Magnet arrangement for a target backing tube, target backing tube including the same, cylindrical target assembly and sputtering system

The disclosure relates to a magnet arrangement for a sputtering system, wherein the magnet arrangement is adapted for a rotatable target of a sputtering system and includes: a first magnet element extending along a first axis; a second magnet element being disposed around the first magnet element symmetrically to a first plane; wherein the second magnet element includes at least one magnet section intersecting the first plane; and wherein a magnetic axis of the at least one magnet section is inclined with respect to a second plane being orthogonal to the first axis. Further, the disclosure relates to a target backing tube for a rotatable target of a sputtering system, a cylindrical rotatable target for a sputtering system, and a sputtering system.

The present disclosure relates to a magnet arrangement for rotatable target. More specifically, the present disclosure relates to a magnet arrangement for a rotatable target of a sputtering system. Further, the present disclosure relates to a target backing tube for a rotatable target of a sputtering system. Further, the present disclosure relates to a rotatable target cylinder of a sputtering system. Additionally, the present disclosure relates to a cylindrical target assembly including a target backing tube. Further, the present disclosure relates to a sputtering system including a vacuum chamber and at least one target backing tube.

BACKGROUND

In many applications, it is necessary to deposit thin layers on a substrate. The term “substrate” as used herein shall embrace both inflexible substrates, e.g., a wafer or a glass plate, and flexible substrates, for example, webs and foils. Typical techniques for depositing layers are evaporating, sputtering, and chemical vapor deposition.

Representative examples include (but are not limited to) applications involving: semiconductor and dielectric materials and devices, silicon-based wafers, flat panel displays (such as TFTs), masks and filters, energy conversion and storage (such as photovoltaic cells, fuel cells, and batteries), solid-state lighting (such as LEDs and OLEDs), magnetic and optical storage, micro-electro-mechanical systems (MEMS) and nano-electro-mechanical systems (NEMS), micro-optic and opto-elecro-mechanical systems (NEMS), micro-optic and optoelectronic devices, transparent substrates, architectural and automotive glasses, metallization systems for metal and polymer foils and packaging, and micro- and nano-molding.

In an evaporation process, the material to be deposited is heated so that it evaporates and condenses on the substrate. Sputtering is a vacuum coating process used to deposit thin films of various materials onto the surface of a substrate. For example, sputtering can be used to deposit a metal layer, such as a thin layer of aluminum, or ceramics. During the sputtering process, the coating material is transported from a target to the substrate to be coated by bombarding the surface of the target with ions of an inert gas which have been accelerated by a high voltage. When the gas ions hit the outer surface of the target, their momentum is transferred to the atoms of the material so that some of them can gain sufficient energy to overcome their bonding energy in order to escape from the target surface and to deposit on the substrate. Thereon, they form a film of the desired material. The thickness of the deposited film is, inter alia, dependent on the duration of the substrate's exposure to the sputtering process.

Typically, sputtering systems are used to coat substrates, for example, window paints, semiconductor devices, displays, and the like. Typically, plasma is formed in a vacuum chamber, in which the sputtering target is disposed. For example, rotating sputtering targets may be used. Typically, the rotating sputtering targets have a cylindrical form and rotate about their longitudinal axis. The sputtering targets are disposed on a backing tube in which magnetrons may be arranged. The magnetrons may be driven by a direct current or an alternating current. The magnetrons are used to create the plasma in the vacuum chamber.

Typically, a magnet arrangement or rotary cathode is disposed in the backing tube. The magnet arrangement includes an inner magnet element and an outer magnet element disposed around the inner magnet element. In operation of the sputtering system, the plasma is confined in a volume, for example, above a target element if the substrate to be coated is located above the target element, between the inner magnet element and the outer magnet element, where the magnetic field is mainly parallel to the target surface. Typically, this region may be called a “race track”, as the plasma forms a closed loop with two straight parts along the long side of the magnet arrangement and a curve at both ends of the magnet arrangement. A typical arrangement of the magnet elements leads to an unbalanced situation at the ends, in particular in longitudinal direction, of the magnet arrangement, also called race track curves or plasma turn arounds. As there is more magnetic mass at the outer position, the plasma is shifted or displaced towards the inner magnet in dependence of the height above the cathode surface. This means that the plasma turn around has no stable position regarding the height above the magnet elements. Thicker targets will have a shorter race track and, therefore, a larger zone with redeposition at the end in longitudinal direction of the targets.

