GB2144453A

GB2144453A - Apparatus for forming thin films in vacuum

Info

Publication number: GB2144453A
Application number: GB08419870A
Authority: GB
Inventors: Yasutomo Sasanuma; Mitsugu Enomoto
Original assignee: Citizen Watch Co Ltd
Current assignee: Citizen Watch Co Ltd
Priority date: 1983-08-03
Filing date: 1984-08-03
Publication date: 1985-03-06
Also published as: GB8419870D0; KR890004617B1; JPS6033350A; HK81587A; KR850002110A; GB2144453B

Abstract

An apparatus for forming thin films in vacuum, in which a vapor generating source (6) and a workpiece (4) are disposed in a spaced relation within a vacuum vessel (5) and a vaporized substance (7) from the vapor generating source is deposited on the workpiece to form a thin film, comprising: a chain (11) stretched endlessly on at least a pair of sprockets (27, 28); a plurality of rollers (20) axially and rotatably supported by the chain; a support shaft (22) fastened each of the rollers for co-rotation therewith; a workpiece mount (3) fixedly secured to the support shaft for supporting the workpiece; and a guide rail (41, 42, 41', 42') fixedly secured in at least an arriving region of the vaporized substance in the vacuum vessel to rotate each of the rollers owing to contact therewith. <IMAGE>

Description

SPECIFICATION Apparatus for forming thin films in vacuum This invention relates to an apparatus for forming thin films in vacuum, using vapor deposition, sputtering, ion plating or the like, wherein a vapor generating source and a workpiece are disposed in a spaced relation within a vacuum vessel and a vaporized substance from the vapor generating source is caused to deposit on the workpiece to form a thin film. More particularly, the invention relates to improvements in a jig for supporting the workpiece.

An apparatus for forming thin films in vacuum, such as an ion plating apparatus generally rises in cost and requires a longer period of time for removal of air in proportion to the capacity of the vacuum vessel. Therefore, it is preferred that the workpieces are charged as many as possible at one time into the vacuum vessel. To form a film uniformly over the entire surface of an irregularly shaped workpiece such as an external component of a timepiece, it is necessary that formation of a thin film is carried out while the workpiece is rotated.

In the conventional apparatus as shown in Fig. 1, it is employed that an arrangement includes a rotary shaft 1 having a rotation transmitting gear 2 fixedly secured to one end thereof, and a number of workpiece mounts 3 fixedly provided on the rotary shaft 1 in a spaced relation, each workpiece mount 3 having a plurality of workpieces 4 mounted thereon. This arrangement is disposed within a vacuum vessel, as shown in Fig. 2 or 3.

In Figs. 2 and 3, numeral 5 denotes a bell jar serving as the vacuum vessel, and numeral 6 designates a vapor generating source. The vapor generating source 6 is supplied with electric current from a power supply (not shown) and vaporizes a substance 7 (e.g. TiN or TiC) by electron-beam or resistance heating. In Fig. 2, five of the rotary shaft 1 are arranged in the same plane and in a spacedapart relation above the vapor generating source 6 with their axes lying in parallel. The rotation transmitting gears 2 fixedly secured to respective ones of the rotary shafts 1 mesh with their neighbors via respective idle gears 8. Accordingly, all of the gears 2 and their rotary shafts 1 will rotate in the same direction (as indicated by the arrows) by rotating any one of the rotary shaft 1.

However, in an arrangement of the conventional apparatus in which a plurality of the rotary shafts 1 equipped with the workpiece mounts 3 are disposed in a line above the vapor generating source 6, the distance between the vapor generating source 6 and the centrally disposed shafts 1 is quite different from the distance between the source 6 and the end shafts 1. This difference of the distance gives rise to a difference in the quality and thickness of the thin films formed on the workpieces.

In addition, the number of workpieces 4 which are charged into the bell jar 5 per batch cannot be increased without increasing the capacity of the bell jar 5. Further, the vaporized substance in the region outside the sector-shaped zone indicated by the angle A is wasted.

