EP1807547A1

EP1807547A1 - An elongated gas ditribution system

Info

Publication number: EP1807547A1
Application number: EP05801451A
Authority: EP
Inventors: Anja Blondeel; Wilmert De Bosscher; Parsifal Goderis; Ivan Van De Putte
Original assignee: Bekaert Advanced Coatings NV
Current assignee: Soleras Advanced Coatings BV
Priority date: 2004-10-11
Filing date: 2005-10-04
Publication date: 2007-07-18
Also published as: CN101040061B; WO2006040275A1; JP5046334B2; CN101040061A; JP2008516084A

Abstract

An elongated gas distribution system is described for use in a plasma deposition or plasma cleaning apparatus. The system is provided in the form of a stack of elongated strips. The strips have grooves milled in them that form channels once the strips are stacked upon each other. Such an arrangement is particularly design flexible and allows for a finely branched gas distribution tree. The incorporation of gas flow controlling means such as valves or vanes inside or on the gas distribution system becomes also possible. By actuating these gas flow controlling means based on the input of a plasma, deposited layer or cleaned substrate feedback parameter, a fast responding gas distribution system is realised. In addition, some of the strips can be used to incorporate a cooling circuit for cooling the elongated gas distribution system.

Description

An elongated gas distribution system

Field of the invention.

The invention relates to an elongated gas distribution system for mounting in a plasma apparatus.

Background of the invention.

The technology to treat large area substrates by means of vacuum related sputtering processes is gaining importance. For example the in- line treatment of large area glass panes in huge vacuum installations is becoming more and more important as it allows to finish building glass with e.g. low-emissivity or soil-resistant coatings. In these sputtering installations the substrate is conveyed across an elongated sputtering source that is oriented perpendicular to the conveying direction. The sputtering source is by preference a rotating sputtering target at the surface of which a magnetically confined plasma racetrack is maintained. The plasma is generated through ionisation of a noble gas, notably argon. Due to the negative bias applied to the target, the ionised argon atoms strike the target surface thereby ejecting target atoms from the target. As the ejected atoms strike the surface of the substrate, a layer starts to form. When - besides the noble gas or even in place of the noble gas - a reactive gas such as oxygen or nitrogen is administered during the process a compound layer will form, while these gases react with the impinging target atoms. Besides the deposition of coatings, a plasma can also be used to clean surfaces. For this application, the substrate is held at a negative bias and the impinging action of the argon ions cleans the surface from contaminants. This plasma cleaning is gaining more and more ground in the field of pre-treatment of difficult to coat polymers (PTFE, PVDF,...) and in the field of cleaning steel sheets from organic contaminants prior to further processing.

In both applications process gases have to be fed into the vacuum equipment. As installations are designed wider and wider, the distribution of the gas is becoming an important issue. Indeed, when the plasma gas is fed on one side of the target only, the other side will be depleted from gas. The problem is even more pronounced for the reactive gas supply where the gas reacts away in the process. Gas feeds at one side of the target result in compound films with a varying stoichiometry along the width of the substrate as the gas is used while it diffuses to the other side.

The gas distribution system in the state-of-the-art apparatus is made out of tubes. One of the earliest described arrangements being a tube with small holes at regular distances extending along the target (see US

5,096,562). US 4,849,087 describes a system where premixed gas is distributed through a gas manifold followed by multiple tubes ending in nozzles in the vicinity of the elongated planar target. The gas flow through each of the tubes is controlled by outside valves actuated by a feedback signal from the deposited film. German patent application DE

4412541 describes a gas inlet arrangement that is characterised by an equal flow resistance value between the gas inlet and each of the outlet openings that are situated along a planar target surface. The structural features by which such a gas arrangement must be implemented are not described. The advantages of such an arrangement have been calculated through in "Gas inlet systems for large area linear magnetron sputtering sources", by Milde et. al. in the 44^th Annual Technical Conference Proceedings of the Society of Vacuum Coaters (ISSN 0737-5921 , p 204). The problems with the existing state of the art gas distribution systems are fourfold:

• When a change in the flow of the gas is needed in the chamber, it takes a while before the change of flow by the control valve reaches the outlet openings in the chamber thus leading to a delay time between signal and response.

