GB2143910A

GB2143910A - A vacuum lock

Info

Publication number: GB2143910A
Application number: GB08415505A
Authority: GB
Inventors: Walter Huber; Hermann Bucher; Rudolf Wagner
Original assignee: Balzers AG
Current assignee: OC Oerlikon Balzers AG
Priority date: 1983-07-21
Filing date: 1984-06-18
Publication date: 1985-02-20
Also published as: JPS6026662A; GB8415505D0; FR2549452A1

Abstract

A vacuum lock for introducing objects (23) into, and removing them from, a vacuum chamber (Fig. 1) comprises a lock channel (8) and a plurality of object carriers (21) each provided with a seal (25), preferably a lip seal, secured thereto. and movable therewith through the channel. The forward end of each object carrier (21) is provided with forwardly-converging approximately wedge shaped guide faces (24) to obviate jamming of the forward end of a carrier passing through the channel (8) and to cooperate with the seal (25) of the preceding carrier to urge the seal into engagement with the wall of the channel (8). <IMAGE>

Description

SPECIFICATION A vacuum lock The invention relates to a vacuum lock having object carriers for introducing objects into, andremoving them from, vacuum chambers, having a lock channel of a cross-section ap propriate to the shape of the object carriers and having seals for providing sealing between the object carriers and the wall of the lock channel. An embodiment of such a vaccuum lock is described in US patent specification 3 486 365. This shows a lock channel in the form of a tunnel, through which the object carriers, which are in the form of cylindrical containers and which receive the objects to be tested (e.g. transistors), are pushed. In this case the vacuum sealing is provided by means of O-ring gaskets, which are secured to the inside wall of the tunnel.Between any two gaskets a closed compartment is formed together with the object carriers conducted therethrough, each of which compartments is connected to a vacuum pump of its own, so that pressure stages result. By means of this known arrangement it is possible to conduct the object carriers and the objects which are carried by them and which are to be treated in vacuo, via a plurality of pressure stages into, and again out of, a vacuum treatment chamber.

Vacuum lock tunnels with mutually separated pressure stages have also become known elsewhere. A disadvantage of known arrangements lies in the fact that the object carriers, as they slide past the seals, can deposit thereon dust and other dirt, which gradually collects and thereon and, in its turn, can then itself again result in pollution of object carriers and objects which are to be locked in. In vacuum coating technology, dust may, for example, drop from the seals on to the substrates which are to be coated, and this may result in faults during the subsequent coating. A further disadvantage results from the fact that possible minor instances of damage to the seals are not readily recognized, because the minor leakages resulting therefrom may also occur for a variety of other reasons, so that the search for faults is often very time consuming.In every case, for the purpose of cleaning a checking the seals which are accommodated in the lock channel, frequent assembly and dismantling of the latter is required, which is not only cumbersome, but above all results in down-time in production and hence economic losses.

The aim of the present invention is to construct a vacuum lock of the above-mentioned kind in such a way that the lock channel and the seals may be checked and kept clean and more readily. This aim of the invention is achieved by securing the seals to the object carriers and making them movable together with the latter through the lock channel.

By moving the seals together with the object carriers through the lock channel, it is made possible to subject each individual seal, prior to the object carrier to which it is secured being introduced into the lock, simply to a visual check for cleanliness and lack of damage. This viewing may readily take place whilst production is in progress and therefore does not entail any interruption of production.

If desired, the seals may readily be cleaned prior to the introduction of the object carriers into the lock. Since, in the case of a lock according to the invention, no seals need to be applied to the inner wall of the lock channel, i.e. also no grooves or retaining devices are required on the inner surface, the further advantage results in that the latter can be completely smooth, so that for this reason also the danger of accumulation of dust and dirt is considerably reduced. Moreover the inner wall of the lock channel is continuously cleaned by and together with the seals which continuously slide past it, and polished, and hence, so to speak, automatically kept clean in operation.

The known lip-seals have been found to be particularly suitable for use as seals which are secured to the object carriers and moved together with the latter through the lock channel.

One embodiment of the invention will now be more particularly explained, by way of example, with reference to the accompanying diagrammatic drawing in which: Figure 1 shows diagrammatically a vacuum coating installation with locks in accordance with Claim 1 for introducing and removing the objects which are to be coated; and Figure 2 shows, to an enlarged scale, an object carrier which is suitable for the lock in accordance with the example of Fig. 1.

The arrangement shown in Fig. 1 comprises a vacuum coating chamber 1, in which an object which is held by an object carrier 2, e.g. a glass plate, is coated by the vapour stream 4 emanating from a vapour source 3.

The source 3 may be a thermal vapour source or, for example, a known apparatus for cathodic sputter coating, which is particularly suitable for coating from above to below. Via a conduit 5, the chamber 1 is connected to an arrangement, consisting of a high vacuum pump 6 and a backing pump 7, for producing the vacuum required for the coating process.

The lock channel 8 serves the purpose of feeding in further object carriers 2a, 2b, 2c etc. In the illustrated example conduits 11 and 1 2 open in two places 9 and 10 into the channel 8, the conduits 11, 1 2 being in turn connected to auxiliary pumping stages, each consisting of a high vacuum pump 1 3a and 1 3b respectively and a backing vacuum pump 1 4a and 1 4b respectively. These auxiliary pumping stages produce, in a manner known per se, in the lock channel 8 pressure stages of a gas pressure which decreases from the entry side 1 5 up to the chamber 1.

