DE1521520B1 - Device for the continuous production of a thin film, in particular made of metal, by vacuum vapor deposition - Google Patents

Description

The invention relates to an apparatus for continuous production a thin film, in particular made of metal, by vacuum vapor deposition, consisting of a housing forming a main vacuum chamber, one mounted in the housing rotatable drum, the circumference of which forms part of the wall of the main vacuum chamber, in the case of vacuum seals to seal the surface of the drum, facilities for evacuating the main vacuum chamber and the vacuum seals and a heated one Crucible for holding the material to be evaporated is provided in the main vacuum chamber are.

The invention provides for the application of materials such as Metal, in a vacuum for the production of foils or films. It affects in particular a continuous production in which, for example, a very substantial amount of film without the vacuum difficulties normally associated with high vacuum processing and problems can be generated. Although it is well known that high vacuum using suitable pump or suction lines as well as suitable vacuum techniques can be produced and maintained even under difficult conditions the general view that such applications are laboratory-based only Restrict recovery or labor. The invention leads to practical application of high vacuum in the vapor deposition of materials for the production of; extremely thin foils. A production with high output numbers and excellent Quality through processing in a high vacuum with the help of a new type of vacuum grading achieved through which the continuous films or the like. Are passed. These Foils or the like are therefore between atmospheric pressure and high vacuum processing areas movable without a loss of vacuum occurring in these areas.

A really high quality vapor deposition can be used in areas with very perform high vacuum in which a substantially free flow of molecules is achieved so that there is no recombination of vaporized molecules in the free flow areas takes place. This leads to the precipitation of an essentially molecular, i.e. H. Molecularly applied layer, so that for the layer the highest possible degree of uniformity is achieved. In on August 1, 1961 in the United States of America under the title "Foil Production" deposited in the name of the same inventor, at the same time pending patent application are a method and an apparatus for manufacture described in thin foils. This method uses the aforementioned high vacuum conditions out, the invention by creating continuity of production by moving the vapor deposited layer between high vacuum areas and essentially atmospheric Conditions on the other hand represents an improvement.

According to the invention, the vacuum seals consist of several vacuum seal chambers, those immediately following the main vacuum chamber around the circumference of the drum arranged around and each with evacuation devices for the production of a graduated vacuum, and is an electron gun for evaporation of the material contained in the crucible is arranged in the main vacuum chamber.

With the help of the device according to the invention, a vapor-deposited Layer on a rotatable, stretching between the vacuum and the outside air Drum moved out of a high vacuum coating area. The flawless one Vacuum is created with the help of separate evacuation of the successive stages maintained around the drum circumference to create a strong pressure gradient on the path of movement to achieve the layer without stressing the same. The device according to the invention allows continuous film production and brings an improvement the handling of the product to facilitate its damage-free removal from the areas of high vacuums.

An embodiment of the invention is shown in the drawing and is described in more detail below. It shows F i g. 1 shows a section in the longitudinal direction through the vertical center plane of a foil furnace according to the invention, F i g. 2 one Section in the transverse direction through the furnace from FIG. 1 along the plane 2-2 in F i G. 1, Fig. Figure 3 is a section through one suitable for use in the invention Heat source in the form of an electron gun.

To the in F i g. 1 and 2 shown preferred embodiment of the invention should first be briefly noted that in the continuously operating film furnace According to the invention, a rotating drum is provided as an essential component is. The material evaporated in a high vacuum chamber is either on this drum applied by itself or on material carried by it. The drum is related arranged on the walls delimiting the high vacuum chamber so that they are between the chamber and the outside atmosphere. At separate spaces a plurality of vacuum barriers or walls are located on the outer circumference of the drum tight against the drum, gradually reducing the pressure between the adjacent steam barrier walls around the drum circumference a multi-level Suction is provided. This is done in the evaporation chamber of the oven Maintain a good vacuum while eliminating the problems limit the vacuum seal to sealing the drum. So that needs applied as a film on the drum or as a film on a wrap around the drum The coating material applied around the substrate does not suffer from the pressures and to be exposed to stresses that are otherwise effective when this film extends (or must move through) vacuum locks.