• For each process gas a different gas distribution system has to be installed leading to an increased cost of the installation. • When a differential feed of gas is needed along the width of the target, more than one (e.g. three : left, middle, right) separate gas distribution systems must installed leading to an increased cost of the gas distribution system. • Particularly in the case of the plasma cleaning apparatus, the gas distribution system can become very hot because it is used as an anode. Such a gas distribution system must then be separately cooled in order to prevent distortion of the distribution system. Also in a sputtering apparatus cooling of the gas distribution can become desirable when the gas distribution system is e.g. in the vicinity of the plasma.

Being dissatisfied with the available state-of-the-art gas distribution systems, the inventors searched for other ways to implement a elongated, fast responding, easy to control and possibly cooled gas distribution system that allows for a differential gas feed along the width of the installation.

Summary of the invention.

The object of the invention is to solve the problems of the state-of-the- art elongated gas distribution system in a plasma deposition or plasma cleaning apparatus. It is a further object of the invention to provide an elongated gas distribution system where different process gases can be distributed through a single device. Another object of the invention is to provide a differential gas supply over the width of the installation. It is a further object of the invention to provide a fast responding gas distribution system in terms of the amount of gas supplied and in terms of change in differential gas feed. Another object of the invention is to have a gas distribution system with an integrated cooling system in it.

A first aspect of the invention relates to the combination of features of claim 1. There, an elongated gas distribution system for mounting in a plasma deposition or plasma cleaning apparatus is claimed that comprises at least one inlet, and at least one series of outlets, each of said series of outlets corresponding to one of said inlets. With a series of outlets is meant at least two outlets but preferably more. Most preferred are around a hundred outlets. Said outlets are holes where the gas flows into the evacuable chamber of the apparatus. These holes may be foreseen with replaceable exit nozzles that fit into the holes. When following back the path followed by the gas from a single outlet of the series, one will always arrive at the same inlet for every outlet belonging to the series. The series of outlets are arranged in elongated rows in a direction substantially perpendicular to the direction of the movement of the substrate and substantially parallel to the elongated target. One series of outlets can span the whole width of the installation e.g. to feed the noble gas. Or different series of outlets can be arranged in a single row e.g. to feed the left side, the middle and the right side of the installation. This is the preferred arrangement for feeding reactive gasses, as it allows for a differential gas feed over the width of the installation, hence a control of the film composition over the width of the substrate. Of course more than three series of outlets can be implemented in one row the limit being set by the number of inlets that also have to be accommodated on the gas distribution system.

The invention is characterised by the way the gas distribution system is constructed. It comprises a series of strips with a length that is substantially equal to the width of the installation. This length can be anywhere between 0.30 m and 10 meters. The strips have a thickness that is dependent on the space available for the gas distribution system and the overall gas flow to be achieved. In practice this will generally be between 1 mm and 70 mm. The width of the strip is determined by the span that has to be overcome and the overall gas flow pattern that has to be achieved. In general this width will be between 1 cm and 30 cm. The number of strips is depending on the number of inlets and/or the number of process gasses that have to be fed to the vacuum chamber. At least two strips are needed to implement the invention.

As the gas distribution system is substantially elongated, the series of outlet openings are arranged in the length dimension. By preference the gas outlets series are arranged in the side formed by the length and thickness dimension of the strips. Another possibility is that the gas outlet series emit the gas in rows that are arranged at the outer side (length by width) of one of the two outermost strips of the stacks.

The strips are made out of an appropriate material that has the correct combination of gas tightness, strength to weight, durability and temperature resistance. For certain cases a good electrical conductivity may be of importance e.g. in a plasma cleaning operation where the gas distribution system can act as an anode. In other cases it can be beneficial to have an isolating gas distribution system e.g. to prevent the formation of arcs. The magnetic properties can be of importance as well in case a plasma forms in the vicinity of the gas distribution system. Depending on the magnetic properties, the gas distribution system can be made neutral (magnetic permeability close to one) or ferromagnetic

(hence the material guides magnetic field lines from magnets possibly attached to the gas distribution system).

Aluminium and stainless steel strips have been found to be practical materials. High performance polymers such Flametec™Kytec®PVDF

(polyvinylidene fluoride) or ECTFE (a copolymer of ethylene and chlorotrifluoroethylene) - without being exhaustive - are relatively strong, electrically insulating and chemically inert materials that can also be used. Composite materials could be envisaged too.