For the removal of the treated objects the lock channel 8 is constructed similarly. At the exit side are also provided two pump conduits 1 7a being equipped with its own auxiliary pumping stage consisting of a high vacuum pump 1 8 and a backing vacuum pump 19, whilst, as shown, the conduit 1 7b leads to the auxiliary pumping stage 13b/14b.

The object carrier shown in Fig. 2 consists of a plate 21 having a recess 22 for a plateshaped object 23 which is to be locked in, the recess 22 being adapted to the shape of the object in such a way that the object 23 does not protrude beyond the limiting faces of the plate 21. The front end portion (as seen in the direction of movement) of the plate 21 is advantageously provided with forwardly converging, approximately wedge-shaped guide faces 24, which prevent the possibility of its becoming jammed in the course of its passage through the channel 8. The rear end portion of the plate 21 is provided with a seal 25 for sealing between the object carrier and the wall of the channel 8.In the example this seal 25 which is borne by the object carrier and movable therewith through the channel 8 is in the form of a lip seal, which seals against all four sides of the channel 8 (of rectangular cross-section). As can be seen from the drawing, the four sealing edges of the lip seal simultaneously form a hollow chamber of a shape similar to that of the faces 24, into which, if a plurality of object carriers are introduced consecutively into the channel 8 at its entry side 15, the front end portion of each successive object carrier engages and thereby presses the edges of the lip seal of the immediately preceding object carrier apart and against the wall of the channel 8, so that sealing with an increased sealing force is achieved.

In a further development of the invention it is advantageous to introduce an auxiliary gas into the channel 8 at a suitable point. In Fig.

1 auxiliary gas conduits 26 and 27 are provided. The admission of an auxiliary gas has the purpose of making it more difficult for air to penetrate through the channel 8 into the chamber 1. This is so because if the auxiliary gas is introduced in the vicinity of the point of inlet at a pressure which is strictly higher than atmospheric pressure, then it flows in both directions, i.e. towards the ambient atmosphere (at 1 5 and 20) as well as towards the chamber 1, only a very greatly reduced auxiliary gas pressure occurring in the latter, the magnitude of which is determined by the efficiency of the auxiliary pumps for the pressure stages and by the sealing quality of the seals which are carried along by the object carriers. The auxiliary gas is so chosen that it does not adversely influence the process which is to be carried out in the chamber 1.

Thus a neutral gas, e.g. argon, may be useful or in vacuum coating technology, possibly also a reactive gas, e.g. oxygen, where possibly a layer which has been deposited on the object is simultaneously to be oxidized. The technique of reactive vapour deposition is known per se and not the subject of the present invention. Likewise the use of an auxiliary gas described, for the purpose of impeding the intrusion of atmospheric air into a receptacle, is known per se from US patent specification 3 000 346.

The symbols used in Fig. 1 for the pumps are conventional; more particularly, 6, 1 3 a and 1 8 represent a diffusion pump, 1 3b a turbo-molecular pump and 7, 14a, 1 4b and 1 9 a mechanical backing pump, e.g. a sliding vane rotary vacuum pump. Obviously, in place of the types of pump indicated in the drawing, other pumps could also be used which are capable of producing the appropriate vacua.

In the case of object carriers of a crosssection other than that shown in the drawing, the seals naturally have to be adapted to the configuration of the former; it is very simple to realise such seals for object carriers of circular and oval cross-section.

Claims

1. A vacuum lock comprising a lock channel leading to and from a vacuum chamber and a plurality of object carriers adapted to carry objects and travel therewith through the channel into and from the vacuum chamber, the object carriers being of a cross-section appropriate to the inner cross-section of the channel, wherein seals for providing sealing between the object carriers and the wall of the channel are secured to the object carriers and arranged to be movable with the latter through the channel.

2. A vacuum lock according to Claim 1, wherein the seals are in the form of lip seals secured to the object carriers and moving, in operation, therewith.

3. A vacuum lock according to Claim 2, wherein the front end portions of the object carriers - viewed in the direction of movement in the course of their passage through the channel - are provided with forwardly converging guide faces and the lip seals are secured to the rear end portions of the object carriers in such a way that they form forwardly converging cavities for engagement by the guide faces of the following object carrier in the course of their passage through the channel.

4. A vacuum according to Claim 3, wherein the lip seals and the front end portions of the object carriers are relatively coordinated in such-a way that, in the course of the passage of the object carriers through the channel, the lip seals are pressed against the wall of the channel by the front end portion of the following object carrier.

5. A vacuum according to any one of Claims 1 to 4, wherein the channel has at least two pressure stages, and a supply conduit for supplying an auxiliary gas and opening into the channel is provided.

6. A vacuum lock according to Claim 1 constructed, arranged and adapted to operate substantially as herein described with reference to, and as shown in, the accompanying drawings.

7. An object treated in a vacuum chamber cooperating with a vacuum lock according to any one of Claims 1 to 6.