Method for making composite sputtering targets and the tartets made in accordance with the method

Abstract

Composite sputtering targets are made by hot pressing metal or metal containing powders into a backing plate which can be comprised of a different material with a depression formed in a surface or can be a used sputtering target of the same or different material. The depression corresponds to the erosion pattern of a target having the same geometry. The depression can be formed for example, by machining. The backing plate is loaded into a graphite die and covered with the sputtering material to form an assembly. A ram is added and the assembly with the ram is loaded into a hot press which is taken to an appropriate pressure and temperature under vacuum to form a composite sputtering target having a sputtering zone of densified sputtering material.

Description

FIELD OF THE INVENTION

The invention relates to composite sputtering target assemblies made by hot pressing metal or metal containing powders into a metal backing plate. More particularly, the invention relates to a method of making a hot pressed composite sputtering target assembly that reduces the amount of relatively expensive materials such as precious metal containing materials required to prepare the target by confining these materials to the area of the target utilized in the sputtering process. The invention further relates to the target, which is produced by the method.

BACKGROUND OF THE INVENTION

Thin layers of many materials may be deposited on a substrate material by a process known as DC-magnetron sputtering. A typical sputtering system includes a means for generating a high energy plasma that removes the material to be deposited from the surface of a source forming a vapor of that material that condenses on the surface of the desired substrate. In such a system, the source of the material to be deposited on the substrate is called a sputtering target. A sputtering target can be composed solely of the material to be deposited or in some cases the material to be deposited is formed into an object called a sputtering target tile that is joined to a dissimilar material called the sputtering target backing plate and the entire assembly is called the sputtering target. The choice of sputter target construction depends on the sputtering system used, the physical and electrical properties of the material to be deposited, and the expense of the material to be deposited.

In the sputtering process, the high energy plasma continuously erodes the surface of the sputtering target material forming a depression known as an “erosion groove” in the surface of the sputtering target. This erosion groove is commonly referred to in the thin film industry as the “racetrack” due to its unique shape. Eventually, the erosion groove becomes deep enough that further sputtering of the target material is impractical and at that point the sputtering target is considered “spent”.

In typical sputtering processes only 20-40% of the target material is utilized and the remaining target material is either discarded or recycled by remelting or refining. Customarily precious metal targets are recycled to capitalize on the value of the sputtering target material. The recycling process increases the amount of precious metal needed to practice a sputtering process considerably since the spent target is tied up in being re-melted and/or refined before it is made available to be made into a new target. It often takes several weeks, or even months to render the remaining material from a spent target available and in addition, there is a significant material loss in the recycling process.

While for most materials used in the sputtering process recycling is economically feasible, this is not necessarily the case for relatively expensive materials such as those that contain precious metals such as Pt, Ru, Pd, Os, Ir, Rh, and Re or combinations of precious metals and other metals or metal oxides. In this case the cost and the amount of material loss from the recycling processes are substantial enough to warrant a significant change in the way precious metal containing sputtering targets are manufactured.

In accordance with the present invention, a method to reduce the amount of precious metal containing materials used in the precious metal containing sputtering target manufacturing process is to confine the precious metal containing material to the actual area where it is consumed; the sputtering erosion groove. It is conceivable to reduce the amount of precious metal containing material used to manufacture a target by greater than 40% by restricting the precious metal containing material to the erosion groove area of the sputtering target. A way to achieve this goal is to manufacture a composite sputtering target whereby the precious metal containing material is formed into a shape similar to the shape of the sputtering erosion groove and applied to a backing plate composed of a relatively inexpensive material specially machined to accommodate the shape of the erosion groove of the sputtering process. Moreover, as the present invention does not require that a spent target go through a refining process, it results in a significant reduction in the inventory of precious metal used for sputtering (and especially in a reduction of the material that is tied up in spent targets which are not serving in production capacity, but instead is undergoing the recycling process.).

Prior art does teach that composite sputtering target assemblies can be advantageously fabricated by powder metallurgical processes. One such process is disclosed in Mueller, U.S. Pat. No. 5,397,050, dated Mar. 14, 1995, which describes a method of producing a composite sputtering target assembly consisting of a tungsten-titanium alloy target and a titanium backing plate. The titanium backing plate is placed in a metal can and tungsten-titanium powder is placed on top of the titanium backing plate in the can. The can containing the powder and backing plate is hot isostatic pressed (HIP'ed) forming a composite sputtering target. However, since the process involves HIP'ing powder contained within a metal can, it is relatively costly due to the use of expensive canning materials, machining, canning as well as HIP procedures and equipment which add to manufacturing cost. In addition, the expensive target material is not confined to the sputtering area of the target, thus the amount of the expensive target material used to form this type of sputtering target is not significantly reduced.

