Device For Passing Substrates Through A Vapor Deposition Zone

Abstract

A device for coating substrates in a vacuum plant comprising a vacuum chamber which is adapted to be subjected to reduced pressures and which includes at least one pair of laterally spaced sources for producing a deposition vapor current of the material to be coated in a deposition zone therebetween. A conveyor is movable through the chamber and through the deposition zone. A slider shield carrier extends over the conveyor and is supported thereon for movement through the deposition zone and provides a covering to shield the conveyor parts against the deposition of the material thereon. The substrates are supported preferably on each side of the slider shield carrier and they are moved with the carrier on the conveyor to expose them to the vapor deposition current.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to vacuum treating devices and in particular to a new and useful device for coating substrates in a vacuum plant and for conveying the substrates through a vapor deposition zone.

2. Description of the Prior Art

The present invention has particular application to a conveying system for substrates to be coated in a vacuum plant, particularly a vacuum evaporation or cathode sputtering plant. Such devices are used for example for applying a thin metallic or non-metallic coating on glass or ceramic plates. Vacuum evaporation and cathode sputtering plants are known where the substrates to be coated are introduced by means of a conveyor device which is moved continuously into the coating chamber and directed out of the chamber after the coating. Such conveyor devices can be so designed that the holders for the substrates are moved by a conveyor belt, chain or cable running on guide rollers. A disadvantage of the know constructions is that the conveyor parts are subjected to coating themselves and the moving conveyor requires a great deal of attention. The conveyor mechanism must be operated at elevated temperatures for example at 300.degree.C and possibly without lubricantsin order to avoid impairment of the vacuum in the chamber. Any deposit of the coating substance on the moving parts of the conveyor mechanism can result in an increased wear of the parts and cause undesired application of material which can accumulate to an extent that it blocks the operation or which can become attached under frictional abrasion so as to form an impurity in the substrates to be coated.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided an improved device for coating substrates which includes a conveyor which is adapted to carry a conveyor slider shield which extends over the conveyor parts and shields them against the possibility that these parts will be coated and it provides an improved carrier for positioning a substrate on each side of the conveyor in the deposition zone. The device of the invention makes it possible to provide a more economical use of the plant. The conveyor itself advantageously includes individual conveyor sections including a support frame carrying two spaced apart guide pulleys around which an endless conveyor belt is movable and a separate drive shaft for driving the pulleys. A slider shield carrier of U-shaped configuration fits over the conveyor and is supported on the upper reach of the conveyor chain or cable so that it assumes a position in which the side leg portions encompass each side of the conveyor and shield it against vapor deposition. The sides of the shield members provide supports for the substrates so that they may be exposed directly to the vapor deposition zone.

Accordingly it is an object of the invention to provide an improved device for coating substrates which includes a chamber which is adapted to be subjected to reduced pressures and which carries at least one pair of laterally spaced sources for producing a deposition vapor current flow of the material to be coated in a deposition zone therebetween, and including a conveyor movable through the zone with a slider shield thereon providing a shield for the conveyor and a support for the substrate to move it through the zone.

A further object of the invention is to provide a conveyor device for transporting substrates through a vapor deposition zone which includes at least one individual endless conveyor section comprising spaced apart pulleys with an endless member trained to run therearound in combination with a slider shield carrier including a top part which is adapted to engage on the upper reach of the endless conveyor member and side parts which extend downwardly on each side and provide a sheild for the conveyor parts and a support for the substrates to move them through the deposition zone.

A further object of the invention is to provide a device for coating substrates and to provide a conveyor which are simple in design, rugged in construction and economical to manufacture.

For an understanding of the principles of the invention, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Drawings:

FIG. 1 is a transverse sectional view of a device for coating substrates in a vacuum plant constructed in accordance with the invention;

FIG. 2 is a partial side perspective view, partly broken away, of the conveyor shown in FIG. 1;

FIG. 3 is a side elevational view of the conveyor; and

FIG. 4 is a top plan view of the conveyor.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in particular, the invention embodied therein comprises a coating chamber 1 which is connected to an evacuation pump 2 through a line 3 for the purpose of subjecting the interior of the chamber to vacuum pressures.

In accordance with the invention, the chamber 1 is adapted to contain means for producing a current or flow of molecules of the substances to be applied on the surface of substrates 6 and 7 which are to be coated. In the embodiment indicated, two insulated electrodes 50 and 52 are arranged in laterally spaced relationship and they carry plates 4 and 4' respectively of the material which is to be coated onto the substrates 6 and 7. The substrates have a ground potential and the plates 4 and 4' are connected by voltage leads 54 and 56 which extend through vacuum seals 58 and 60 respectively into the chamber 1. By this arrangement, the plates 4 and 4' are subjected to a high negative potential relative to the substrates 6 and 7 so that the cathode material is sputtered in a known manner by means of an electric discharge in the under pressure of the coating chamber 1. The sputtering cathodes consist of the material which the coating is to be produce for example a tantalum metal if tantalum coats are to be applied on the substrates 6 and 7 in the course of the production of electrical condensers. It should be appreciated that the means for producing a transverse zone of coating material vapor deposition flow and generally designated 62 may also be an electrically heatable evaporation source which permits the heating of the coating material in order to produce a vapor current which is directed toward the substrates. In the arrangement shown however the zone is formed between the plates 4 and 4'.