Each of said strips has a first and a second side. With a side is meant the surface formed by the length and the width dimension. At least one of the sides has grooves in it. The grooves are so configured, that when the strips are stacked upon each other channels form. Each of said channels connects one of said inlets with the corresponding series of outlets. The grooves can be made by any kind of suitable process: • by far the most preferred way to make the grooves is that they are milled out by means of a semicircular or U-shaped milling borehead. The most convenient is to use a numerically controlled steered milling machine that allows the grooving of very complex patterns, thus forming channels that can never be accomplished by means of traditional tubing.

• a method similar to the above is the use of selective etching although this is less preferred due to the magnitude of the strips.

• the grooves can be made by successive embossing of a suitably formed rod into the strip by means of a hydraulic press. The rod must be much harder than the material of the strip. The desired pattern can also be obtained in one stroke by means of a negative of the pattern to be imprinted. This negative must of course be harder than the strip material.

• the grooves can be obtained by casting the strip material in a mold having the negative shape of the distribution channel. This is the least preferred method due to its cost and inflexibility. The stacking of the strips should be such that the channels are substantially gastight at lower pressure differences. This can be achieved by bolting the strips together or by pressing them together by means of a clamping system, or by means of gluing or by any other means that allows a substantially gastight stack to be formed.

Another way of achieving gastight channels (dependent claim 2) is to cut out the channels through the strip by means of e.g. a laser-cutting machine or a torch burner or any other cutting apparatus that is fit to cut the material. The strip will then loose its coherency and will have to be positioned (much like a jigsaw puzzle with gaps between the pieces) between two adjacent strips before stacking the strips together.

More complex channels can be achieved by drilling holes in the strips at the appropriate places to allow channels that can change levels from one strip to the other (dependent claim 3).

Gas flow controlling means can be mounted in or on said stack of strips (dependent claim 4). With gas flow controlling means is meant any means known in the art to block, partially block or divert a flow of gas.

The gas flow controlling means can mounted on the stack of strips e.g. on the outer length by width sides of the outermost strips. For example a channel can be led to the outer side of the outer strip through a first hole made in this outer strip. On this outer strip a gas controlling means is mounted before the channel continues its path through a second hole in the same strip. The gas controlling means can also be implemented inside the stack of strips e.g. by implementing shutters or diverters in the strip.

The gas flow controlling means can be adjustable off-line i.e. whenever the apparatus is down and the controlling means is reachable. More preferred is however if the gas flow controlling means can be adjusted remotely when the sputtering apparatus is functioning. This can be done in several ways (dependent claim 5): • mechanically, when force is transmitted to the gas controlling means by means of solid intermediates like rods, levers, gearwheels, cables or the like that are actuated from outside the vacuum.

• electrically, when force is applied to the gas controlling means in the vacuum by means of electromagnetic or piezoelectric transducers that are fed by electrical current leads that connect to the outside. • pneumatically, when force is applied to the gas controlling means through a gas intermediate. Such a gas intermediate is by preference the noble gas used in the process as this e.g. can be discharged in the chamber after use. Also the noble gas will not distort the process too much if a small leak would occur.

Combinations of the methods above could of course be envisaged too.

The gas flow controlling means can be split into two major families: valves and vanes (dependent claim 6). Valves can stepwise or continuously adjust the gas flow from no flow to the maximum flow allowed through the channel. Such valves must be mounted in line with the channels. Vanes divert the gas flow from one single feed channel into two or more receiving channels. Vanes will therefore always be mounted at a branching of a channel.

A channel structure that is particularly easy to implement according the invention is a tree structure (dependent claim 7). Any tree structure can be readily implemented as long as it fulfils the requirements of a tree i.e. that the structure has a root that splits into two or more branches, that each branch can on its turn split into other branches and that all branches finally end up in leaves. The inlet of the gas distribution system then corresponds to the root, the channels to the branches and the outlet series to the leaves. In the channels an adjustable valve can regulate the total flow of gas and at the splitting of two branches, a vane can adjust the balance of the gas flows going into either of the connecting branches.