Fig. 3 shows another conventional apparatus. Like elements corresponding to those of Figs. 1 and 2 are indicated by like numerals.

In Fig. 3, a number of the rotary shafts 1 are rotatably supported in spaced relation by a ring frame 9 so as to surround the vapor generating source 6, and the rotation transmitting gears 2 of the rotary shafts 1 mesh with the inner teeth provided along an inner surface of a ring gear 10 fixedly provided on the outer side of the ring frame 9.

When the ring frame 9 is rotated in the direction of the arrow a, the gears 2 and the rotary shafts 1 revolve in the same direction while they are rotated the direction of the arrow h This apparatus tentatively solves the problems encountered in the apparatus of Fig. 2.

Specifically, the distance from the vapor generating source 6 is the same in all directions, the interior of the bell jar is utilized efficiently, and loss of the vaporized substance is reduced.

However, since the workpiece are annularly arranged about the periphery of the vapor generating source 6, it is difficult to select freely distances between the vapor generating source 6 and the workpieces. Moreover, since the vapor generating source 6 has a support member, current feeders, cooling water piping and the like, which are not shown, mounting the source 6 is very difficult. In addition, it is difficult to carry in and carry out the workpieces through a continuous process by arranging the thin film forming apparatus in a production line. Furthermore, scraps such as thin-film fragments which have peeled off the upper workpieces fall on and adhere to the lower workpieces.

According to the present invention, there is provided an apparatus for forming thin films in vacuum, in which a vapor generating source and a workpiece are disposed in a spaced relation within vacuum vessel and a vaporized substance from said vapor generating source is deposited on said workpiece to form a thin film, comprising: a chain stretched endlessly on at a pair of sprockets, a plurality of rollers axially and rotatably supported by said chain, a support shaft fastened to each of said rollers for co-rotation therewith, a workpiece mount fixedly secured to said support shaft for supporting said workpiece, and a guide rail fixedly secured in an arriving region of said vaporized substance in said vacuum vessel to rotate each of said rollers owing to contact therewith.

In the accompanying drawings, in which: Fig. 1 is a perspective view illustrating an example of a jig for supporting workpieces within a vacuum vessel in an apparatus according to the prior art; Figs. 2 and 3 are schematic views illustrating different arrangements of the jig shown in Fig. 1 in an apparatus according to the prior art; Fig. 4 is a perspective view illustrating a principal portion of a jig in an embodiment of the present invention; Fig. 5 is a perspective view illustrating an end portion of a support shaft for insertion into a roller in the arrangement of Fig. 4; Fig. 6 is a sectional view axially of the arrangement of Fig. 4 showing the connection between a chain and roller; Figs. 7 and 8 are schematic views illustrating jig arrangements according to different embodiments of the present invention; and Fig. 9 is a sectional view illustrating an example of the transverse cross-section of a guide rail shown in Fig. 8.

Referring now to Fig. 4, there is shown a principal portion of a jig for supporting a workpiece in an embodiment of the present invention. Like elements corresponding to those of Fig.1 are indicated by like numerals.

A roller 20 is axially and rotatably supported on a connecting pin 1 2 of an endless chain 11 stretched between a pair of sprockets( not shown). The roller 20 has a boss 20a formed on the side thereof opposite the side facing the chain 11, and a notch groove 20b provided in the boss 20a. A clip 21 formed of a leaf spring is fixedly secured in the notch groove 20b.

A support shaft 22 extending along the axis of the roller 20 is fitted securely into the clip 21 so as to be co-rotatable with the roller 20.

A plurality of the workpiece mounts 3 are fixedly provided on the support shaft 22 and arranged in spaced-apart relation as in the manner shown in Fig. 1. As shown in Fig. 5, the end of the support shaft 22 held by the clip 21 is chamfered into a plane configuration on both sides 22a thereof. The support shaft 22 will not rotate relative to the roller 22 in the cause of the end thereof. Further, the support shaft 22 is adapted so as to be easily detachable from the roller 20, as shown in Fig. 4, then this will serve to shorten the time needed to exchange workpices when the bell jar is opened. Therefore, it is possible to shorten the period of time the bell jar is open, thereby reducing the adsorption of moisture and the like.

