GB1587566A

GB1587566A - Sputtering device and method

Info

Publication number: GB1587566A
Application number: GB27861/77A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1976-07-07
Filing date: 1977-07-04
Publication date: 1981-04-08
Also published as: NL7607473A; FR2358020A1; AT352493B; IT1076083B; ES460405A1; CA1081656A; ATA482777A; JPS6028689Y2; DE2729286C2; JPS5947654U; CH618289A5; ZA773538B; DE2729286A1; BR7704375A; FR2358020B1; SE7707729L; AU506847B2; JPS536282A; AU2668877A

Abstract

An atomising device includes a cathode (1), the upper surface (3) of which consists of the material to be atomised, a magnetic device for generating one or more magnetic fields (2), by which at least one electron trap for the surface (3) of the cathode is determined, and an anode (5). These electron traps can be moved along the cathode surface (3). In this way, it is possible to atomise the cathode very evenly by continuous or periodic movement of the electron traps, so that the cathode material is very efficiently used. <IMAGE>

Description

(54) SPUTTERING DEVICE AND METHOD (71) We, N.V. PHILIPS' GLOEILAMP ENFABRIEKEN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingel 29, Eindhoven, the Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a sputtering device comprising a cathode having at a surface thereof material to be sputtered, magnetic field means to produce one or more electron trap(s) (as herein defined) over the surface, and an anode.

The invention also relates to methods of sputtering material using such a device, and to a tube having a layer of material provided by such a method.

An electron trap is herein defined as being formed by magnetic field lines which extend from the cathode surface, describe an arc thereabove, and return thereto. Said field lines thus form a magnetic mirror for the electrons originating from the cathode surface. In this manner the electrons are retained near the cathode.

Such a device and method are known from the published Netherlands patent application 7,211,911. Such a device is used in providing thin films on flat and curved substrates, layers for the manufacture of integrated circuits, layers having magnetic properties, optical layers, in providing internal coatings in hollow articles, during the manufacture of resistors, and sputtering processes in which a low substrate temperature is desired.

It is known from the published German patent application 2,417,288 that by using a magnet device, an electron trap can be obtained which retains the electrons originating from the cathode until they have consumed their energy in ionizing collisions, so that extra plasma is formed. This results in a higher sputtering rate. However, it is also known from Physical Vapour Deposition, pages 114 and 115, Airco Inc., U.S.A.

1976, that said sputtering takes place very unevenly and results in a channel-like cavity in the cathode surface. This has a number of disadvantages. The cathode has to be replaced when only a small part of the cathode has been eroded by sputtering. In addition, the channel-like cavity in the cathode surface detrimentally influences the direction in which the particles of material move away from the cathode and the reproduceability of the sputtering process.

It is an object of the invention to provide a device and a method in which the above disadvantages are alleviated.

According to a first aspect of the invention, a device as set forth in the opening paragraph is characterized in that the magnetic field means and the cathode surface are movable relative to one another so as to move the electron trap(s) along said surface to select different portions of said surface for sputtering within the trap(s). As a result, it is possible periodically or continuously to select different portions of the cathode surface to be exposed to the discharge within the trap(s), so that very uniform sputtering is possible.

The cathode surface may be substantially flat, said means and said surface being relatively movable substantially parallel to one another, preferably in one direction.

Preferably, however, the cathode is tubular and has a longitudinal axis, said means comprises a plurality of axially-spaced magnets which are disposed inside or around said tubular cathode and have their north or south poles facing each other, and said means and said cathode are relatively movable axially. Such a sputtering device having magnets inside the cathode is particularly suitable for providing a very uniform coating in a hollow article, for example a metal mirror in a lamp or tube.

A tubular cathode may have a square or circular cross-section or may have any other shape with which the direction in which the sputtered particles move can be influenced.

The cathode surface may comprise portions of different materials to be sputtered; thus, a combination of sputtered materials may be realised in a simple manner by moving the electron trap(s).

A titanium cathode may be used as a sputter source in a titanium sublimation pump.

Devices embodying the invention are suitable for high frequency and direct current applications.

According to a second aspect of the invention, in a method of sputtering material using a device embodying the first aspect of the invention, the magnetic field means and the cathode surface are moved relative to and substantially parallel to one another to move the electron trap(s) so as to obtain substantially uniform erosion of the cathode surface.

According to a third aspect of the invention, in a method of sputtering material using a device embodying the first aspect of the invention with a cathode surface comprising portions of different materials to be sputtered, the magnetic field means and the cathode surface are moved relative to and substantially parallel to one another so as to move the electron trap(s) over portions of different materials.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows schematically a flat cathode for a device embodying the invention having a movable electron trap; Figures 2 and 3 are longitudinal sectional views of parts of tubular cathodes with several movable electron traps; Figure 4 is a longitudinal sectional view of a tubular cathode for a device embodying the invention Figures 5 and 6 are axial sectional views of two such tubular cathodes; Figure 7 shows schematically a device embodying the invention, and Figure 8 is a longitudinal sectional view of a tubular cathode for a device embodying the invention.