SUMMARY

In light of the above, a magnet arrangement, a target backing tube, a cylindrical target assembly, a cylindrical rotatable target, and a sputtering system are provided.

According to one aspect, a magnet arrangement for a sputtering system is provided, wherein the magnet arrangement is adapted for a target backing tube for a rotatable target of a sputtering system and includes: a first magnet element extending along a first axis, a second magnet element being disposed around the first magnet element symmetrically to a first plane, wherein the second magnet element includes at least one magnet section intersecting the first plane, and wherein a magnetic axis of the at least one magnet section is inclined with respect to a second plane being orthogonal to the first axis.

According to a further aspect, a target backing tube for a rotatable target of a sputtering system is provided, wherein the target backing tube has a longitudinal axis, wherein the target backing tube contains a magnet arrangement including, a first magnet element extending along a first axis; a second magnet element being disposed around the first magnet element symmetrically to a first plane; wherein the second magnet element includes at least one magnet section intersecting the first plane; and wherein a magnetic axis of the at least one magnet section is inclined with respect to a second plane being orthogonal to the first axis, wherein the first axis is parallel to the longitudinal axis of the backing tube.

According to another aspect, a cylindrical target assembly is provided including a target backing tube, wherein the target backing tube has a longitudinal axis, wherein the target backing tube contains a magnet arrangement including, a first magnet element extending along a first axis; a second magnet element being disposed around the first magnet element symmetrically to a first plane; wherein the second magnet element includes at least one magnet section intersecting the first plane; and wherein a magnetic axis of the at least one magnet section is inclined with respect to a second plane being orthogonal to the first axis, wherein the first axis is parallel to the longitudinal axis of the backing tube, and the cylindrical target assembly further including at least one target cylinder being disposed around the target backing tube.

According to a further aspect, a cylindrical rotatable target for a sputtering system, wherein the cylindrical rotatable target has a longitudinal axis, wherein the cylindrical rotatable target contains a magnet arrangement including a first magnet element extending along a first axis; a second magnet element being disposed around the first magnet element symmetrically to a first plane; wherein the second magnet element includes at least one magnet section intersecting the first plane; and wherein a magnetic axis of the at least one magnet section is inclined with respect to a second plane being orthogonal to the first axis, wherein the first axis is parallel to the longitudinal axis of the backing tube.

According to another aspect, a sputtering system including a vacuum chamber and at least one cylindrical rotatable target including has a longitudinal axis, wherein the cylindrical rotatable target contains a magnet arrangement including a first magnet element extending along a first axis; a second magnet element being disposed around the first magnet element symmetrically to a first plane; wherein the second magnet element includes at least one magnet section intersecting the first plane; and wherein a magnetic axis of the at least one magnet section is inclined with respect to a second plane being orthogonal to the first axis, wherein the first axis is parallel to the longitudinal axis of the backing tube, wherein the cylindrical rotatable target is disposed in the vacuum chamber.

Further aspects, advantages, and features of the present invention are apparent from the claims, the description, and the accompanying drawings.

DETAILED DESCRIPTION

Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet further embodiments. It is intended that the present disclosure includes such modifications and variations.

Referring to the drawings, where like or similar elements are designated with identical reference numbers throughout the different figures,FIG. 1shows a schematic cross-section of a sputtering system100having a vacuum chamber110. The vacuum chamber has an inlet port112, which may be used to provide a sputtering gas into the vacuum chamber110, and may include an outlet (pumping) port (not shown). The vacuum chamber is limited by vacuum chamber walls114. In typical embodiment, the sputtering system100includes two rotating cylindrical target assemblies120a,120b. The cross-section ofFIG. 1is in a plane orthogonal to the rotating axis of the cylindrical target assemblies.