The workpiece mount 3 comprises a cylindrical base portion 31 fitted over the support shaft 22, three rods 32 extending radially outwardly from the outer circumferential surface of the base portion 31, and an engaging piece 33 comprising an approximately triangular leaf spring fixedly secured to the distal end of each of the rods 32. A workpiece 4 is supported by the engaging piece 33 in a point-contact manner.

The chain 11 is composed of outer links 13,13 and inner links 14, 14 having substantially B-shaped configurations. The outer links 13, 1 3 and inner links 14, 14 are connected by hollow pins 1 2 so as to be rotatable back and forth as shown in Fig. 6. A shaft 24 has one end thereof securely inserted into the roller 20 via a ball bearing 23. The other end of the shaft 24 is inserted into a bore 1 2a formed in the connecting pin 1 2 and is secured by a stopper ring 25 and nut 26. Thus, a plurality of the rollers 20 are rotatably supported on a plurality of the connecting pins 1 2 of chain 11 in a spaced-apart rela- tion.

Fig. 7 is a schematic illustration of one example of the jig arrangement in an ion plating apparatus according to the present invention. The workpiece mounts 3 and workpiece 4 are deleted from the illustration.

In this embodiment, a pair of sprockets 27, 28 are rotatably provided on respective shafts 27a, 28a above the vapor generating source 6 inside the bell jar 5. The sprockets 27, 28 are spaced apart along a direction in which the amount of vaporized substance 7 emitted by the vapor generating source 6 tends to produce a difference. The chain 11 is endlessly stretched between the sprockets 27, 28 and axially and rotatably supports the rollers 20 as described above.

Guide rails 41, 42 are fixedly provided on the lower side of the upper and lower travelling segments of the chain 11 over a prescribed region for rolling the rollers 20 owing to contact therewith.

When the sprockets 27, 28 are rotated in the direction of the arrows a, the upper segment of the chain 11 travels in the direction of the arrow b and the lower segment of the chain 11 travels in the direction of the arrow c. Each roller 20 travels in the same direction as the respective segment of the chain 11 and is rotated in the direction of the arrows owing to the contact with the guide rails 41, 42. As a result, the supports shafts 22 and the workpiece mounts 3, which are shown in Fig.

4, also rotate while travelling together with the rollers 20.

The vapor generating source 6 in Fig. 7 is an electron beam vapor generating source and emits an electron beam from a heater to which heat is applied by a vapor generating source power supply 43. The electron beam is deflected by a magnet to irradiate the substance 7 on a grounded crucible, whrerby the substance is heated and vaporized.

In the present case, the amount of the substance 7 vaporized is approximately 30% greater in the sector indicated by A2 than in the sector indicated by A,. Therefore, as shown in Fig. 7, the chain 11 preferably is arranged so as to transport the workpiece over the total of the angular sectors where the amount of vaporization differs.

A high-voltage DC power supply 44 applies a voltage of a polarity opposite to the ionizing polarity of the evaporated particles to the workpieces 4 (Fig. 4) via the sprocket 27, chain 11, rollers 20, support shafts 22 and workpiece mounts 3, all of which are made of metal. Though not illustrated, an ionizing electrode may be provided between the vapor generating source 6 and the chain 11 when it is necessary to promote the ionization of the vaporized particles.

According to this embodiment, in contrast with the prior art arrangement of Fig. 1, a large number of workpieces can be charged into the bell jar 5 in two rows, one above the other. Further, the workpieces are rotated, with revolution of the chain 11, while the positions thereof are shifted from side to side and both up and down with respect to the vapor generating source 6 in order that the workpieces may experience different conditions. As a result, a thin film of substantially uniform quality and thickness can be formed over the entire surface of each workpiece.

