressure within the pre-evacuation chamber increases. In this way, the pressure within the processing chamber can be rapidly reduced from atmospheric pressure to the processing pressure when loaded with articles, thus reducing the time taken to process the articles.

Advantageously, a plurality of pre-evacuation chambers 36 may be connected in series with the vacuum pumping arrangement 30 and the process chamber 12. The pre-evacuation chambers 36 can be selectively placed in fluid communication with one or more of the process chambers such that any of the pre-evacuation chambers can reduce the pressure of any of the process chambers. In this manner, one pre-evacuation chamber 36 can be used to evacuate the process chamber 12 while the other is being evacuated by the vacuum pumping device 30. The number of pre-evacuation chambers that can be selected is a function of, among other things, the process pressure, the number of process chambers, and the time taken to process the articles.

In an alternative arrangement of the pressure control means 28, not shown in the drawings, the high pressure pumping units are operable to reduce the pressure within the pre-evacuation chambers, and a plurality of low pressure pumping units are connected between respective ones of the process chambers 12 and the pre-evacuation chambers to selectively increase the pressure differential between one or more of the process chambers and the pre-evacuation chamber. This arrangement may preferably be such that it is not required to keep the pre-evacuation chamber shown in the figures at a very low process pressure, but instead the pre-evacuation chamber is evacuated to an intermediate pressure which is more easily or efficiently maintained.

Figure 3 shows an alternative apparatus 40 for coating the surface of an article with a thin film polymer layer by plasma deposition. For ease of understanding, not all of the structures described above with reference to fig. 1 and 2, such as the sensing device and the active material delivery system, are shown in fig. 3.

In fig. 3, the plurality of process chambers 12 are housed in an intermediate chamber 42, the intermediate chamber 42 being adapted to be maintained at a pressure less than atmospheric pressure, and preferably a pressure lower than the process pressure, by a vacuum pumping device 44. The apparatus also includes one or more load lock chambers (two load lock chambers 46, 48 are shown) adapted to cycle between atmospheric pressure and the pressure of the intermediate chamber to allow the transfer of items 50 from outside the apparatus to the intermediate chamber without increasing the pressure in the intermediate chamber. This apparatus is advantageous because it eliminates the need to reduce the pressure within the processing chamber after the article is placed. Thus, the time taken to reduce the pressure and the additional energy consumption can be avoided, thereby increasing the throughput of the articles.

A robotic device 52 is necessary and operable at a pressure less than atmospheric pressure to transfer the article 50 from the load lock chamber 46 to the processing chamber 12 and to transfer the article after processing to another load lock chamber 48. The robotic device 52 is shown in phantom to indicate the range of motion required. Three robots are shown in fig. 3. The first robot 51 transfers the article from the atmosphere to the intermediate chamber 42 and is housed in the first load lock chamber 46. The second robot 53 transfers articles to and from the process chamber 12 and is movable within the intermediate chamber. The third robot 54 transfers the processed articles from the intermediate chamber to the atmosphere and is housed in the second load lock chamber 48.

Another arrangement of apparatus 60 for coating a surface of an article with a thin film polymer layer by plasma deposition is shown in figure 4. For ease of understanding, not all of the structures described above with reference to fig. 1 and 2 or 3, such as the sensing device and the active material delivery system, are shown in fig. 4.

A plurality of process chambers 62 are supported for movement between a loading or unloading position and a processing position. The process chamber 62 is supported for rotational movement about an axis X on a base (not shown in the plan view of fig. 4). The movement is controlled by an electric motor (also not shown).

The process chamber 62 is adapted to be maintained at a pressure (which may be atmospheric) that is higher than the process pressure in the load or unload position, and at the process pressure in the process position. The loading/unloading position is indicated by a solid arrow in fig. 4, while the processing position is indicated by a dashed arrow. The entry and exit of gas into and from the chamber is preferably controlled by suitable valves 63. These valves may be one-way valves. The pressure control device 64 includes a vacuum chamber 66 and a vacuum pumping unit 68 to evacuate the vacuum chamber 66 to the processing pressure.

Movement of the process chamber 62 between the loading or unloading position and the processing position automatically initiates a reduction of the pressure within the process chamber to the processing pressure. Each process chamber may be fitted with a one-way valve 63 that allows gas to exit the chamber so that when the process chamber is rotated into the vacuum chamber 66, gas is caused to flow through its one-way valve into the vacuum chamber. When the process has been completed and the process chamber is rotated away from the vacuum chamber 66, the chamber may be vented to atmosphere and reloaded with an article.

