Copper-backed ceramic ring-segment target

Abstract

The invention relates to a target (1) comprising a target material and a supporting element connected thereto, characterized in that the target material is designed as an outer ring (3), wherein the outer ring (3) is divided in the circumferential direction into two or more segments (2), which consist of a brittle material with a plastic elongation at break at 20°C of less than or equal to 2%, wherein the supporting element is designed as an inner ring (4) and consists of copper or a copper alloy, and also relates to a method for producing such a target (1).

Description

[0001]Segmented ring target The present invention relates to a segmented ring target. The present invention further relates to a method for producing such a target. Targets for use in physical vapor deposition (PVD) processes are known in the art. These targets are used to deposit layers from the gas phase, such as arc evaporation or sputtering, also referred to below as sputtering. The present invention particularly relates to sputter targets as used in a PVD sputtering process for depositing layers onto a substrate material provided for this purpose. Such sputter targets always comprise the target material and, depending on the target material, optionally a support element, typically designed as a backing plate, which is connected to the support element if necessary via a bonding layer.Most sputtering targets are so-called planar targets, which can be circular or rectangular. However, these planar targets have the disadvantage that only about 30% to 40% of their material is effectively sputtered. To increase sputtering efficiency, tubular targets are increasingly being used. However, their production is technologically more difficult than that of planar targets. This is especially the case when the tubular sputtering targets are made of brittle materials or contain brittle materials. During use in a coating system, targets are exposed to mechanical and thermomechanical stresses that can lead to bending and / or tensile stresses.In particular, the industrially required process control with high power densities to accelerate the coating process through higher deposition rates requires very good cooling in order to reduce thermal load and the resulting mechanical stress or tensions that can lead to the fracture of targets made of brittle materials. The use of coolants, typically water at high pressure, requires the targets to be equipped with an internal support element, typically an inner tube as a coolant-carrying support structure, onto which the target material is applied. The pressure of the cooling water on the inside of the cooling tube can lead to its expansion, whereby the target material resting on it is mechanically stressed by elastic deformation and can be damaged. Such a support element can also serve as a heat sink, i.e.By applying a support element with a higher thermal conductivity than the coating material, the heat generated during the coating process can be dissipated more effectively. In such a case, the entire arrangement of target material and support element is referred to as a target. Such support elements / heat sinks can be applied to coating materials with low toughness (brittle material behavior) using various processes, such as soft soldering or brazing with known solders. However, it is a particular technical challenge to join the target material to the support element / tube in the case of a tubular target, since the target material cannot simply be manufactured as a tube using the powder metallurgy route, as is usual for brittle materials. In typical industrial designs of tubular targets, these are made of ductile metals orMetal alloys are usually monolithic and therefore designed without a support element, or are provided with corrosion protection layers such as electroplated nickel layers to protect against potential corrosion in contact with the cooling medium. In the case of metallic materials with low plastic elongation at break, these can be applied using a hot isostatic pressing (HIP) process to the support tube with higher strength or elongation at break in combination with the compaction process from powdered components during the HIP process. In other designs of targets made of metals or metal alloys, these can be inserted into one another by shrinking, utilizing the expansion of the target tube by heating and shrinking the support element tube by cooling, and can be connected by adjusting to room temperature via the shrink fit without the use of intermediate layers.Another typical design for brittle target materials consists of a tubular target with a significantly larger inner diameter than the outer diameter of the support element tube. The resulting space between the two components is filled with liquid indium or other low-melting solder and solidified. The disadvantage of this design is its limited ability to withstand high thermal loads, which can arise from high sputtering power, due to the low melting point of the solder material. WO 2017 / 088842 A1 proposes a cylindrical cathode for depositing layers using the PVD process, comprising a tubular central support with a target arranged on its circumference. The central support is provided, at least in the region of the target, with a flow chamber that is separated from the target by an elastic tube.If the target is made of brittle, difficult-to-machine materials, such as TiB2 or B4C, the target material is manufactured in the form of rings, which are then slid side by side onto the tube. The thin, elastic tube deforms when subjected to pressure from the cooling water during operation, thus adapting to the inside of the rings. WO 2017 / 088842 A1 thus succeeds in avoiding solder or adhesive layers, which, due to their reduced thermal resilience, represent