Fig. 8 is a schematic illustration of another example of the jig arrangement in an ion plating apparatus according to the present invention. Portions corresponding to those of Fig. 7 are designated by like numerals.

In this embodiment, the pair of sprockets 27, 28 are disposed on both side of the vapor generating source 6 within the bell jar 5 at the lower portion thereof. In order to run the chain 11 in a reverse U-shaped configuration substantially along the inner wall of the bell jar 5, guide rails 41', 42' are secured above the vapor generating source 6 and at the upper portion of the bell jar 5. The guide rails 41', 42' are curved in arcs and are concentrically disposed in respect to the evaporation center of the vapor generating source 6. Further, the guide rails 41', 42' support the outer and inner sides of the chain 11 and also come into rotatably contact with the rollers 20.

In this case, it is required that the transverse cross-section of the guide rails 41', 42' have a channel-shaped configuration, as shown in Fig. 9, to limit axial movement of the rollers 20.

In the present embodiment, the high-voltage DC power supply 44 supplies current to the guide rails 41', 428 to apply a voltage upon the workpieces 4 through the rollers 20 and workpiece mounts 3. With an arrangement, of this embodiment, the current supply path is shortened to reduce resistance loss. If an insulator is interposed between the chain 11 and the rollers 20, or if the chain 11 is made of an insulative material, then ion plating can also be carried out by applying a voltage to the workpieces only when the corresponding rollers 20 are in rolling contact with the guide rail 41', 42'.

According to this embodiment, even a greater number of workpieces can be charged into the bell jar 5 at one time in comparison with the embodiment shown in Fig. 7, and both the film quality and thickness of the formed thin film can be held constant.

Further, since there are no workpieces disposed below the vapor generating source 6, film quality will not be diminished by scraps such as peeled-off fragments which fall from above, as in the prior art of Fig. 3. This also facilitates mounting of the vapor generating source as well as the carrying in and carrying out of jigs in a production iine. It is also possible to adjust the height of the vapor generating source comparatively freely.

The arrangement of the jig within the bell jar is not limited to that of the foregoing embodiments, for the manner in which the chain is disposed, as well as the shape and position of the guide rails, can be modified in various ways. In such case a required number of intermediate sprockets can be used depending upon the disposition and configuration of the chain.

Though the described embodiments relate to an ion plating apparatus in which an electron beam vapor generating source is used as the vapor generating source, various configurations of a vapor generating source can be used, such as those which use resistance heating or high-frequency heating manner.

The present invention is applicable not only to an ion plating apparatus but can be applied to other thin-film forming apparatus such as those which adopt vapor deposition and sputtering.

Claims

1. An apparatus for forming thin films in vacuum, in which a vapor generating source and a workpiece are disposed in a spaced relation within a vacuum vessel and a vaporized substance from said vapor generating source is deposited on said workpiece to form a thin film, comprising: a chain stretched endlessly on at least a pair of sprockets; a plurality of rollers axially and rotatably supported by said chain; a support shaft fastened each of said rollers for co-rotation therewith; a workpiece mount fixedly secured to said support shaft for supporting said workpiece; and a guide rail fixedly secured in at least an arriving region of said vaporized substance in said vacuum vessel to rotate each of said rollers owing to contact therewith.

2. An apparatus for forming thin films in vacuum according to claim 1, in which each of said rollers has a boss formed on the side thereof, said supporting shaft being fastened to said boss.

3. An apparatus for forming thin films in vacuum according to claim 2, in which a notch groove is provided in said boss of said roller, and a clip is fixedly secured in the notch groove, said support shaft being detachably fastened by said clip.

4. An apparatus for forming thin films in vacuum according to claim 1 , in which said guide rail are curved in arcs and are concentrically disposed in respect to said vapor generating source.

5. An apparatus for forming thin films in vacuum according to claim 4, in which said guide rail has a channel-shaped configuration in cross section.

6. An apparatus for forming thin films in vacuum substantially as herein described with reference to and as illustrated in Figs.4 to 9 of the accompanying drawings.