Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
  • H01J37/3411—Constructional aspects of the reactor
  • H01J37/3414—Targets
  • H01J37/3432—Target-material dispenser
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/24—Vacuum evaporation
  • C23C14/246—Replenishment of source material
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/24—Vacuum evaporation
  • C23C14/32—Vacuum evaporation by explosion; by evaporation and subsequent ionisation of the vapours, e.g. ion-plating
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
  • C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
  • C23C14/3414—Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
  • H01J37/3402—Gas-filled discharge tubes operating with cathodic sputtering using supplementary magnetic fields
  • H01J37/3405—Magnetron sputtering
  • H01J37/3408—Planar magnetron sputtering

Definitions

• the invention relates to a method for the deposition of a metal layer on a substrate according to which the cold plasma deposition is carried out inside a heated confinement enclosure so as to avoid the formation of a metallic deposit. on its surface, this enclosure having an inlet opening and an outlet opening by
• a metal vapor source constituting an electrode, being provided in this enclosure allowing the formation of plasma therein.
• This method allows in particular the metallization continuously and at high speed of substrates, such as for example strips, wires and metal beams (steels
• hot rolled, cold rolled steels, stainless steel, aluminum, copper, etc.), and non-metallic substrates such as strips of polymeric materials or paper, or even textile fibers, glass fibers, particularly optical fibers, and carbon fibers.
• One of the essential aims of the present invention is to provide practical solutions to these various drawbacks and problems. To this end, at least the part of the confinement enclosure adjacent to the metal vapor source is maintained at a floating potential.
• Another aspect of the problem concerns the continuous supply of liquid metal to the deposition system and the control and regulation of this supply.
• the consumption of liquid metal can become very high.
• it is in particular very important to keep the distance between the substrate to be coated and the surface of molten metal constant. It is therefore necessary to provide a continuous supply of liquid metal to the tank in order to compensate for consumption. Since the feed must be automatic, it is also necessary to provide a precise control system for this level which is not liable to be contaminated by the metallic vapors prevailing inside this confinement enclosure.
• the metal, of which the metal layer has to be formed on the substrate is introduced in the liquid state into a retention tank communicating with the confinement enclosure and the liquid metal is kept in this tank. at a substantially constant level during the formation of this metallic layer.
• the liquid metal is heated substantially uniformly in the plasma retention tank, in particular by forming a magnetron discharge near this tank, and preferably at least partially around that -this.
• the liquid metal contained in the retention tank therefore constitutes the cathode of the deposition device, either continuously or discontinuously.
• the anode may be the substrate to be coated and in this case the potential of the anode is most often that of the mass of the installation.
• the anode can also be a separate electrode installed in the containment. In this case it is heated to a sufficiently high temperature to avoid being contaminated by metallic vapor and thus avoid short circuits.
• the anode when the device operates on alternating current, can be produced intermittently, at the frequency of the electrical supply, by another retention tank fed separately from the first in liquid metal and placed in the same containment.
• the two tanks then operate successively as an anode and cathode at the frequency of the power supply.
• frequencies from 1 kHz to 1 MHz are possible, power supplies work optimally for frequencies between 10 kHz and 100 kHz.
• the retention tank is weighed in order to determine the level of the liquid metal therein.
• the tank is supplied with liquid metal, depending on the weight measured to regulate this level of liquid metal.
• the retention tank is supplied from a liquid metal tank, the level of liquid metal of which is lower than the level of liquid metal in the retention tank, by adjusting the level of metal in the tank according to the level of metal in the retention tank.
• the invention also relates to a device for implementing the method as defined above.
• This device is characterized in that means are provided for maintaining at least the neighboring part of the retention tank at a floating potential and for electrically isolating the liquid metal with respect to the enclosure.
• Figure 1 is a schematic sectional view of a device according to a first embodiment of the invention.
• Figure 2 is a schematic sectional view, on a larger scale, of the containment and the retention tank of Figure 1.
• Figure 3 is a schematic sectional view of a device according to a second embodiment of the invention.
• Figure 4 is a schematic sectional view of a device according to a third embodiment of the invention.
• Figure 5 is a schematic sectional view of a device according to a fourth embodiment of the invention.
• Figure 6 is a schematic sectional view of a device according to a fifth embodiment of the invention.
• Figure 7 is a schematic sectional view of a device according to a sixth embodiment of the invention.
• Figure 8 is a schematic sectional view of a device according to a seventh embodiment of the invention.
• Figure 9 is a cross section along line A- A 'of Figure 8.
• Figure 10 is a section similar to that of Figure 9 for a device which is suitable for coating a substrate in the form of 'a wire.
• the method according to the invention consists in creating and confining in a substantially closed space maintained under vacuum, traversed in a substantially continuous manner by the substrate to be coated, a cold plasma in a metallic vapor generated from a metal melt brought continuously in a controlled manner into a retention tank.
• the free surface of the liquid metal contained in this tank is called the target.
