WO2018130301A1

WO2018130301A1 - Sputter deposition apparatus for coating a substrate and method of performing a sputter deposition process

Info

Publication number: WO2018130301A1
Application number: PCT/EP2017/050693
Authority: WO
Inventors: Andreas KLÖPPEL; Andreas Lopp
Original assignee: Applied Materials, Inc.
Priority date: 2017-01-13
Filing date: 2017-01-13
Publication date: 2018-07-19
Also published as: KR20190103336A; CN110168697A; KR102219774B1; JP2020506287A

Abstract

A sputter deposition apparatus is provided. The sputter deposition apparatus includes a plurality of cathode assemblies configured for sputtering target material in a sputter deposition process, wherein each of the plurality of cathode assemblies includes a rotatable target and a magnet assembly arranged in the rotatable target, wherein the plurality of cathode assemblies includes an outermost cathode assembly. The sputter deposition apparatus further includes a plurality of anode elements configured for influencing a plasma generated in the sputter deposition process, wherein the plurality of anode elements includes an outermost anode element. The sputter deposition apparatus further includes an ancillary magnet assembly. The outermost cathode assembly, the outermost anode element and the ancillary magnet assembly are arranged in this order, wherein the ancillary magnet assembly is configured for providing a magnetic field to compensate a boundary effect at an outer region of the plasma.

Description

SPUTTER DEPOSITION APPARATUS FOR COATING A SUBSTRATE AND METHOD OF PERFORMING A SPUTTER DEPOSITION PROCESS

FIELD

[0001] Embodiments described herein relate to layer deposition by sputtering from a target. Some embodiments particularly relate to sputtering layers on large area substrates. Some embodiments particularly relate to static deposition processes. Embodiments described herein relate specifically to a sputter deposition apparatus including a plurality of cathode elements and a plurality of anode elements.

BACKGROUND

[0002] Coated materials may be used in several applications and in several technical fields. For instance, substrates for displays are often coated by a physical vapor deposition (PVD) process. Further applications of coated materials include insulating panels, organic light emitting diode (OLED) panels, as well as hard disks, CDs, DVDs and the like.

[0003] Several methods are known for coating a substrate. For instance, substrates may be coated by a PVD process, a chemical vapor deposition (CVD) process, or a plasma enhanced chemical vapor deposition (PECVD) process etc. Typically, the process is performed in a process apparatus or process chamber, where the substrate to be coated is located. A deposition material is provided in the apparatus. In the case that a PVD process, such as sputtering, is used, the deposition material is present in the solid phase in a target. By bombarding the target with energetic particles, atoms of the target material, i.e. the material to be deposited, are ejected from the target. The atoms of the target material are deposited on the substrate to be coated. Typically, a PVD process is suitable for thin film coatings.

[0004] In a sputtering process, the target is used to serve as cathode. Both are arranged in a vacuum deposition chamber. A process gas is filled in the process chamber at a low pressure (for instance at about 10^" mbar). When voltage is applied to the target and the substrate, electrons are accelerated to the anode, whereby ions of the process gas are generated by the collision of the electron with the gas atoms. The positively charged ions are accelerated in the direction of the cathode. By impingement of the ion, atoms of target material are ejected from the target. [0005] Cathodes are known which use a magnetic field in order to increase the efficiency of the above described process. By applying a magnetic field, electrons spend more time near the target, and more ions are generated near the target. In known cathode assemblies, one or more magnet yokes or magnet bars are arranged in order to ameliorate the ion generation and, thus, the deposition process.

[0006] However, there is a continuous need for improving such systems. In particular, due to increasing demands, there is a need for improving the efficiency and lifetime of known coating apparatuses.

[0007] In view of the above, it is an object of the present invention to provide a sputter deposition apparats and a method of performing a sputter deposition process which overcomes at least some of the problems in the art.

SUMMARY

[0008] According to an embodiment, a sputter deposition apparatus is provided. The sputter deposition apparatus includes a plurality of cathode assemblies configured for sputtering target material in a sputter deposition process, wherein each of the plurality of cathode assemblies includes a rotatable target and a magnet assembly arranged in the rotatable target, wherein the plurality of cathode assemblies includes an outermost cathode assembly. The sputter deposition apparatus further includes a plurality of anode elements configured for influencing a plasma generated in the sputter deposition process, wherein the plurality of anode elements includes an outermost anode element. The sputter deposition apparatus further includes an ancillary magnet assembly. The outermost cathode assembly, the outermost anode element and the ancillary magnet assembly are arranged in this order, wherein the ancillary magnet assembly is configured for providing a magnetic field to compensate a boundary effect at an outer region of the plasma.

[0009] According to a further embodiment, a method of performing a sputter deposition process is provided. The method includes providing a plasma. The method further includes sputtering target material with a plurality of cathode assemblies. The method further includes influencing the plasma with a plurality of magnet assemblies arranged in the plurality of cathode assemblies. The method further includes influencing the plasma with a plurality of anode elements. The method further includes providing an ancillary magnetic field at an outer region of the plasma to compensate a boundary effect.

[0010] According to a further embodiment, a method of performing a sputter deposition process is provided. The method includes providing a plasma. The method further includes sputtering target material with a plurality of cathode assemblies forming a deposition array. The method further includes providing a magnetic field to influence an outer region of the plasma, wherein the magnetic field is provided by an ancillary magnet assembly outside of the deposition array.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A full and enabling disclosure to one of ordinary skill in the art is set forth more particularly in the remainder of the specification including reference to the accompanying drawings wherein:

Fig. 1 shows a sputter deposition apparatus including an ancillary magnet assembly according to embodiments described herein;

Fig. 2 illustrates a boundary effect at an outer plasma region;

Fig. 3 shows a sputter deposition apparatus according to embodiments described herein, including an ancillary magnet assembly in a dummy cathode assembly;

Figs. 4-5 shows sputter deposition apparatuses according to embodiments described herein;

Figs. 6-7 show examples of one-dimensional deposition arrays embodiments described herein; and

Figs. 8a-c show examples of magnet assemblies according to embodiments described herein.

DETAILED DESCRIPTION

[0012] Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation and is not meant as a limitation. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0013] Embodiments described herein relate to apparatuses and methods for coating a substrate. In a coating process, a layer of target material is deposited on a substrate. The terms "coating process" and "deposition process" are used synonymously.