In other embodiments, which may be combined with other embodiments disclosed herein, the sputtering system may include one, three, four or more cylindrical target assemblies. In a typical embodiment, which may be combined with other embodiments disclosed herein, the rotating cylindrical target assemblies120a,120bare driven by a drive assembly not shown inFIG. 1. The rotating cylindrical target assemblies120a,120beach include a backing tube122a,122bin which magnet arrangements124a,124bare disposed. Further, cylindrical target elements126a,126bare disposed around the backing tube122a,122b. For example, the cylindrical target elements126a,126bmay be not bonded to the respective backing tube122a,122b. For example, the cylindrical target elements126a,126bmay be exchanged after they have been used up. InFIG. 1, horizontal rotating cylindrical target assemblies are shown. In some embodiments, which may be combined with other embodiments disclosed herein, vertical cylindrical target assemblies may be used. In some embodiments, which may be combined with other embodiments disclosed herein, the magnet arrangement124a,124bmay be disposed in cylindrical target elements, in particular without backing tube. Then, the cylindrical target elements are connected to a driving mechanism for rotating the cylindrical target elements around their longitudinal axis.

Further, in the vacuum chamber110, a substrate130is disposed below the cylindrical target assemblies120a,120b. The substrate130may be arranged, in a typical embodiment, which may be combined with other embodiments disclosed herein, on a substrate support132. In operation, a plasma is formed inside the vacuum chamber110between the cylindrical target assembly and the substrate by exciting a sputtering gas. In a typical embodiment, the sputtering gas includes argon. In further embodiments, the vacuum chamber may include substrate drive systems for driving a substrate to be coated130in or out of the vacuum chamber110. For that reason, the vacuum chamber may include a vacuum lock chamber disposed in a wall of the vacuum chamber110. In an embodiment, which may be combined with other embodiments disclosed herein, the rotating axis of the cylindrical target assemblies120a,120bare substantially parallel.

Typically, the magnet arrangements124a,124bhave an elongated structure extending parallel to the longitudinal extension of the backing tube122a,122bin which they are disposed, for example, parallel to the longitudinal or rotating axis of the backing tubes122a,122b. For example, each magnet arrangement has a symmetry plane A. For example, the rotating axis of the backing tubes122a,122b, lies on the symmetry plane. Typically, the magnet arrangements124a,124bhave substantially the same length as the backing tubes. For example, the magnet arrangement may have a length of about 80% or more, for example, 90% or more, of the longitudinal extension of a portion of the backing tube and/or the targets elements in the vacuum chamber110.

FIG. 2shows a cross section of an embodiment of a magnet arrangement200for a target backing tube. Typically, magnetrons for large area coating systems may have in embodiments a magnet arrangement as shown inFIGS. 2 to 13. The cross section is in a plane orthogonal to the symmetry plane and to a longitudinal axis of a first magnet element210. The first magnet element210extends along the longitudinal or first axis of the magnet arrangement200. Typically, the cross-section ofFIG. 2corresponds to the cross-section ofFIG. 1. The magnet arrangement is symmetric to a symmetry plane A. The symmetry plane A may be also be denominated as first plane A. Typically, when mounted in the backing tube122a,122b, the rotating axis of the backing tube122a,122blies on the symmetry plane A. The magnet arrangement200may include in one embodiment, which may be combined with other embodiments disclosed herein, a basic body202having a portion with a semi-cylindrical surface208. In an embodiment, the basic body202is arranged in the backing tube of a vacuum chamber, such that the semi-cylindrical surface208is adapted to face the substrate to be coated130.

In an embodiment, which may be combined with other embodiments herein, a first magnet element210and a second magnet element220are disposed on the semi-cylindrical surface208. The first magnet element210extends along a first axis X which lies on the symmetry plane. In a typical embodiment, the first axis X is parallel to the rotating axis of the cylindrical target assembly shown inFIG. 1. The second magnet element220is disposed around the first magnet element210. For example, the second magnet element has two magnet portions224,225, each extending in parallel to the first axis X.

The first and second magnet elements210,220typically include a plurality of magnets which are arranged one after the other to form the first and second magnet elements210,220. In other embodiments, the first and second magnet elements210,220may be formed by a single magnet.