• Plasma is obtained by negatively polarizing the surface of the molten metal with respect to a counter electrode. This can be done either continuously, the counter electrode then constituting an anode, preferably formed by the substrate to be coated if the latter is sufficiently conductive, or discontinuously in alternating current. In the latter case, the counter-electrode may possibly be constituted by another target maintained in the same confinement enclosure. If the substrate to be coated is not electrically conductive, the counter-electrode is constituted by a separate electrically conductive element.
• the aforementioned metallic vapor and the plasma are confined in a confinement enclosure made of a material with a low bonding coefficient for the metallic vapor considered and sufficiently hot not to be contaminated by the latter.
• At least the part of this confinement enclosure adjacent to the liquid metal retention tank is at floating potential to avoid the formation of electric arcs between the latter and the retention tank.
• the containment is either directly or indirectly heated to a potential close to its working potential to avoid the formation of arcs.
• Direct heating takes place by the Joule effect by passing an electric current through the walls of the enclosure.
• Indirect heating takes place by radiation by means of an electric heating resistor placed near the walls of the containment.
• the walls of this containment are substantially fixed. Provision is of course made for means, such as slides, central fixings or folds, allowing the walls to expand while ensuring the confinement of the plasma and the metallic vapor during their evolution in temperature from stopping until in operating mode.
• the substrate enters and leaves this fixed confinement enclosure by entry and exit slots or entry and exit holes of shapes adapted to those of the cross sections of the substrates to be coated.
• These inlet and outlet openings are, according to the invention, provided with hot lips intended to reduce the conductance at the passage of the gas.
• the seal between the liquid metal retention tank and the walls of the containment is ensured according to the same principle.
• Substrates of different formats i.e. with variable widths and thicknesses, are coated evenly despite possible lateral displacements.
• the size of the liquid metal retention tank in the direction transverse to the substrate reaches at least the value of the maximum width of a substrate to be treated, for example in the form of a strip.
• the supply of liquid metal is ensured continuously from a holding furnace, outside the vacuum chamber, via a tube making it possible to take up, by the height of the column of liquid metal, the pressure difference existing between the gas inside the liquid metal holding furnace and the inside of the confinement enclosure located in the vacuum chamber.
• the particularity of this liquid metal supply system is to avoid any mechanical connection between the tube and the liquid metal retention tank, so as to be able to precisely control the level of the latter in the retention tank by its weighing.
• Two types of means can advantageously be envisaged to ensure the mechanical independence of the feed tube and of the retention tank so as not to distort the measurement of the weight of liquid metal contained in the retention tank.
• a first solution consists in feeding the container through a bent tube passing over the edge of the container and the end of which dips into the liquid metal contained therein without touching the container.
• the metal crosses the difference in height between the rim of the tank and the metal level by siphon effect.
• a second solution consists in making the feed tube pass through the bottom of the tank while maintaining a free space between the outside surface of the tube and the surface of the hole drilled in the bottom of the tank.
• the tightness between the tube and the retention tank, between which there is therefore a clearance, is ensured by the surface tension of the metal.
• the maximum hydrostatic height of the liquid metal in the retention tank ensuring this tightness, measured from the bottom of the tank, is therefore limited. This maximum height decreases with increasing play and increasing the temperature of the liquid metal. It is typically from a few centimeters, for example in the case of zinc and tin, of the order of 3 to 6 cm for a clearance of less than 1 mm.
• the invention also relates to a particular method and device making it possible to produce a magnetron discharge all around the liquid metal retention tank passing through the confinement enclosure.
• the advantage of this configuration is that it allows more uniform heating of the surface of the metal and of the retention tank.
• Another advantage is to allow the production of long and narrow sources of liquid metal.
• the invention implements several characteristics in obtaining the intended goal, ie: 1.
• the metal deposition must be carried out for a very short time, which is generally less than a second, on a substrate traveling continuously and at very high speed in this enclosure during fairly long production periods of, for example, seven days.
• the confinement enclosure is specially designed to avoid being contaminated by metallic deposits (material constituting the interior walls of the enclosure with a low bonding coefficient for metallic vapor and possibility of heating the walls), to carry out electrical insulation cannot be contaminated by the deposit, in order to obtain a stable discharge in the metallic vapor, i.e.
• a particular electrical and magnetic configuration allowing uniform heating of the surface of the liquid metal contained in the retention tank.
• This configuration allows the formation of a magnetron discharge in the metal vapor all around the retention tank, which becomes essential when long and narrow products such as fibers must be coated at very high speed economically.
• the retention tank must pass through the confinement enclosure, be constructed from an electrically conductive material, constitute the cathode of the deposition system, continuously or discontinuously, and be in the presence of a field magnetic induction inside the containment oriented in the direction of a series of its generators, so that this induction field is parallel to its outer surface and completely surrounds it.
• the process according to the invention is moreover naturally adapted to variations in strip formats in width or in thickness, which is essential in the steel industry, but also has the advantage of being insensitive to slight displacements. sides of the substrate in the containment. It allows the production of uniform deposits in thickness, both longitudinally, but also laterally.
• Figures 1 and 2 show a device according to the invention, which is suitable for coating a face of a substrate 1 in the form of a strip which passes in a substantially continuous manner through a confinement enclosure 7 in the direction indicated by arrow 13.
