Arc evaporation source

Abstract

Provided is an arc evaporation source for melting and evaporating a cathode material by arc discharge for film formation on a surface of a substrate, and including a cathode formed in a substantially disc shape and a magnetic field generating apparatus, disposed at a back side of the cathode. The magnetic field generating apparatus generates a magnetic field which forms magnetic lines that form an acute angle with respect to a substrate direction at an outer circumferential surface of the cathode, magnetic lines that are substantially perpendicular to the discharge surface at an outermost circumference part of the discharge surface of the cathode, and magnetic lines that form an acute angle with respect to a center direction of the cathode at a region towards the outer circumferential surface of the discharge surface of the cathode, by at least one permanent magnet disposed at the back side of the cathode.

Claims

1. An are evaporation source, for melting and evaporating a cathode material by arc discharge in a vacuum for film formation on a surface of a substrate, the arc evaporation source comprising: a cathode formed in a substantially disc shape; and a magnetic field generating apparatus disposed at a back side of the cathode, wherein the magnetic field generating apparatus generates a magnetic field by at least one permanent magnet disposed at a back surface of the cathode, the permanent magnet is oriented in a direction that is 20 to 50 with respect to a discharge surface of the cathode, which forms magnetic lines that form an acute angle with respect to a substrate direction at an outer circumferential surface of the cathode, magnetic lines that are substantially perpendicular to the discharge surface at an outermost circumference part of the discharge surface of the cathode, and magnetic lines that form an acute angle with respect to a center direction of the cathode at a region towards the outer circumferential surface of the discharge surface of the cathode.

2. The arc evaporation source as claimed in claim 1, wherein the permanent magnet is oriented in a direction that is 40 to 45 with respect to the discharge surface of the cathode.

3. The arc evaporation source as claimed in claim 1, wherein at least one other magnetic field generating apparatus, which rotates in a plane substantially parallel to the discharge surface of the cathode, is disposed at the back side of the cathode.

4. The arc evaporation source as claimed in claim 1, wherein at least one magnetic field generating apparatus with a displacement apparatus such that a distance between the permanent magnet and the cathode is changeable is disposed at the back surface of the cathode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram showing a magnetic field formed in an arc evaporation source.

(2) FIG. 2 is a diagram showing angles formed by a discharge surface and a magnetic field in an arc evaporation source.

(3) FIG. 3 is a diagram showing a magnetic field formed when a ring shaped permanent magnet is disposed near the outer circumference of a back surface of a cathode, such that the magnetic poles are oriented parallel to the axis direction of the cathode.

(4) FIG. 4 is a diagram showing a magnetic field formed when a ring shaped permanent magnet is disposed at a back surface of a cathode, such that the magnetic poles are oriented parallel to the discharge surface of the cathode.

(5) FIG. 5 is a diagram showing a magnetic field formed when a permanent magnet is disposed in a slanted direction near the outer circumference of a cathode.

(6) FIG. 6 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 0.

(7) FIG. 7 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 10.

(8) FIG. 8 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 20.

(9) FIG. 9 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 30.

(10) FIG. 10 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 40.

(11) FIG. 11 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 45.

(12) FIG. 12 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 50.

(13) FIG. 13 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 60.

(14) FIG. 14 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 70.

(15) FIG. 15 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 80.

(16) FIG. 16 is a diagram showing a magnetic field formed when an angle formed by the direction of the magnetic poles and the discharge surface is 90.

(17) FIG. 17 is a diagram showing a magnetic field formed when a rotating magnetic field generating apparatus is disposed in a secured space at a back surface of a cathode.

(18) FIG. 18 is a diagram showing a movement of arc spots formed on a discharge surface of the cathode shown in FIG. 17.

(19) FIG. 19 is a diagram showing a magnetic field formed when a magnetic field generating apparatus with a displacement apparatus is disposed in a secured space at a back surface of a cathode.

(20) FIG. 20 is a diagram showing a movement of arc spots formed on a discharge surface of the cathode shown in FIG. 19.

(21) FIG. 21 is a diagram showing a configuration of an arc evaporation source used in embodiment 1.

(22) FIG. 22 is a diagram illustrating a vertical moving speed of a permanent magnet.

(23) FIG. 23 is a figure illustrating a relationship of the number of batches of TiN film formation and a film thickness.

(24) FIG. 24 is a diagram showing an exemplary configuration of a conventional arc evaporation source.

(25) FIG. 25 is a diagram illustrating a change in shape of a cathode in a conventional arc evaporation source.

(26) FIG. 26 is a diagram showing another exemplary configuration of a conventional arc evaporation source.