When using only one middle strip having grooves at both its length times width sides and two side strips, already a gas distribution system can be implemented that allows for the distribution of two gases

(dependent claim 8). When the gas is ejected from the nozzle into the vacuum chamber, a diffusor is preferably used so that the gas is emitted evenly into the vacuum chamber. A foraminated plate that covers the outlets can conveniently be used to this end. Also strips of fabric made out of sintered or woven or knitted metal fibre covering the outlets have been found to be practical in order to scatter the gas atoms in all directions (dependent claim 9). The fibres making up such a fabric are made of stainless steel (preferably AISI 316L) and are between 1 and 80 micron thick. A combination of a foraminated plate with a sintered metal fibre strip is also possible and included into the inventive concept.

The gas distribution system can be further completed with the integration of a cooling system (dependent claim 10). Indeed when using at least one of the sides of the strips in the identical manner by which the gas distribution channels are made, a cooling channel can conveniently be incorporated. Such a channel will have a fluid inlet and a corresponding fluid outlet, the fluid inlet for introducing the cooled fluid and the outlet for extraction of the heated fluid. The shape of the channel can be serpentine-like having the inlet at one end of the single channel and the outlet at the other end. Or it can comprise a broader feed channel that feeds a set of parallel subchannels which on their turn end in a collector channel that connects to the single outlet. Or it can have a net-like structure. In case one cooling channel is not enough more cooling channels can of course be incorporated on different sides of the strips. The fluid can be a gas or a liquid.

According a second aspect of the invention, the plasma deposition or plasma cleaning apparatus comprising the above described gas distribution system is also claimed (independent claim 11).

Preferably the gas distribution system according the invention is used in conjunction with a feedback system (dependent claim 12). The feedback system uses specific parameters of the plasma (such as gas composition by means of on-line mass spectroscopy or ion concentration of certain species by optical emission spectroscopy or the target voltage that varies with the plasma condition) as an input to remotely control the gas controlling means of the gas distribution system. Alternatively the feedback signal can be based on the properties of the coating as deposited on the substrate such as e.g. refractive index, conductivity, transparency or any other measurable quantity. In case the plasma is used to remove material from the substrate, the gas distribution system can also be steered by the properties of the coating that remains e.g. the amount of coating that remains.

Brief description of the drawings.

The invention will now be described into more detail with reference to the accompanying drawings wherein

- FIGURE 1 descibes the prior art implementation of the "tube-in- tube" system

- FIGURE 2 is a schematic drawing on where the gas distribution system can normally be found in a large area coater.

- FIGURE 3 shows an exploded view of a first implementation of the invention where the gas distibution system allows to distribute two process gasses.

FIGURE 4 shows another way to implement the invention.

- FIGURE 5 describes a system where the gas flow can be controlled by means of a vane.

- FIGURE 6 'a', 'b' and 'c' is a more detailed description of an adjustable vane

- FIGURE 7 'a' and 'b' shows how an electromagnetically controlled membrane valve can be implemented according the invention.

- FIGURE 8 'a' and 'b' shows very simple but convenient types of valves that can be adjusted off-line. - FIGURE 9 shows an additional strip that can be used to cool the gas distribution system.

- FIGURE 10 'a' shows another way to implement the elongated gas distribution system when no space is available sideways from the targets. - FIGURE 10 'b' shows a layout of the elongated gas distribution system as seen from the top (length times width face), 'c' as seen from the one side (length times thickness face), 'd' as seen from the bottom (length times width face), 'e' as seen from the other side (length times thickness face). Description of the preferred embodiments of the invention.

The prior art gas distribution system is shown in FIGURE 1 : the gas 140 enters the process chamber 110 through a first tube 120. The first tube distributes the gas a first time through holes 122 along the length of the tube into a second, larger tube 130 that is fixed coaxially to the first tube 120. In this second tube a series of nozzles 132 further distributes the gas into the chamber 110. The cavity between both tubes acts as a expansion buffer vessel and allows the gas to expand evenly at an intermediate pressure across the width of the process chamber. However, the cavity withholds the gas for an amount of time such that a fast change in the amount of gas fed in response to a change in the plasma parameters is delayed.