• the containment 7, in which a plasma 6 and a metallic vapor are created, is at floating electrical potential and is heated to a sufficiently high temperature so as to avoid the formation of a metallic coating on its interior surfaces.
• the material used to constitute the interior surfaces of the enclosure 7 is chosen so as to reduce the bonding coefficient of the metal atoms as a function of their nature.
• a metallic vapor which essentially comprises zinc atoms carbon or a hot oxidized stainless steel is used for the interior surfaces of the enclosure 7.
• This retention tank 8, and consequently the liquid metal is electrically insulated with respect to the lower part of the enclosure 7 while maintaining a space free between the latter and the retention tank 8.
• a feed tube 5 for the liquid metal is provided which extends through an orifice in the bottom wall of the retention tank 8.
• the feed tube 5 of the liquid metal in the retention tank 8 is not linked to the latter.
• a relatively large clearance exists, in fact, between the outer surface of this tube 5 and the outline of the orifice drilled in the tank 8 for the passage of the tube 5.
• the clearance is of such dimension that the seal between the outer surface of the tube 5 and the bottom wall of the tank 8 is ensured because of the surface tension of the liquid metal, so that the metal cannot flow through this clearance.
• the retention tank 8 rests on supports 19 which constitute a balance.
• These supports 19 comprise, for example, a piezoelectric strain sensor.
• the level of liquid metal in this tank 4 is below the level of liquid metal in the retention tank 8.
• This tank is arranged in an electric oven, not shown, which melts the metal.
• the length of the supply tube 5 makes it possible to compensate for the pressure difference existing between the interior of the vacuum chamber 2 and the interior of the reservoir 4 by the height of liquid metal which it contains measured from the level of metal in the tank 4.
• the electric power of the furnace only serves to melt the metal and to maintain it in the liquid state in the tank 4, the atmosphere of which is reducing or neutral to prevent oxidation of the metal.
• the pressure of the gas present in the tank 4, above the liquid metal is either equal to or greater than the value of the external atmospheric pressure.
• the regulation of the supply of liquid metal into the retention tank 8 by the supply tube 5 is done by modifying the distance between the level of the metal in the tank 4 and the level of the metal in the retention tank 8, ie by vertically moving the tank, or by modifying the value of the gas pressure in the tank 4.
• the supply of liquid metal into the retention tank 8 is adjusted as a function of the level of the liquid metal in the latter by varying the height of the level of the liquid metal contained in the tank 4.
• means adjustment are provided allowing the tank 4 to be moved in a vertical direction relative to the retention tank 8 and to the supply tube 5.
• Another means consists in varying the height of the upper level of liquid metal contained in the tank 4, without modifying the vertical position of the tank 4, but by varying the neutral gas pressure therein reign.
• neutral gas is meant a gas which does not react chemically with the liquid metal.
• an electrical discharge i.e. a plasma is produced in metallic vapor between the surface of the liquid metal 12, constituting a cathode, and the substrate 1, forming an anode, kept to ground 15 by means of a DC generator 14.
• the discharge is confined magnetically near the surface 12 of the liquid metal by means of the magnetic circuit 10 in order to obtain a magnetron discharge.
• the magnetic circuit 10 is protected from heat by thermal insulation 9 cooled by circulation of water.
• the ions and activated species formed in the plasma and which bombard the surface 12 of the liquid metal dissipate there enough energy to allow its evaporation, so that a metallic vapor is generated.
• the lower face of the substrate 1 comes into contact with the vapor and the plasma and is thus coated with a metallic deposit, unlike its upper face relatively close to the upper part of the confinement enclosure 7.
• the substrate 1 is kept at a distance of less than 1 cm from the upper part of the enclosure 7. This proximity greatly limits the passage of metallic vapor over the substrate 1.
• the metal vapor pressure varies according to a decreasing exponential law as a function of the ratio of the distance at the edge of the product 1 to the distance separating the product from the surface considered of the confinement enclosure 7.
• the losses of metallic vapor through the free space between the hot surfaces of the retention tank 8 and those of the confinement enclosure 7 are also greatly limited by making long and narrow slits. Typically, it is arranged to be in a molecular flow regime in these slots. This condition is generally achieved for a slit of a few millimeters in distance between walls.
• the free distance between the enclosure 7 and the retention tank is therefore generally between 1 and 5 mm and is preferably of the order of 2 to 3 mm. Under these conditions, for a ratio between this distance and the length of the slit from 1 to 33, it can be shown that the probability of transmission of a metal atom is 0.11. This probability must be multiplied with the molecular flux to assess the magnitude of the loss of metallic vapor.
• the vacuum chamber 2 is connected to a “high vacuum” pumping group 3 generally comprising molecular pumps, such as, for example, turbo-molecular hybrid pumps, Root pumps and primary pumps.
• molecular pumps such as, for example, turbo-molecular hybrid pumps, Root pumps and primary pumps.
• the deposition device according to the invention is capable of operating in the presence of a relatively high partial pressure.
• an additional gas with metallic vapor such as for example: Ar, He, N 2 , O 2.
• the pressure of this additional gas must however remain less than 1 Pa (or 10 mbar).