Each magnet element has at each location a respective magnetic axis212,222. For the sake of convenience, the magnetic axes are shown in the respective magnet elements210,220from the south pole to the north pole. Typically, the magnetic axes according to embodiments of the disclosure have a direction. Thus, the poles of the magnet elements210,220facing the backing tube and the target elements are alternatingly disposed in a cross-section orthogonal to the first axis X. For example the north pole of the second magnet elements faces the target element and the substrate to be coated and the south pole of the first magnet element faces the target material and the substrate to be coated. Typically, the magnetic axis of second magnet element of portions224,225extending in parallel to the first axis X is disposed is inclined with respect to the first plane A. Typically, the magnet axis of the first magnet element is arranged parallel to a normal of a surface to be coated of the substrate to be coated.

FIG. 3shows a further embodiment of a magnet arrangement in a cross section orthogonal to the first plane A of the magnet arrangement and the orthogonal to the first axis X corresponding to the longitudinal axis of a first magnet element310. The same reference numbers increased by 100 refer to the same features as inFIG. 2. The magnet arrangement300includes two magnet elements310,320, namely first magnet element310and a second magnet element320disposed on a basic body302. The basic body has a substantially flat surface308to be directed to a substrate to be coated. In a typical embodiment, said surface308is parallel to a surface to be coated of the substrate to be coated. The magnet elements are arranged on the surface308of the basic body302, such that in the cross section orthogonal to the first axis shown inFIG. 3the magnetic axis312of the first magnet element310is anti parallel to the magnetic axis322of the second magnet element320.

FIGS. 4,5, and6are used to describe the arrangement of the plasma generated by magnet elements of a balanced and unbalanced magnet arrangements. In particularFIGS. 4,5, and6shows a cross-section orthogonal to the first axis X along which a first magnet element extends.

FIG. 4shows a magnet arrangement including two magnets similar to the magnet assembly ofFIG. 3. The same features are designated with the same reference numbers increased by 100. Further, a target element480and a substrate460to be coated are shown. For the sake of simplicity, inFIGS. 4,5, and6the target element is shown having a substantial planar surface. However, the target elements used in rotating target assemblies are normally substantially cylindrical.

Further, inFIG. 4, the magnetic field between the first magnet element and the second magnet element is shown. Typically, in operation of a sputtering system, a plasma is generated between the target480and the substrate460to be coated. The plasma forms, when looking onto the target480in direction446, a closed loop (see alsoFIGS. 8 and 9). Thus, inFIG. 4, only the cross-section of the plasma440a,440bis shown. For the sake of simplicity, the plasma is shown inFIG. 4with a rectangular cross section. In reality, the plasma does not have such an ideal rectangular form. The plasma has a reference curve444a,444bextending, in the cross-sectional view ofFIG. 4, along positions, where the plasma has the highest density

Typically, the plasma440a,440bis located between the magnet arrangement400and the substrate to be coated460.

As it can be seen, the field lines of the magnet field of the first and second magnet elements410,420have a tangent442a,442b,442cwhich are substantially parallel to the surface of the target480facing the substrate460to be coated. Further, the points of the magnet fields which have the substantially parallel tangent442a,442b,442cto the surface of the target element480are disposed on a straight line. At these positions, where the magnetic field lines have a substantially parallel tangent, the plasma has the highest density. In other words, plasma has the highest density extending along the straight lines ore reference curves444a,444b.

In case of balanced magnetic elements, the reference curve at which the plasma has the highest density corresponds to the straight line444a,444bbeing substantially orthogonal to the surface of the target element480facing the substrate460to be coated as shown inFIG. 4. In case of a balanced cylindrical target, the reference curves444a,444bare straight lines and inclined with respect to each other (not shown for the sake of simplicity), wherein each reference curve444a,444bbeing substantially orthogonal to a respective tangent of the surface of the target element, where a portion of the plasma closest to the target element is generated.

If the plasma stays focused between the inner and the outer magnet elements on the same position perpendicular to the target surface, the magnetron is called balanced.