[0014] A sputter deposition apparatus according to embodiments described herein includes several cathode assemblies. As used herein, the term "cathode assembly" should be understood as an assembly which is adapted for being used as a cathode in a coating process, such as a sputter deposition process.

[0015] A cathode assembly may include a rotatable target. A rotatable target may be rotatable around a rotation axis of the rotatable target. A rotatable target may have a curved surface, for example a cylindrical surface. The rotatable target may be rotated around the rotation axis being the axis of a cylinder or a tube. A rotatable target may include a backing tube. A target material forming the target, which may contain the material to be deposited onto a substrate during a coating process, may be mounted on the backing tube.

[0016] A cathode assembly may include a magnet assembly. A magnet assembly may be arranged in a rotatable target of the cathode assembly. A magnet assembly may be arranged so that the target material sputtered by the cathode assembly is sputtered towards a substrate. A magnet assembly may generate a magnetic field. The magnetic field may cause one or more plasma regions to be formed near the magnetic field during a sputter deposition process. The position of the magnet assembly within a rotatable target affects the direction in which target material is sputtered away from the cathode assembly during a sputter deposition process.

[0017] A sputter deposition apparatus according to embodiments described herein includes a plurality of anode elements, e.g. anode bars. An anode element is configured for influencing, particularly electrically influencing, the plasma generated in the deposition process. For example, the plasma may include charged particles such as e.g. electrons. An anode element may be configured for attracting the charged particles, e.g. the electrons, of the plasma. Accordingly, a return path for the charged particles, e.g. back to a power generator of the apparatus, may be provided by the plurality of anode elements.

[0018] Embodiments described herein relate to sputter deposition apparatuses and methods of performing a sputter deposition process wherein a boundary effect associated with the outermost cathode assemblies of the deposition array can be compensated by means of one or more ancillary magnet assemblies arranged at the ends of the deposition array.

[0019] Fig. 1 illustrates a sputter deposition apparatus 100 according to an embodiment. The sputter deposition apparatus 100 includes a plurality of cathode assemblies 110 forming a deposition array. The plurality of cathode assemblies 110 are configured for sputtering a target material towards a substrate 180, e.g. a large area substrate.

[0020] In the exemplary embodiment illustrated in Fig. 1, the plurality of cathode assemblies 110 consists of two cathode assemblies, namely cathode assembly 112 on the left and cathode assembly 114 on the right. According to embodiments, which can be combined with other embodiments described herein, the plurality of cathode assemblies 110 may include or consist an even number of cathode assemblies, such as two, four, six, ten, twelve or even more cathode assemblies.

[0021] Cathode assembly 112 includes a rotatable target 122 (i.e. a tubular target or rotary target), a rotation axis 142 and a magnet assembly 132 arranged in the rotatable target 122. Similarly, cathode assembly 114 includes a rotatable target 124, a rotation axis 144 and a magnet assembly 134 arranged in the rotatable target 124. Rotatable targets 112 and 114 are configured for rotating a target material around their rotation axes 142 and 144, respectively. The target material of the cathode assemblies 112 and 114 is sputtered towards the substrate 180 for coating the substrate 180, e.g. in a static sputter deposition process. According to embodiments, which can be combined with embodiments described herein, a rotatable target may include target material arranged according to a curved surface, may be cylindrically shaped and/or may include a backing tube.

[0022] The sputter deposition apparatus 100 includes a plurality of anode elements 160, e.g. anode bars. In the exemplary embodiment illustrated in Fig. 1, the plurality of anode elements 160 consists of three anode elements 162, 164 and 166. The anode element 162 is an outermost anode element and the anode element 164 is a further outermost anode element of the plurality of anode elements 160. According to embodiments, which can be combined with other embodiments described herein, the plurality of anode elements 160 may include or consist an odd number of cathode assemblies, such as three, five, seven, eleven, thirteen or even more anode elements. The total number of anode elements included in the plurality of anode elements 160 may be one more than the total number of cathode assemblies included in the plurality of cathode assemblies 110. According to some embodiments, which can be combined with other embodiments described herein, and as shown in Fig. 1, the plurality of cathode assemblies 110 and the plurality of anode elements 160 may be alternately arranged.

[0023] A sputter deposition process performed by the sputter deposition apparatus 100 involves providing a plasma 190. The shape, position, distribution and/or density of the plasma 190 may be influenced by magnetic fields generated by the magnet assemblies included in the plurality of cathode assemblies 110. A magnetic field generated by a magnet assembly, e.g. magnet assembly 132 or 134 shown in Fig. 1, may cause one or more plasma regions of increased density to be formed near the magnet assembly during the sputter deposition process.

[0024] The plasma 190 is also influenced by the plurality of anode elements 160, which may provide a return path for electrons in the plasma back to a power generator of the sputter deposition apparatus 100.

[0025] The sputter deposition apparatus 100 shown in Fig. 1 further includes an ancillary magnet assembly 172 and a further ancillary magnet assembly 174 provided on opposite ends of the plurality of cathode assemblies 110, i.e. the deposition array. In the exemplary embodiment shown in Fig. 1, the ancillary magnet assembly 172 and the further ancillary magnet assembly 174 are stand-alone magnet assemblies. In particular, these ancillary magnet assemblies are not included in a cathode assembly. Alternative embodiments, e.g. involving ancillary magnet assemblies arranged in dummy cathode assemblies, are also considered and will be discussed below.

[0026] An ancillary magnet assembly, such as e.g. ancillary magnet assembly 172 or further ancillary magnet assembly 174, is configured for providing a magnetic field. The magnetic field provided by an ancillary magnet assembly will herein sometimes be referred to as an "ancillary magnetic field". [0027] According to embodiments, which can be combined with other embodiments described herein, the magnetic field provided by an ancillary magnet assembly is configured for compensating a boundary effect at an outer region of the plasma 190.

[0028] For example, for a plurality of cathode arrangements 110 which are arranged according to a linear deposition array (or a slightly curved but essentially linear deposition array) according to a left-right direction, an outer region of the plasma, as described herein, may refer to a region associated with the rightmost or leftmost cathode assembly in the plurality of cathode assemblies 110. Fig. 1 schematically shows an outer region 192 on the left-hand side near cathode assembly 112 and near outermost anode element 162. Fig. 1 also schematically shows a further outer region 194 on the right-hand side near cathode assembly 114 and near further outermost anode element 164. An outer region 192 and a further outer 194 are also illustrated for a larger deposition array, e.g., in Fig. 4 for a plurality of cathode assemblies 160 including four cathode assemblies. Again, the outer region 192 is provided on the left-hand side of the deposition array near cathode assembly 112, i.e. the leftmost cathode assembly of the plurality of cathode assemblies 110, and near outermost anode element 162. Further outer region 194 is provided on the right-hand side of the deposition array near cathode assembly 114, i.e. the rightmost cathode assembly of the plurality of cathode assemblies 110, and near further outermost anode element 164.