the limiting factor when using high power densities. As already mentioned, cooling tubes, particularly the elastic tube of the device in WO 2017 / 088842 A1, generally exert mechanical stress on the coating source, which in turn can lead to deformation of the coating source and even its fracture.This effect is further aggravated by the fact that the strength of the coating source, in particular of the coating material, decreases during the coating process. This makes failure due to fracture even more likely. In practice, brittle target materials must therefore be enriched with a binder, such as nickel, to prevent cracking when the cooling tube / membrane is subjected to water pressure and before actual commissioning. The binder, in turn, precipitates in the layers deposited with the target, which is undesirable. The object of the present invention is to provide a more stable target for use with a tubular, coolant-carrying support element in deposition processes at high power density.This object is achieved by a target comprising a target material and a support element connected thereto according to claim 1, characterized in that the target material is designed as an outer ring, wherein the outer ring is divided into two or more segments in the circumferential direction and consists of a brittle material with a plastic elongation at break at 20 °C of less than or equal to 2%, the support element is designed as an inner ring and consists of copper or a copper alloy, and by a method for producing such a target according to claim 8. Advantageous developments of the invention can be found in the dependent claims, which can be freely combined with one another. According to the present invention, a target has target material and a support element connected thereto. The target is ring-shaped because it is constructed from an outer ring made of target material and an inner ring connected thereto as a support element.Geometrically, the target has the shape of a ring, i.e. the shape of a special hollow cylinder with an outer radius R, an inner radius r and a height h, where the height h of the hollow cylinder is less than the outer radius R and the outer radius R and the inner radius r are assigned to concentric circles. Such a special hollow cylinder is also referred to as a perforated disc with a concentric, circular opening. The wall thickness b results from the difference between the outer radius and the inner radius: b = R - r. R is typically in the range from 40 mm to 300 mm and r in the range from 30 mm to 290 mm with the proviso that b is in the range from 10 mm to 50 mm. The height h is in a range from 10 mm to 100 mm. The ratio of the target material thickness h. s to the copper ring thickness is typically in a range of 1:1 to 10:1. The height of the inner ring can be 0.01 mm to 0.8 mm, preferably 0.2 mm to 0.6 mm larger than the width b sThe segments of the outer ring are made of the target material. This makes it possible to achieve a defined gap between the ring targets arranged on a cooling tube. The target material is designed as an outer ring interrupted in the circumferential direction and consists of a brittle material. The ring is divided into two or more segments and the support element is designed as an inner ring made of back-cast copper or copper alloy. The segmentation of the ring from the target material makes it possible to permanently bond the materials of the target material and the support element in a way that withstands the component stresses during use as a sputtering target with high power and thus high, possibly cyclic, thermomechanical stresses. Copper and copper alloys, which are used here as support elements, have a high coefficient of thermal expansion (CTE) in the order of 16.5 x 10 -6 K-1 . The expansion coefficients of the brittle materials considered here, especially ceramic materials, are in the range of 5 x 10 -6 K -1 up to 8 x 10 -6 K -1and thus by a factor of approximately 2 lower. This difference in the CTE values ​​must be taken into account by the multi-part design of the outer ring made of the target material, since this shrinks far less than the copper or copper alloy during the cooling phase of the inner ring, which is applied using back-casting from molten copper or a copper alloy. For this reason, defined gaps (recesses) must be created between the individual ring segments before the back-casting process, preferably using filler material made of compressible graphite foils. The width of the gaps to be created is a function of the number of ring segments and the difference between the CTE values ​​of the target material and the copper material used. The use of copper or some copper alloys is advantageous given the low yield strength of these materials at high temperatures.This makes it possible for a large proportion of the stresses that arise during cooling in the contact zone between the target material and the support element, resulting from the aforementioned differences in the CTE values, to be reduced through plastic deformation. The segmentation therefore makes it possible to manufacture a coating source with a coating material made of a brittle material and to operate the coating source stably, i.e. without structural failure, such as cracking or breaking, of the target material, at very high line densities. In particular, it should be mentioned that due to the direct connection of the target material to the support element, without the use of low-melting solders, the thermal stability of the target is very high and is in principle stable up to the drastic drop in the yield strength of the copper at temperatures just below the melting point of the copper or the copper alloy used.The target material consists of a brittle material. For the purposes of this description, brittle materials are those that break near the