Another such method is disclosed in Stellrecht, U.S. Pat. No. 5,963,778, dated Mar. 14, 1999 in which a composite target is fabricated using powder metallurgical processes and which attempts to confine the expensive sputtering material to the sputtering area of the target. However, like the previous invention, the process used to prepare the composite target is HIP'ing and thus, the same cost implications described above apply.

Sandlin et al. disclose a method to refurbish spent sputtering targets in U.S. Pat. No. 7,175,802 whereby new sputtering material is applied to a spent sputtering target by filling the sputtering erosion groove with the new material. This process is also accomplished using HIP'ing. The invention does not confine the expensive sputtering material to the sputtering area of the target, but does reuse the spent target instead of recycling it. However, there still remains a considerable amount of expensive material in use that is not used in the sputtering process leading to a still relatively high cost of ownership. In addition, the disclosed process requires the spent targets to be thoroughly immersed in the powder of the expensive material that requires removal and recycling after pressing.

The present invention provides an efficient and relatively low cost method of producing composite sputtering target assemblies whereby the precious metal containing sputtering material is confined to the sputtering area of the target assembly. This is achieved by applying the precious metal containing sputtering material to a backing plate assembly of a substantially lower cost material that has a cavity machined into its surface that approximates the sputtering erosion groove of spent targets. Additionally, the process can be applied such that the erosion groove of a spent target is filled using the process of the present invention. In this instance, the spent target becomes the backing plate, and does not require additional machining to form a form for the newly added precious material.

Furthermore, the composite target of the present invention is fabricated using vacuum hot pressing that utilizes re-usable graphite dies instead of single-use metal cans and the amount of precious metal containing material powder used in the forming process is greatly reduced. The result is a composite sputtering target that requires at least 50% less of the expensive material than a target produced purely of the precious metal containing material. The process significantly reduces amount of precious metal that needs to be dedicated to a sputtering process since it eliminates side lining of the spent target material into the recycling portion of the production cycle of precious material used in sputtering targets. This advantage results in a tremendous and unforeseen increase in the efficiency of the precious material dedicated to the sputtering process.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a method of making a sputtering target assembly that confines precious metal containing sputtering target materials to the sputtering area of the target thereby reducing the amount of precious metal containing sputtering material required to produce the sputtering target assembly, and further increases the efficiency of the material dedicated to the sputtering process, and thus reduces the cost of ownership of the sputtering target assembly as well as the capital investment needed for the sputtering process. The method involves providing a backing plate of a relatively inexpensive material, that is chemically and mechanically compatible with the precious metal containing sputtering material, with a depression in the surface, (which can in the first instance be machined into the backing plate) that corresponds to the sputtering erosion pattern observed in used sputtering targets, placing the backing plate into a graphite die shaped to accommodate the geometry (i.e., the size and shape) of the backing plate, filling the depression in the backing plate with a powder of the precious metal containing sputtering material, then placing a graphite ram on top of the powder layer. The die containing the backing plate powder assemblage is then placed in a vacuum hot press to consolidate and densify the precious metal containing sputtering target material powder into the backing plate depression. Not only does vacuum hot pressing consolidate and densify the precious metal containing sputtering target material, the hot pressing also facilitates the formation of a strong inter-metallic bond between the precious metal containing sputtering material and the backing plate material creating a strong mechanical attachment as well as an intimate electrical and thermal conduction path between the precious metal containing sputtering target material and the backing plate. After hot pressing, a minimal amount of machining may be required to obtain the required dimensional specifications for the particular sputtering target design.

In a preferred embodiment of the invention, a method of making a precious metal containing sputtering target assembly comprises 1) providing backing plate including a surface having a depression; 2) placing the backing plate into the cavity of a graphite die set prepared to accommodate the geometry backing plate; 3) forming a die assemblage by placing a sputtering material into the cavity in contact with the depression so as to completely cover the surface of the backing plate to a predetermined depth; 4) placing a graphite ram into the cavity of the assemblage so as to contact the top of the sputtering material; 5) placing the ram and die assemblage into the chamber of a vacuum hot press furnace and pressing them in vacuum at a sufficient pressure and a sufficient temperature for a sufficient period of time in order to densify and consolidate the sputtering material into the depression in the backing plate so as to form a sputtering target perform, and subsequently reducing the pressure on the ram to zero, cooling or allowing the hot press furnace chamber to cool to ambient temperature, and raising or allowing the vacuum level to go to ambient pressure once the furnace has cooled; 6) removing and optionally machining of the sputtering target pre-form to obtain a composite sputtering target. In a further advantageous embodiment of the invention, the backing plate is comprised of a material which differs from the sputtering target material and is comprised of one or more of molybdenum, niobium, tantalum or other refractory metals or alloys. Advantageously, the depression at least corresponds to the sputtering erosion pattern of a used sputtering target. More preferably, the depression corresponds to the erosion pattern of a spent target (i.e. a target that has been used to the point at which it is no longer acceptable for further use.) Further it is preferred that the sputtering material is a powder comprising precious metal or a mixture of precious metal powders, or a mixture of precious metal powders and non-precious metal powders, or a mixture of precious metal powders, non precious metal powders, and metal oxide powders. In an additional preferred aspect of the invention, the graphite die is of a geometry determined for the particular sputtering target assembly design being produced.