[0029] According to embodiments, which can be combined with other embodiments described herein, an outer region of the plasma 190, e.g. outer region 192 or further outer region 194, may be a plasma region associated with or in the vicinity of an outermost cathode assembly of the plurality of cathode assemblies 110, e.g. cathode assembly 112 or cathode assembly 114. The distance from an outer region of the plasma to an outermost cathode assembly of the plurality of cathode assemblies 110 may be smaller than the distance from the outer region of the plasma to an inner cathode assembly of the plurality of cathode assemblies 110.

[0030] Additionally or alternatively, an outer region of the plasma 190 may be a plasma region associated with or in the vicinity of an outermost anode element of the plurality of anode elements 160, e.g. outermost anode element 162 or outermost anode element 164. The distance from an outer region of the plasma to an outermost anode element of the plurality of anode elements 160 may be smaller than the distance from the outer region of the plasma to an inner anode element of the plurality of anode elements 160. [0031] Still additionally or alternatively, an outer region of the plasma 190 may be a plasma region associated with or in the vicinity of an ancillary magnet assembly, e.g. ancillary magnet assembly 172 or further ancillary magnet assembly 174.

[0032] A boundary effect at an outer region of the plasma is compensated by way of an ancillary magnet assembly according to embodiments described herein. Such boundary effect can be reduced or even avoided for apparatuses according to embodiments described herein.

[0033] To provide a better understanding of the boundary effects avoided by embodiments described herein, in the following a discussion is given of apparatuses which do not include an ancillary magnet assembly for compensating the boundary effect according to embodiments described herein. In such apparatuses, the boundary effect may be particularly present.

[0034] A boundary effect as described herein relates to the fact that, in apparatuses which do not include an ancillary magnet assembly according to embodiments described herein, the plasma may have different properties, e.g. different distribution, density or shape, in the outer regions of the plasma as compared to the inner regions of the plasma.

[0035] For example, Fig. 2 shows an apparatus 200 including a cathode array and an array of anode bars in a processing chamber 210. The cathode array includes a leftmost cathode assembly 212, a rightmost cathode assembly 214 and inner cathode assemblies 216, 217, 218 and 219. The array of anode bars includes a leftmost anode bar 262, a rightmost anode bar 264 and inner anode bars 266, 267, 268, 269 and 270. The apparatus 200 does not include an ancillary magnet assembly according to embodiments described herein. A plasma 190 is shown. Outer region 292 and outer region 294 of the plasma 190 are associated with the leftmost and rightmost cathode assembly 212 and 214, respectively. Inner regions 296, 297,

298 and 299 of the plasma 190 are associated with inner cathode assemblies 216, 217, 218 and 219, respectively. As shown, the plasma density in the inner regions 296, 297, 298 and

299 are substantially similar to each other or even substantially periodic. A boundary effect occurs at the outer regions 292 and 294. In particular, the plasma density in these outer regions differs substantially from the density in the inner regions of the plasma. As shown, plasma regions of high density (indicated by the dark areas) are formed near the leftmost cathode assembly 212 and the rightmost cathode assembly 214. Particularly, the plasma regions of high density are formed near the leftmost anode bar 262 and the rightmost anode bar 264, since plasma electrons are electrically attracted towards these outermost anode bars. In contrast, such high-density plasma regions are not formed near the inner anode bars 266, 267, 268, 269 and 270, since these inner anode bars experience magnetic shielding due to the magnetic fields provided by the magnet assemblies (not shown) in the cathode assemblies of the cathode array.

[0036] In other words, in the apparatus 200 shown in Fig. 2, which does not include an ancillary magnet assembly, the plasma density may be substantially periodic for the inner cathode assemblies and inner anode bars, but this periodicity is broken in the outer regions 292 and 294 of the plasma.

[0037] According to embodiments described herein, one or more ancillary magnet assemblies are provided for compensating the boundary effects described above. Referring again to Fig. 1, an ancillary magnet assembly 172 may be provided. As shown, the ancillary magnet assembly 172 may be arranged on the left-hand side of the outermost anode element 162, i.e. to the left of the leftmost anode element. As further shown, a further ancillary magnet assembly 174 may be provided at an opposite end of the deposition array. The further ancillary magnet assembly 174 may be arranged on the right-hand side of the outermost anode element 164, i.e. to the right of the rightmost anode element.

[0038] Embodiments described herein allow reducing or even avoiding a boundary effect at the outer regions 192 and 194 of the plasma. By way of the ancillary magnetic fields provided by the ancillary magnet assemblies, the plasma conditions for the outer plasma regions 192 and 194 are substantially the same as the plasma conditions for an inner plasma region. In particular, by way of the ancillary magnet assemblies, the magnetic field conditions and the accessibility for plasma electrons to the outermost anode elements 162 and 164 are substantially the same as for the inner anode element(s). For example, due to the ancillary magnetic fields, a magnetic shielding may be experienced by the inner anode elements and by the outermost anode elements of the plurality of anode elements alike, in contrast to e.g. the apparatus 200 shown in Fig. 2, in which only the inner anode elements experience such magnetic shielding, as discussed above.

[0039] By providing same or similar plasma conditions for all cathode assemblies in the deposition array, the lifetime and utilization of the outermost cathode assemblies of the deposition array, and thus of the entire deposition array, can be increased. In particular, in apparatuses not including ancillary magnet assemblies according to embodiments described herein, due to the different plasma conditions at the outer regions of the plasma as compared to the inner regions, the outermost cathode assemblies can be subject to increased erosion. Accordingly, in such apparatuses the lifetime of the outermost cathode assemblies is decreased as compared to the inner cathode assemblies. Since the lifetime of an array of cathode assemblies is determined by the target with the shortest lifetime, this means that the lifetime of the entire deposition array is thereby decreased. In contrast, in apparatuses according to embodiments described herein, the boundary effect at the outer plasma regions is compensated and the plasma conditions are the same for all cathode assemblies in the deposition array. Accordingly, the outermost cathode assemblies of the deposition array do not suffer from increased erosion, so that the lifetime and utilization of the outermost cathode assemblies, and thus of the entire deposition array, can be increased.

