Arc source for graphite target

Abstract

The arc evaporation source according to the present invention therefore comprises - a target (101) to be operated as cathode comprising material to be evaporated, the target exhibiting a target front surface (103), said target front surface (103) being made of material to be evaporated, a target back surface (105) and a target lateral surface (107), where the target lateral surface (107) extends from the border of the target front surface (101) to the border of the target back surface (103) and were a perpendicular axis A-A on the target front surface (103) can be defined preferably going through the center of the target front surface (103), - a magnetic guidance system comprising means for creating magnetic fields comprising magnetic field lines located in front of the target front surface (103), whereinthe arc evaporation source according to the present invention is characterized in that - the target front surface (103) at its periphery is chamfered forming a chamfer area (111) the profile of which may deviate from a linear profile but preferably is linear, and - the magnetic guidance system comprises magnetic means (109) with positions within the space as defined by the plane of the target front surface (103) and the target back surface (105) and close to the line where the chamfer (111) of target front surface (103) meets the target lateral surface (107) and at least some elements of the magnetic means (109) oriented in such a manner that the axis defined by the two poles of an element of the at least some elements preferably is parallel to the radial connection line between the perpendicular axis A-A and said element but in any case forms an angle not larger than 30° so that as a result of this configuration the magnetic field above the chamfer area (111) has a component parallel to the surface of the chamfer area (111) which is larger than the component perpendicular to the surface and the magnetic field in the chamfer area increases along the radial direction from the perpendicular axis A-A to the at least some elements.

Description

[0001] Arc source for graphite target

[0002] The present invention relates to an arc evaporation source and a method for deposition of coating layers, wherein the inventive arc evaporation source allows carbon layers. In particular deposition of carbon layers from graphite targets is possible without a working gas.

[0003] The present invention is especially suitable for stable deposition of carbon layers and allows even stable deposition of thick carbon layers.

[0004] Prior art

[0005] Many arc evaporation sources are well known from the prior art and are used as coating material sources in physical vapor deposition (PVD) processes of the type arc evaporation.

[0006] For example in WO 2021 / 001536 A1 an arc evaporation source (in in WO 2021 / 001536 A1 also called cathodic arc source or cathodic arc evaporation apparatus) is described, which comprises a target as cathode, an electrically floating confinement located adjacent, preferably surrounding or at least partially surrounding the side-target surface, and electrode as anode, a magnetic guidance system, wherein the magnetic guidance system is designed and adjusted for producing at least a first magnetic field region and a second magnetic field region, wherein the first region comprises magnetic field lines located in front of the fronttarget surface which exit the front-target surface and end in the inner surface of the confinement member, and the second region comprises magnetic field lines located in front of the front-target surface which exit the front-target surface and end in the electron receiving surface of the anode.

[0007] Hard Carbon (t-aC) by arc evaporation from a graphite targets needs specific techniques for reliable working in a vacuum deposition process. Its inertia against magnetic steering and very slow travel velocity on the target surface makes the arc spot very difficult to control.

[0008] In these circumstances it has to be dealt with a very intense arc-spot accompanied by a slow steering speed. In addition the arc-spot cannot be confined to remain on the target surface by mechanical means.

[0009] Objective of the present invention

[0010] The main objective of the present invention is to develop a carbon target source according to mechanical, electrical needs. This goes along with the development of a magnet system needed to confine the arc-spot on the graphite target surface. Preferably measures are taken to be able to run the arc discharge without working gas.

[0011] Detailed description of the present invention

[0012] The invention will now be described with the help of the figures.

[0013] Figure 1 schematically shows an arc evaporation source according to the present invention.

[0014] Figure 2 schematically shows the right side of the target together with a target plate and in the target plate embedded magnetic means.

[0015] Figure 1 schematically shows an arc evaporation source comprising a target 101 with a target front surface 103 and a target back surface 105 as well as a target lateral surface 107. The periphery of the target front surface 103 comprises a chamfer 111 . The figure shows as well an axis A-A through the center of the target front surface 103 and perpendicular to it. Figure 1 shows as well some of the magnetic means 109.

[0016] According to one embodiment of the present invention the arc evaporation source comprises as well a target plate 113 for holding the target 101 in place. According to a most preferred embodiment the magnetic means 109 are integrated into the target plate 113.

[0017] Figure 2 schematically shows the right side of the target together with a target plate and in the target plate embedded magnetic means. This figure is shown in order to explicitly point out the magnetic field as established by the magnetic means positioned close to the target lateral surface. As indicated in and above the area of the chamfer 111 , the magnetic field has a strong component Bl parallel to the chamfer surface and a smaller component Bp perpendicular to the chamfer surface. As can be seen as well the strength of the magnetic field in the area is strongest at the outer edge of the chamfer and decreases dramatically on the target front surface if going from this edge in direction to the center of the target. Indicated is a field strength of 20000 Gauss at the edge and of only 20 Gauss close to the center of the target front surface. These numbers are just examples how the magnetic field strength could be chosen.