• the distance between the surface of the liquid metal 12 and the face to be coated with the substrate 1 must at least be a few cm, and preferably at least 3 cm.
• the tank 8 is supplied, as described above, by means of the tube 5 immersed in molten metal in a tank 4 whose upper level of the liquid is adjusted either by adjusting the pressure of a neutral gas introduced into a sealed tank 4 either by climbing or descending the reservoir 4 relative to the end of the tube 5.
• the neutral gas can comprise argon, nitrogen and hydrogen, or another neutral gas.
• the initiation of the process according to the invention always consists in injecting a rare gas such as argon into the confinement enclosure 7 or into the vacuum chamber 2 in order to maintain a pressure of less than 10 Pa in l enclosure 7.
• a rare gas such as argon
• the rare gas is injected by means of 'An injector 11 which, in Figure 1, opens directly into the containment 7.
• the process is stopped by emptying the retention tank 8 through the supply tube 5 and cutting off the electrical supply 14 of the device.
• the injection of argon for example is gradually reduced so as to reach a partial pressure of argon of less than 1 Pa.
• the argon injection is completely stopped and the residual pressure in the vacuum chamber 2 is less than 0.01 Pa (10 "4 mbar) while the pressure in metallic vapor in the confinement enclosure 7 generally exceeds 0.1 Pa (10 mbar).
• the average power densities to be applied to the target surface i.e. at the surface 12 of the liquid metal, of course depend on the nature of the metal, but remain below 200 W / cm.
• the average power density is between 5 W / cm 2 and 100 W / cm 2 for potential differences between the cathode 12 and the anode 1 less than 1500 V.
• the potential differences between the anode and the cathode are, in general, between 300 N and 1000 N.
• the electrical discharge is preferably carried out by negatively polarizing the surface 12 of liquid metal in direct current or in pulsed current, for example, simply rectified.
• this new technique does not require the presence of a chemical plant annexed to the coating line for the treatment of effluents in electrolysis. It also does not require heavy investment in an indispensable continuous annealing furnace before dipping the sheet in the zinc tank in a dip galvanizing installation.
• the process according to the invention is of course not limited to this single metal, and in addition to the deposition of Zn and its alloys, it is suitable for the deposition of any metal or metallic alloy which can be brought in liquid form by the device described here. above in the containment enclosure 7 of the landfill.
• Other metals which can be used are, for example tin, magnesium, aluminum and their alloys.
• Adaptations in temperature and in the materials constituting the confinement enclosure 7 and the retention tank 8 must of course be made to avoid problems of contamination by metallic vapor and corrosion by liquid metal depending on the nature of the last. Adaptations must also be made regarding the choice of materials for tube 5 and tank 4.
• FIG. 3 relates to a twin adaptation of the previous configuration shown in FIGS. 1 and 2.
• This embodiment allows the coating of the underside of a substrate 1 in the form of a strip moving in the direction of the arrow 13.
• Two tubs different retention 8 and 8 'for a liquid metal are provided below the containment 7.
• the two tanks 8 and 8' can contain the same metals or two different metals.
• an alternating excitation is used to negatively polarize, alternately, the two surfaces 12 of liquid metal in the 8 and 8 'retention tanks.
• the power supply 14 is completely electrically isolated, both from the walls of the confinement enclosure 7, but also from the substrate 1 to be coated, so as to form an electrical discharge, i.e.
• each tank 8 and 8 ' is made not only at the level of the tanks 4 and 4' but also at the level of the tanks 8 and 8 'themselves for their preheating before the introduction of the liquid metal via tubes supply 5 and 5 '. It is therefore obvious that in this configuration the two reservoirs 4 and 4 ′ must be electrically insulated from the potential of the substrate 1, from the potential of the walls of the enclosure 7, but also from each other.
• the substrate 1 is kept at ground 15. This embodiment of the device makes it possible to coat substrates 1 which are not electrically conductive.
• FIG. 4 relates to the coating of the upper surface of a substrate 1 in the form of a moving strip in a containment enclosure 7 having an L-shaped section.
• the retention 8 is supplied with liquid metal by a tube 5 mechanically independent of the tank 8.
• the tank is connected to an electric generator, not shown in FIG. 4.
• the level of the metal 12 in the retention tank 8 is also checked by simple weighing of the tank 8. In order not to have a deposit on the underside of the substrate 1, the latter is kept close to the bottom wall 23 of the containment 7.
• the confinement enclosure 7 is supplied with argon gas at the start of the process by an injector 11.
• a constant magnetic induction field 17 is created by means of a solenoid 16 in order to allow the electrons emitted by the surface 12 of the liquid metal to reach the surface 24 of the substrate 1 to be coated, the latter playing the role of anode.
• the magnetic induction field typically amounts to at least 0.005 T (or 50 Gauss), the direction of the vector 18 of the induction field being indifferent.
• the solenoid 16 surrounds the confinement enclosure 7 and is arranged in such a way that the magnetic field created is substantially transverse to the surface 24 of the substrate 1 to be coated.