The use of the apparatus shown in the figures will now be described with particular reference to figures 1 and 2, but this use is also relevant to the apparatus shown in figures 3 and 4.

In fig. 1 and 2, the article 14 is loaded onto the fixture 16 in the process chamber 12, and the process chamber 12 is evacuated to a process pressure by the pressure control device 28. Because the pressure control means comprises a pre-evacuation pressure, the pressure in the process chamber can be reduced relatively quickly. If desired, a pretreatment gas and vapor can be introduced into the chamber. The monomer is caused to flow into the associated process chamber by the use of valves 20 and 21 and an electric current is induced in the monomer gas causing the formation of a plasma. The plasma treatment step is continued for between 1 second and 10 minutes (depending on the article to be treated). The movement of the article during processing may be controlled by the movement of the clamp 16. Upon completion of the deposition/processing step, all gases and vapors are isolated from the evacuated to low pressure chamber prior to venting to atmospheric pressure. The processed articles are removed and new articles are loaded into the processing chamber 12.

An advantage of the present apparatus is that any steps required to process an article can be performed independently of any of the process chambers. For example, any of the loading, evacuating, plasma deposition, cleaning, repair, and maintenance steps may be performed in or to any one of the process chambers while any of these steps is being performed in another process chamber. Such an arrangement significantly increases the potential throughput of the equipment and limits downtime by allowing preventative maintenance.

With particular reference to evacuation of the process chamber, the process chamber is evacuated, which causes an increase in pressure in the pre-evacuation chamber. The vacuum pumping arrangement may be operated to reduce the pressure within the pre-evacuation chamber when a process in that process chamber is being carried out, such that the pre-evacuation chamber is at the required pressure when evacuation of a further process chamber is required. This arrangement reduces the time taken to process the articles.

Additional articles that may be coated with a water repellent/repellent coating include: sports equipment, high value fashion items such as fashion accessories, electrical products, personal electronic devices such as BLUETOOTH (trademark) devices, mobile telephones, pagers, Personal Digital Assistants (PDAs), MP3 devices, cables, Compact Discs (CDs), laptop computers and keyboards.

It will be appreciated that the invention can be used with a range of different active substances, independently of the desired characteristics and properties of the article to be coated and in order to achieve the desired technical effect.

Thus, for example, a corrosion inhibiting substance may be introduced to provide a corrosion inhibiting coating in or on such articles, such as: bandages, dressings, and emergency medical devices; furniture items, bathroom furniture, first aid kits (first aid kits), clothing items; and medical, surgical, and dental equipment.

Alternatively, flame retardant materials may be incorporated to provide fire resistant properties to such articles, such as: articles of clothing, leather, textile materials and covers, paper, electrical products, personal electronic devices such as BLUETOOTH (trademark) devices, mobile telephones, pagers, Personal Digital Assistants (PDAs), MP3 devices, cables, Compact Discs (CDs), banknotes and credit cards.

In another embodiment, the substance to be introduced is a protein binding agent suitable for introduction into bone and dental implants to promote bone growth and binding of bone material to promote regrowth/repair of fractured bone or tooth.

In another embodiment, the substance to be introduced may be a conductive material suitable for being introduced to a specific surface/area of the article to be coated.

It is to be understood that the present invention is suitable for coating knitted, sewn, woven or connected fabrics or materials such as, for example: leather and uppers with or without an incorporated sole.

It is also within the scope of the present invention to coat an article multiple times with two or more different substances in order to provide two or more different effects, such as, for example, imparting water and fire resistant properties to the article.

Although the invention has been described by way of various examples and embodiments, along with improvements and modifications, further embodiments and modifications will become apparent to those skilled in the art upon reading and understanding the present specification. All such embodiments and modifications are intended to fall within the scope of the present invention as defined by the appended claims.

Claims (24)

1. An apparatus for coating a surface of an article with a thin film polymer layer by plasma deposition, the apparatus comprising:

at least one processing chamber into which one or more items can be placed;

means for providing a substance to the at least one process chamber, the substance capable of being formed into a plasma;

a plasma forming device associated with the processing chamber, the plasma forming device being operable to establish an electric field within the associated processing chamber when the substance is provided to the associated processing chamber so as to form a plasma such that a surface of the article can be coated with a thin film polymer layer by plasma deposition;

means for providing a time-varying current for the plasma forming device; and

pressure varying means for selectively controlling the pressure within the processing chambers so that the pressure in any one or more of the chambers can be controlled independently of the pressure in another of the chambers.