In addition to the features of the invention discussed above for the condensation of the vaporized coating material on a heated one Document taken care of. Namely, it was found that the degree of adhesion of the evaporated Materials by controlling the temperature of the substrate on which the materials applied, can be controlled. The rotating drum according to the invention is for a controlled heating to keep the surface within the desired temperature range for the improved Monitoring certain characteristics of film formation ideally suited. In these circumstances the manufacture of a separate Foil by means of vapor deposition with the help of the oven, it is very advantageous for the foil, if it can be easily separated from the surface on which it is vapor-deposited. By keeping the base within a particular temperature range, the adhesive force between the vapor-deposited layer and the actual base, even when using extremely clean surfaces and under conditions which are indicated for a firm adherence, reduced to a minimum.

F i g. 1 and 2 show in detail one at least partially the walls 12 delimited vacuum chamber 11. high-performance pumping systems, such as the diffusion pumps 13 are connected to the interior of the chamber 11 via the walls 12, backing pumps 14 can be used in connection with these diffusion pumps. While other pumping equipment can be used, it should be briefly noted that quite a bit high pumping capacities are required to maintain the pressure in the chamber 11, in particular during the vacuum vapor deposition in this chamber, on a desired one To keep the minimum value.

Inside the vacuum or vapor deposition chamber 11 is a source of steam 16 arranged. According to the illustration, this source consists of a molten one Material 18 for the vapor deposition containing crucible 17 and an electron beam generator 19, the electron beam directed onto the top of this molten metal 21 generated for its heating by means of electron beam bombardment. Furthermore, for direct observation of the interior of the housing 12 in the wall of an observation device 22 are provided. The crucible 17 can be loaded with material 18 in many ways be, wherein a channel 26 is provided in the illustration, the melted Material from a crucible 27 passes into the crucible 17. The coating material 118 is via a vacuum lock 28 extending through a wall of the furnace in placed in the furnace and fed to the crucible 27, in which it is melted. This melting takes place according to the drawing by means of heating by electron bombardment with one or more electron beams 29 emanating from a source 31 into the crucible 27 to be set up there.

The in F i g. 1 shown and described above for the supply and evaporation of the coating material it is advisable to as. with her the original melting of the material at some distance from the vapor deposition point. Thus, the cleaning of the vacuum chamber can be supplied Coating material in the crucible27 can be made by adding the volatile impurities at a distance from the evaporation site Material removed. The coating material can initially pass through the vacuum lock 28 through it in any form, for example as solid pieces of metal scrap, be introduced with the help of more suitable than the vacuum lock shown 28 belonging to the considered supply means successively into the crucible 27 be poured.

The production of a continuous or continuous film is achieved by using a movable base on which the coating material is vaporized. This moving base is formed into a drum 41, which is rotatably mounted above the steam generator 16 with the aid of a shaft 42. As in Fig. 2, one is preferably attached outside of the vacuum chamber 11 Drive device, for example an electric motor 43, with the shaft 42 of the drum 41 coupled. Inside the drum 41, a device shown in FIG. 1 in the form of cooling tubes 44 schematically illustrated cooling device may be provided. This cooling device serves, for example, to prevent overheating of the bearing surfaces and can also, as explained in more detail below, to control the temperature of the drum surface be used.