• the confinement enclosure 7 is maintained at a floating potential, which makes it possible to avoid the formation of electric arcs between the walls of the enclosure 7 and the retention tank 8 containing the liquid metal, on the one hand, and between the walls of the enclosure 7 and the substrate 1 constituting the anode of the device, on the other hand.
• a generator 14, not shown, negatively polarizes the liquid metal 12 with respect to the electrical potential of the substrate 1 either continuously or alternatively, by a pulsed current. In the latter case a simply rectified current can be used.
• FIG. 5 represents an embodiment of the device, according to the invention, which comprises two retention tanks 8 and 8 ′ containing a liquid metal and which has a T-shaped containment enclosure 7.
• the enclosure 7 thus shows, between the two retention tanks 8 and 8 ′, a vertical tubular part 25 surrounded by a solenoid 16.
• An inlet 21 and outlet 22 opening for a substrate 1 are provided in the lower part of this tubular part 25 of the containment 7.
• an alternative excitation is used to negatively polarize, alternately, the two surfaces 12 of liquid metal in the retention tanks 8 and 8 '. It is very important to provide an electrical supply 14 which is completely isolated from the walls of the confinement enclosure 7, but also from the substrate 1 to be coated, so as to form an electrical discharge, i.e. a plasma, stable between the two retention tanks 8 and 8 '.
• the electrical supply of each retention tank is made not only at the level of the tanks 4 and 4 ', but also at the level of the tanks 8 and 8' themselves for their preheating before introduction of the liquid metal via tubes 5 and 5 ' . It is therefore obvious that in this configuration the two reservoirs 4 and 4 ′ must be electrically isolated from the potential of the substrate, from the potential of the walls of the confinement enclosure 7, but also one with respect to the other.
• the device represented in FIG. 6 allows the simultaneous coating of the two faces of a strip-shaped substrate 1, or of a series of wires, or even of beams passing through the confinement enclosure 7.
• This device is similar to that of FIG. 4 except for the fact that a second retention tank 8 ′ is provided below the substrate 1, as in FIG. 1.
• the coating of the upper face 24 of the substrate 1 requires the presence of an induction field 17 produced by a solenoid 16.
• the lower face 26 of the substrate 1 is coated with liquid metal contained in the lower retention tank 8 '.
• the substrate which passes through the confinement enclosure 7 through an inlet 21 and outlet 22 opening acts as an anode.
• the walls of the confinement enclosure 7 are kept at floating potential, in particular so as to avoid the formation of electric arcs, as already mentioned above.
• the two retention tanks 8 and 8 ′ are continuously supplied with liquid metal by means of tubes 5 and 5 ′, not shown in the figure, mechanically independent from the retention tanks 8 and 8 ′, so that the level regulation by weighing of retention tanks 8 and 8 'is possible.
• the walls of the confinement enclosure 7 as well as the tanks 8 and 8 ′ are at a sufficiently high temperature to avoid being contaminated by the metallic vapor formed in the enclosure 7.
• the losses of metallic vapor are limited by the use of seals in the form of slots both at the entry and exit openings of the substrate or substrates, but also in the free spaces located between the upper surfaces of the retention tanks 8 e 8 ′ and the walls of the containment enclosure 7 which is adjacent to them.
• the device according to the particular embodiment of the invention shown in FIG. 7 allows a uniform coating to be carried out on all the faces of the substrates 1 which pass through the device by means of a single retention tank 8 located below these substrates.
• the retention tank 8 is at least twice as long in the transverse direction of the substrates as the total width of the area projected by these substrates on the surface 12 of the liquid metal.
• the distance from the top surface of the confinement enclosure 7, in front of which is an anode 20, and the upper face of the substrate 1 must be sufficient for the metal vapor pressure to be substantially constant there.
• a distance of several centimeters, for example 5 to 10 cm, fulfills this condition. Indeed, for such distances, the gas flow regime becomes viscous, which greatly increases the conductance of the section considered.
• two solenoids 16 are placed behind the retention tank, on the one hand, and behind the anode, of on the other hand, so as to create a magnetic induction field 17 such as that shown in FIG. 7.
• This magnetic induction field is oriented mainly in the direction of the arrow 18 and extends between the anode 20 and the surface 12 of the liquid metal, so as to allow the transport of electrons from the surface 12 of the liquid metal, which constitutes a cathode, up to the anode 20. In this way the diffusion of the plasma throughout the confinement enclosure 7 is obtained, which makes it possible to produce a compact and adherent metallic coating on all the faces of the product.
• a generator 14, not shown, is provided operating in direct or pulsed current, or in simply rectified current.
• the plasma is formed in front of the surface 12 of liquid metal only when the polarization of the latter is negative with respect to the anode 20.
• the retention tank 8 and the liquid metal at the level of the reservoir 4 (not shown) are connected to the negative pole of the generator 14.
• the reservoir 4, not shown, is of course electrically isolated from the potential of the substrates 1, from the potential of the walls of the vacuum chamber 2 and from the potential of the walls of the confinement enclosure 7 which are kept at floating potential.
• the upper part of the confinement enclosure 7 can be formed simply by means of a hot anode, i.e. at a temperature avoiding the deposition of the evaporated metal on the anode.