2. The apparatus of claim 1, wherein the plasma forming device comprises an induction device operable to induce an electric field within the process chamber.

3. The apparatus of claim 1, wherein the plasma forming means comprises capacitive means arranged to form an electric field within an associated process chamber so as to form a plasma.

4. The apparatus of any one of claims 1 to 3, wherein the coating is a nano-coating of the surface of the article.

4. The apparatus of claim 2, wherein the induction device comprises a coil of conductive material.

5. The apparatus of claim 4, wherein the coils are embedded in a wall of the respective processing chamber.

6. The apparatus of claim 5, wherein the coils are external to the respective process chambers.

7. The apparatus of any one of the preceding claims, wherein the process chamber is formed of a dielectric material.

8. The apparatus of any one of the preceding claims, wherein the process chamber is made of a conductive material.

9. Apparatus as claimed in any preceding claim, wherein the pressure varying means comprises vacuum pumping means selectively positionable in fluid communication with the process chamber.

10. Apparatus as claimed in claim 9, wherein said vacuum pumping means comprises a high pressure pumping unit for reducing pressure from atmospheric pressure to a first pressure and a low pressure pumping unit for reducing pressure from said first pressure to a process pressure.

11. Apparatus according to claim 9 or 10, wherein the pressure control means comprises a pre-evacuation chamber connected in series with the vacuum pumping means and the processing chambers such that the pre-evacuation chamber can be maintained at a pressure less than atmospheric pressure by the vacuum pumping means such that the pressure in any one or more of the processing chambers is reduced on fluid communication between the pre-evacuation chamber and the one or more processing chambers.

12. Apparatus as claimed in claim 11 when dependent on claim 10, wherein the high pressure pumping unit is operable to reduce the pressure within the pre-evacuation chamber and a plurality of the low pressure pumps are connected between respective ones of the process chambers and the pre-evacuation chamber to selectively increase the pressure differential between one or more of the process chambers and the pre-evacuation chamber.

13. The apparatus of claim 11 or 12, the internal volume of the pre-evacuation chamber being greater than the internal volume of any of the process chambers.

14. Apparatus as claimed in any of claims 11 to 13, wherein a plurality of pre-evacuation chambers are connected in series with the vacuum pumping means and the processing chamber.

15. The apparatus of any of claims 11 to 14, wherein the pre-evacuation chambers are selectively positionable in fluid communication with one or more of the process chambers such that any one of the pre-evacuation chambers can reduce pressure in any one of the process chambers.

16. Apparatus according to any preceding claim, wherein the plurality of processing chambers are housed within an intermediate chamber adapted to be maintained at a pressure less than atmospheric pressure by the pressure control means, the apparatus further comprising one or more load lock chambers adapted to cycle between atmospheric pressure and the pressure of the intermediate chamber to allow items to pass from outside the apparatus to the intermediate chamber without increasing the pressure in the intermediate chamber.

17. The apparatus of claim 16, comprising a robotic device operable at a pressure less than atmospheric pressure to transfer articles from the one or more load lock chambers to the processing chamber and to transfer articles to the one or more load lock chambers after processing.

18. The apparatus of any one of the preceding claims, wherein the plurality of processing chambers are supported for movement between a loading or unloading position and a processing position.

19. The apparatus of claim 18, wherein in the loading or unloading position the process chamber is adapted to be maintained at a pressure higher than the process pressure, and in the processing position the process chamber is adapted to be maintained at the process pressure.

20. The apparatus of claim 19 wherein movement of the process chamber between a loading or unloading position and a processing position automatically initiates a reduction of pressure within the process chamber to the processing pressure.

21. An apparatus as claimed in any one of claims 18 to 20 wherein the process chamber is supported for rotational movement on a base about an axis.

22. Apparatus according to any preceding claim, wherein means are provided for effecting molecular rearrangement, thereby to impart new surface properties to the article being coated.

23. A method for coating a surface of an article with a thin film polymer layer by plasma deposition, the method comprising using an apparatus according to any of claims 1 to 22.

24. An article coated according to the method of claim 23.