Vacuum sealing means are provided around the drum 41 to maintain a proper vacuum inside the chamber 11 and can be of any conventional desired shape at the ends of the drum. Since the drum is arranged to rotate between atmospheric conditions outside the furnace and high vacuum conditions inside it, special provisions are made to create a vacuum seal around the drum circumference. This vacuum seal is achieved in that a plurality of vacuum stages offset from one another on the outer circumference of the drum are provided. The individual steps are delimited by separate walls 51, 52, 53 and 54 which, in a substantially parallel, mutually separated position, can extend from the side walls of the chamber and close to the two sides of the outer circumference of the drum. Between the walls 51 to 54, intermediate vacuum chambers 56, 57 and 58 are delimited, which are each connected to suction devices shown schematically at 61, 62 and 63. The walls 51 to 54 extend so far that they fit snugly against the outer circumference of the drum 141, and at the inner end of each wall there may be resiliently mounted rollers 64 which bear substantially against the drum proper. Under conditions in which a layer of substantial thickness is to be vapor-deposited onto the drum in order to subsequently be removed or peeled off as a thick film from it, it is clear that the total radius of the drum on the side leaving the chamber 11 is considerably larger than on the side their side entering the chamber. In these circumstances it is advisable to use adjustable wall ends, but in most cases, provided suitable suction lines are available to evacuate chambers 56, 57 and 58, it is not necessary to increase the clearance between the inner ends of the walls and the drum circumference regulate.

The steam generator 16 serves as a steam source for the material to be formed into a film or the like, wherein, as in FIG. 1, this vapor rises from the surface level of the molten material 18 present in the crucible 17 and condenses on the relatively cool drum surface above the crucible. The rotating movement of the drum forms a steadily advanced support for the condensation of steam on it, namely the drum surface, this continuous layer being moved out of the evaporation zone as a result of the rotating movement of the drum. The coating material is brought on the drum from the vacuum chamber 11 via the intermediate vacuum chambers or stages to the outside of the furnace. Outside the furnace, the material present on the drum and deposited in a vacuum, ie the layer 71, is separated from the drum as a film. This detachment of the layer from the drum can take place by attaching a blade 72 which rests against the drum surface and which is directed towards the coated surface of the drum as the drum moves past the doctor blade. As in Fig. 1, a freely rotatable roller 73 is attached in the vicinity of the separation point of the layer, so that the vapor-deposited material runs over this roller in the form of a film after it has been separated from the drum. The film 71 can. then, for example, as shown, can be wound up onto a take-up reel 74 via suitable intermediate rollers or the like.

In the device according to the invention for the continuous production of a film, the most varied of electron beam generating devices can be used, from. those in Fig. Fig. 3 shows an example of an electron beam source suitable for use in the device according to the invention. The electron beam source 19 according to FIG. 3 contains an electron-emitting filament 81 which is arranged in a reflector electrode 82 and is electrically connected to a supply source 83 which allows a current to flow through the filament. which allows the temperature of the filament to rise to electron emission temperature. An acceleration electrode 84 is arranged outside the reflector electrode 82 and is kept at a positive potential with respect to the filament with the aid of an acceleration voltage source 86. The electrons emitted by the filament 81 are sucked out of the reflector electrode with the aid of the potential difference existing between the acceleration electrode 84 and the filament 81 in the form of an electron beam. According to the drawing, this electron beam is initially directed essentially upwards from the electron source, being curved by the arrangement of a magnetic field running transversely through the electron beam path. This magnetic field can be built up between magnetic pole pieces 87 by exciting a magnetic coil 88 arranged between them from a magnetic supply source 89. By the electron beam 21 through the perpendicular to the plane of FIG. 3 extending magnetic field, it is, as shown in the drawing, curved so that the electrons travel a curved path and strike the surface of the material in the crucible 17. The electron gun described briefly above corresponds to an electron gun described in a co-pending patent application by Charles W. H anks, the above description being deemed sufficient to designate a suitable type of electron gun. Of course, other types of electron guns can also be used, but it is extremely useful to arrange these electron guns in locations inside the chamber that are protected from vapors and ions. According to FIG. 3, the electron gun 19 is arranged below the upper edge of the crucible 17 so that the vapor rising from the molten material 18 located in the crucible generally moves away from the electron gun and does not precipitate on it. It is also possible to use electron beam generators arranged remotely, in which precautions are preferably taken to limit ion bombardment of the electron-emitting filament.