FIGURE 2 illustrates where the gas distribution system according the invention can preferably be found in a large area plasma apparatus

200. Such an apparatus is in essence a large vacuum chamber 210 having the necessary ancillary equipment to maintain a vacuum (not shown) and to feed and convey large substrates 220 usually by means of rollers 230 inside this vacuum. On top of the chamber, top boxes such as 240 are mounted that are modular and can easily be exchanged. These top boxes 240 carry two tubular targets 250; 250' by means of two pairs of end blocks (not shown) that connect the targets to the top box. The top box further contains all necessary piping, electrical networking and mechanical drive equipment (not shown) in order to feed the targets 250, 250' with respectively coolant and electrical current while they are rotatably driven. The gas distribution systems 260 and 270 are mounted alongside the targets while gas feeds 280 and 290 feed the necessary gasses from the gas supply (not shown) through the top box 240 and the gas distribution systems 260, 270 into the vacuum chamber 210. A first embodiment of the inventive gas distribution system will now be described in more detail with the help of FIGURE 3. There a stack of three strips 310, 320 and 330 builds up the gas distribution system 300. The strips are made of an aluminium alloy commonly known as AIMgSiI (composition in percent by weight: Si (0.7 - 1.3), Mg (0.4 - 0.8),

Fe (max. 0.5), Cu (max. 0.1), Mn (0.4-0.8), Zn (max 0.2) Ti (max 0.2), the remainder being Al) having a thickness of 7 mm, a width of 100 mm and a length of 900 mm. However, the length can easily be scaled up to 3860 mm - which is the largest target length in use today (152 inch) - and even more. In the first strip 310, a binary tree pattern has been milled out. The grooves 316 have a U shape with a width of 8 mm. The inlet 312 connects to the outlet series of which two outlets are indicated with 314, 314'. The depth of the U-grooves varies from 8 mm to 0.5 mm. The depth depends on the bifurcation level of the channel: at each bifurcation, the depth of the split branches is half of the depth of the feeding branch. In this way the gas flow splits substantially equal at each bifurcation and the pressure difference remains equal between bifurcation levels. When the inlet groove 312 thus has a depth of 8 mm, the outlet 314 will have a depth of 0.5 mm while outlet 314' will have a depth of 2 mm. However, in order to ensure a laterally uniform gas feed across the width of the gas distribution system, the interdistance between individual outlets will have to be accommodated as well. It will be clear from the above that the by far the most preferred way to achieve such lateral uniformity is to use a balanced binary tree having 2ⁿ outlets with 'n' being the number of bifurcation levels (preferably n is larger than 4).

In strip 320 two buffer volumes 322 and 328 have been milled out. The volumes enlarge in the widthwise direction of the strip from the inlet 321 towards the middle of the strip. Grooves such as 324 have been milled out that split into two channels 326 that have an outlet 327 in order to allow the gas to expand into the vacuum chamber. The strip 330 forms the channels engraved in strip 320 when attached to it. Strip 330 has no particular embossing. The bottom side of strip 320 likewise forms the channels as engraved in strip 310. The three strips are tightly connected to one another by fastening means such as the bolt and nut pairs 340, 350, 340', 350' and 340", 350".

The channels of strip 310 are used to feed the noble gas, while the patterning of strip 320 is used to feed the reactive gas. The double structure in strip 320 allows for a differential gas feed between the left and right side of the gas distribution system. The gas distribution system is mounted with the widthwise dimension vertical thus allowing a space saving mount in the vicinity of a tubular target. Additionally, when mounted in this direction, the stack of strips has a sufficient stiffness in order to prevent sagging of the gas distribution system.