• the sealing as well as the electrical insulation with the side walls of the enclosure 7 is produced by slits in a similar manner which is carried out the sealing between the walls of the enclosure 7 and the retention tank 8 as described above.
• the advantage of the device shown in Figure 7 is its great technological simplicity.
• FIG. 8 represents a particular electrical and magnetic configuration making it possible to carry out a magnetron discharge in a metal vapor coming from a retention tank 8, the metal vapor extending all around this retention tank 8.
• the tank retention 8 constructed of an electrically conductive material, passes through the confinement enclosure 7 in the direction of movement of a substrate 1.
• the retention tank 8 passes through the side walls of the confinement enclosure 7, which are at floating potential, without touching them, leaving a relatively small space, a few millimeters, between the tank 8 and the walls to limit the metal losses through this space and to allow the displacement of the retention tank relative to the confinement enclosure 7.
• the retention tank 8 is supported and weighed outside the confinement enclosure 7 by supports 19. In this way, it is avoided that the system of p esée is contaminated by metallic vapor.
• the supports 19 are fitted with sensors, not shown in the figure, making it possible to measure the weight of liquid metal contained in the retention tank 8.
• the retention tank 8 constitutes the cathode of the system either with respect to hot anodes 20, or with respect to the substrate 1 to be coated, if the latter is electrically conductive.
• two retention tanks can be located in the same confinement enclosure 7 so as to be able to be polarized with respect to each other by means of a supply operating with alternating current, typically at a frequency between 1 kHz and 1 MHz and preferably between 10 kHz and 100 kHz.
• alternating current typically at a frequency between 1 kHz and 1 MHz and preferably between 10 kHz and 100 kHz.
• Each time a retention tank 8 is negatively polarized the entire surface 12 of liquid metal is bombarded with ions and activated species contributing to the evaporation of the metal, while the other tank plays the role of anode.
• the process is reversed at the operating frequency of the power supply.
• the advantage of this configuration is to avoid the formation of arcs in the discharge, especially in the case of injection of a reactive gas, such as for
• the retention tank 8 is supplied with liquid metal by means of a tube 5 separated from the latter, as described above, and itself supplied by means of a tank 4 of liquid metal, not shown in FIG. 8 .
• This magnetic induction field 18 can be produced either at by means of one or more solenoids 16, or by means of permanent magnets, which surround the confinement enclosure 7.
• the presence of the magnetic induction field B perpendicular to the electric field existing in the cathode cladding of the electric discharge contributes to the drift of the electrons in a direction corresponding to that of the vector product of the magnetic field vector 18 and of the electric field vector in the cladding cathodic and therefore the diffusion of the plasma around the retention tank 8.
• bulges 26 and 27 are at the potential of the cathode, i.e. at the potential of the retention tank 8, and are used for the electrostatic reflection of the electrons towards the center of the electric discharge. Instead of using these electrostatic reflectors, one can imagine the use of magnetic mirrors. When the retention tank 8 is long enough, these electron reflectors are no longer essential.
• FIG. 9 shows a cross section along line AA 'of Figure 8.
• the retention tank 8 is located between two anodes 20 which are located near the surfaces of the containment 7.
• the substrate 1 in the form of sheet metal moves between the surface 12 of the liquid metal contained in the retention tank 8 and the upper anode 20.
• the electrical discharge and the metallic vapor are formed all around the retention tank 8 and of the substrate 1.
• the retention tank and the surface liquid metal is wider than the maximum width of the sheet to be treated.
• Figure 10 shows a cross section similar to that of Figure 9 for a device which is specifically adapted for coating wire-shaped substrates.
• the retention tank 8 of Figure 10 is relatively narrow and extends below a substrate 1 in the form of wire or fiber.
• the anodes 20 are maintained at a sufficiently high temperature in order to avoid the deposition of the atoms of the metallic vapor on these anodes.
• a single hot anode 20 is provided which surrounds the retention tank 8 so that only the walls transverse to the direction of movement of the substrate 1 are kept at floating potential. Between these walls and the anode a slot is provided in order to electrically insulate the walls with respect to the anode while limiting the losses of metallic vapor.
• the process implemented by the device shown in FIG. 8 is particularly well suited for the metallization of wires and fibers because all the vapor and the plasma remain confined in the confinement enclosure around a retention tank 8 which can be very narrow so as to reduce the energy consumption necessary for the deposit.
• the hot anode completely surrounds the retention tank.
• the various walls are made of a material with low coefficient of sticking for metallic vapor and are sufficiently hot not to be contaminated by the latter. Sealing and electrical insulation between the ends of the retention tank 8 and the side walls of the confinement enclosure 7, their crossing points are ensured in the same way, that is to say also by making narrow slits.
• a hot-rolled steel sheet 1 m wide and 1 mm thick at a line speed of 100 m / min the latter is introduced continuously into a vacuum chamber comprising, in addition to the device according to the invention, airlocks in cascades of entry and exit, as well as a section of cleaning by pickling ("etching") preceding the section of zinc plating, and a section of passivation by deposit of chromium by cathode sputtering (“ sputtering ”) located behind the cold plasma zinc plating section, before the sheet comes out of the exit airlock.