Suitable sputtering material include powders of pure Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals such as Co, Cr, Ni, Fe, or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals such as Co, Cr, Ni, Fe, and oxides such as TiO₂ or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt with oxides such as TiO₂. In the presently preferred embodiment, a pure Ru powder is as used sputtering material and pure Mo is used for the backing plate. In an alternative embodiment, the backing plate is composed of pure Nb metal. In another alternative embodiment, the backing plate is composed of pure Ta.

The present invention results in a savings of at least 25%, preferably at least 35% and most preferably at least 40% or more of the sputtering material needed for a sputtering target assembly as compared to the prior art solid sputtering target. As an example, a precious metal containing sputtering target of a rectangular geometry can be prepared using this invention with only 50% of the precious metal material requirement of a precious metal containing sputtering target prepared using only the precious metal containing material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a cross-sectional view of a used precious metal containing sputtering target with a rectangular or circular geometry;

FIG. 2 represents a top view of a used precious metal containing sputtering target with a rectangular geometry;

FIG. 3 represents a top view of a used precious metal containing sputtering target with a circular geometry;

FIG. 4 represents a cross-sectional view of a backing plate containing a depression that corresponds to the sputtering erosion pattern for targets with either a rectangular or circular geometry;

FIG. 5 represents a cross-sectional view of a first embodiment of this invention for a precious metal containing sputtering target with either a rectangular or a circular geometry;

FIG. 6 represents a hot pressing die assemblage prior to hot pressing for consolidating sputtering material into a depression in the surface of a backing plate.; and

FIG. 7 represents the hot pressing die assemblage of FIG. 6 after hot pressing.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method of making a composite sputtering target which is comprised of a backing plate and a sputtering zone which has been incorporated into a depression in the backing plate so as to provide a sputtering target assembly with sputtering material substantially only where is will be used in the sputtering process. In one embodiment, the backing plate is a used target of the same material that is added as the sputtering material. In this embodiment, the used target has a top surface with a depression that has been eroded during the sputtering process. This depression is filled with new sputtering material that is uniaxially pressed under vacuum at a suitable temperature and for a suitable time to cause the additional material to bond with the used target so that it can be used in the process as a substitute for the original target. In a second embodiment, the backing plate is a different material, such as a less expensive material that will bond with the sputtering material and provide chemical, thermal and electrical properties that are suitable to allow the composite target to be substituted for a target made exclusively from the sputtering material. In this embodiment, the backing plate included in FIGS. 1-3 illustrate the appearance of a spent precious metal containing sputtering target of rectangular or circular geometry. FIG. 1 describes the cross-section of a spent or used precious metal containing sputtering target 10, showing the depth and shape of the sputtering erosion groove 12. The erosion groove, 12, represented in FIG. 1 is consistent with erosion grooves found in precious metal containing sputtering targets that have either a rectangular or circular geometry. FIG. 2 shows the top view of a spent precious metal sputtering target 20 of rectangular geometry, showing the shape of the sputtering erosion groove 22. FIG. 3 shows the top view of a precious metal containing sputtering target of circular geometry, 30, showing the shape of the sputtering erosion groove 32. An examination of these drawings shows that a considerable amount of precious metal sputtering material is left in the used target with as little as 25% of the material actually used in the sputtering process.