[0018] The invention will now be described in detail and again with the help of the figures.

[0019] The objective of the present invention is reached by a special magnetic field confinement at a specially prepared target edge.

[0020] The inventors realized that the very slow moving arc-spot cannot be mechanically confined. Surprisingly they found that with an adaption of the target surface, preferably accompanied by a specific setup of magnetic means the confinement of the slow moving arc spot to the target surface can be realized.

[0021] According to the present invention the modification of the target surface comprises to realize a chamfer at the periphery of the target front surface.

[0022] The arc evaporation source according to the present invention therefore comprises

[0023] - a target 101 to be operated as cathode comprising material to be evaporated, the target exhibiting a target front surface 103, said target front surface 103 being made of material to be evaporated, a target back surface 105 and a target lateral surface 107, where the target lateral surface 107 extends from the border of the target front surface 101 to the border of the target back surface 103 and were a perpendicular axis A-A on the target front surface 103 can be defined preferably going through the center of the target front surface 103

[0024] - a magnetic guidance system comprising means for creating magnetic fields comprising magnetic field lines located in front of the target front surface 101 .

[0025] The arc evaporation source according to the present invention is characterized in that:

[0026] - the target front surface 103 at its periphery is chamfered forming a chamfer area 111 the profile of which may deviate from a linear profile but preferably is linear.

[0027] The magnetic guidance system of the arc evaporation source according to the present invention in addition comprises magnetic means 109 with positions within the space as defined by the plane of the target front surface 103 and the target back surface 105 and close to the line where the chamfer 111 of target front surface 103 meets the target lateral surface 109 and at least some elements of the magnetic means 109 oriented in such a manner that the axis defined by the two poles of an element of the at least some elements preferably is parallel to the radial connection line between the perpendicular axis A-A and said element but in any case forms an angle not larger than 30° so that as a result of this configuration the magnetic field in above the chamfer area 111 has a component parallel to the surface of the chamfer area 111 which is larger than the component perpendicular to the surface and the magnetic field in the chamfer area increases along the radial direction from the perpendicular axis A-A to the at least some elements.

[0028] Preferably the at least some elements of the magnetic means are arranged in the form of a continuous or discontinuous ring, the ring surrounding target and preferably being located within the space as defined by the plane of the target front surface 103 and the target back surface 105.

[0029] Preferably the at least some elements are permanent magnets and / or magnetic coils. Preferably at least part of the magnetic means are integrated into a removable target plate 113 the target plate 113 surrounding the target and designed to hold the target after mounting.

[0030] Preferably the target is a carbon comprising target and most preferably is a graphite target.

Claims

Claims1 . An arc evaporation source, comprising:- a target (101 ) to be operated as cathode comprising material to be evaporated, the target exhibiting a target front surface (103), said target front surface (103) being made of material to be evaporated, a target back surface (105) and a target lateral surface (107), where the target lateral surface (107) extends from the border of the target front surface (101 ) to the border of the target back surface (103) and were a perpendicular axis (A-A) on the target front surface (103) can be defined preferably going through the center of the target front surface (103),- a magnetic guidance system comprising means for creating magnetic fields comprising magnetic field lines located in front of the target front surface (103), and characterized in that- the target front surface (103) at its periphery is chamfered forming a chamfer area (111 ) the profile of which may deviate from a linear profile but preferably is linear, and in that- the magnetic guidance system comprises magnetic means (109) with positions within the space as defined by the plane of the target front surface (103) and the target back surface (105) and close to the line where the chamfer (111 ) of target front surface (103) meets the target lateral surface (107) and at least some elements of the magnetic means (109) oriented in such a manner that the axis defined by the two poles of an element of the at least some elements preferably is parallel to the radial connection line between the perpendicular axis (A-A) and said element but in any case forms an angle not larger than 30° so that as a result of this configuration themagnetic field above the chamfer area (111 ) has a component parallel to the surface of the chamfer area (111 ) which is larger than the component perpendicular to the surface and the magnetic field in the chamfer area increases along the radial direction from the perpendicular axis (A-A) to the at least some elements.

2. The arc evaporation source according to claim 1 , characterized in that the at least some elements of the magnetic means are arranged in the form of a continuous or discontinuous ring, the ring surrounding target and preferably being located within the space as defined by the plane of the target front surface (103) and the target back surface (105).

3. The arc evaporation source according to claim 1 or 2, characterized in that the at least some elements are permanent magnets and / or magnetic coils.

4. The arc evaporation source according to any one of the previous claims, characterized in that at least one part of the magnetic means is / are integrated into a removable target plate (113) surrounding the target and designed to hold the target after mounting.

5. The arc evaporation source according to any one of the previous claims, characterized in that the target is a carbon comprising target and preferably is a carbon target.