Magnetic latch for a vapour deposition system

TECHNICAL FIELD [0002] The present invention relates to a magnetic latch for use in a vacuum evaporation system, in particular to a mildly operating magnetic latch by which the substrate housing is suspended in a vacuum chamber, or in a physical vacuum deposition (PVD) system or system for chemical vacuum deposition (CVD).

BACKGROUND ART [0003] The flow of coating material from its source in a PVD system or in a CVD system is relatively stable, however, there is its spatial distribution, which may result in the application of layers of heterogeneous thickness, if the substrates are stationary. To improve homogeneity, the geometrical relationships between the source of the coating and the substrate must be properly selected. Good results were observed when the substrate rotated about an axis perpendicular to the coated plane, especially when many substrates were placed on multiple spindles in a planetary system.

[0004] Known planetary gear coating systems, for example the system disclosed in US Patent No. 5,106,346, published April 21, 1992 (Stefan Locher et al.) Includes a large rotating platform with several spindles (planets) rotating thereon in a sealed vacuum chamber. Unfortunately, each substrate luminaire must be connected to the mounting flange on each spindle with mechanical connectors, for example screws that require manual replacement. These mechanical systems not only require additional manual work, but they are also more likely to be misaligned due to temperature and pressure changes. [0005] To isolate the bearing and gear from the vacuum chamber as much as possible, Hurwitt et al. Disclosed in US Patent No. 5,795,448, published August 18, 1998, a planetary gear coating system that includes a magnetic coupling in the shaft of each spindle. The substrate housings are not suspended above the cathodes and still require mechanical joints to attach them to the spindle mounting flanges.

[0006] The coating systems disclosed in US Patent No. 5,795,448 published October 15, 2002 (Shinozaki) includes a robot arm moving between a pressure loading / unloading chamber and a main vacuum chamber, minimizing the amount of dust getting into the main vacuum chamber. The Shinozaki system also includes a magnetic rotary drive and a magnetic lifter, minimizing particle formation due to mechanical interaction. However, Shinozaki discloses a single rotary platform with a complicated lift platform and electromagnets that completely surround the ground support. Unfortunately, this idea cannot be applied in a planetary gear coating system, because it is very difficult to separate power supply to rotating individual substrate housings in a planetary system, activated in a vacuum and elevated temperature.

[0007] The object of the present invention is to overcome the drawbacks of the prior art solutions by using a magnetic latch to attract the substrate housing to the spindle suspended above the cathode in a planetary gear coating system, without shaking the substrate and without producing material particles.

DESCRIPTION OF THE INVENTION [0008] The present invention relates to a planetary support of a substrate of the type intended for mounting in a working chamber of a coating system intended for coating substrates located on substrate bindings, comprising:

[0009] a main support rotating about a first axis, [0010] a plurality of spindles protruding from the main support, rotating about their respective axes, and [0011] a magnetic latch located at the end of each spindle comprising a permanent magnet and a bearing surface to which the housing adheres substrates, wherein each magnetic latch comprises a first part and a second part moving relative to the first part between the first position, in which the permanent magnet magnetizes the contact surface to attract the substrate housing, and a second position in which the contact surface is not magnetized. BRIEF DESCRIPTION OF THE DRAWINGS [0013] The invention will be described in detail with reference to the accompanying drawings showing its preferred embodiments, wherein:

[0014] Fig. 1 is an isometric view of the coating system according to the present invention. [0015] Fig. 2 is an isometric view of the coating system of Fig. 1 after removing several outer walls.

[0016] Fig. 3 is a schematic view of a planetary support with a magnetic latch according to the present invention.

[0017] Figs. 4a to 4c are schematic illustrations of the basic principle of operation of a magnetic latch according to the present invention.

[0018] Fig. 5 is an isometric view of a magnetic latch according to the present invention.

[0019] Fig. 6a is a top view of the stator of the magnetic latch according to Fig. 5.

[0020] Fig. 6b is a section of the stator according to Fig. 6a.

[0021] Fig. 7 is a top view of the magnetic latch of Fig. 5 in a non-latched position, and [0022] Figs. 8a to 8d are schematic illustrations of a substrate housing according to the present invention.

DETAILED DESCRIPTION Referring to Figures 1 to 3, a vacuum deposition system, e.g., a physical vacuum deposition system (PVD) or a Chemical Vapor Deposition (CVD) system according to the present invention, includes a loading sluice generally designated as reference 1 and working chamber 2 with a slide 3 between them. The gate valve 3 allows the pressure in the loading sluice 1 to be brought to atmospheric pressure for loading and unloading the substrates, or allows the working chamber 2 to return to pressure for the transfer of substrates, regardless of the pressure in the working chamber 2. The loading sluice 1 is equipped with a loading container 4 with the cassette lift 5, and the transfer channel 6 with the robot arm 7 placed in it. The robot arm control mechanism 7 is located in a cylindrical container 8 protruding from the transfer channel 6.

[0024] Inside the working chamber 2 are placed cathode 12 and planetary support 14 of the substrate. The planetary ground support 14 includes a main cylindrical platform 16 rotating about a first axis, with a plurality of, for example, six spindles 17 protruding therefrom, each spindle 17 rotating about its axis, preferably parallel to the first axis, but the spindle axes can be inclined at a different angle. During operation, the main platform 16 rotates, each spindle 17 also rotates, ensuring even coating of all parts of all substrates. Each spindle 17 at its outer free end has a magnetic latch 18 for hanging the substrate over the cathode 12, as will be described below.