The present invention reduces the amount of precious metal containing material in a sputtering target by confining the precious metal containing material to the areas consumed in the sputtering process. This invention achieves this by using a backing plate, which in one embodiment is composed of a relatively inexpensive material, such as Mo, Ta, Nb, or other refractory metals and alloys, that is mechanically and chemically compatible with the precious metal containing material. FIG. 4 illustrates a cross sectional view of a backing plate 40, that has a top surface 41 with a depression 42 or in this case, a groove. The depression can be the wear path or erosion groove of a used target in the event that the backing plate comprises a used or spent target. In a different embodiment, the depression 42 can be a groove machined into the top surface, 41 of the backing plate. The groove, which corresponds to or approximates the geometry of the sputtering erosion groove, is illustrated in FIG. 1. The geometry of the erosion groove is used to determine the configuration of the depression. Preferably, this information is used to maximize the configuration of the depression to balance the amount of sputtering target so that as small a volume of sputtering material as possible can be used while allowing the target to be configured to maximize the production life of the target. FIG. 5 illustrates the cross section of a composite sputtering target 50 where the precious metal containing sputtering material 51 forms a sputtering zone 52 which is mostly confined to the sputtering area of the composite sputtering target and most of the volume of the precious metal containing sputtering targets is composed of backing plate material 53. A savings of more than 50% in the amount of precious metal containing material required to produce a precious metal containing sputtering target can be achieved by this invention.

An example of how to produce this invention is illustrated in FIGS. 6 and 7. As shown in FIG. 6, the refractory metal or alloy backing plate 60 having a surface including a machined groove 62 is placed inside a graphite hot press die 64 with the grooved surface up. Then a specified amount of sputtering material 66 is poured into the die on top of the backing plate 60 and the assemblage 65 is vibrated for a specified amount of time to evenly settle the powder onto the surfaces of the backing plate. After vibrating the assemblage, a graphite hot press die ram 67 is placed into the die cavity until it contacts the surface of the sputtering material. The assemblage 65 is then placed in a hydraulic press and pressurized to a preset pressure for a specific amount of time to compact the powder onto the surfaces of the backing plate. After compaction, the assemblage is placed inside the furnace chamber of a vacuum hot press (not shown in the drawing). The ram of a hydraulic press that passes through the furnace chamber is lowered until it makes contact with the top of the hot press die ram. The furnace chamber is then sealed and is evacuated to between 50 to 200 mTorr. The assemblage is heated in the furnace chamber to a temperature between 800° and 1000° C. and at that point pressure is applied to the hot press die ram via the hydraulic press ram in contact with it. The initial pressure applied is between 5 and 20 tons. As the assemblage is heated up to a temperature between 1400° and 1900° C., preferably between 1500° and 1550° C., ram pressure is slowly increased to a pressure between 10 and 200 tons; the ultimate ram pressure depending upon the size and geometry of the precious metal containing sputtering target being manufactured. The assemblage 65 is held at temperature and ram pressure for between 15 and 240 minutes; preferably between 20 and 60 minutes. After this time has elapsed, both the ram pressure and temperature are decreased until the assemblage 65 reaches ambient temperature and pressure and the vacuum level is raised to ambient pressure once the furnace has cooled to ambient temperature.

FIG. 7 illustrates the cross section of the assemblage 70 illustrated in FIG. 6 after hot pressing has been completed. As can be seen in the drawing, the sputtering material has been consolidated into the machined groove of the backing plate 73 to form a sputtering zone 74 which has a density of greater than 95% of the theoretical density of the sputtering material. The precious metal containing sputtering target pre-form composed of the consolidated sputtering material and backing plate 73 is removed from the hot press die 75, after the removal of the graphite die ram 77. The pre-form is then machined to final dimensions using CNC milling, diamond grinding, or electrical discharge machining (EDM).

In some applications in which the carbon content of the precious metal containing material must be maintained at an extremely low level, the internal surfaces of the graphite die and the bottom of the graphite die ram can be lined with Mo or an other refractory metal foil to prevent the diffusion of carbon from the graphite die parts into the precious metal containing material.

Another advantage in using this invention is that when the sputtering target is spent, the spent target can be used to produce a new sputtering target using the process described above where the spent target is substituted for the refractory metal or alloy backing plate containing the machined groove in the process. By doing so the amount of precious metal containing sputtering material used in the process is further reduced and the cost of the refractory metal or alloy backing plate containing the machined groove is eliminated. The process of reusing the spent composite sputtering target can be repeated numerous times.

Yet another advantage in using this invention to produce precious metal containing sputtering targets is realized when the oxygen content of the precious metal containing material must be kept extremely low. During the hot pressing process oxygen is removed from the precious metal containing material due to its exposure to the graphite die under vacuum which provides an extremely reducing atmospheric condition within the graphite die even when the die surface are lined with Mo or other refractory metals. This reducing condition is capable of reducing the oxygen content of the precious metal containing material to below specified levels even when the oxygen content of the starting precious metal containing material exceeds said specification. This feature, which is not encountered on other processes such as hot isostatic pressing (HIP'ing) where the precious metal containing material is isolated from reducing conditions by containment in a sealed metal can, provides for the use of precious metal containing materials with a wide range of starting oxygen contents leading to great flexibility in precious metal material sourcing, thus reducing costs.