• etching cleaning by pickling
• sputtering a section of passivation by deposit of chromium by cathode sputtering
• the two faces of the steel sheet are coated simultaneously by means of eight deposition units of the type shown in FIG. 6.
• the aim is to deposit zinc, on two faces, 7.5: m thick by face.
• These units are capable of coating sheets up to 1 m wide for product thicknesses of up to 1 cm. Processing smaller formats poses no problem except lower energy consumption per depot unit.
• the eight deposition units are placed in pairs in four vacuum chambers each connected to a molecular pumping group which allows residual pressure to be reached in operating mode
• Each deposition device is supplied with metallic vapor by two graphite retention tanks 8 for liquid zinc 12.
• Each retention tank is connected to the negative pole of a DC generator 14.
• the positive pole is connected to the sheet and is therefore grounded in the system.
• the sheet metal is the anode of the system in this configuration.
• the bins have a rectangular shape and have a dimension of 150 mm x 1000 mm.
• the long side of the tank is oriented perpendicular to the direction of movement of the sheet.
• Each retention tank is supplied with zinc by means of an alumina tube.
• the tube could also be made of ceramic or steel coated internally with ceramic.
• the retention tank is crossed by the tube 5 as shown in FIG. 2.
• the tube 5 is flush with the bottom of the tank 8 and there is a clearance of 1 mm between the outside diameter of the latter and the diameter of the hole drilled in the tray.
• the level of zinc 12 in the tank can reach more than 4 cm without causing a leak through the opening left by this play.
• the tube passes through the tank on the side of the latter so as not to hinder the passage of the sheet, since one of the bins is located above the sheet.
• Supports 19, not shown in FIG. 6, are protected from the heat of the retention tank 8 by thermal insulation 9. Under the latter is arranged a network of permanent magnets 10 allowing the realization of a magnetron discharge.
• the supports 19 are fitted with sensors for permanently measuring the weight of each retention tank 8. This weight measurement allows precise control of the level of liquid metal 12 in the tank.
• the signal sent by these sensors makes it possible to ensure automatic and continuous regulation of the level of liquid metal in the tanks by varying the pressure of gas injected into reservoirs 4 constituted by furnaces for supplying and holding the molten metal.
• the height of the zinc in each of the retention tanks 8 is adjusted to 1 cm from the bottom of the tank.
• the two ovens, adjoining the same containment, are electrically isolated from each other, but also from the rest of the installation.
• the liquid zinc of each furnace 4 is also placed in direct electrical contact with the negative terminal of the generator 14 of the retention tank which it supplies.
• Each alumina tube 5 passes through the wall of the vacuum chamber 2 by means of a sealed passage, not shown, and is of sufficient length to allow compensation, by the height of liquid zinc in the tube between the level top of the bath in the oven 4 and the surface of the liquid zinc 12 in its retention tank 8, pressure differences between the outside and the inside of the vacuum chamber, typically between 87,780 Pa and 105,070 Pa. To do this, the length of the tube 5 is 2.3 m.
• the sealing of the deposition device for zinc vapor and for plasma is ensured by means of a containment enclosure 7, as shown in FIG. 6.
• the inlet 21 and outlet 22 slots have a cross section in the direction of movement of the 20 mm x 1000 mm strip for a length of 100 mm.
• the losses due to these slits are less than 1 kg of Zn per week, under production conditions.
• the heaviest losses are observed at the level of the hot seals constituted by slots of 3 mm over a length of 100 mm and located near the upper surfaces of the retention tanks 8 which are flush with the exterior surfaces of the walls of the enclosure. 7.
• These material losses are less than 10 kg per 24 h, under production conditions for each depot unit of the type represented in FIG. 6.
• the zinc lost by the confinement enclosure is recovered in the vacuum chamber, in solid form, by condensation on cold plates, not shown, provided for this purpose. This zinc is finally reintroduced into the furnace 4.
• the walls of the confinement enclosure 7 are electrically isolated from the sheet metal, the retention tank and the vacuum chamber. They have floating potential. These walls are double so as to form cavities inside which a Joule effect heating system is protected. This heating system allows the interior faces of the walls of the confinement enclosure 7 to reach a temperature of the order of 450 ° C., sufficient to prevent them from contamination by zinc.
• the current generator allowing this wall heating is electrically isolated from the rest of the installation in order to maintain the walls of the confinement enclosure 7 at floating potential.
• the walls are designed to be able to expand and contract without damaging the tightness of the system.
• the outer surfaces of the containment 7 are made of polished stainless steel ("stainless steel") with low emissivity (0.25), while the inner surfaces are made of high temperature oxidized stainless steel, of higher emissivity (0 , 85), in order to absorb the radiation produced by the heating system and preferentially heat the interior surfaces of the containment 7.
• This configuration has the advantage of minimizing the energy consumption necessary for heating the containment 7 .
• a solenoid 16 is placed around the confinement enclosure 7 in order to produce an induction field whose intensity is greater than 0.005 T ( 50 Gauss).
• This field allows, on the one hand, to ensure the return of electrons from the upper target to the sheet which constitutes an anode, and, on the other hand, ensures a preferential diffusion of the plasma along the lines of induction field magnetic rather than perpendicular to them.