elastic limit with little or no plastic deformation. These materials, and thus also the sputtering targets made from them, therefore have only a low plastic deformation capacity. For the purposes of the present invention, brittle materials are materials with an elongation at break at room temperature (20°C) of less than or equal to 2%, preferably less than or equal to 1%, and more preferably less than or equal to 0.2%. Suitable brittle materials for the purposes of the present invention are selected from the group consisting of ceramic materials, metallic materials, semi-metallic materials, intermetallic phases, and mixtures of these materials.Preferred brittle materials are selected from the group consisting of optionally carbon-doped borides, nitrides, carbides, silicides, oxides, chromium, chromium alloys with a chromium content of at least 50 at% chromium, metallic materials, semi-metallic materials, intermetallic TiAl phases, intermetallic AlCr phases, and mixtures of these materials. Particularly preferred brittle materials are selected from the group consisting of TiB2, VB2, W2B5, CrB2, TaB2, WC, WC / C, TiC, SiC, SiC / C, B4C, B4C / C, TiN, AlN, TiSi2, CrSi2, MoSi2, Cr, Si, Ge, and mixtures of these aforementioned materials. To ensure stable process control during sputtering, the target material typically has a density higher than 80% of the theoretical density, preferably higher than 90%, more preferably higher than 95%, more preferably 98% to 100%.The theoretical density applicable to the respective composition of the target material is, by definition, calculated from the averaging of the theoretical densities of the individual phase components, weighted by the molar fractions. The actual density of the target material is determined using Archimedes' principle. Preferably, the outer ring is divided into 2 to 16, more preferably into 4 to 12, and even more preferably into 6 to 8 segments. When dividing the ring of target material into the individual segments, an optimum must be sought between the following competing features: minimizing the stresses in the contact zone between the target material and the support ring by using as many segments as possible, simplicity of design of the arrangement when back-casting with the copper orCopper alloy through as few segments as possible, cost-effective production through optimal, near-net-shape production of the segments from the target material, which is best achieved when divided into 6 to 8 segments. According to a development of the invention, all segments of a ring have the same dimensions. This has the advantage that segments for producing the ring-shaped target can be provided from different target materials, like in a modular system, and can then be combined with one another as desired. In one embodiment, such a target only has segments made of the same target material. In another embodiment, the target has segments made of different target materials. This has the advantage that different materials can be simultaneously or co-sputtered on a common target and the composition of the materials can be tailored to the requirements of the PVD layer to be deposited.It is furthermore possible for a target according to the invention to have graphite foil between facing surfaces of two segments adjacent in the direction of rotation. This graphite foil originates from the manufacture of the target and can be used to prevent the penetration of back-cast, liquid copper / copper alloy into recesses between segments adjacent in the direction of rotation during the manufacture of the target. The graphite foil is preferably a compressible foil with a thickness of 0.2 mm to 1.5 mm. Such compressible graphite foils are sold as standard products by manufacturers of graphite materials. After manufacture, in the cooled and shrunken state of the back-cast copper / alloy, a correspondingly manufactured target therefore has graphite-filled recesses in a range of 0.01 mm to 0.8 mm. The graphite-filled recesses between the segments are preferably in a range of 0.2 to 0.6 mm.The support element, designed as an inner ring, consists of essentially pure, back-cast copper or a copper alloy and has an average grain size of > 0.5 mm, preferably > 1 mm, particularly preferably > 2 mm. Furthermore, a person skilled in the art can recognize (from a cross-section of the support element) a coarse-grained crystal structure typical of copper / alloy solidified from the melt. This does not exhibit any characteristics of a formed, textured material. Copper alloys herein are understood to be alloys with copper, where copper is the main constituent and the total proportion of alloying elements is < 50 wt.%, preferably < 10 wt.%, and particularly preferably < 5 wt.%. The following copper casting materials are examples of copper alloys: CuCr, CuCrZr, CuZn, CuSn, CuSnZn, CuAl, CuMnAl, CoNi, and CuMg. Back-casting with copper / copper alloy provides a stable connection between the target material and the support element, even at high power densities.Similar to WO 2017 / 088842 A1, the present invention completely eliminates the use of conventional solder or adhesive bonds between the cooling element and the target material. In the present invention, the ring segments directly adjoin the inner ring or, in the case of segments made of TiB2 or a TiB2-based ceramic, are advantageously connected to the inner ring via a titanium-containing intermediate layer. A TiB2-based ceramic is understood here to mean a ceramic that contains at least 50 mol% TiB2, preferably at least 70 mol% TiB2, and particularly preferably at least 80 mol% TiB2.At the same time, the present invention succeeds in counteracting the influence of the pressure of the cooling water used through the special ring shape of the target, the segmentation of the target material, and the provision of an annular