The by the in F i g. 3 can be used for initial melting of the material introduced into crucible 27 and for evaporation of the material contained in evaporation source 16. In addition, the heating of the rotating drum 41 is also provided according to the invention. This can be accomplished fairly easily by electron bombardment of the surface of the drum just prior to its vapor deposition zone. An electron gun 77 as described above blasts the drum with electrons made of a metal such as stainless steel so that it easily withstands the heating.

According to the mode of operation of the embodiment of the invention described above, a very high vacuum is first produced in the chamber 11 with the aid of the pumps 13 and 14. In addition, the pumps 61, 62 and 63 work for the purpose of maintaining a forevacuum in the vacuum stages 56, 57 and 58, which are arranged separately from one another around the drum circumference Torr held. At atmospheric pressure outside the film production line, the first vacuum stage 56 was kept at 0.1 atm, the next stage 57 at 0.01 atm and the third stage 58 at a pressure of 10-4 atm. Copper scrap was brought into the vacuum lock and fed from there to the cleaning or premelting crucible127. When the electron beam generator 31 was in operation, this copper scrap was heated and melted in the premelting crucible, whereby the impurities present in the scrap, which easily evaporate at the melting temperature of copper, are removed the melt have been removed. With the premelting crucible 127 essentially full, the molten copper flowed via a channel 26 into the crucible 17 forming the evaporation source. The molten copper 18 in this crucible 17 was then further heated by electron bombardment in order to raise the temperature of the copper to its evaporation temperature. The drum 41 was driven by the motor 43 at a peripheral speed on the order of 24 to 75 in / min. driven. The drum was about 1.8 inches in diameter so that at the aforementioned peripheral speed, an excessively high drum speed was not required.

It has been found that the adhesion of vapor deposited material to a moving substrate can be limited by controlling the temperature of the substrate. In the example of the formation of a copper foil, easy detachment of the vapor-deposited material from the drum surface was desired. A control of the temperature of the surface of the drum 41 was achieved in that the drum surface was heated, for example by electron bombardment from the source 77, and the interior of the drum was cooled with the aid of the cooling tubes 44. In this example of the production of a copper foil, the drum was heated by electron bombardment to a temperature between 135 and 155 ° C. By heating the drum surface immediately before it entered the vapor deposition zone, it was possible to control the temperature of the substrate onto which the film material was vapor deposited. With the drum rotating and the copper in the crucible 17 heated to the evaporation temperature, copper vapor rose from the crucible and settled on the moving drum surface. This deposit then formed a layer 71 on the drum, the constant rotating movement of the drum moving the vapor-deposited layer out of the chamber through the successive vacuum stages 58, 57 and 56 to the outside of the housing: Outside the chamber 11, the pressure was applied at atmospheric pressure Blade 72 against the drum surface to peel layer 71 from the drum. This layer 71, in the form of a copper foil or a thin copper sheet, was then wound onto a take-up reel 74 or the like via intermediate rollers conducting the foil.

According to the invention there is a truly continuous film production carried out to the extent that the drum 41 continues to rotate steadily, while maintaining of molten material in the evaporation source a constant evaporation of Foil material takes place on the moving drum surface. In this way the production of extremely wide foil surfaces is possible, in which no crack is available. A control of the thickness of the film can easily be carried out by Control of the speed of rotation of the drum, taking of course the rate of evaporation of the copper can also be controlled by controlling the amount of heat supplied to it is. Preferably the rate of evaporation becomes substantially constant kept, but it should be noted that excessive boiling of the copper can express itself in a splash out of the molten copper from the crucible. Of the The distance between the evaporation source and the drum can also be changed, however, it has been found in practice that a distance in this regard 15 to 45 cm is desirable. Too great a distance between the evaporation source and drum or moving pad manifests itself in the loss of a proportionate large amount of steam that then spreads to other parts of the interior of the oven precipitates.