If the outer magnet element is much stronger than the inner magnet element, the plasma will be focused more towards the inner magnets. If the inner magnet arrangement is stronger than the outer magnet element, the plasma will be focused more towards the outer regions. These two situations are typically referred to as unbalanced magnetrons. Magnetron and magnet assembly are used in this disclosure exchangeable.

FIGS. 5 and 6show magnet elements500and600which respectively have an unbalanced magnet arrangement. The same features are designated with the same reference numbers as inFIG. 4increased by 100 inFIG. 5and 200 inFIG. 6.

InFIG. 5, the first magnet element510has a higher magnetic mass than the second magnetic element420. Thus, the positions, where the magnetic field has a substantially parallel tangent to the target element are shifted with respect to each other, such that a reference curve connecting the points of the substantially parallel tangent of the magnetic field to the surface of the target element580facing the substrate to be coated has an angle to the surface of the target element580different to 90 degrees. In other words, the reference curves544a,544b, where the plasma has the highest density moves outwardly, when the distance to the target is increasing.

In other words, in case of a cylindrical target, the reference curve is not disposed on a straight line extending in radial direction through the axis of the target element and a surface portion of the target element, where a portion of the generated plasma being closest to the target element.

The reference curves544a,544b,644a,644bare shown inFIGS. 5 and 6as a straight line. However, the reference curves544a,544b,644a,644b, where the plasma has the highest density may have also a curved or bent shape, in particular in case of unbalanced magnet arrangements. The straight line544a,544bconnecting the points of the substantially parallel tangents of the magnetic field corresponds to points of the plasma540a,540b, where it has the highest density. In particular, reference curves544a,544bof the plasma540a,540bare tilted or bent with respect to the first plane A outwardly in case of planar target element or with respect to a normal of a portion of the surface of the target element, where a portion of the generated plasma being closest to the target element, the portion of the surface facing a substrate to be coated, in case of a cylindrical target element.

FIG. 6shows an embodiment of a magnet arrangement including a second magnetic element620have higher magnetic mass than the first magnet element610. Thus, the plasma640a,640bin operation of the sputtering assembly has a reference curve644a,644b, where the plasma has its highest density, which is bent or tilted inwardly with respect to a normal of a portion of the surface of the target element, where a portion of the generated plasma being closest to the target element, the portion of the surface, the portion of the surface facing the substrate660to be coated, in case of a cylindrical target element or with respect to the first plane A, in case of a planar target element.

In case of an unbalanced magnet arrangement and, thus, a plasma having a reference curve644a,644btilted with respect to the target surface or a portion of the target element, where a portion of the generated plasma being closest to the target element, the position of the plasma with respect to the surface of the target elements580,680may depend on the thickness of the target element580,680. This may lead to an uneven deposition or an uneven usage of the target material.

FIG. 8shows a cross section along the first plane A and the first axis X of a conventional magnet arrangement700of a cylindrical target assembly.FIGS. 8 and 9show, respectively, a view onto the magnet arrangement ofFIG. 7, corresponding to the direction446ofFIG. 4, indicating the position of the plasma at a first distance I to the magnet arrangement700(FIG. 8) and a second distance II to the magnet arrangement700(FIG. 9), wherein the second distance II is greater than the first distance I. The same features are indicated with the same reference number as inFIG. 4increased by 300.

FIGS. 7,8and9show the plasma740,740a,740bgenerated by the magnet arrangement. Further a target element780is shown inFIG. 7. InFIG. 7, only the position of the plasma740a,740bis illustrated without the field lines of the magnetic field.FIGS. 8 and 9show that the plasma forms a ring. This is also called race track.

The magnet arrangement has a first end704and a second end706in direction of the first axis or longitudinal axis X of the magnet arrangement700. The second magnet element720includes two first magnet portions being arranged substantially parallel to the first magnet element710and two second magnet portions726,727connecting the two first magnet portions724,725of the magnet element. The first and second end704,706of the magnet arrangement may be also called turn around portions of the magnet arrangement or magnet assembly. The turn around portions of the magnet arrangement is unbalanced because the outer, second magnet element has much more magnetic mass in the turn around than the first, inner magnet element. In particular, the second magnet portions726,727of the second magnet element have a higher magnetic mass than an end of the first magnet element710in direction of the first axis X. Thus, in operation the reference curves744a,744bof the plasma, where it has its highest density, is tilted or curved in the first plane A with respect to the surface of the target element780. Thus, as illustrated in theFIGS. 9 and 10, in which a cross section of the plasma740is shown with different distance to the magnet assembly, in particular, the first distance I and the second distance II shown inFIG. 7. For example, the surface of a target element780directed to a substrate to be coated may be arranged at the first distance I and the second distance II.