(27) FIG. 27(a) and FIG. 27(b) are diagrams illustrating a change in shape of a cathode in a conventional arc evaporation source.

DESCRIPTION OF THE EMBODIMENTS

(28) The invention will be described in detail according to the embodiments below.

1. Manufacture of an Arc Evaporation Source

(1) Embodiment 1

(29) An arc evaporation source of embodiment 1 was manufactured by disposing a permanent magnet 4 (configured by lining 45 pillar shaped isotropic ferrite magnets (diameter of 8 mm, thickness of 2 mm) into a ring shape at a 45 direction relative to the discharge surface of the cathode 1) at a back side of a cathode 1 machined into the shape shown in FIG. 21 from a disc shaped Ti cathode material with a diameter of 150 mm and thickness of 15 mm. At this time, the magnetic field near the outer circumference of the cathode was approximately 20 gauss.

(30) In addition, as for the magnet, a ring shaped magnet magnetized in a slanted direction may be used, or a cube shaped magnet may be disposed to be aligned slanted on the circumference, for example.

(2) Embodiment 2

(31) An arc evaporation source of embodiment 2 was manufactured similar to embodiment 1 except for that a magnetic field generating apparatus, constructed by a ring shaped permanent magnet (a neodymium magnet with thickness of 2 mm, outer diameter of 46 mm and inner diameter of 31 mm, wherein the magnetic poles are oriented at the outside and inside direction) mounted on a rotating platform such that the center axis of the rotating platform and a center axis of the ring shaped permanent magnet are displaced, is disposed in the space of the back side of the cathode as shown in FIG. 17. Then, rotating the ring shaped permanent magnet in the ranges of 18 to 340 rpm and observing the surface roughness of the film, it was determined that the film has the lowest surface roughness when the rotation speed is approximately 60 rpm. In addition, the magnetic field of the aforementioned ring shaped permanent magnet at the discharge surface of the cathode was approximately 150 gauss.

(3) Embodiment 3

(32) An arc evaporation source of embodiment 3 is manufactured similar to embodiment 1 except for that a magnetic field generating apparatus with a displacement apparatus using the same ring shaped permanent magnet as embodiment 2 is disposed in the space of the back surface of the cathode as shown in FIG. 19.

(33) The displacement apparatus is constructed by an electric actuator, and the permanent magnet is movable in the range of 50 mm in the vertical direction as shown in FIG. 19. As a result, as shown in FIG. 20, the arc spots mostly circulate around the vicinity of the center of the discharge surface of the cathode when the permanent magnet is moved to the top, and the arc spots mostly circulate around the vicinity of the outer circumference of the discharge surface of the cathode when the permanent magnet is moved to the bottom.

(34) When the arc spots circulate around the vicinity of the center of the discharge surface of the cathode, the arc spots need to stay for a short period of time since the cathode is consumed quickly due to the short circumference length. Therefore, the movement of the magnet is made to be a patterned movement as shown in FIG. 22 instead of a fixed movement, such that the consumption of the cathode at the center and the outer circumference is balanced. In addition, here, one cycle was made to be 34 seconds and the time the magnet is at the top is shortened. In this way, the consumption of the cathode is made consistent across a large area.

(4) Comparison Example 1

(35) An arc evaporation source of comparison example 1 is manufactured by disposing a permanent magnet 4 at a back surface of a cathode 1 which is machined into the bank shape shown in FIG. 24 from a disc shaped Ti cathode material with a diameter of 150 mm and thickness of 15 mm such that the direction of the magnetic poles is oriented along the axis direction of the cathode.

(5) Comparison Example 2

(36) An arc evaporation source of comparison example 2 is manufactured by disposing a permanent magnet 4 at a back side of a cathode 1 which is machined into the shape shown in FIG. 26 from a disc shaped Ti cathode material of diameter 150 mm, thickness 15 mm such that the direction of the magnetic poles is oriented along the axis direction of the cathode.

(6) Embodiments 4 to 6 and Comparison Examples 3 and 4

(37) Arc evaporation sources of embodiments 4 to 6 and comparison examples 3 and 4 are manufactured similar to embodiments 1 to 3 and comparison examples 1 and 2 respectively, except for using TiAl (50:50 atm %) as the cathode material.

(7) Embodiments 7 to 9 and Comparison Examples 5 and 6

(38) Arc evaporation sources of embodiments 7 to 9 and comparison examples 5, 6 are manufactured similar to embodiments 1 to 3 and comparison examples 1 and 2 respectively, except for using AlCr (70:30 atm %) as the cathode material.