With regard to the type of vapor-deposited layer, it should be noted that the extremely high vacuum produced and maintained in the chamber 11 during the vapor-deposition process creates ideal conditions for an essentially molecular, ie molecular-by-molecule, vapor deposition. Before these molecules are deposited on the substrate, only very slight, if any, recombination phenomena occur on the vaporized molecules. The vapor molecules move when they rise from the level of the molten copper or other material in the crucible 17 , in essentially straight paths, since the high vacuum minimizes the number of gas molecules present to collide with the vapor molecules. An extremely fine layer is thus obtained on the drum surface, so that extremely thin foils or films can be produced in this way. In accordance with the method and apparatus for continuous film production according to that issued on August 1, 1961 in the United States. under the Ser. Nr. 132 423 patent application filed by the same inventor, the present invention employs the difficulties of the formation of very thin films to a minimum down. In contrast to other types of film production, in which thick material webs are reduced in thickness to produce a film, according to the invention the film is built up from a thickness of zero, so that the production of extremely thin films does not require greater effort or expense than the production required by thicker foils.

The invention described above is extremely useful in providing a simplified and improved way of removing evaporated material from a highly evacuated chamber in which the evaporation process is carried out. The rotating drum 41 is extremely useful for continuous film production since it extends between the vacuum chamber and the atmospheric conditions prevailing outside the chamber. The plurality of intermediate vacuum stages around the outer circumference of the drum makes it possible to maintain the high vacuum in the chamber, while the vapor-deposited layer is nevertheless carried out of the chamber. In the case of a drum 41 with a diameter of approximately 1.8 m and a length of approximately 1.5 m, the opening between the outside atmosphere and the first vacuum stage 56 can be restricted to approximately 3.2 cm 2. This restriction is fairly easy to implement in the construction of the device according to the invention, it being possible to use a corresponding gap between the successive vacuum stages. With a restriction to the entire connection zone between the individual vacuum stages, customary vacuum pump devices are able to maintain the pressure differences indicated in the above example. In particular, it should be noted that the high vacuum of the order of magnitude of 0.02 m Torr in the chamber 11 is not only initially established therein, but is maintained in it during the entire vapor deposition process. This vacuum is maintained notwithstanding the fact that a substantial amount of gas is evolved from the premelting crucible and also that a certain amount of steam is distributed throughout the chamber. To maintain this low pressure, suction devices of fairly high capacity are required, but conventional suction devices are suitable for this purpose.

Under the conditions in which relatively low-melting metals, such as copper, are vapor-deposited onto the drum, the crucibles 17 and 27 in the vacuum chamber 11 can be made of graphite, for example. For example, if copper is used as the deposit or vapor deposition material, the drum can be made of stainless steel, although many other metals have been found suitable. By using a suitable backing surface, essentially any desired film surface can be produced. For example, if it is desired to achieve a matt film surface, only the surface of the drum needs to be roughened. Under the conditions in which a very high melting point material is to be vapor deposited, cooling of the crucible may be necessary, in which case water-cooled copper crucibles have proven to be useful.