[0040] In light of the above, a sputter deposition apparatus for coating a substrate is provided. The sputter deposition apparatus includes a plurality of cathode assemblies configured for sputtering target material in a sputter deposition process. The plurality of cathode assemblies forms a deposition array. Each of the plurality of cathode assemblies includes a rotatable target and a magnet assembly arranged in the rotatable target. The plurality of cathode assemblies includes an outermost cathode assembly, e.g. cathode assembly 112. The sputter deposition apparatus further includes a plurality of anode elements configured for influencing a plasma generated in the sputter deposition process, wherein the plurality of anode elements includes an outermost anode element, e.g. outermost anode element 162. The sputter deposition apparatus further includes an ancillary magnet assembly, e.g. ancillary magnet assembly 172. The outermost cathode assembly, the outermost anode element and the ancillary magnet assembly are arranged in this order. The ancillary magnet assembly is configured for providing a magnetic field to compensate a boundary effect at an outer region of the plasma.

[0041] According to an embodiment, which can be combined with other embodiments described herein, an ancillary magnet assembly is not arranged in a cathode assembly. For example, Fig. 1 shows ancillary magnet assembly 172 as a stand-alone magnet assembly not included in any cathode assembly. The ancillary magnet assembly 172 may be configured to be in contact with a processing gas during a sputter deposition process.

[0042] Embodiments described herein involve a distinction between, on the one hand, cathode assemblies which belong to the deposition array and which are thus specifically configured for sputtering target material in a sputter deposition process for coating the substrate and, on the other hand, "dummy" cathode assemblies not belonging to the deposition array.

[0043] The plurality of cathode assemblies 110 forms a deposition array. It shall be understood that each cathode assembly in the plurality of cathode assemblies 110, i.e. each cathode assembly in the deposition array, is configured for sputtering target material in a sputter deposition process for coating the substrate. In particular, the "outermost cathode assembly" and the "further outermost cathode assembly" of the plurality of cathode assemblies, as described herein, form part of the deposition array and are configured for sputtering target material in a sputter deposition process for coating the substrate.

[0044] In particular, according to embodiments, each cathode assembly in the plurality of cathode assemblies 110 is configured for rotating around its rotation axis and for being bombarded with particles so that target material can be sputtered from its rotatable target for coating the substrate. Such a cathode assembly should be distinguished from a "dummy" cathode assembly. A dummy cathode assembly forms part of the sputter deposition apparatus and may, in some cases, be structurally similar or even identical to a cathode assembly belonging to the deposition array. However, a dummy cathode assembly does not form part of the deposition array and/or may be arranged outside of the deposition array. A dummy cathode assembly is, for example, not configured to sputter target material for coating the substrate. In an example, the target of a dummy cathode assembly is, for example, not configured to rotate during the sputter deposition process. In another example, a dummy cathode assembly may be arranged at an offset position, along the first direction 10, with respect to the substrate to be coated, such that, different from the cathode assemblies in the deposition array, the dummy cathode assembly does not directly face the substrate. Other examples for configuring a dummy cathode may be complemented, as long as a dummy cathode assembly is considered to be a cathode assembly not part of the deposition array.

[0045] According to some embodiments, which can be combined with other embodiments described herein, an ancillary magnet assembly is arranged in a dummy cathode assembly.

[0046] Fig. 3 shows as apparatus 110 according to embodiments described herein, wherein the apparatus 110 includes a dummy cathode assembly 302. As shown, a dummy cathode assembly 302 may include a rotatable target 322 and a magnet assembly. The magnet assembly of the dummy cathode assembly 302 may be an ancillary magnet assembly 172 according to embodiments described herein. In a sputter deposition process performed by the apparatus, target material may be emitted or sputtered by each cathode assembly in the plurality of cathode assemblies 110 for coating the substrate, but not by the dummy cathode assembly 302. The dummy cathode assembly 110 does not form part of the deposition array. The deposition array is schematically indicated in Fig. 3 by a region 310. That is, the deposition array is formed by those cathode assemblies included in the region 310. As shown, the deposition array includes all cathode assemblies of the plurality of cathode assemblies 110 but does not include the dummy cathode assembly 302. The dummy cathode assembly 302 serves a different purpose. The function of the dummy cathode assembly in the sputter deposition process is linked to its magnet assembly, which may be an ancillary magnet assembly 172 according to embodiments described herein. While the sputtering of target material may be performed by the plurality of cathode assemblies 110, the ancillary magnet assembly 172 in the dummy cathode assembly 302 may be configured for generating an ancillary magnetic field for compensating a boundary effect at an outer region of the plasma 190 as described herein. Accordingly, an ancillary magnet assembly provided in a dummy cathode assembly, as e.g. shown in Fig. 3, performs the same function as a stand-alone ancillary magnet assembly, as e.g. shown in Fig. 1.

[0047] According to an embodiment, which can be combined with other embodiments described herein, the sputter deposition apparatus may include a substrate receiving area. Each cathode assembly of the plurality of cathode assemblies may face or be arranged in front of the substrate receiving area. Each cathode assembly of the plurality of cathode assemblies may be configured for sputtering target material towards a substrate provided in the substrate receiving area. According to embodiments, a dummy cathode assembly may be arranged at an offset position along the first direction with respect to the substrate receiving area.

[0048] According to embodiments, a maximal distance, along a first direction, between the outermost cathode assembly 112 and the further outermost cathode assembly 114 of the plurality of cathode assemblies 110 may be from 50% to 150%, particularly from 80% to 120%, of the extent of the substrate receiving area along the first direction.

[0049] As illustrated in Figs. 1 and 3, an outermost cathode assembly of the plurality of cathode assemblies 110 may, but need not be, the last cathode of the entire chain of cathodes. In Fig. 1, cathode assembly 112 is an outermost cathode assembly of the plurality of cathode assemblies 110 and is also the last cathode of the sputter deposition apparatus 100. As shown in Fig. 3, cathode assembly 112 is an outermost cathode assembly of the plurality of cathode assemblies 110, i.e. the deposition array, but is not the last cathode of the apparatus 100. Dummy cathode assembly 302 is the last cathode of the sputter deposition apparatus 100, but dummy cathode assembly 302 is not configured for sputtering target material towards the substrate and is thus not part of the plurality of cathode assemblies 110, i.e. is not part of the deposition array.

