Vacuum arc source

Abstract

A vacuum arc source for arc evaporation of boride includes: a cathode made of at least 90 at-% of boride, in particular made of more than 98 at-% of boride; an anode, which is preferably in the shape of a disk; a body made of a material which is less preferred by arc discharge compared to the cathode, the body surrounding the cathode in such a way that during operation of the vacuum arc source, movement of an arc on an arc surface of the cathode is limited by the body. At least 90 at-% of the material of the anode is of the same chemical composition as the cathode.

Claims

1. A vacuum arc source for arc evaporation, the vacuum arc source comprising: a cathode made of at least 90 at-% of boride; an anode; a body made of a material which is less preferred by arc discharge compared with said cathode, said body being disposed to abut said cathode and, during an operation of the vacuum arc source, to limit a movement of an arc on an arc surface of said cathode; and at least 90 at-% of a material of said anode being of a same chemical composition as said cathode; said body made of a material selected from the group consisting of molybdenum, tungsten, tantalum, niobium, an alloy of molybdenum, an alloy of tungsten, an alloy of tantalum, and an alloy of niobium; wherein said anode, in a view onto the arc surface of said cathode, covers an end face of said body, with an exception of a slit for a trigger pin of an ignition system, leaving an aperture allowing transport of a material flux from the arc surface of said cathode.

2. The vacuum arc source according to claim 1, wherein said cathode is made of more than 98 at-% of boride.

3. The vacuum arc source according to claim 1, wherein said anode is a disk-shaped anode.

4. The vacuum arc source according to claim 1, wherein said cathode is made of a material selected from the group consisting of TiB.sub.2, ZrB.sub.2, VB.sub.2, TaB.sub.2, CrB.sub.2, NbB.sub.2, W.sub.2B.sub.5, WB.sub.2, HfB.sub.2, AlB.sub.2, MoB.sub.2, MoB, and mixtures thereof.

5. The vacuum arc source according to claim 1, wherein a shape of said cathode is prismatic or cylindrical and/or a shape of said body is prismatic or cylindrical.

6. The vacuum arc source according to claim 5, wherein the shape of said cathode and the shape of said body are at least substantially equal.

7. The vacuum arc source according to claim 5, wherein said cathode tapers towards the arc surface.

8. The vacuum arc source according to claim 1, wherein one of the following is true: said body protrudes axially over the arc surface of said cathode; said cathode protrudes axially over an end surface of said body; the arc surface of said cathode and an end surface of said body are coplanar.

9. The vacuum arc source according to claim 1, wherein a height of said body is at least 30% of a height of said cathode.

10. The vacuum arc source according to claim 1, wherein more than 99 at-% of the material of said anode has the same chemical composition as the material of said cathode.

11. The vacuum arc source according to claim 1, Wherein a minimum distance between: said cathode and said anode, or said body and said anode; is 0.5 millimeters to 10 millimeters.

12. The vacuum arc source according to claim 1, further comprising an ignition system of the vacuum arc source having a trigger pin disposed to touch said body surrounding said cathode.

13. The vacuum arc source according to claim 12, wherein said body has a radial width greater than a diameter of said trigger pin, enabling reliable ignition.

14. The vacuum arc source according to claim 1, wherein, during an operation of the vacuum arc source, motion of an arc discharge is governed by electric field lines extending between said cathode and said anode.

15. The vacuum arc source according to claim 14, wherein no magnets are provided for guiding the arc discharge.

16. A deposition method, comprising: providing a vacuum arc source according to claim 1; and depositing a thin-film coating by physical vapor deposition onto a substrate.

17. The method according to claim 16, which comprises forming the thin-film coating of a cutting tool or a forming tool.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) FIG. 1 shows a cathode-assembly for arc evaporation of TiB.sub.2 with a cathode 1 made of TiB.sub.2, the cathode 1 being surrounded by a body 2 made of a material (here: Mo) which is less preferred by arc discharge compared to the TiB.sub.2-cathode 1. An ignition system 3 comprising a trigger pin 4 is shown.

(2) FIG. 2 shows a vacuum arc source for arc evaporation of TiB.sub.2 using the cathode-assembly of FIG. 1. The body 2 in form of a Mo cylinder protects the cathode 1 from undesired effects accompanying ignition of the arc and, at the same time, it keeps the arc spot at the operational cathode surface.

(3) The anode 5 has the shape of a disk with an aperture 7 for transport of the generated material flux to a substrate. It can also be noted that performed experiments showed that arc spots ignited below the anode 5 tend to go to the cathode area below the anode aperture.

(4) The disk is provided with a slit 6 for the trigger pin 4 providing arc discharge ignition such that the trigger pin 4 can pass through the plane of the disk to touch the body 2.

(5) FIGS. 3a to 3i show different possible configurations of cathode 1, body 2 and anode 5. In all Figures, cathode 1, body 2 and anode 5 are in the form of rotating bodies: In FIGS. 3a to 3f, the cathode 1 is in the shape of a cylinder having a groove for the body 2 which is in the shape of a hollow cylinder. In FIGS. 3g and 3h, the cathode 1 is in the shape of a (truncated) cone and the body 2 is in the shape of a hollow (truncated) cone. In FIG. 3i the cathode 1 is in the shape of a cylinder which is tapering towards the arc surface. In FIGS. 3a to 3i the anode 5 is in the form of a ring.

(6) In all Figures, a height H.sub.B of the body 2 is at least 30% of a height H.sub.C of the cathode 1.

(7) In all Figures, the body 2 abuts a mantle surface of the cathode 1. However, a small gap between body 2 and cathode 1 below 1 Millimeter, preferably below 0.5 Millimeter would be acceptable.

(8) In FIGS. 3a to 3c a top or end surface of the body 2 is coplanar with the arc surface of the cathode 1.

(9) In FIG. 3d the body 2 protrudes over the arc surface of the cathode 1.

(10) In FIGS. 3e and 3g to 3i the cathode 1 protrudes over the body 2.

(11) In FIG. 3f the body 2 is coplanar with an outer rim of the arc surface of the cathode 1. In a radial direction towards the center an inner, central region of the arc surface of the cathode 1 lies below the outer rim of the arc surface of the cathode 1.

LIST OF REFERENCE SIGNS

(12) 1 cathode 2 body surrounding the cathode 3 ignition system 4 trigger pin 5 anode 6 slit in the anode 7 aperture of anode H.sub.B height of body H.sub.C height of cathode