The following examples illustrate specific embodiments of the invention and are not to be considered as limiting the invention in any manner.

EXAMPLE 1

A 2.03″ diameter by 0.31″ thick circular Ru composite sputtering target was fabricated with a Mo backing plate using the disclosed invention. Using a lathe, a 2.03″ diameter by 0.25″ thick piece of Mo was machined in such a way as to provide a cavity concentric with the diameter of the Mo piece with a depth of 0.115″ deep and top diameter of 1.84″ and a bottom diameter of 1.55″ (forming a frustum shape). The machined Mo piece was placed into a graphite hot press die and 100 grams of Ru powder was poured into the die cavity so as to fill the cavity in the Mo piece and cover the top of it. A graphite die ram was then placed into the die cavity and lowered onto the top of the Ru powder.

The die assemblage was subsequently placed in a hydraulic press and pressed to a few hundred pounds of load to pre-compress the Ru powder. Then the die assemblage was placed into a vacuum hot press and processed at 1525° C. for 0.5 hours at 500 psi at a vacuum level of 200 mTorr. After hot pressing the Ru/Mo composite piece was removed from the hot press and the surfaces machined to facilitate visual inspection.

A visual inspection of the part indicated that the Ru and Mo bonded together during the hot pressing process without reacting significantly with one another indicating chemical compatibility. Furthermore, no cracks in either material were noted, indicating mechanical compatibility. The composite part was then placed in an EDM machine and sectioned so as to inspect the cross section of the composite. Visual and microscopic inspection reveal that no significant reaction occurred and no cracking or gaps were present in the composite further indicating chemical and mechanical compatibility between the two materials.

To check the density of the Ru portion of the composite, a section of the composite piece was placed in the EDM machine and a piece of Ru free of Mo with dimensions of 0.701″ by 0.537″ by 0.185″ thick was cut out of the composite. The density was determined using the physical dimensions and the weight of the piece. The density of the Ru piece cut from the Ru/Mo composite was found to be 98.9% of the theoretical density of Ru; a density suitable for precious metal containing sputtering target applications.

The amount of Ru used to make this composite sputtering target was 100 grams which is less than 50% of the amount required, 202 grams, to make a pure Ru sputtering target of the same geometry.

EXAMPLE 2

A 2.03″ diameter by 0.31″ thick circular Ru composite sputtering target was fabricated with an Nb backing plate using the disclosed invention. Using a lathe, a 2.03″ diameter by 0.25″ thick piece of Nb was machined in such a way as to provide a cavity concentric with the diameter of the Nb piece with a depth of 0.115″ deep and top diameter of 1.84″ and a bottom diameter of 1.55″ (forming a frustum shape). The machined Nb piece was placed into a graphite hot press die and 100 grams of Ru powder was poured into the die cavity so as to fill the cavity in the Mo piece and cover the top of it. A graphite die ram was then placed into the die cavity and lowered onto the top of the Ru powder.

The die assemblage was subsequently placed in a hydraulic press and pressed to a few hundred pounds of load to pre-compress the Ru powder. Then the die assemblage was placed into a vacuum hot press and processed at 1525° C. for 0.5 hours at 500 psi at a vacuum level of 200 mTorr. After hot pressing the Ru/Nb composite piece was removed from the hot press and the surfaces machined to facilitate visual inspection.

A visual inspection of the part indicated that the Ru and Nb bonded together during the hot pressing process with out reacting significantly with one another indicating chemical compatibility. Furthermore, no cracks in either material were noted, indicating mechanical compatibility. The composite part was then placed in an EDM machine and sectioned so as to inspect the cross section of the composite. Visual and microscopic inspection reveal that no significant reaction occurred and no cracking or gaps were present in the composite further indicating chemical and mechanical compatibility between the two materials.

The amount of Ru used to make this composite sputtering target was 100 grams which is less than 50% of the amount required, 202 grams, to make a pure Ru sputtering target of the same geometry.

EXAMPLE 3

A 2.03″ diameter by 0.31″ thick circular Ru composite sputtering target was fabricated with a Ta backing plate using the disclosed invention. Using a lathe, a 2.03″ diameter by 0.25″ thick piece of Ta was machined in such a way as to provide a cavity concentric with the diameter of the Ta piece with a depth of 0.115″ deep and top diameter of 1.84″ and a bottom diameter of 1.55″ (forming a frustum shape). The machined Ta piece was placed into a graphite hot press die and 100 grams of Ru powder was poured into the die cavity so as to fill the cavity in the Ta piece and cover the top of it. A graphite die ram was then placed into the die cavity and lowered onto the top of the Ru powder.