[0050] In the present disclosure, the term "outermost cathode assembly" shall be taken to mean an outermost cathode assembly of the plurality of cathode assemblies 110, i.e. of the cathode assemblies configured for sputtering target material towards the substrate, i.e. of the deposition array, such as cathode assemblies 112 or 114 shown as outermost cathode assemblies of the plurality of cathode assemblies 110 in the figures.

[0051] According to embodiments, which can be combined with other embodiments described herein, the outermost cathode assembly, the outermost anode element and the ancillary magnet assembly are arranged in this order.

[0052] According to embodiments, which can be combined with other embodiments described herein, the outermost cathode assembly, the outermost anode element and the ancillary magnet assembly may be arranged in this order along a first direction, e.g. the first direction 10 shown in Fig. 1. For example, in Fig. 1, the cathode assembly 112, the outermost anode element 162 and the ancillary magnet assembly 172 are arranged in this order along the first direction 10. The provision that these components are arranged "in this order along the first direction" does not imply that these components are necessarily strictly arranged on an axis passing through each of these components and extending in the first direction. For example, according to an embodiment, one of these components may be at an off-set position with respect to an axis passing through the two remaining components, as long as the outermost cathode assembly, the outermost anode element and the ancillary magnet assembly are arranged in this order. Specifically, the provision "arranged in this order along the first direction" may refer to an arrangement such that the orthogonal projection of a center of the outermost anode element onto the first direction is between the orthogonal projection of a center of the ancillary magnet assembly onto the first direction and the orthogonal projection of a center of the outermost cathode assembly onto the first direction.

[0053] The first direction, as described herein, may e.g. refer to first direction 10 shown in Fig. 1. The plurality of cathode assemblies 110 and/or the plurality of anode elements 160 may be arranged along the first direction 10. [0054] According to embodiments, which can be combined with other embodiments described herein, a rotation axis of an outermost cathode assembly, a rotation axis of a further outermost cathode assembly, a rotation axis of a dummy cathode assembly, and/or a rotation axis of any of the cathode assemblies in the plurality of cathode assemblies 110 may extend in a direction perpendicular or substantially perpendicular to the first direction 10. An outermost anode element, a further outermost anode element, or any of the anode elements in the plurality of anode elements may extend in a direction perpendicular or substantially perpendicular to the first direction 10.

[0055] According to embodiments, which can be combined with other embodiments described herein, the rotation axes of the cathode assemblies in the plurality of cathode assemblies may be parallel or substantially parallel to each other. Each of the plurality of anode elements may be parallel or substantially parallel to each other.

[0056] As described herein, substantially perpendicular directions may refer to directions which are at an angle from 75 degrees to 105 degrees, particularly 80 degrees to 100 degrees. Substantially parallel directions may refer to directions which are at an angle from -15 degrees to 15 degrees, particularly -10 degrees to 10 degrees.

[0057] The sputter deposition apparatus may include a substrate support for supporting a substrate. The substrate support may extend along the first direction. Each cathode assembly of the plurality of cathode assemblies 110 may be arranged on a same side of the substrate support. Each cathode assembly of the plurality of cathode assemblies 110 may be configured for sputtering material for coating a same surface of the substrate supported by the substrate support.

[0058] According to embodiments, which can be combined with other embodiments described herein, an outermost cathode assembly and/or outermost anode element is "outermost" with respect to the first direction. Specifically, when considering the orthogonal projections onto the first direction of each cathode assembly of the plurality of cathode assemblies, the orthogonal projection of the outermost cathode assembly may be the outermost of such orthogonal projections.

[0059] Fig. 4 shows a plurality of cathode elements 110 forming a deposition array. The plurality of cathode elements 110 shown in Fig. 4 consists of cathode elements 112, 416, 418 and 114. Cathode assembly 112 is an outermost cathode assembly and cathode assembly 114 is a further outermost cathode assembly of the deposition array. Cathode assemblies 416 and 418 are inner cathode assemblies of the deposition array. Cathode assembly 416 includes a rotatable target and a magnet assembly 436. Cathode assembly 418 includes a rotatable target and a magnet assembly 438. The plurality of anode elements shown in Fig. 4 consists of anode elements 162, 464, 466, 468 and 164. Anode element 162 is an outermost anode element and anode element 164 is a further outermost anode element. The outermost cathode assembly 112, the outermost anode element 162 and the ancillary magnet assembly 172 are arranged in this order along the first direction 10. The further outermost cathode assembly 114, the further outermost anode element 164 and the further ancillary magnet assembly 174 are arranged in this order along the first direction 10. The ancillary magnet assemblies 172 and 174 shown in Fig. 4 are stand-alone magnet assemblies.

[0060] Alternatively, as shown in Fig. 5, the ancillary magnet assemblies 172 and 174 may be included in respective dummy cathode assemblies 302 and 304 according to embodiments described herein.

[0061] Fig. 4 shows a distance 482 from the ancillary magnet assembly 172 to the outermost anode element 162 and a distance 484 from the outermost anode element 162 to the magnet assembly 132 of the outermost cathode assembly 112. In the embodiment shown, the distance 482 is equal to the distance 484. In other words, the distance 482 from the ancillary magnet assembly 172 to the outermost anode element 162 and the distance 484 from the outermost anode element 162 to the magnet assembly 132 of the outermost cathode assembly 112 is about 50 % of a distance from the ancillary magnet assembly 172 to the magnet assembly 132 of the outermost cathode assembly 112.

[0062] According to an embodiment, which can be combined with other embodiments described herein, a distance 482 from the ancillary magnet assembly to the outermost anode element and/or a distance 484 from the outermost anode element to the magnet assembly of the outermost cathode assembly may be from 30% to 70% of a distance from the ancillary magnet assembly to the magnet assembly of the outermost cathode assembly. Particularly, such distance may be from 40% to 60%, e.g. about 50 %, of a distance from the ancillary magnet assembly to the magnet assembly of the outermost cathode assembly.

[0063] If the distances 482 and 484 lie in the above-defined ranges, the effect of the ancillary magnet assembly of compensating the boundary effect is even further enhanced, since such substantially equal distances 482 and 484 provide spatial symmetry and periodicity. [0064] According to an embodiment, which can be combined with other embodiments described herein, the distance from the ancillary magnet assembly to the outermost anode element and/or the distance from the outermost anode element to the magnet assembly of the outermost cathode assembly may be in the range from 30% to 70% of the distance between the ancillary magnet assembly to the outermost cathode assembly.