FIGURE 4 describes a second embodiment of the invention with a stack of 3 strips made of stainless steel (AISI 316) 410, 420, 440. Strips 410 and 440 are blank and do not have any embossing or engraving. Strip 420 has now been cut into pieces. As the cutting has been done with a constant width, the gas pressure difference between different bifurcation levels will decrease towards the outlets. After cutting the strip 420 falls apart in several pieces such as 422, 424, 426; 428; 430, 432. These pieces must be put back in place on the mounting strip 410 by means of e.g. gluing. By gluing strip 440 on top of the strips, a channel structure is formed with an inlet 434 and several outlets such 436. The elongated gas distribution system is completed with a U- shaped foraminated plate 452 having slots 450 for diffusing the gas into the apparatus. The plate 452 can be clipped onto the assembled stack and fixed to it by means of e.g. screws (not shown). Not shown, put equally well conceivable is that in stead of the plate 452 a strip of sintered metal fibre fabric is used. Or the strip of metal fibre fabric can be held in place by means of a foraminated plate. The embodiment of FIGURE 5 introduces the concepts of level change by means of holes drilled into the strips and the use of a gas controlling means. The gas distribution system comprises three strips 510, 520 and 540 that are stacked on top of each other. Gas enters through the inlet 522 engraved in strip 520. A hole 524 drilled through strip 520 feeds part of the gas supplied into the tree structure 512 engraved in the adjacent strip 510. The other part of the gas is fed through groove 526 to a gas controlling means 550 incorporated in the strip 540. The gas controlling means divides the gas flow into the grooves 528 and 532. The gas controlling means 550 will be further explained in the explanation of FIGURE 6. At the ends of the grooves 528 and 532 the gas is transferred to the next strip 510 by means of feed-through holes 530 and 534. Strip 510 has three engravings 516, 512 and 514 each feeding a series of outlets: while the middle series of outlets fed by tree 512 provides a constant supply of gas in the middle of the gas distribution system, the balance in gas flow between the left tree 516 and right tree 514 can be changed at will by means of the gas controlling means 550. The use of feed-through holes greatly adds to the design flexibility of the gas distribution system as it makes crossovers from different gas channels possible.

The gas controlling means 550 of FIGURE 5 will now be described in more detail by means of FIGURE 6. At least two strips 630 and 640 are needed to implement the gas controlling means that in this case is a vane. In the first strip 630 three grooves at 120° angles to one another are milled out: 610 where the gas is supplied and fed into the channels 614 and 612 (shown from the side in FIGURE 6b and from the top in FIGURE 6c). In the second strip 640 a stepped, circular hole has been machined. A tightly fitting diverter 600 comprising a circular cap 606 and a 120° segment diverter piece 602 can rotate in this hole. The diverter piece 602 is made of a sliding but compressible material such as PTFE or Hypalon® available from "DuPont Dow elastomers". The diverter piece partly or completely blocks the the entrance to the channels 612 and 614 but due to the 120° angular arrangement, the total area for the gas to escape remains constant and equal to the area of the feeding channel 610. The arrangement thus allows to partition the incoming gas flow into two separate gas flows without changing the total amount of exiting gas. The diverter is held in place by a holding ring 604 that is fastened to the strip 640 by means of screws or the holding ring can be threaded into the hole in strip 640. An O-ring 605 ensures the gas tightness of the whole structure. The outgoing gas flow balance can now conveniently be adjusted by turning the diverter 600.

Such an adjustment can be done off-line by manual intervention or it can be done on-line by means of a remotely controlled electrical stepper motor or a remotely actuated mechanical gear and toothed lath arrangement.

FIGURE 8 a and b show two simple implementations of an on-line valve that nevertheless are very practical. FIGURE 8 a shows a first strip 820 and a second strip 810 that are attached to one another. Strip 820 has a channel 822 grooved in it with a certain groove width. A bolt 802 is threaded into the strip 810 and can be turned down to the receiving hole 812. When the bolt is screwed into the threaded hole, the path of the gas is partially or completely blocked. It is of course necessary that the diameter of the bolt is larger than the width of the channel. FIGURE 8 b shows again a channel 852 formed between two strips 854 and 853 that can be blocked by a turnable bolt 856 that has a tight fit into a hole drilled through strip 853 and partly into strip 854. The bolt 856 has a diametrically through-drilled hole 858. The bolt is held in place by means of a U-shaped clip 864 fixed to the strip 852 that engages into the circumferential groove 866 of the bolt 856. O-ring 862 ensures that the valve remains gastight. By adjusting the orientation of the bore hole

858 with respect to the channel 852 by turning the bolt 856 with a screwdriver into slot 860, the gasflow through the channel 852 can be adjusted.