The example described above, according to which the operation of the Invention was described in connection with the production of copper foils, is in no way to be regarded as limiting the invention, since the most diverse Types of materials can be processed according to the invention. So is for example the system according to the invention for continuous film production is excellent suitable for the production of very thin tantalum foil, which is used in the production of electrical Capacitors are widely used. Since the drum cools down pretty quickly, it is clear that the vapor-deposited material is at its detachment point from the drum is relatively cool outside the vacuum chamber. As discussed above, suitable the plant for continuous film production according to the invention for production both extremely thin foils and foils of greater thickness. Especially with The manufacture of very thin film is the passage of this film through each one Vacuum levels while it is still adhering to the rotating drum, very desirable, because the film then (as it passes through the individual vacuum levels) does not have any is exposed to mechanical stresses. By looking at the slide as it emerges from the vacuum chamber into the atmospheric conditions on the circulating Leaving the drum in place, it is possible to keep the evacuated chamber fairly clean and light to seal, without any structural property of the actual film to be dependent. The advantage of this becomes even more clear when you consider that copper foil with a thickness of, for example, a few hundredths of a millimeter by excessive pressure exerted on them, as required in other designs can be, in which the film is pulled out of the vacuum chamber alone, pretty much easily broken or damaged.

The application of materials, such as metal, in which very high vacuum used in the system according to the invention is expressed in a uniformity of the layer that was previously not achievable. The vapor molecules from the steam generator move in essentially straight lines until they hit on the substrate to be coated, with the almost complete absence of gas molecules In the path of movement of the steam, the molecule collisions and clumping of the steam molecules reduced to a minimum. As a result, these vapor molecules become almost single applied to the substrate, so that an extremely uniform layer is achieved will. Thus, the layer produced according to the invention covers although it is extremely thin can be held, anyway the pad perfectly without a normally Porosity or irregularity encountered in coating processes. To this So it is possible to apply a much thinner layer and still one to achieve full and complete coverage of the object to be coated.

In all of the embodiments of the invention described in the foregoing special precautions are taken to remove the layer from the high vacuum chimney, in which the coating is carried out. This is especially important when using very thin layers, as these layers usually have almost no structural inherent strength to have. By using rotating drums with one arranged on their outer circumference A plurality of intermediate vacuum stages, the invention provides for the effortless movement very thin foils or layers from highly evacuated rooms in atmospheric Pressure in without affecting the high vacuum of the chamber.

Claims (5)

Claims: 1. Device for the continuous production of a thin film, in particular made of metal, by vacuum evaporation, consisting of a a housing forming a main vacuum chamber, a rotatable one mounted in the housing Drum, the circumference of which forms part of the wall of the main vacuum chamber, in which Vacuum seals for sealing the surface of the drum, devices for evacuation the main vacuum chamber and the vacuum seals and a heated crucible for receiving of the material to be evaporated are provided in the main vacuum chamber, d a d u r c h g e -k e n n n e i n e t that the vacuum seals consist of several vacuum sealing chambers (56, 57, 58), which are directly connected to the main vacuum chamber (11) arranged around the circumference of the drum (41) and each with evacuation devices (61, 62, 63) are connected to produce a graduated vacuum, and that a Electron beam generator (19) for evaporating the contained in the crucible (17) Material (18) is arranged in the main vacuum chamber. 2. Device according to claim 1, characterized in that the electron beam generator (19) next to the crucible is arranged with the electron beam at one below the material level is generated in the crucible location, and that the electron gun (19) a magnetic alignment device (87, 88, 89) is assigned to the electron beam (21) to the surface of the material (18) contained in the crucible (17) essentially steers arcuately. 3. Apparatus according to claim 1 and 2, characterized by in the main vacuum chamber (11) arranged cooling tubes (44) and an electron beam generator (77) to control the temperature of the drum surface. 4. Device after one of claims 1 to 3, characterized by an outside of the vacuum chamber (11) arranged blade (72) on the roller (73) for removing the vapor deposited foil \ on the drum as well as through a take-up spool (74). 5. Device according to one of the Claims 1 to -1, characterized by one provided in the main vacuum chamber Premelting crucible (27), a vacuum lock (28) for introducing solid vapor deposition material in the crucible (27), an electron gun (31) for melting and Cleaning of the evaporation material in the melting die ((; el, control devices for the electron gun (31) to the evaporation material in the crucible to keep in the molten state, and a channel (26) for transferring the molten Evaporation material (18) from the crucible (27) into the evaporation crucible (17).