• each of the sixteen DC generators of the eight deposition devices consumes a power of 30 kW under a potential difference of 950 V.
• Each of the sixteen ovens all being electrically isolated from each other and from the earth, is equipped with a heating power of 4 kW.
• Each heating system for the walls of the containment enclosures consumes 10 kW, i.e. a total power of 80 kW for the eight depot units.
• the total power required to produce a Zn deposit of 7.5: m thick on both sides of the sheet at a line speed of 100 m / min in 1 m width is therefore 624 kW.
• An optical fiber is continuously treated in the device according to the invention, under vacuum by cold plasma at a speed of 1000 m / min.
• the entry and exit of the device are equipped with cascades.
• the fiber is cleaned on the surface by passing through an argon and oxygen plasma before being sensitized by a deposit of chromium of a few nanometers produced by sputtering.
• the deposition of metal produced in the next step of the process by a device according to the invention is passive by a 10 nm layer of chromium, also produced by sputtering before leaving the fiber from the vacuum chamber via the exit airlock.
• the metallization step consists either of making a layer of 5: m of Zn, or a layer of 5: m of Sn on the surface of the fiber.
• the metallization is carried out in a device as shown in FIG. 8, with however a modification as regards the confinement enclosure.
• the containment is mainly constituted by a cylindrical anode with an internal diameter of 150 mm, made of graphite surrounding a retention tank 8, also made of graphite, of semi-cylindrical section and diameter of 40 mm.
• the lateral sealing is ensured by means of two walls of the containment with floating potential, in graphite.
• the losses of metallic vapors are limited by making narrow slits between these side walls and the anode and the metal retention tank 8, respectively.
• the length of the retention tank useful for storage inside the containment is 1 m.
• the anode can be heated, as well as the side walls with floating potential, by the Joule effect.
• the respective potentials of the different walls are not modified by the heating system.
• the radiative losses of the confinement enclosure are possibly limited by means of one or more cylinders of polished stainless steel (“stainless steel”) with an emissivity of 0.25, with floating potential surrounding the anode.
• the fiber passes right through the device over its entire length.
• the retention tank crosses the side walls so that it can be supported by the supports 19 provided with the weighing device.
• the feed tube is made of alumina.
• a magnetron discharge is produced in the metallic vapor around the retention tank, constituting the cathode of the system due to the presence of a magnetic induction field 18 of 0.05 T (or 500 Gauss) obtained at by means of a solenoid 16 surrounding the deposition device over its entire length.
• a magnetic induction field 18 of 0.05 T (or 500 Gauss) obtained at by means of a solenoid 16 surrounding the deposition device over its entire length.
• Each of the eight retention tanks 8 for liquid zinc is supplied by its own tank 4 consisting of an oven, electrically isolated both from other ovens, but also from the mass of the installation.
• the zinc consumption is 673 g / h per fiber.
• the power required for deposition is mainly used to compensate for energy losses given the low consumption of zinc.
• the power to be supplied to each deposition system is 1.2 kW for deposition and 2 kW for Joule heating of the anode. This results in a total consumption of 26 kW for obtaining the target deposit.
• the zinc plating of a mild steel wire by cold plasma is carried out with the same type of deposition system as that used for the zinc plating of an optical fiber, i.e. such as shown in Figure 8. It is simply adapted to the inlet and outlet to limit losses of zinc vapor and allow the passage of a wire of 5 mm in diameter. Inlet and outlet losses are limited by passing the wire through hollow cylinders 50 mm long and 10 mm in internal diameter fixed respectively to the side inlet and outlet walls of the containment enclosure of the metallic vapor.
• Two deposition devices of 1 m of useful length are sufficient to produce a deposition of 5: m of Zn on the wire at a line speed of 300 m / min with a consumption of 4 kW for deposition, per deposition system.
• the total power required for galvanizing the wire is therefore 16 kW, i.e. 8 kW per deposition system, for zinc consumption of 10 kg per hour, i.e. a consumption of 5 kg / h per deposition system.
• the present invention realizes a plasma in a relatively vapor-tight metallic vapor enclosure, with hot walls and for which the junctions of the surfaces of antagonistic potentials, in particular the anode and the cathode, are made by walls hot with floating potential.
• the electrical insulation is carried out by leaving a free space in the form of the narrowest possible gap between the surfaces to be insulated.
• the use of an electrical insulator inside the containment would quickly lead to the formation of electrical short circuits by contamination by metallic vapor deposition.
• Different configurations are proposed which make it possible to metallize the upper face of a substrate.
• a magnetic field is used to ensure the return of electrons to the anode.
• the invention also provides a liquid metal supply system which comprises a tube without mechanical connection to the metal retention tank. It is therefore possible to control and regulate the level of the metal in the retention tank, forming the target, by simple weighing of the latter.
• the inlet opening and the outlet opening of the containment is adapted to the shape of the cross section of the substrates to be coated.
• the inlet and outlet opening have the form of a cylindrical tube whose internal diameter is slightly greater, by 2 to 5 mm for example, than the external diameter of the substrate.

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