(8) Embodiments 10 to 12 and Comparison Examples 7 and 8

(39) Arc evaporation sources of embodiments 10 to 12 and comparison examples 7 and 8 are manufactured similar to embodiments 1 to 3 and comparison examples 1 and 2 respectively, except for using Cr as the cathode material.

2. Film Formation

(40) Each arc evaporation source was assembled to an ion plating device, and then sufficient vacuuming as well as out gassing by heater heating was performed, and 500 ccm of nitrogen gas was introduced and the pressure in the chamber was set to each of the pressures shown in TABLE 1.

(41) For the substrate, a test piece of a high speed tool steel (SKH-51) is used and each of the bias voltages shown in Table 1 is applied, then a trigger mechanism (not shown) is used to start arc discharge of each of the cathodes, and arc currents shown in TABLE 1 are fed respectively and a 180 minute coating process is carried out. The film type, film thickness, film hardness, and surface roughness Rz of each of the obtained films are shown in TABLE 1.

(42) Then, film formation is repeated until the film thickness reduces to 70% of the film thickness obtained by the first film formation, and the number of batches up until then is measured. That is to say, when the film thickness drops below 70%, there is not sufficient film thickness, and there is a possibility that the performance of the tools and mold which are the substrate (work) has decreased. It should be noted, as a counter measure, it is possible to extend the coating time in response to the reduction of the film thickness; however, due to difficulty of management it is not ideal. Therefore, the 70% point was set as the life span of the cathode. Results are shown in TABLE 1.

(43) A relationship of the number of batches of film formation and the film thickness in the case of embodiments 1 to 3 and comparison examples 1 and 2 are shown in FIG. 23.

(44) TABLE-US-00001 TABLE 1 Film Formation Results of Batch No. 1 Film Film Surface Cathode Film Film Formation Thickness Hardness Roughness Number of Material Type Condition (m) Hv 25 gf (um) Batches Comparison Ti TiN Pressure: 2.6 Pa 3 2230 1.6 10 Example 1 Voltage Bias: 200 V Comparison Arc Current: 100 A 2.8 2250 1.5 10 Example 2 Embodiment 1 3.8 2230 1.6 20 Embodiment 2 3.9 2190 1.2 51 Embodiment 3 3.9 2200 1.1 69 Comparison TiAl TiAlN Pressure: 3.9 Pa 2.8 2440 2.1 8 Example 3 (50:50 atm %) Voltage Bias: 125 V Comparison Arc Current: 100 A 2.6 2400 2.2 8 Example 4 Embodiment 4 3.5 2500 2.4 15 Embodiment 5 3.7 2440 1.7 38 Embodiment 6 3.6 2560 1.7 55 Comparison AlCr AlCrN Pressure: 5.2 Pa 2.5 2310 2.3 9 Example 5 (70:30 atm %) Voltage Bias: 125 V Comparison Arc Current: 100 A 2.3 2300 2.2 9 Example 6 Embodiment 7 3.1 2300 2.2 17 Embodiment 8 3.1 2310 1.6 45 Embodiment 9 3.1 2350 1.7 60 Comparison Cr CrN Pressure: 2.6 Pa 2.8 1780 2.2 15 Example 7 Voltage Bias: 50 V Comparison Arc Current: 120 A 2.5 1750 2.3 15 Example 8 Embodiment 10 3.4 1700 2.3 30 Embodiment 11 3.6 1810 1.9 72 Embodiment 12 3.5 1790 1.6 101

(45) It is known from TABLE 1 that, in the case of any cathode material, the embodiments have an increase in the number of batches and the expensive cathode material can be used effectively by adopting the invention, compared to the comparison examples.

(46) Furthermore, referring to FIG. 23, in embodiments 1 to 3 which use Ti as the cathode material for film formation, it is seen that embodiments 2 and 3 have a gradual reduction in film thickness even when the number of batches increases, and therefore it is understood that the cathode material is more effectively used in embodiments 2 and 3.

(47) In addition, in embodiments 2 and 3, the surface roughness of the film is also reduced, and it is thought to be due to the arc spots being forcibly moved by the rotation and movements of the magnet.

(48) Furthermore, results such as the above are the same in other embodiments where the cathode material is different.

(49) Embodiments of the invention were described above. However, the invention is not limited to the above mentioned embodiments. Various modifications can be made to the above mentioned embodiments within the same or equivalent range of the invention.

DESCRIPTION OF THE LABELS

(50) 1 Cathode 2 Fixing Ring 3 Magnetic Line 4 Permanent Magnet 5 Confinement Ring