InFIG. 8, the plasma740is shown on the surface of a thin target and, inFIG. 10, the plasma740is shown on the surface of a thick target. As it can be seen at the first end704and the second end706in longitudinal direction of the first magnet element710, the extension of the plasma740in direction of the first axis X is shorter on the surface of the thick target than of the thin target shown inFIG. 9. Thus, in case the substrate is used or worn during a deposition process, the substrate is not evenly used throughout the complete width of the rotatable target. Thus, a portion of the targets may be not used or may result in a more inhomogeneous deposition of the material of the target780.

InFIGS. 10 and 11, a magnet arrangement800is shown in which the same reference numbers are designated for the same features increased by 100 with respect to the embodiments shown inFIGS. 8,9and10.FIG. 10further shows a cross section of the magnet arrangement800in the symmetry plane A. InFIG. 12, a respective view onto the magnet element800from the side of the target element is shown. In a typical embodiment, the first and second magnet elements include a plurality of magnets each having substantially the same size. In other embodiments, the magnet assembly may be specifically fabricated for a first magnet element or a second magnet element.

The first magnet element810is arranged as in the magnet arrangement shown inFIGS. 8,9and10. The second magnet element820has a plurality of portions, namely first magnet portions824,825arranged substantially parallel to the first magnet element810and, respectively, a second magnet portion826,827at the ends804,806of the magnet arrangement in direction of the first axis X, which typically corresponds to the longitudinal axis of the first magnet element. The second magnet portions826,827of the second magnet element820are connecting the first magnet portions824,825of the second magnet element820. Further, the first magnet portions824,825are symmetrically arranged with respect to the first plane A. The second magnet portions826,827are disposed on the first plane and the first axis X. As it can be seen inFIG. 10, the second magnet portions826,827have a magnetic axis822which is tilted outwardly by an angle of 90° with respect to a second plane B orthogonal to the first axis X and/or with respect to the first magnet element. Further, the magnetic axis822are tilted by 90° outwardly with respect to the magnetic axis of the first magnet portions824,825of the second magnet element820. In other embodiments, the tilting angle of the magnetic axis822of the second magnet portion826,827of the second magnet element820lying on the first axis X may be greater than 45 degrees, in particular greater than 60 degrees, for example, greater than 90 degrees with respect to the second plane B orthogonal to the first axis and/or the magnetic axis of the first magnet portions824,825of the second magnet element820extending in parallel to the first magnet element. In any case, the angle with respect to the second plane B orthogonal to the first axis X and/or the magnetic axis of the second magnet element at the first magnet portions824,825is selected to provide a balanced magnet arrangement and the first end804and the second end806of the magnet arrangement in direction of the first axis X. In other embodiments not the complete second magnet portions have a tilted magnet axis with respect to the second plane B orthogonal to the first axis, but a section of the second magnet element820included in the second magnet portions826,827.

Thus, the magnet arrangement according toFIGS. 10 and 11is balanced at the first end and the second end804,806such that the reference curves844a,844bof the plasma, where it has its highest density, is in operation of the magnet arrangement800substantially normal to the surface of a target element880facing a substrate to be coated and/or orthogonal the first axis X in the first plane A. Thus, a balanced magnet arrangement is provided by tilting the second magnet portions826,827at the ends of the magnet arrangement804,806, in particular outwardly with respect to the magnetic axis of the second magnet element820at the first magnet portions824,825. The plasma stays in operation of the sputtering apparatus at the same position perpendicular to the target surface for different target thicknesses or different distances to the magnet arrangement. Typically, in rotating target assemblies the first plane traverses the rotating axis.