[0025] At least one cathode 12, especially low voltage arc cathodes, are located inside the working chamber 2. Additional cathodes 12 may be used as a backup for cathode failures, or when the substrate source of one cathode coating 12 is depleted. Alternatively, several different electrodes 12 may be used to allow subsequent deposition of different coatings without opening the working chamber 2 and accessing the atmosphere from the surroundings. Advantageously, due to the movement of the mounting platform (not shown), carried out manually or by remote control, small adjustments of the cathode position 12 can be made.

[0026] The working chamber 2 is emptied through the suction connection 22 for the pump, while the process gases are fed to the working chamber 2 via flow controllers (not shown).

[0027] Although the document describes vacuum deposition of sputtering systems, the planetary support of the present invention can be used with any other suitable coating system, for example with evaporator systems or with CVD systems. The coating process can be extended by using additional equipment, such as shutters, masks, ion bombarding devices, special anodes or plasma excitation systems. [0028] Although herein, the coating system is shown in an up-spray configuration, the magnetic latch of the present invention can be used in other orientations, such as downward deposition and side coating. [0029] The uncoated substrates housed in the substrate housings 23 are loaded onto the cassette elevator 5 with the shutter 3 closed, maintaining the pressure in the working chamber 2. When air is removed from the loading sluice 1, the slider into the working chamber 2 opens, and the robot arm 7 moves the substrate housing 23 through the transfer channel 6 and the open slider 3 to the working chamber 2 for seating on the spindles 17 by means of magnetic latches 18.

[0030] The basic operating principle of the magnetic latch 18 is illustrated in Figs. 4a to 4c, in which the permanent magnet 31 is shown in the non-engaged position (Figs. 4a and 4b) or in the engaged position (Fig. 4c). In Fig. 4a, the magnetic circuit marked by arrow 32 is closed by a bypass section 33 leaving the poles 34a and 34b not magnetized. In Fig. 4b, the luminaire 23 of the substrate has been brought into contact with the poles 34a and 34b constituting an alternative magnetic circuit. To close the alternate magnetic circuit indicated by the arrow 36 in Fig. 4c, the permanent magnet 31 is rotated to the position where it is the connector between poles 34a and 34b ensuring that the substrate housing 23 is magnetically engaged with poles 34a and 34b. Alternatively, the permanent magnet 31 may remain stationary, while the bypass section 33 and poles 34a and 34b may be moved between the alignment and the non-alignment.

In a preferred embodiment, the magnetic latch 18 shown in Figs. 5, 6a, 6b and 7 comprises a cylindrical stator 41 and a cylindrical rotor 42 rotating thereon. The stator 41 includes three sets of poles 43a and 43b attached to the base 44 by means of a plurality of mechanical fasteners, e.g., hexagon bolts 46, for good contact. The rotor 42 includes three radially spaced permanent magnets 47 positioned between the rotor poles 48a and 48b. The north and south poles of permanent magnets extend along its long edges, close to poles 48a and 48b respectively of the rotor. Each magnetic latch 18 includes an elongated actuating member 49 reaching down through the main platform 16 and each spindle 17, causing, from the outside of the working chamber 2, rotation of the rotary element 42 between the engaging position (Fig. 5) and the non-engaging position (Fig. 7) . The actuating member 49 has at its upper end a tab or other element cooperating with another mechanical assembly, for example with a shaft 50 (fig. 3) located above the planetary support of the substrate. In the non-engaged position, both rotor poles 48a and 48b closely rotate adjacent one of the stator poles 43b, thereby shorting the permanent magnet 47, breaking the magnetic circuit passing through the stator 41 and releasing the substrate housing 23.

[0032] To facilitate the alignment of the substrate frame 23 with the stator 41, a conical pin 51 protruding from the center of the base 44 is used. One cone pin 51 in the center of the base 44 ensures correct alignment of the substrate frame 23 without determining its exact angular position. The conical pins can be placed in different places on the perimeter of the fixed element or in different radial positions.

[0033] Examples of substrate supports 23 are shown in Figs. 8a to 8d. The substrate housing 23a of Fig. 8a includes a base 53 attached to an annular lid 54 with an annular projection 56 on which only one substrate 57 rests. In the base 53 there is a cylindrical recess 55 in which a conical pin 51 is located, which is a cooperating element providing alignment. The base 53 is made entirely or at least partly of a material that is attracted by a magnetic latch 18, i.e. it is a ferromagnetic material containing at least one substance among iron, cobalt and nickel. The base 53 also provides a protective cover for the uncoated surface of the substrate 57, preventing inadvertent and undesirable back covering of the substrate. The substrate housing 23b of Figure 8b includes a multi-disc annular cover 58 attached to the base 53. The multi-disc annular cover 58 includes several annular projections 59 on which several small substrates 61 rests. For other special substrates, e.g. prisms 62, a multi-cover prism 63 attached to base 53, see Fig.8c.

[0034] As an alternative to base 53, a surrounding substrate 72 (Fig. 8d) is used, ferromagnetic ring 71, attracted to rotor 41. The advantage of ring 71 is that the substrate 72 can be covered with the same or different coatings on opposite surfaces without removing it from ring 71. Furthermore, substrate 72 and ring 71 need not be removed from the working chamber 1 between coating operations, for example they only need to be turned over by means of the robot arm 7.

[0035] A typical substrate may be a glass plate 200 mm in diameter and 0.7 mm to 1.4 mm thick, however substrates with other shapes are possible, for example having a thickness of up to 32 mm and a weight of up to 2 kg.

JDS Uniphase Inc., USA Representative

EP 1 630 260 B1

Ζ-85Ί8 / 11