In accordance with a further feature of the invention there is provided a device generally designated 5 for conveying the substantially plate shaped substrates 6 and 7 which are to be coated through a path in which they move through vapor deposition zone between the plates 4 and 4'. In the arrangement shown, the substrates 6 and 7 are supported on side leg portions 8 and 9 of a slider shield carrier generally designated 10 which includes a central portion or roof part 10a which rests on an endless member 11 of a conveyor mechanism generally designated 66. In the arrangement shown the side supports 8 and 9 form cassettes which hold the substrates 6 and 7 in a substantially vertical orientation so that their outer surfaces face the molecular currents which issue from the plates 4 and 4' respectively.

The conveyor 66 of the invention includes an endless belt or chain 11 which is guided over rollers 12 and 12' arranged at respective ends of a U-shaped upstanding frame 13 and which have axles 14 which are journaled in the frame. The U-shaped frame 13 is secured by means of a supporting base assembly on the bottom of the coating chamber 1. As indicated in FIG. 2 the endless belt 11 is driven by a driving pulley 17 which is driven from a clutch 18. The construction of the conveyor 66 is such that the sides are unobstructed in order to permit the slide shield carrier 10 to be positioned thereover as indicated in FIG. 1 and to shield all of the operating parts from exposure to the vapor deposition flow between the plates 4 and 4'.

During the operation of the device, the individual slider shield carriers 10 are first loaded with the substrates 6 and 7 to be coated and then they are passed successively on to the individual endless conveyor belt members 11 so that they move in close succession through the vapor deposition zone to effect coating of the substrates 6 and 7. As shown in FIG. 2 several individual conveyor units or assemblies 66 are arranged in end to end alignment to extend through the chamber 1 in an arrangement in which the slider shield carriers 10 pass from one conveyor section to another automatically. This makes it possible to manufacture the individual conveyor units economically in a uniform size and to combine or more of them as needed into the length of conveyor track which is required for the particular plant. Because of their compact design such units are particularly suitable for passing the substrates through any gate valves of series connected lock chambers having graduated vacuum pressure conditions as it is frequently the case in a continuous coating plant of this nature. The conveyor units are preferably installed so that the driving mechanism is not exposed directly to the molecular current. The simplest way is to select the length of the conveyor devices which are to be arranged in the coating chamber so that the driving mechanism lies outside the vapor zone. If necessary, additional screening plates can be used to protect the driving mechanism against the possibility that they become coated.

The attachment and the removal of the individual carriers 10 can be effected in a plant which has pressure locks at a location outside the vacuum by hand or with known mechanical lifting devices if desired. In plants which do not employ pressure locks the slider shield carriers 10 can be loaded with the substrates and arranged in a supply stack in the interior of the plant by means of suitable charging devices and they can be removed from the last coating unit in the line after treatment has taken place. Preferably the individual carriers 10 should follow each other so closely that no gaps are formed between carriers which would cause any disruption of the shielding of the conveyor.

The inventive device permits the non destructive and the attendance free operation of the vapor deposition plant for periods of several thousands of hours. It is obvious that this represents a considerable progress with regard to the known conveyor devices for vacuum coating plants. Naturally, the invention while particularly applicable to the treating of objects in a vacuum treatment plant is not limited to vacuum evaporation and sputtering in plants per se but can be used in all plants where coating methods must be carried out at underpressure.

Claims

1. A device for coating substrates in a plant in which under underpressures are employed, comprising a chamber adapted to be subject to reduced pressures, at least one pair of laterally spaced sources for producing a deposition vapor current of the material to be coated in a deposition zone therebetween, a conveyor movable through said chamber and through said deposition zone, a slider shield-carrier extending over said conveyor and supported thereon for movement through said deposition zone and covering and shielding said conveyor against the deposition of material thereon and having means thereon for supporting a substrate on at least one side of said conveyor in a position to expose it to the vapor current for

2. A device according to claim 1, wherein said laterally spaced sources for producing a deposition vapor current comprises a plate of the material arranged on each side of said conveyor, and means for supplying an electrical potential to the each plate on each side of said conveyor for generating a vapor deposition zone of the material of the plate between

3. A device according to claim 1 wherein said conveyor comprises an endless conveyor member with guide roller means over which said conveyor member is directed, said slider shield carrier being of U-shaped configuration and

4. A device according to claim 1 wherein said slider shield carriers comprises substantially symmetrical U-shaped members having a central roof portion adapted to engage at its interior on said conveyor and including a side like portion on each side extending downwardly on each respective side of said conveyor from said roof portion said side legs having means for supporting a substrate thereon in a position facing outwardly from

5. A device according to claim 3 wherein said slider shield carriers comprise individual cassettes which are loaded with substrate plates and have internal supporting flanges at their lower ends of each side engaging

6. A device for conveying substrates through a zone of reduced pressure for receiving a coating on the substrates comprising a conveyor frame, a pair of spaced apart rollers carried on said frame, an endless member guided over said rollers and defining an upper movable reach between said rollers, drive means for driving said rollers, a slider shield carrier comprising a longitudinally elongated member of generally U-shaped configuration having a leg portion on each side extending downwardly over said conveyor and protecting said conveyor and a top portion between said leg portions supported on the upper reach for movement thereon along with the endless member, and means on each of said leg portions for supporting

7. A device according to claim 5 wherein said conveyor frame comprises a U-shaped member having upright leg portions, said conveyor rollers having shafts journaled in respective upright leg portions and being disposed

8. A device according to claim 6 including a drive pulley engaged with said endless member and located below one end of said U-shaped frame.