[0065] According to an embodiment, which can be combined with other embodiments described herein, the distance from the ancillary magnet assembly 172 to the magnet assembly 132 of the outermost cathode assembly 112 may be from 80% to 120%, particularly from 90 to 110%, such as e.g. about 100%, of the distance between the magnet assembly 132 of the outermost cathode assembly 112 and the magnet assembly of the cathode assembly adjacent to the outermost cathode assembly. Having distances between respective magnet assemblies in such ranges, particularly distances between subsequent magnet assemblies which are substantially equal distances, the effect of the ancillary magnet assembly of compensating the boundary effect is even further enhanced, since such substantially equal distances also further spatial symmetry and periodicity.

[0066] According to an embodiment, which can be combined with other embodiments described herein, the ancillary magnet assembly is movable with respect to the plurality of cathode assemblies 110 and/or with respect to the plurality of anode elements 160. The ancillary magnet assembly may be movable with respect to an outermost cathode assembly and/or with respect to an outermost anode element. The ancillary magnet assembly may be movable in the first direction. The ancillary magnet assembly may be movable for adjusting a distance from the ancillary magnet assembly to the outermost anode element and/or for adjusting a distance from the ancillary magnet assembly to the outermost cathode assembly. With such adjustable distances, a flexible system is provided which allows selecting an optimal position of the ancillary magnet assembly for compensating the boundary effect as described herein.

[0067] According to an embodiment, which can be combined with other embodiments described herein, the plurality of cathode elements and the plurality of anode elements are alternately arranged. For example, Fig. 4 shows an alternate arrangement of the cathode assemblies 112, 416, 418 and 114 with respect to the anode elements 162, 464, 466, 468 and 164, respectively. An alternate arrangement may include an arrangement wherein a single anode element is provided in each region between two adjacent cathode assemblies. [0068] According to an embodiment, which can be combined with other embodiments described herein, the plurality of cathode assemblies 110 includes a second cathode assembly, e.g. cathode assembly 114 shown in Fig. 1 or cathode assembly 416 shown in Fig. 4. The second cathode assembly and the outermost cathode assembly may be adjacent cathode assemblies of the plurality of cathode assemblies.

[0069] According to an embodiment, which can be combined with other embodiments described herein, the plurality of anode elements 160 includes a second anode element, e.g. anode element 166 shown in Fig. 1 or anode element 464 shown in Fig. 4. The second anode element and the outermost anode element may be adjacent anode elements of the plurality of anode elements.

[0070] Two cathode assemblies may be considered "adjacent" if no further cathode assembly is provided between them. Similarly, two anode elements may be considered "adjacent" if no further cathode assembly is provided between them. This definition of adjacency does not preclude that, between two adjacent cathode assemblies, another component which is not a cathode assembly may be provided. For example, as shown in the figures, an anode element may be provided between two adjacent cathode assemblies. Similarly, between two adjacent anode elements a component which is not an anode element may be provided, e.g. a cathode assembly provided between two adjacent anode elements.

[0071] According to an embodiment, which can be combined with other embodiments described herein, the second cathode assembly, the second anode assembly, the outermost cathode assembly, the outermost anode element and the ancillary magnet assembly may be arranged in this order, particularly along the first direction.

[0072] According to an embodiment, which can be combined with other embodiments described herein, a magnet orientation of the ancillary magnet assembly may be parallel or substantially parallel to a magnet orientation of the magnet assembly of the outermost cathode assembly. The magnet orientation of a magnet assembly may correspond to a direction in which one or more poles extend outward of a body of the magnet assembly.

[0073] The magnet orientations of each magnet assembly of the plurality of cathode assemblies may be parallel or substantially parallel to each other. Substantially parallel magnet orientations may include magnet orientations at an angle of up to 15 , particularly 10%. [0074] Having substantially parallel magnet orientations provides for a further increased symmetry, e.g. periodicity, of the cathode arrangement. By aligning the magnet orientation of the ancillary magnet assembly with that of the magnet assembly in the outermost cathode assembly, the symmetry and periodicity of the magnetic field can be extended to the end of the system, thereby further reducing the boundary effect.

[0075] The magnet assemblies in each of the cathode assemblies of the plurality of cathode assemblies 110 may have a same or similar design and same or similar magnetic properties.

[0076] According to an embodiment, which can be combined with other embodiments described herein, the plurality of cathode assemblies 110 and/or the plurality of anode elements 160 are arranged according to a one-dimensional arrangement. A one-dimensional arrangement may include an arrangement according to a straight line as shown in Fig. 4, an arrangement according to an arc 610 as shown in Fig. 6, or an arrangement as shown in Fig. 7 including inner cathode assemblies arranged according to a straight line and the outermost cathode assemblies arranged at an off-set position with respect to the line.

[0077] According to an embodiment, which can be combined with other embodiments described herein, the sputter deposition apparatus includes a further ancillary magnet assembly. The plurality of cathode assemblies may include a further outermost cathode assembly. The plurality of anode elements may include a further outermost anode element. For example, Figs. 1 and 4 show a further ancillary magnet assembly 174, cathode assembly 114 as further outermost cathode assembly and anode element 164 as further outermost anode element.

[0078] The further outermost cathode assembly, the further outermost anode element and the further ancillary magnet assembly may be arranged in this order, particularly along the first direction. The further ancillary magnet assembly is configured for providing a magnetic field to compensate a boundary effect at a further outer region of the plasma, e.g. further outer region 194.

[0079] According to an embodiment, which can be combined with other embodiments described herein, the ancillary magnet assembly 172 and the further ancillary magnet assembly 174 are arranged on opposite ends of the plurality of cathode assemblies 110.

[0080] The properties, features and examples discussed in relation to the ancillary magnet assembly 172, the outermost cathode assembly 112, the outermost anode assembly 162 and the outer region 192 of the plasma apply in a corresponding manner to the further ancillary magnet assembly 174, the further outermost cathode assembly 114, the further outermost anode assembly 164 and the further outer region 194 of the plasma. By way of example, similar to the ancillary magnet assembly 172, the further ancillary magnet assembly 174 may be a stand-alone magnet assembly not included in any cathode assembly or may alternatively be included in a further dummy cathode assembly, e.g. cathode assembly 304.

[0081] According to an embodiment, which can be combined with other embodiments described herein, the sputter deposition apparatus includes a vacuum chamber, e.g. vacuum chamber 350 shown in Fig. 3. The plurality of cathode assemblies 110, the plurality of anode elements 160, the ancillary magnet assembly 172 and/or the further ancillary magnet assembly 174 may be arranged in the vacuum chamber 350.