Figure 1 shows schematically a flat cathode 1 for a device embodying the invention, and the direction of the field lines 2 generated by a magnet device (not shown). Said field lines form an electron trap because a magnetic mirror is created over the cathode surface 3. In a region 4 below the field lines, a channel-shaped cavity will be formed by the sputtering of the cathode material.

By moving the electron trap, preferably in the direction indicated by the double-headed arrow 33, the erosion can be distributed over the whole surface 3. When the cathode surface is composed of several types of material, any desired composition of materials can be realized by moving the electron trap.

During sputtering, the cathode 1 may have a negative potential with respect to an anode 5 of approximately 800 Volts. In practice, voltages are used of a few hundred Volts up to a few kVolts. In the sputtering space a pressure of 10-3 to 10-2 Torr usually prevails.

The gas used for sputtering may be, for example, argon or neon, or reactive gases such as 02, N2 or mixtures thereof.

Figure 2 shows part of a tubular cathode 6 for a device embodying the invention. Said tubular cathode contains a number of magnets 7 which are spaced from each other along the cathode and have their corresponding poles facing each other. Said magnets 7 are permanent magnets in this case. However, they may be electromagnets In this case, discs 8 of soft iron are provided between the magnets and influence the direction of the entrance and exit of the field lines. However, said discs may be manufactured from a material other than soft iron, or may be absent. As a result of the magnets, electron traps 9 situated around the cathode are formed.The magnet device 20 comprising the magnets can be moved with respect to the cathode surface so that the formation of channel-like grooves around the cathode can be prevented by periodic or continuous displacement of the magnet device in the direction indicated by the double-headed arrow 33. It is, of course, alternatively possible to move the cathode surface with respect to the magnet device.

The anode is in the form of a ring 10.

Figure 3 also shows a tubular cathode.

In this case the magnets consist of permanent magnetic rings 11 around the cathode 6 and the electron traps 9 are situated on the inside of the tubular cathode. In this case the anode is in the form of a rod 12.

Figure 4 is a longitudinal sectional view of a tubular cathode for a device embodying the invention. The cathode surface is determined by a tube 13 which has an inside diameter of 28 mm and an outside diameter of 32 mm and which is closed at one end. Said tube, 300 mm long, contains a number of 6 mm thick annular magnets 14 which are situated around a water inlet tube 15 for cooling water. The cooling water flows along the wall of the tube 13 via spaces 16 to a water outlet 17. The water is admitted via an inlet aperture 18. By means of an O-ring seal 19 the magnet device 20 is located in a holder 21 so as to be movable. The holder 21 is arranged so as to be insulated with respect to a housing 23 for the device by means of a glass plate 22. When a large number of magnets is used, a large number of electron traps is obtained. Known cylindrical sputtering systems require very strong and large magnets, since the magnetic field must be constant and parallel to the surface of the cathode throughout the length of the cylindrical cathode.

Figures 5 and 6 show respectively two alternative cross-sections of such a cathode.

The space 16 for passing the cooling water is situated between a magnet 14 and the inner wall of the tube 13. The magnets 14 are situated around the cooling water tube 15.

The electrons trapped by the electron trap will cover a cycloidal track 32 as is shown in Figure 6.

It is alternatively possible to construct the tube 13 so as to be double-jacketed, so that the inner tube always serves as a holder for the magnet device and the outer tube, which may be movable around the inner tube, provides a cathode surface which can easily be replaced.

Figure 7 shows schematically a device embodying the invention. A cathode 24 is secured in the housing 23 by means of a glass plate 22 and is connected to a high frequency or direct current supply 25 for applying the desired potential between the cathode 24 and an anode 26 which in this case is annular.

After evacuating the housing 23 via a gas outlet aperture 27, the housing 23 is filled with argon to a pressure of 10-3 Torr via a gas inlet aperture 28. The cathode 24 is cooled by cooling water, as described, via connections 29 and 30. The material sputtered from the cathode is deposited on a substrate 31 as a layer or a thin film. The magnet device is reciprocated continuously or periodically by means of a driving mechanism 34.

As would be expected, the sputtering rate for a device embodying the invention is substantially equal to that of comparable known devices. For example, a sputtering rate for copper of 10,000 A/minute was measured with a direct current discharge with a supplied power of 2 kW and a distance between the cathode and the substrate of 5 cm. With a high frequency discharge, the sputtering rate was approximately 5000 A/ minute with the same power and electrode/ substrate arrangement. However, the cathode of the device embodying the invention could be used 3 to 5 times longer than when the magnet device was not moved.

Hence, the use of the invention means that the sputtering process need be interrupted less frequently and that the available cathode material to be sputtered is used more efficiently.