The die assemblage was subsequently placed in a hydraulic press and pressed to a few hundred pounds of load to pre-compress the Ru powder. Then the die assemblage was placed into a vacuum hot press and processed at 1525° C. for 0.5 hours at 500 psi at a vacuum level of 200 mTorr. After hot pressing the Ru/Ta composite piece was removed from the hot press and the surfaces machined to facilitate visual inspection.

A visual inspection of the part indicated that the Ru and Ta bonded together during the hot pressing process with out reacting significantly with one another indicating chemical compatibility. Furthermore, no cracks in either material were noted, indicating mechanical compatibility. The composite part was then placed in an EDM machine and sectioned so as to inspect the cross section of the composite. Visual and microscopic inspection reveal that no significant reaction occurred and no cracking or gaps were present in the composite further indicating chemical and mechanical compatibility between the two materials.

The amount of Ru used to make this composite sputtering target was 100 grams which is less than 50% of the amount required, 202 grams, to make a pure Ru sputtering target of the same geometry.

EXAMPLE 4

A 2.03″ diameter by 0.31″ thick circular Ru composite sputtering target was fabricated with a Ti backing plate using the disclosed invention. Using a lathe, a 2.03″ diameter by 0.25″ thick piece of Ti was machined in such a way as to provide a cavity concentric with the diameter of the Ti piece with a depth of 0.115″ deep and top diameter of 1.84″ and a bottom diameter of 1.55″ (forming a frustum shape). The machined Ti piece was placed into a graphite hot press die and 100 grams of Ru powder was poured into the die cavity so as to fill the cavity in the Ti piece and cover the top of it. A graphite die ram was then placed into the die cavity and lowered onto the top of the Ru powder.

The die assemblage was subsequently placed in a hydraulic press and pressed to a few hundred pounds of load to pre-compress the Ru powder. Then the die assemblage was placed into a vacuum hot press and processed at 1525° C. for 0.5 hours at 500 psi at a vacuum level of 200 mTorr. After hot pressing the Ru/Ti composite piece was removed from the hot press and the surfaces machined to facilitate visual inspection.

A visual inspection of the part indicated that the Ru and Ti bonded together during the hot pressing process however there was evidence of reaction between the two materials with slight erosion of the Ti along the edges of the piece indicating possible chemical incompatibility. No cracks in either material were noted, indicating possible mechanical compatibility. The composite part was then placed in an EDM machine and sectioned so as to inspect the cross section of the composite. Visual and microscopic inspection revealed that significant reaction occurred between the two materials leaving a gap between the Ru and the Ti pieces further indicating chemical incompatibility between the two materials under the conditions used to process the composite. If Ti is to be used as a backing plate, a barrier material such as Mo, Nb, Ta, or other material that is chemically and mechanically compatible with both Ru and Ti could be inserted between the Ti backing plate and Ru powder load. The barrier material could be in the form of a foil, powder layer or coating applied with such methods as sputtering, flame spraying, or plasma spraying or other coating techniques.

EXAMPLE 5

A ruthenium/niobium composite part was prepared that was 7.07″ long by 2.30″ wide by 0.5″ thick by pressing ruthenium powder into a Nb backing plate 7.07″ long by 2.30″ wide by 0.400″ thick containing a groove that was 1.77″ wide at the top and 1.05″ wide at the bottom and 0.233″ deep running along the length of the backing plate. The plate was placed in a graphite die and filled with 715 grams of ruthenium powder which filled the groove and covered the backing plate. A die ram was place into the graphite die so that it would make contact with the ruthenium powder and the die pre-pressed before insertion into a vacuum hot press which was larger than the vacuum hot press used in the first four examples. In the vacuum hot press the die was heated to 1600° C. and 26 tons of pressure was applied to the die ram. The die and contents were held under these conditions for four hours before cooling to room temperature. A higher density was achieved for this example and the following example than in the first four examples by holding the parts at temperature for a longer period of time. An evaluation of the ruthenium in the groove of the composite part indicated that the relative density of the ruthenium was 99% of the theoretical density of ruthenium which is 12.41 g/cc. Then an approximation of an erosion groove was machined into the surface of the ruthenium portion of the composite along the length to a maximum depth of 0.200″. The composite was placed back into the graphite die and filled with 400 grams of ruthenium powder, which filled the groove and covered the composite part. A die ram was place into the graphite die so that it would make contact with the ruthenium powder and the die pre-pressed before insertion into a vacuum hot press. In the vacuum hot press the die was heated to 1600° C. and 26 tons of pressure was applied to the die ram. The die and contents were held under these conditions for four hours before cooling to room temperature. An evaluation of the ruthenium pressed into the simulated erosion groove of the composite part indicated that the relative density of the ruthenium was 99% of the theoretical density of, which is 12.41 g/cc. These results indicate the possibility of reusing spent ruthenium/niobium composite sputtering targets to produce new ruthenium/niobium sputtering targets.