[0082] Figs. 8a-b shows a top view and a cross- sectional side view, respectively, of a magnet assembly 800 according to embodiments described herein. Magnet assembly 800 may be a magnet assembly included in a cathode assembly of the plurality of cathode assemblies 110, i.e. a magnet assembly used in the deposition array. Alternatively, magnet assembly 800 may be an ancillary magnet assembly. For example, magnet assembly 800 may be an ancillary magnet assembly included in a dummy cathode assembly according to embodiments described herein.

[0083] Magnet assembly 800 has an inner pole 820 and outer pole 810. Magnet assembly 800 may be or include a magnet yoke. The cross-sectional side view of magnet assembly 800 as shown in Fig. 8b has the shape of a fork, wherein the prongs of the fork represent the inner and outer poles. The inner and outer poles may face an inner surface of the rotatable target in which the magnet assembly 800 is arranged. Inner pole 820 and/or outer pole 810 may be formed of a plurality of permanent magnets.

[0084] Fig. 8c shows a side view of a magnet assembly 870. The magnet assembly 870 may correspond to a portion of magnet assembly 800, e.g. to outer pole 810 or a portion thereof. The magnet assembly 870 may be an ancillary magnet assembly 870 according to embodiments described herein. For example, magnet assembly 870 may be a stand-alone ancillary magnet assembly.

[0085] According to an embodiment, which can be combined with other embodiments described herein, a magnet assembly, e.g. a magnet assembly included in one of the plurality of cathode assemblies 110, may include a magnet pole. A magnet assembly may include an inner magnet pole and/or at least one outer magnet pole.

[0086] According to an embodiment, which can be combined with other embodiments described herein, an ancillary magnet assembly includes a permanent magnet or a plurality of permanent magnets. An ancillary magnet assembly may be of a same type as a magnet assembly used in a cathode assembly of the deposition array. As compared to a magnet assembly used in an cathode assembly of the deposition array, the design of an ancillary magnet assembly may be adapted for optimizing the effect provided by the ancillary magnet assembly, namely to compensate, reduce or avoid boundary effects at the outer regions of the plasma.

[0087] According to a further embodiment, a method of performing a sputter deposition process is provided. The sputter deposition process may be a magnetron sputtering process.

[0088] According to embodiments, which can be combined with other embodiments described herein, a deposition process is a static deposition process. The distinction between static deposition and dynamic deposition is the following, and applies particularly for large area substrate processing, such as processing of vertically oriented large area substrates. A dynamic sputtering is an inline process where the substrate moves continuously or quasi- continuously adjacent to the deposition source. Dynamic sputtering has the advantage that the sputtering process can be stabilized prior to the substrates moving into a deposition area, and then held constant as substrates pass by the deposition source. Yet, a dynamic deposition can have disadvantages, e.g. with respect to particle generation. This might particularly apply for TFT backplane deposition. It should be noted that the term static deposition process, which is different as compared to dynamic deposition processes, does not exclude every movement of the substrate as would be appreciated by a skilled person. A static deposition process can include, for example, a static substrate position during deposition, an oscillating substrate position during deposition, an average substrate position that is essentially constant during deposition, a dithering substrate position during deposition, a wobbling substrate position during deposition, or a combination thereof. Accordingly, a static deposition process can be understood as a deposition process with a static position, a deposition process with an essentially static position, or a deposition process with a partially static position of the substrate. Thereby, a static deposition process, as described herein, can be clearly distinguished from a dynamic deposition process without the necessity that the substrate position for the static deposition process is fully without any movement of the substrate or of the cathode assemblies during deposition.

[0089] The method includes providing a plasma. The method further includes sputtering target material with a plurality of cathode assemblies. The method further includes influencing the plasma with a plurality of magnet assemblies arranged in the plurality of cathode assemblies. The method further includes influencing the plasma with a plurality of anode elements. The method further includes providing an ancillary magnetic field at an outer region of the plasma to compensate a boundary effect.

[0090] Embodiments of the method may be performed by a sputter deposition apparatus according to embodiments described herein. In particular, the ancillary magnetic field may be provided by an ancillary magnet assembly according to embodiments described herein.

[0091] According to an embodiment, which can be combined with other embodiments described herein, the method may include providing a process gas. The process gas may be provided in a vacuum chamber. The ancillary magnet assembly may be in contact with the process gas. For example, ancillary magnet assembly 172 shown in Fig. 1 may be in contact with a processing gas during a sputter deposition process.

[0092] According to an embodiment, which can be combined with other embodiments described herein, the ancillary magnetic field is provided by an ancillary magnet assembly of a dummy cathode assembly. According to embodiments, which can be combined with other embodiments described herein, no target material for coating the substrate is sputtered by the dummy cathode assembly while the ancillary magnetic field is provided by the ancillary magnet assembly.

[0093] According to an embodiment, which can be combined with other embodiments described herein, the target material is sputtered towards or on a substrate, particularly a large area substrate.

[0094] According to a further embodiment, a method of performing a sputter deposition process is provided. The method includes: providing a plasma; sputtering target material with a plurality of cathode assemblies forming a deposition array; and providing a magnetic field to influence an outer region of the plasma, wherein the magnetic field is provided by an ancillary magnet assembly outside of the deposition array. Embodiments of the method may be performed by a sputter deposition apparatus according to embodiments described herein. [0095] According to embodiments, which can be combined with other embodiments described herein, the ancillary magnet assembly is arranged within a dummy cathode assembly.

[0096] According to embodiments, which can be combined with other embodiments described herein, the cathode assembly outside of the deposition array is a dummy cathode assembly according to embodiments described herein.

[0097] According to embodiments, which can be combined with other embodiments described herein, the method may include influencing the plasma with a plurality of magnet assemblies arranged in the plurality of cathode assemblies.

[0098] According to embodiments, which can be combined with other embodiments described herein, the method may include influencing the plasma with a plurality of anode elements.

[0099] According to embodiments, which can be combined with other embodiments described herein, a substrate is a large area substrate.