Figure 8 is a sectional view of a tubular cathode of a device embodying the invention in which the cathode surface consists of a chromium portion 35 and a copper portion 36. By moving the magnet device 20, a choice can be made of chromium, copper, or a mixture thereof. In the shown position of the magnet device, copper is sputtered and deposited on the inner wall of a glass tube and forms a thin coating. Of course, it is alternatively possible for the magnet device to be formed not from one group of magnets as is shown in Figure 8, but from several groups. It is also possible for the cathode surface to comprise more than two different materials. This type of cathode is particularly suitable for coating the inside of tubes of metal or glass or of envelopes of, for example, lamps.The whole cathode with the associated anode 38, in this case annular, can be moved through a tube during sputtering so that said tube is coated inside. By means of a cathode as shown in Figure 3, rods or tubes can be coated on the outside.

WHAT WE CLAIM 1S: 1. A sputtering device comprising an anode, a cathode having at a surface thereof material to be sputtered, and magnetic field means to produce one or more electron traps (as herein defined) over said surface, wherein said means and said surface are movable relative to one another so as to move the electron trap(s) along said surface to select different portions of said surface for sputtering within the trap(s).

2. A sputtering device as claimed in claim 1, characterized in that the cathode surface is substantially flat and in that said means and said surface are relatively movable substantially parallel to one another.

3. A sputtering device as claimed in claim 1, characterized in that the cathode is tubular and has a longitudinal axis, in that said means comprises a plurality of axiallyspaced magnets which are disposed inside or around said tubular cathode and have their north or south poles facing each other, and in that said means and said cathode are relatively movable axially.

4. A sputtering device as claimed in claim 1, 2 or 3, characterized in that the cathode surface comprises portions of different materials to be sputtered.

5. A method of sputtering material using a device as claimed in any of the preceding claims, characterized in that the magnetic field means and the cathode surface are moved relative to and substantially parallel to one another to move the electron trap(s) so as to obtain substantially uniform erosion of the cathode surface.

6. A method of sputtering material using a device as claimed in claim 4, characterized in that the magnetic field means and cathode surface are moved relative to and substantially parallel to one another so as to move the electron trap(s) over portions of different materials.

7. A tube having a layer of material provided by a method as claimed in claim 5 or 6.

8. A sputtering device or a method of sputtering material substantially as herein described with reference to any of Figures 1, 2, 3, 4, 4 and 5, 4 and 6, 7, or 8 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. alternative cross-sections of such a cathode. The space 16 for passing the cooling water is situated between a magnet 14 and the inner wall of the tube 13. The magnets 14 are situated around the cooling water tube 15. The electrons trapped by the electron trap will cover a cycloidal track 32 as is shown in Figure 6. It is alternatively possible to construct the tube 13 so as to be double-jacketed, so that the inner tube always serves as a holder for the magnet device and the outer tube, which may be movable around the inner tube, provides a cathode surface which can easily be replaced. Figure 7 shows schematically a device embodying the invention. A cathode 24 is secured in the housing 23 by means of a glass plate 22 and is connected to a high frequency or direct current supply 25 for applying the desired potential between the cathode 24 and an anode 26 which in this case is annular. After evacuating the housing 23 via a gas outlet aperture 27, the housing 23 is filled with argon to a pressure of 10-3 Torr via a gas inlet aperture 28. The cathode 24 is cooled by cooling water, as described, via connections 29 and 30. The material sputtered from the cathode is deposited on a substrate 31 as a layer or a thin film. The magnet device is reciprocated continuously or periodically by means of a driving mechanism 34. As would be expected, the sputtering rate for a device embodying the invention is substantially equal to that of comparable known devices. For example, a sputtering rate for copper of 10,000 A/minute was measured with a direct current discharge with a supplied power of 2 kW and a distance between the cathode and the substrate of 5 cm. With a high frequency discharge, the sputtering rate was approximately 5000 A/ minute with the same power and electrode/ substrate arrangement. However, the cathode of the device embodying the invention could be used 3 to 5 times longer than when the magnet device was not moved. Hence, the use of the invention means that the sputtering process need be interrupted less frequently and that the available cathode material to be sputtered is used more efficiently. Figure 8 is a sectional view of a tubular cathode of a device embodying the invention in which the cathode surface consists of a chromium portion 35 and a copper portion 36. By moving the magnet device 20, a choice can be made of chromium, copper, or a mixture thereof. In the shown position of the magnet device, copper is sputtered and deposited on the inner wall of a glass tube and forms a thin coating. Of course, it is alternatively possible for the magnet device to be formed not from one group of magnets as is shown in Figure 8, but from several groups. It is also possible for the cathode surface to comprise more than two different materials. This type of cathode is particularly suitable for coating the inside of tubes of metal or glass or of envelopes of, for example, lamps.The whole cathode with the associated anode 38, in this case annular, can be moved through a tube during sputtering so that said tube is coated inside. By means of a cathode as shown in Figure 3, rods or tubes can be coated on the outside. WHAT WE CLAIM 1S:

1. A sputtering device comprising an anode, a cathode having at a surface thereof material to be sputtered, and magnetic field means to produce one or more electron traps (as herein defined) over said surface, wherein said means and said surface are movable relative to one another so as to move the electron trap(s) along said surface to select different portions of said surface for sputtering within the trap(s).