FIGURE 7 illustrates how an electrically actuated valve can conveniently be implemented between two strips 710 and 720 of the gas distribution system. FIGURE 7a shows the valve in a cross section along the plane AA' that is represented in FIGURE 7b the latter being a top view of the valve with the cap 730 removed. The ingoing channel 722 and the outgoing channel 712 are milled out of the facing sides of the strips 710, 720. The ingoing channel 722 ends in a hole 723 through strip 720. The outgoing channel 712 ends in a semicircle. Concentrically with this semicircle, a ring 725 is fastened to strip 710. On top of this ring 725 an O-ring 724 is fixed. This O-ring is made of a resilient and gas tight material such as Viton® from "DuPont Dow elastomers". A disk-like membrane 740 (preferably made from very thin stainless steel) having a ring shaped corrugation at its outer rim closes off the O-ring 724 in neutral condition. In the region of the membrane 740 opposite to the O-ring 724 a magnetic anchor 736 is attached to the membrane 740. The magnetic anchor can freely move in the cavity 737 in which also a small amount of - preferably the noble - gas is kept under a pressure higher than the working pressure of the gas admitted through the ingoing channel 722. An electromagnet 732 as part of the cap 730 can be remotely actuated by application of electrical current through leads 734. The cap 730 is kept gas tight by means of O-ring 738. The membrane 740 is attached gas tight to the cap 730 by means of welding or brasing or by any other means suitable for the purpose. When now electrical current is applied to the leads 734, the electromagnet 732 lifts the magnetic anchor 736 and the membrane attached to it from its O-ring 724 seat. The gas can then flow from the ingoing channel 722 to the outgoing channel 712. Upon removal of the electrical current, the gas under pressure held in the cavity 737 will seat the membrane back in place, thus blocking the gas flow. The inventors also found that the need for a high pressure, gas tight cavity 737 can also be circumvented by using a helical spring (not shown) to push the membrane 740 onto to the O-ring 724: an alternative not depicted in the figures provided. The cap 730 can also be integrated in another strip on top of 720.

The integration of the gas controlling means on or in the stack of strips as described in the last two embodiments greatly improves the time responsiveness of the whole system. Indeed as the control of the gas is now done in the vicinity of where the gas is used, the delay between cause and effect has been greatly diminished leading to better process control. Of course this advantage can only be fully exploited when the gas controlling means are remotely controlled from outside the vacuum chamber and such control is based on plasma parameters and/or properties of the coating deposited on or removed from the substrate by the plasma.

A further embodiment of the invention is provided by an 'add-on' cooling system that can conveniently be mounted onto the gas distribution systems described up to now. Indeed FIGURE 9 shows again a strip 910 wherein a single channel 914 has been milled out. The channel has a serpentine -like shape for ensuring a large contacts surface between the cooling liquid and the gas distribution system 930. The cooling liquid is fed through the inlet 912 and extracted through the outlet 916 - in this case by way of example - both mounted on the width by length side of the strip 910. A high temperature resistant gasket 920 (or even better two gaskets, parallel to one another, for double safety) is also included to prevent liquid leakage into the vacuum. A set of screws 922 firmly fixes the cooling strip 900 against the gas distribution system 930 with which it forms one single entity. Another advantageous embodiment is shown in FIGURE 10 'a'. There the elongated gas distribution system 1070 is mounted above two rotatable targets 1050, 1050'. The elongated gas distribution system is carried by a top box 1040 mountable on a module 1010 of a large area coater. Different feeds for inert gas 1060 and reactive gas 1060' are provided. The complete lay-out of the channels is shown in FIGURE 10 'b', 'c', 'd', and 'e'. All channels are milled out of a single rectangular strip of aluminium alloy (AIMgSiI). In total five inlet openings 1080, 1090, 1100, 1110, and 1120 are provided at one end of the strip. The closing strips at either side of the elongated gas distribution system are not shown. The exit holes are provided at both length times thickness sides of the strip. The one (length times width) face - for convenience called the 'upper' face although no particular orientation should be implied therewith - as shown on FIGURE 10 'b' shows the distribution tree 1082 of the inert gas. This tree 1082 is a binary tree with two main branches at either side of the gas distribution system. In total there are 32 exit openings that are all fed through the single gas inlet 1080 that is fed by the inert gas feed 1060'. In the 'lower' face, the distribution channels for the reactive gas are milled. Through feed 1060' reactive gas is fed to four different inlets 1090, 1100, 1110, and 1120 that connect to different corresponding binary trees 1092, 1102, 1112, and 1122. Each of the trees emits gas at either side of and in different zones along the elongated gas distribution system. The gas flow to each of the individual inlets can be controlled through throttle valves mounted in the top box 1040. Crossovers for the channels are made possible through loopholes that lead the gas to the other side of the strip. For example, tree 1092 is fed by inlet 1090. First the gas is led through channel 1098. A loophole 1096 at the other side of the strip is needed to cross the inert gas supply tree 1082. The channel than continues through channel 1094 that finally ends in tree 1092. As a further elaboration on this embodiment, gas flow controlling means 1093, 1103, 1113, 1123 in the form as the ones described in FIGURES 6, 7 or 8 can easily be incorporated in the elongated gas distribution system. As these gas flow controlling means are in the vicinity of the outlet tree of the gas, they allow for a fast response to needed changes in the gas flow. In this embodiment, the gas flow controlling means can be adjusted on-line by mechanical means 1062, 1062', 1062", 1062'" (1062", 1062'" not being visible because they are hidden by 1062, 1062') that are reachable through the top box 1040. These means can take the form of rotating pins that rotate in a vacuum tight bearing and engage with the gas flow controlling means 1093, 1103, 1113, 1123.