support element. This allows the target to be operated at extremely high power densities and correspondingly high cooling rates without failure phenomena such as cracking or breakage, without the need to enrich the target material with binders such as nickel, thus increasing its ductility. The segmentation of the target material also achieves a very high target resistance to the cyclic thermomechanical stresses that occur during industrial sputtering operations, which can otherwise lead to damage due to material fatigue during continuous use.Since the outer wall of the cooling device, typically a copper tube or an elastic copper membrane, as in the case of WO 2017 / 088842 A1, expands due to the pressure of the cooling water, the annular targets of the present invention form a force-fitting connection with the outer wall of the cooling device and do not need to be firmly bonded to the outer wall of the cooling device. Due to the particularly high strength of the annular target, achieved thanks to this invention, the pressure in the copper tube or the elastic copper membrane can be set very high in order to achieve a higher heat transfer coefficient without the risk of brittle fracture of the target ring. Furthermore, the invention offers the advantage that different rings can be arranged in combination on a target-supporting cooling tube of a system, or rings with different material segments can be combined.The present invention also encompasses a method for producing an annular target described herein. First, ring segments made of a brittle material with a plastic elongation at break at room temperature of less than or equal to 2% are provided. See the definition of elongation at break in DIN EN ISO 6892-1:2019. Production from brittle materials typically occurs via the powder metallurgy route. The target material is compacted using pressure, heat, or pressure and heat and densified to a density higher than 80% of the theoretical density, preferably higher than 90%, and more preferably higher than 95% of the theoretical density. Common methods known in the art for densifying the material include sintering, pressure sintering, hot isostatic pressing, hot pressing, and spark plasma sintering, both in a protective gas atmosphere, a reducing atmosphere, such as hydrogen, or in a vacuum.For the purposes of the present invention, the segments can be shaped by directly compacting the target material into a corresponding shape; segments can be produced by cutting a ring formed from a corresponding shape made of compacted target material; or preferably, a sheet-like structure of the target material, for example in the form of a rectangular or round plate, can be produced from which the segments are individually cut out. The cutting or cutting out of the segments is preferably carried out by spark erosion-based processes such as wire erosion or by mechanical cutting processes such as abrasive cutting. The former process is only suitable for electrically conductive materials. More preferably, the segments are produced by wire erosion from a plate of the compacted target material. Advantageously, the thickness of such a plate corresponds to the width bs of the segments.The exact thickness of the plate can be adjusted if necessary by mechanical processing of the plate, advantageously by grinding the plate, after compaction. In this way, precisely shaped segments with very good density homogeneity and high density can be manufactured in large quantities and with optimal use of material close to the net shape. This is followed by a step of arranging the ring segments to form an outer ring interrupted by recesses in the circumferential direction. In a shape corresponding to the target, preferably made of graphite with an inner punch, the recesses between the ring segments being dimensioned such that, after contraction by cooling of an inner ring produced by back-casting with liquid copper or liquid copper alloy, they have distances of between 0.01 and 0.8 mm, preferably 0.2 to 0.6 mm between the segments. The dimensions of the recesses (gaps) can be calculated by a person skilled in the art.The width of the gap to be applied is a function of the number of ring segments as well as the difference between the CTE values ​​of the target material and the copper material used. This relationship can be represented by the following formula: S B = (2 x 3.14 x R KZ x (CTE Cu – CTE TM ) x 1000K) / N, where S B the gap width, R KZ the radius of the circular contact zone between the target material and the support element, CTE Cu and CTE TMare the coefficients of expansion of copper / alloy or the target material and N is the number of ring segments that make up the target material. The 1000 K roughly corresponds to the solidification interval of the copper or copper alloy. The formula calculates the difference in the extent of shrinkage along the circumference where the two materials are joined, resulting from the CTE differences, during the cooling phase of the solidifying copper melt and divides this difference by the number of gaps to be taken into account. The method advantageously comprises a step of positioning a compressible graphite foil with a thickness of 0.2 to 1.5 mm in the recesses between the segments in the circumferential direction. This can suppress or prevent the penetration of liquid copper or liquid copper alloy into the recesses between the segments in the circumferential direction.This is followed by a step of back-casting the outer ring with liquid copper or a liquid copper alloy. Back-casting is the melt-metallurgical application of a material to a base material, in this case the target material, which is always in a solid state under the process parameters used. During back-casting, the arranged segments of the target material, and optionally graphite foil, are coated