EXAMPLE 6

Two spent ruthenium target pieces each measuring 7.07×1.09×0.25″ with a target erosion groove of roughly triangular shape and about 0.24″ deep eroded along the length of each strip were placed in a graphite hot press die. 500 grams of ruthenium powder was poured into the graphite die in such a way as to fill the erosion grooves and completely cover the strip pieces. A die ram was place into the graphite die so that it would make contact with the ruthenium powder and the die pre-pressed before insertion into a vacuum hot press. In the vacuum hot press the die was heated to 1600° C. and 20 tons of pressure was applied to the die ram. The die and contents were held under these conditions for four hours before cooling to room temperature. After hot pressing, the resultant part was characterized for density and found to be 98% dense relative to a ruthenium x-ray density of 12.41 g/cc. Upon microscopic examination, the interface between the spent target and the new material was not discernable without extensive chemical etching. These results indicated that spent ruthenium sputtering targets could be refilled with new ruthenium and used for sputtering operations.

While in accordance with the patent statutes the best mode and preferred embodiment have been set forth, the scope of the invention is not intended to be limited thereto, but only by the scope of the attached claims.

Claims

1. A method of manufacturing composite sputtering targets comprising the steps of:

(a) providing a backing plate having a geometry and a surface which includes a depression,

(b) placing the backing plate into a graphite die designed to accommodate a geometry of the backing plate,

(c) adding a sputtering material to the graphite die on top of the backing plate to from a die assembly

(d) placing a graphite die ram into the die assembly so that the ram contacts the sputtering material,

(e) placing the die assembly and ram into an hydraulic press and pressing the graphite die ram into graphite die to a specific pressure,

(e) placing the compacted die assembly and ram into a vacuum hot press furnace chamber and contacting the die ram with the hydraulic ram of the hot press,

(g) sealing and evacuating the vacuum hot press furnace chamber to a vacuum level of between about 200 and 50 mTorr,

(h) heating the vacuum hot press furnace chamber and contents to a pre-determined temperature and applying pressure to the graphite die ram via the hydraulic press ram,

(i) lowering the pressure on the ram, and cooling and raising the vacuum level of the hot press vacuum furnace chamber, and

(j) removing the die assembly and ram from the vacuum hot press furnace.

2. The method of claim 1 further including the step of removing a composite sputtering target pre-form from the graphite die.

3. The method of claim 2 including the further step of machining the surface of the composite sputtering target pre-form.

4. The method of claim 3 wherein the machining step includes one or more of diamond grinding and electrodynamic machining.

5. The method of claim 1, wherein the backing plate comprises a material that is a refractory metal or alloy that is mechanically and chemically compatible with the sputtering material.

6. The method of claim 5 wherein the backing plate material comprises is Mo, Ta, or Nb.

7. The method of claim 1, wherein said sputtering material is comprises pure Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals, or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals and oxides or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt with oxides.

8. The method of claim 1, wherein the sputtering material is comprised of precious metals or precious metal alloys or mixtures with other metals or metal alloys or metal oxides.

9. The method of claim 1, wherein the composite sputtering target geometry is circular, rectangular, delta, or oval shaped.

10. The method of claim 1, wherein the composite sputtering target is comprised of more than one section requiring a multi-tile sputtering target design.

11. The method of claim 1, including the further step of forming the depression in the backing plate.

12. The method of claim 11 including the further step of calculating the erosion pattern of a used sputtering target having a geometry which corresponds to the geometry of the composite sputtering target, using that erosion pattern to calculate an optimal shape for the depression, and forming the depression to correspond to the optimal shape in a surface of the backing plate by machining the backing plate.

13. The method of claim 1 in which the backing plate is a used sputtering target.

14. The method of claim 1 in which the backing plate is comprised of a material which is different than the sputtering material.

15. The method of claim 1, wherein a barrier material is used, and the material of the barrier material is inserted between the sputtering material and backing plate so as to prevent adverse reactions between the precious metal containing material and the machined backing plate material.

16. The method of claim 15, wherein the barrier material is comprised of one or more of Nb, Ta, Mo of one of more of a foil, a powder or a coating.