In typical embodiments, which may be combined with other embodiments disclosed herein, the same magnets may be used for the first magnet element and the second magnet element.

Embodiments disclose magnet arrangements for sputter magnetrons with tilted magnets at the plasma turn around positions. The advantage is that the plasma has the same race track curve positions for different target thicknesses. This is applicable for rotary magnetrons, as well as for planar magnetrons. A further advantage is that the plasma is located on the top of the end magnet and not between the end magnet and the inner magnet in a section in the symmetry plane. This brings the advantage that, for the same length of magnet assemblies, the plasma covers more target surface in case of a tilted end magnet or second magnet portions826,827, or a section of the second magnet element on the first axis.

For example, the magnetic axis of the magnet section being arranged on the symmetry plane at the first end804and the second end806of the magnet arrangement may have an inclination angle greater than about 45° and, particularly, greater than 60°, for example, greater than 80°, with respect to a plane being orthogonal to the longitudinal axis of the magnet arrangement.

FIG. 12andFIG. 13shows respectively different turn around portions or second magnet portions926,927,1026,1027of a magnet arrangement900inFIG. 12, and1000inFIG. 13. Each magnet arrangement900,1000includes a first magnet element910,1010extending along a first axis X lying on a symmetry plane A of the magnet arrangement900,1000. A second magnet element920,1020is arranged around the first magnet element910,1010. The same reference numbers are used as in the drawings ofFIGS. 10 and 11with respect to the same features increased by 100 inFIG. 12and 200 inFIG. 13.

InFIG. 12, the turn around portion or the second magnet portions926,927of the second magnet element920has a half circular or half oval shape in a view onto the magnet arrangement, i.e. in a direction orthogonal to the first axis in the first plane. The magnetic axis of the second magnet portions926,927of the second magnet element920are tilted as in the previous embodiment shown inFIGS. 11 and 12. In other embodiments only each second magnet portion926,927include a section, in particular lying on the first axis X and/or the first plane A, which has a magnetic axis being tilted with respect to the a plane being orthogonal to the first axis and/or to the magnetic axis of the first magnet portions924,925of the second magnet element920.

InFIG. 13, the second magnet portions1026,1027of the second magnet element1020include respectively a plurality of single magnets1028at the first and second end1004,1006of the magnet arrangement1000. For example, as shown inFIG. 13, the second magnet portions1026,1027are respectively composed of 5 single magnets1028. In other embodiments, the second magnet portions are composed of more than five single magnets1028, for example seven, nine or more single magnets.1028. In typical embodiments, the number of single magnets1028is uneven. Typically, to form the turn-around portion of the second magnet element820, the single magnets1028are arranged such that the second magnet portions1026,1027are substantially V-shaped in a view in a direction orthogonal to the first axis in the first plane.

In a typical embodiment, the outermost of the single magnets1028or the single magnets1028at the extremities in direction of the first axis X of the second magnet portion1026,1027is disposed on the first axis X. The magnetic axis of the outermost magnet1028is tilted with respect to a plane orthogonal to the first axis X to provide a balanced magnet arrangement at the first end1004and a second end1006of the magnet arrangement1000. In other embodiments, the magnetic axis of the other magnets of the second magnet portions1026,1027may be tilted with respect to the second plane B being orthogonal to the first axis and/or with respect to the magnetic axis of the first magnet portions1024,1025of the second magnet element1020. In an embodiment, the tilting of each single magnet1028may be different with respect to the second plane B orthogonal to the longitudinal axis X and/or the magnetic axis of the first magnet portions1024,1025of the second magnet elements1020.

In a typical embodiment, the normal of the surface of a substrate to be coated is parallel to the first plane A.

Typically, the second element may have in embodiments small interstices, however these interstices have a shape such that the plasma forms a continuous race track.

The first magnet element extending along a first axis has a longer extension in direction of the first axis than in a direction transversal to the first axis, for example orthogonal to the first axis. For example the extension in direction of the first axis may be more than 0.5 m, for example more than 2 m, in particular more than 3.5 m. Typically, the first axis is the longitudinal axis of the first magnet element.