with solid copper or a copper alloy. The copper or copper alloy is preferably in lumps, more preferably in the form of ingots. The required quantity can be calculated from the density of the copper (8.96 g / cm³) orthe copper alloy and the volume between the inner walls of the target segments assembled into a ring and the outer diameter of the graphite cylinder (punch) installed in the backcasting mold, and the height of the target rings with an allowance of preferably at least 2 mm to allow for excess for the subsequent mechanical processing of the backcast blank into the finished target. This is followed by a step of placing the mold, equipped with the segments, copper or copper alloy, and optionally graphite foil, into a furnace.The initially not yet compact and materially bonded target is heated in a suitable process atmosphere, such as vacuum, H2, N2 or a noble gas such as Ar, possibly with a ramp function, until the material lying on it, consisting of copper or a copper alloy, melts and fills the space between the non-melting target material and the graphite cylinder in the center of the mold, wetting the inside of the segments of the target material. For example, the melting point of pure copper is 1085°C. The temperature of the furnace must be selected so that the temperature is above the melting point of the copper or above the liquidus line of the copper alloy in the phase diagram, preferably 50°C to 100°C higher. When backcasting, the furnace must be maintained at a temperature above the melting point or liquidus line for a sufficient period of time.The liquidus line is maintained so that the copper or copper alloy can completely melt. After a desired holding time above the melting point, the furnace is cooled again to below the melting point of the copper or copper alloy. Cooling is preferably achieved by lowering the component from the hottest zone of the furnace into the cooler zone to ensure directional solidification without the formation of pores or cavities. A stable bond is formed between the segments and the copper / copper alloy.After the copper or copper alloy has solidified, the cooled target shows a first part consisting of target material which is designed as an outer ring, wherein the outer ring is divided into two or more segments in the circumferential direction and consists of a brittle material with a plastic elongation at break at 20 °C of less than or equal to 2%, and a second part which is designed as a support element as an inner ring and consists of copper or a copper alloy. This is typically followed by a step of mechanical processing or post-processing of the solidified target, in particular to the final dimensions, by turning, milling, cutting, grinding, lapping, in particular by turning or milling. Welding, soldering, joining, shrink-fitting or gluing processes can also be carried out on the target, in particular for equipping a cooling tube. Furthermore, the target can subsequently be engraved.In addition to the mechanical processing of the target, thermal post-treatments of the target can also be carried out, such as annealing or annealing and tempering, in order to achieve the desired structural properties, in particular of the support element made of copper and in particular of a copper alloy, which can be optimized in this way with regard to the high hardness. In the event that the segments are TiB2 or a TiB2-based ceramic, the inner side of the outer ring is advantageously coated with a layer of titanium before the back-casting step. The titanium layer is preferably applied in a thickness of 10 to 100 μm, typically by thermal spraying or cold gas spraying, preferably by cold gas spraying. Further advantages and usefulness of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures. The figures show: Fig.1: a perspective view of a ring target according to the invention; Fig. 2a: a side view of a segment for producing a ring target according to the invention; Fig. 2b: a cross-sectional view of a segment for producing a ring target according to the invention; Fig. 2c: a perspective view of a segment for producing a ring target according to the invention; Fig. 3: a top view of a ring target according to the invention. Figure 1 shows a target 1 according to the invention with an outer ring 3 formed from segments 2 and an inner ring 4. The segments 2 are separated from one another in the circumferential direction of the outer ring 3 by a gap 5. The gap 5 can be filled with a graphite foil 6. In addition, h denotes the total height of the target according to the invention. Figure 2a shows a segment 2 for producing a target 1 according to the invention of Figure 1 in a side view.The outer side 22 of segment 2 extends along a portion of the outer circumference of outer ring 3 and, as part of an outer ring 3, is designed in the shape of a circular arc. Segment 2 has lateral connection surfaces 21 for connection to an adjacent segment 2. The connection surfaces 21 are shown, by way of example, following the radius and oriented orthogonally to the direction of rotation. However, it is also conceivable for the connection surfaces 21 to be oriented differently, with the proviso that adjacent connection surfaces 21 of adjacent segments 2 are oriented parallel to one another. By attaching the connection surfaces at an angle, not parallel to the radius of the ring target, it could additionally be achieved that the gaps, in the event that they are not filled with graphite foils, are not aligned frontally to the plasma in the coating chamber.The angle α shown here corresponds to approximately 60° in the case of the segmentation into 6 segments shown here as an example and originates from the center point of the concentric circles that delimit the target 1, so that the segment 2 shown as an example extends approximately over a section of one sixth