[00100] The term "substrate" as used herein embraces both inflexible substrates, e.g., a glass substrate, a wafer, slices of transparent crystal such as sapphire or the like, or a glass plate, and flexible substrates, such as a web or a foil. According to some embodiments, which can be combined with other embodiments described herein, embodiments described herein can be utilized for Display PVD, i.e. sputter deposition on large area substrates for the display market. According to some embodiments, large area substrates or respective carriers, wherein the carriers may carry one substrate or a plurality of substrates, may have a size of at least 0.67 m². The size may be from about 0.67m (0.73x0.92m - Gen 4.5) to about 8 m², more specifically from about 2 m² to about 9 m² or even up to 12 m². The substrates or carriers, for which the structures, apparatuses, such as cathode assemblies, and methods according to embodiments described herein are provided, can be large area substrates as described herein. For instance, a large area substrate or carrier can be GEN 4.5, which corresponds to about 0.67 m² substrates (0.73x0.92m), GEN 5, which corresponds to about 1.4 m² substrates (1.1 m x 1.3 m), GEN 7.5, which corresponds to about 4.29 m² substrates (1.95 m x 2.2 m), GEN 8.5, which corresponds to about 5.7m² substrates (2.2 m x 2.5 m), or even GEN 10, which corresponds to about 8.7 m² substrates (2.85 m x 3.05 m). Even larger generations such as GEN 11 and GEN 12 and corresponding substrate areas can similarly be implemented. [00101] According to some embodiments, which can be combined with other embodiments described herein, target material can be selected from the group including or consisting of: aluminum, silicon, tantalum, molybdenum, niobium, titanium, copper and oxides, nitrides, oxi-nitrides and alloys thereof. Particularly, the target material can be selected from the group including or consisting of aluminum, copper and silicon. Reactive sputter processes can provide deposited oxides of these target materials. Sputter materials also include ITO (Indium-Tin-Oxide), IZO (Indium-Zinc-Oxide), IGZO (Indium-Gallium-Zinc-Oxide), AZO (Aluminum-doped Zinc-Oxide). These materials may be sputtered in a partly reactive manner. Nitrides or oxi-nitrides might be deposited as well. Process gases for sputtering target materials, that may be used in connection with embodiments described herein, can include inert gases such as argon and/or reactive gases such as oxygen, nitrogen, hydrogen and ammonia (NH3), Ozone (03), activated gases or the like.

Claims

CLAIMS:

1. A sputter deposition apparatus (100), comprising: a plurality of cathode assemblies (110) configured for sputtering target material in a sputter deposition process, wherein each of the plurality of cathode assemblies includes a rotatable target and a magnet assembly arranged in the rotatable target, wherein the plurality of cathode assemblies includes an outermost cathode assembly (112); a plurality of anode elements (160) configured for influencing a plasma (190) generated in the sputter deposition process, wherein the plurality of anode elements includes an outermost anode element (162); and an ancillary magnet assembly (172), wherein the outermost cathode assembly, the outermost anode element and the ancillary magnet assembly are arranged in this order, wherein the ancillary magnet assembly is configured for providing a magnetic field to compensate a boundary effect at an outer region (192) of the plasma.

2. The sputter deposition apparatus according to claim 1, wherein the ancillary magnet assembly is not arranged in a cathode assembly.

3. The sputter deposition apparatus according to claim 1, wherein the ancillary magnet assembly is arranged in a dummy cathode assembly (302).

4. The sputter deposition apparatus according to any of claims 1 to 3, wherein the ancillary magnet assembly is movable with respect to the plurality of cathode assemblies and/or with respect to the plurality of anode elements.

5. The sputter deposition apparatus according to any of claims 1 to 3, wherein a distance (482) from the ancillary magnet assembly to the outermost anode element and/or a distance (484) from the outermost anode element to the magnet assembly of the outermost cathode assembly may be from 30% to 70% of a distance from the ancillary magnet assembly to the magnet assembly of the outermost cathode assembly.

6. The sputter deposition apparatus according to any of claims 1 to 5, wherein the plurality of cathode elements and the plurality of anode elements are alternately arranged.

7. The sputter deposition apparatus according to any of claims 1 to 6, wherein the plurality of cathode assemblies includes a second cathode assembly (114, 416) and the plurality of anode elements includes a second anode element (166, 464), wherein the second cathode assembly and the outermost cathode assembly are adjacent cathode assemblies of the plurality of cathode assemblies, and the second anode element and the outermost anode element are adjacent anode elements of the plurality of anode elements, wherein the second cathode assembly, the second anode assembly, the outermost cathode assembly, the outermost anode element and the ancillary magnet assembly are arranged in this order.

8. The sputter deposition apparatus according to any of claims 1 to 7, wherein the plurality of anode elements include a plurality of anode bars.

9. The sputter deposition apparatus according to any of claims 1 to 8, wherein a magnet orientation of the ancillary magnet assembly is substantially parallel to a magnet orientation of the magnet assembly of the outermost cathode assembly.

10. The sputter deposition apparatus according to any of claims 1 to 9, further comprising: a further ancillary magnet assembly (174), wherein the plurality of cathode assemblies includes a further outermost cathode assembly (114), the plurality of anode elements includes a further outermost anode element (164), wherein the further outermost cathode assembly, the further outermost anode element and the further ancillary magnet assembly are arranged in this order, wherein the further ancillary magnet assembly is configured for providing a magnetic field to compensate a boundary effect at a further outer region (194) of the plasma.

11. The sputter deposition apparatus according to any of the preceding claims, wherein the ancillary magnet assembly and the further ancillary magnet assembly are arranged on opposite ends of the plurality of cathode assemblies.

12. A method of performing a sputter deposition process, comprising: providing a plasma (190); sputtering target material with a plurality of cathode assemblies (110); influencing the plasma with a plurality of magnet assemblies arranged in the plurality of cathode assemblies; influencing the plasma with a plurality of anode elements (160); and providing an ancillary magnetic field at an outer region (192) of the plasma to compensate a boundary effect.

13. The method of claim 12, further comprising: providing a process gas, wherein the ancillary magnetic field is provided by an ancillary magnet assembly (172) wherein the ancillary magnet assembly is in contact with the process gas.

14. The method of claim 12, wherein the magnetic field is provided by an ancillary magnet assembly of a dummy cathode assembly (302).

15. A method of performing a sputter deposition process, comprising: providing a plasma (190); sputtering target material with a plurality of cathode assemblies (110) forming a deposition array (310); and providing a magnetic field to influence an outer region (192) of the plasma, wherein the magnetic field is provided by an ancillary magnet assembly (172) outside of the deposition array.

16. The method of claim 15, wherein the ancillary magnet assembly is arranged within a dummy cathode assembly.