Typically, the second magnet element forms a ring around the first magnet element. For example in a view onto the magnet element the second magnet element surrounds the first magnet element. For example the view onto the magnet element may be a view in direction of a straight line being orthogonal to the first axis and lying in the first plane.

Typically, the magnet arrangement is balanced, in particular at least at one of the ends of the first magnet element in direction of the first axis. According to embodiments disclosed herein, the zone of redeposition in direction of the first axis is substantially the same for target elements having a different thickness. Hence, the target material is better used during a sputtering process.

In an embodiment, the second magnet element has two first magnet portions extending in parallel to the first axis. In an embodiment, the straight line in which magnetic axis of these first magnet portions are disposed may be inclined with respect to the first plane. For example, the first and second magnet element may be arranged on a semi-circular or semi-oval surface.

In an embodiment, the magnetic axis of the magnet section has an inclination angle greater than about 45 degrees, in particular greater than 60 degrees, for example, greater than 80 degrees, with respect to the second plane.

According to a further embodiment, which may be combined with other embodiments disclosed herein, the magnetic axis of the magnet section is tilted away from the first magnet element, in particular to provide a substantially balanced magnet arrangement.

In a typical embodiment, the first axis lies in the first plane.

For example, in an embodiment, the magnetic axis of the magnet section has an inclination angle of greater than about 45 degrees, in particular greater than 60 degrees, for example greater than 80 degrees, with respect to the magnetic axis of a first magnet portion of the second magnet element being arranged or extending substantially in parallel to the first magnet element, in particular to the first axis. In particular the magnet axis of the magnet section is tilted in an outward direction, away from the first magnet portion of the second element being arranged or extending substantially in parallel to the first magnet element.

According to an embodiment, which may be combined with other embodiments disclosed herein, the magnet section extends symmetrically on both sides of the first plane.

For example, in an embodiment, the form of the magnet section selected of the group consisting of a substantially U-shape, a substantially V-shaped, a half-circle, an arc of a circle, and a bar.

In an embodiment, the magnet section corresponds to at least 30 percent, in particular, at least 50 percent, of the extension of the second magnet element in a direction orthogonal to the first axis and orthogonal to the magnetic axis of the first magnetic element, for example in a direction of a normal of the first plane.

For example, in an embodiment, which may be combined with other embodiments, the first magnet element has, in the direction of the first axis, a first end and a second end opposite to the first end; wherein the at least one magnet section connects the first magnet portions of the second magnet element extending in parallel to the first axis at the first end and/or the second end of the first magnet element.

In some embodiments, the first magnet element has, in the direction of the first axis, a first end and a second end opposite to the first end, the second magnet element includes first magnet portions extending in parallel to the first axis and second magnet portions connecting the first magnet portions at the first end and/or the second end, wherein the second magnet portions include the magnet sections.

In an embodiment, the second magnet element includes two magnet sections.

According to a further aspect, a target backing tube for a rotatable target of a sputtering system is provided, wherein the target backing tube has a longitudinal axis, wherein the target backing tube contains a magnet arrangement according to one of the embodiments disclosed herein, wherein the first axis is parallel to the longitudinal axis of the backing tube.

In a typical embodiment, the longitudinal extension, in particular in the direction of the first axis, of the target backing tube in a vacuum chamber into which the target backing tube is adapted to be disposed corresponds substantially to the longitudinal extension of the first and/or second magnet element.

For example, in an embodiment, at least one target cylinder is disposed around the target backing tube.

According to a further aspect, a cylindrical rotatable target for a sputtering system is provided, wherein the cylindrical rotatable target has a longitudinal axis, wherein the cylindrical rotatable target contains a magnet arrangement according to one of the preceding claims, wherein the first axis is parallel to the longitudinal axis of the backing tube.

According to a further aspect, a sputtering system is provided including a vacuum chamber and at least one cylindrical rotatable target according to an embodiment disclosed herein, wherein the cylindrical rotatable target is disposed in the vacuum chamber.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the described subject-matter, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, those skilled in the art will recognize that the spirit and scope of the claims allow for equally effective modifications. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope is defined by the claims, and may include such modifications and other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.