of the outer ring 3. The segment 2 describes a part of an outer ring 3 comprising several segments 2 and interrupted in the circumferential direction of a target 1 according to the invention. According to the invention, segments 2 can also extend over a larger or smaller section of the outer ring 3. As shown in Figure 2b, the segment 2 has a rectangular cross-sectional area with a height h perpendicular to the circumferential direction. s and a width b sFigure 2c shows a perspective view of segment 2 with an inner surface 23 that extends along a portion of the inner circumference of outer ring 3. If the segment is made of TiB2 or a TiB2-based ceramic, inner surface 23 has a layer of elemental titanium. Figure 3 shows a plan view of target 1 according to the invention. Shown are the outer radius R and the inner radius r of the concentric circles that define target 1. The wall thickness b of the target results from the difference R - r. The segments 2 shown here comprise approximately 1 / 6 of outer ring 3 in the circumferential direction for producing a target 1 with an outer ring 3 with six identical segments 2, together with gaps 5, 6 that may be filled with graphite due to the manufacturing process.According to the invention, an outer ring 3 can also comprise fewer, preferably two, three, four, or five, or more, preferably seven, eight, nine, ten, eleven, or twelve segments 2. The segments 2 of a ring 3 can also have different extensions in the circumferential direction. The adjacent surfaces 21 of two adjacent segments 2 are typically aligned parallel to one another, preferably following the radius, orthogonal to the circumferential direction of the outer ring 3, so that the gaps 5 can be kept as narrow as possible. Segments 2 consist of a brittle material as defined herein as the target material. An outer ring 3 can consist of segments 2 made of identical target material or of segments 2 made of different target materials. The target 1 in Figure 3 also shows the inner ring 4 made of back-cast copper / copper alloy in direct connection to the inner surface 23 of the segments 2 of the outer ring 3.In the case of TiB2 or a TiB2-based ceramic, the target has a titanium-containing layer between the inner side 23 of the segments 2 and the inner ring 4 consisting of copper / copper alloy (not shown). During the back-casting process, the titanium largely dissolves in the copper / copper alloy, and a titanium-containing intermediate layer consisting of titanium and copper, or titanium and copper alloy, then forms. The height of the inner ring 4 can correspond to the width b. s of the segments 2. However, it is also possible that the height of the inner ring 4 is 0.01 to 0.8 mm, preferably 0.2 to 0.6 mm larger than the width b sof the segments 2 of the outer ring 3 is made of the target material. This makes it possible to achieve a defined gap between the target rings arranged on the cooling tube. Production examples: For the examples according to the invention, segments with bs = 30 mm and hs = 22 mm were made of target materials for an outer ring as follows: -TiB2, six identical segments, with an inner surface of the segments coated with CGS titanium before back-casting - TiB2, three identical segments, with an inner surface of the segments coated with CGS titanium before back-casting - VB2, six identical segments - W2B5, six identical segments - TaB2, six identical segments - WC, two identical segments were compacted into a plate by hot pressing powders of the respective target material, which was then ground to a thickness of 30 mm and served as the primary material for cutting out segments by wire EDM.Before back-casting, the inner surface of each TiB2 segment was coated with a 50 μm layer of pure titanium using CGS. The following CGS process parameters were used for the titanium layer (see Table 1): Table 1. The segments were then back-cast with copper. The segments were arranged in an outer ring in a graphite mold corresponding to the target, and adjacent segment surfaces were separated from each other by graphite foil. Copper part(s) (cylinders cut from copper rods) made of essentially pure copper were placed on the mold. The graphite mold was then placed in a furnace and heated to 1150°C in an H2 atmosphere. After reaching 1150°C, the graphite molds were held in an N2 atmosphere at 1150°C for 1 hour (Note: above the melting temperature of copper, which is 1085°C). The graphite mold was then lowered from the hot zone of the furnace at a speed of 33 cm / h.The cooling of the segment-copper composite thus occurred via directional solidification of the melt, resulting in a largely stress-free, yet coarsely crystalline microstructure of the back-cast copper. After final cooling to room temperature, targets back-cast with copper in this way exhibit excellent bonding between the two materials (target material and copper). Targets manufactured in this way exhibit no cracks or delamination at the transition between the two materials. The slow cooling process also minimizes the thermal stresses between the segments, consisting of brittle materials, and the solidified copper inner ring. The targets were then machined to their final dimensions by turning.The inside of the copper inner ring was machined to the inner diameter of 80.8 mm specified in the drawing, and the height of the copper ring was adjusted to 30.2 mm to achieve an oversize of 0.1 mm on both sides compared to the 30 mm high outer ring of the target material. Targets with the following dimensions were obtained: Ø110 / 80.8 x 30.2 mm. Finally, the ceramic sides of the targets were cleaned by blasting with glass beads and inspected for compliance with the dimensions specified in the drawings. The targets were successfully tested in sputter mode in a coating system under continuous operation without any failures.