Many modifications and alterations of the embodiments may come to the mind of the skilled person based on the teachings presented in the foregoing descriptions and the associated drawings. For example the embodiments can be easily designed with a different orientation such as to allow for sputtering upward in stead of downward, sputtering from a vertically oriented target in stead of a horizontal target. Therefore it is to be understood that the invention is not limited to the specific embodiments disclosed, and that modifications and alternate embodiment are intended to be included within the scope of the appended claims.

Claims

Claim 1. An elongated gas distribution system for mounting in a plasma deposition or plasma cleaning apparatus comprising at least one inlet, and at least one series of outlets, each of said series of outlets corresponding to one of said inlets characterised in that said elongated gas distribution system comprises a stack of strips, said strips having a first and a second side at least one of said sides having grooves so that when the strips are stacked upon each other channels form, said channels connecting said at least one inlet to said corresponding series of outlets.

Claim 2. An elongated gas distribution system according claim 1 wherein said grooves are cut through said strip.

Claim 3. An elongated gas distribution system according any one of claim 1 or 2 wherein at least one of said strips having a hole, said hole for connecting said grooves on one side of said strip to the grooves on another side of a strip.

Claim 4. An elongated gas distribution system according any one of claim 1 or 3 further comprising a gas flow controlling means to control the gas flow through at least one of said channels, said gas flow controlling means being mounted on or in said stack of strips.

Claim 5. An elongated gas distribution system according claim 4 wherein said gas controlling means are adjustable by means of remotely controlled electrically or mechanically or pneumatically actuating systems.

Claim 6. An elongated gas distribution system according any one of claim 4 or 5 wherein said gas flow controlling means is a valve or a vane.

Claim 7. An elongated gas distribution system according any one of claim 1 to 6 wherein said inlet, said series of outlets and said channels are structured according a tree, said inlet corresponding to the root of said tree structure, said channels corresponding to the branches of said tree structure and said series of outlets corresponding to the leaves of said tree structure.

Claim 8. An elongated gas distribution system according any one of claims 1 to 7 comprising a middle strip, and two side strips, said middle strip having grooves on said first and on said second side, said grooves defining channels on each one of said first or second side, said two side strips forming said channels on said first side and said second side.

Claim 9. An elongated gas distribution system according any one of claims 1 to 8 wherein said outlets are covered with a gas spreading foraminated metal plate or metal fibre fabric.

Claim 10. An elongated gas distribution system according any one of claims 1 to 9 further comprising an integrated cooling wherein at least one of said sides comprises a channel, said channel being formed by grooves in said at least one side, said channel having a fluid inlet and a fluid outlet, said fluid outlet being connected to said fluid inlet by said channel.

Claim 1 1. A plasma deposition or plasma cleaning apparatus comprising an elongated gas distribution system according any one of claims 1 to 10. Claim 12. A plasma deposition or plasma cleaning apparatus according claim 11 where said remotely controlled gas flow controlling means are steered by a feedback signal from said plasma or from a property of a coating deposited from or removed by said plasma.