Claims

CLAIMS 1. Target (1) comprising a target material and a support element connected thereto, characterized in that the target material is designed as an outer ring (3), wherein the outer ring (3) is divided in the circumferential direction into two or more segments (2) consisting of a brittle material with a plastic elongation at break at 20°C of less than or equal to 2%, the support element is designed as an inner ring (4) and consists of copper or a copper alloy.

2. Target according to claim 1, wherein the target material has a density higher than 80% of the theoretical density, preferably higher than 90%, and preferably higher than 95%.

3. Target material according to one of the preceding claims, wherein the brittle material is selected from the group consisting of ceramic materials, metallic materials, semi-metallic materials, intermetallic phases, and mixtures of these materials. 4.Target material according to one of the preceding claims, wherein the brittle material is selected from the group consisting of borides, nitrides, carbides, silicides, oxides, where the borides, nitrides, carbides, silicides, and oxides may optionally be doped with carbon, chromium, chromium alloys with a chromium content of at least 50 at% chromium, metallic materials, semi-metallic materials, intermetallic TiAl phases, intermetallic AlCr phases, and mixtures of these materials.

5. Target according to one of the preceding claims, wherein the outer ring (3) has 2 to 16 segments (2).

6. Target according to one of the preceding claims, wherein the target has graphite foil (6) between facing surfaces (21) of two adjacent segments (2). 7.Target according to one of the preceding claims, wherein the segments (2) are directly connected to the support element or the segments (2) consist of TiB2 or a TiB2-based ceramic and are connected to the support element via a titanium-containing intermediate layer.

8. A method for producing an annular target (1) comprising the following steps:. - Providing ring segments (2) made of a brittle material with a plastic elongation at break at room temperature of less than or equal to 2%, - Arranging the ring segments (2) to form an outer ring (3) interrupted by recesses in the circumferential direction in a mold, wherein the recesses (5) are dimensioned such that, after contraction by cooling of an inner ring (4) produced by back-casting with liquid copper or liquid copper alloy, they have distances of between 0.01 mm and 0.8 mm between the segments (2), - Back-casting the outer ring (3) with liquid copper or a liquid copper alloy in a vacuum or under a protective gas atmosphere to produce an inner ring (4) connected to the outer ring (3) as components of an annular target (1), - Cooling the annular target (1), and optionally - Mechanically reworking the annular target (1). 9.Method according to claim 8, wherein the step of providing the ring segments (2) is preceded by the production of the ring segments (2), comprising the following steps: - Providing the brittle material in powder form - Compacting the material to a density higher than 80% of the theoretical density, preferably higher than 90% and preferably higher than 95%, to form a sheet - Cutting out the ring segments (2) by wire EDM.

10. Method according to one of the preceding claims 8 to 9, wherein the step of arranging the segments (2) includes positioning a compressible graphite foil (6) with a thickness of 0.2 to 1.5 mm in the recesses (5).

11. Method according to one of the preceding claims 8 to 10, wherein the mold is made of graphite. 12.Method according to one of the preceding claims 8 to 11, wherein the step of arranging and the step of back-casting follow one another directly or segments (2) consist of TiB2 or a TiB2-based ceramic and are formed before the step of. After the step of arranging and the step of back-casting, a titanium intermediate layer is applied to the inner side (23) of the segments (2) made of TiB2 or a TiB2-based ceramic.

13. The method according to one of the preceding claims 8 to 12, wherein the annular target (1) is mechanically finished to the final dimensions.

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