17. A method of manufacturing composite sputtering target including a sputtering material comprising the steps of:

(a) selecting a backing plate material that is chemically and mechanically compatible with the sputtering material,

(b) forming a groove in the backing plate material that approximates the erosion groove of a spent sputtering target to form a backing plate having a geometry including a top surface,

(c) placing the backing plate into a graphite hot press die designed to accommodate the geometry of the backing plate,

(d) adding a predetermined amount of powder of the sputtering material onto the top surface of the backing plate so as to as to fill the groove and cover the top surface of the backing plate to form a graphite die backing plate assembly,

(e) vibrating the graphite die backing plate assembly so as to evenly distribute the sputtering material powder over the top surface of the backing plate and thus form a top surface of the sputtering material powder,

(f) placing a graphite die ram having a top surface and bottom surface into the graphite die so that the bottom surface of the ram contacts the top surface of the sputtering material powder to form an assemblage of the graphite die backing plate assembly and the graphite die ram,

(g) placing the assemblage into an hydraulic press and pressing the graphite die ram to a predetermined pressure so as to compact the sputtering material powder into the backing plate groove and unto the surface of the machined backing plate to from a compacted assemblage,

(h) placing the compacted assemblage into a vacuum hot press furnace chamber and lowering the hydraulic ram of the hot press onto the graphite die ram so as to contact the top surface of the die ram,

(i) sealing and evacuating the vacuum hot press furnace chamber to a vacuum level of between about 200 and about 50 mTorr,

(j) heating the vacuum hot press furnace chamber and contents to a pre-determined temperature suitable for the densification of the sputtering material powder into a solid, dense form,

(k) applying pressure to the graphite die ram via the hydraulic press ram to a pre-determined pressure suitable for the densification of the sputtering material powder into a solid, dense form,

(l) holding the assemblage at the applied temperature and pressure for a pre-determined amount of time suitable for the densification of the sputtering material powder into a solid, dense form to form a sputtering target pre-form,

(m) releasing the pressure on the hydraulic press ram, and cooling and releasing the vacuum level of the hot press vacuum furnace chamber,

(n) removing the assemblage from the vacuum hot press furnace and removing the composite sputtering target pre-form from the graphite die,

(o) finishing the surface of the composite sputtering target pre-form to obtain a composite sputtering target.

18. The method of claim 17, wherein the backing plate comprises a material that is a refractory metal or alloy that is mechanically and chemically compatible with the sputtering material.

19. The method of claim 18 wherein the backing plate material comprises is Mo, Ta, or Nb.

20. The method of claim 17, wherein said sputtering material is composed of pure Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals and oxides or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt with oxides such as TiO2.

21. The method of claim 17, wherein the sputtering material is composed of precious metals or precious metal alloys.

22. The method of claim 21 wherein the sputtering material is Ag or Au or mixtures of Ag or Au with other metals or metal alloys or metal oxides.

23. The method of claim 17, wherein the composite sputtering target has a geometry which is circular, rectangular, or delta shaped.

24. The method of claim 17, wherein the composite sputtering target is composed of more than one section requiring a multi-tile sputtering target design.

25. The method of claim 17, wherein a spent composite sputtering target is used as the backing plate to produce the composite sputtering target.

26. The method of claim 17, wherein a spent composite sputtering target is used a plurality of times as the backing plate to produce the composite sputtering target.

27. The method of claim 17, wherein a barrier material or other material chemically and mechanically compatible with the sputtering material and the backing plate material is inserted between the precious metal containing material and the machined backing plate.

28. The method of claim 27, wherein the barrier material is inserted between the sputtering material and the backing plate material by the use of foils, powders or coatings composed of the barrier material.

29. A method of increasing the production efficiency of a sputtering material comprising the steps of: using the composite sputtering target for a sputtering process to form a used composite sputtering target; and

forming a sputtering target perform by

(a) providing a backing plate having a geometry which includes a surface which provides a depression,

(b) placing the backing plate into a graphite die designed to accommodate the geometry of the backing plate,

(c) adding a sputtering material to the graphite die on top of the backing plate to from a die assembly

(d) placing a graphite die ram into the die assembly so that the ram contacts the sputtering material,

(e) placing the die assembly and ram into an hydraulic press and pressing the graphite die ram into the graphite die to a specific pressure to form a compacted die assembly,

(f) placing the compacted die assembly and ram into a vacuum hot press furnace chamber and contacting the die ram with the hydraulic ram of the hot press,

(g) sealing and evacuating the vacuum hot press furnace chamber to a vacuum level of between about 200 and 50 mTorr,

(h) heating the vacuum hot press furnace chamber and contents to a pre-determined temperature and applying pressure to the graphite die ram via the hydraulic press ram,

(i) lowering the pressure on the hydraulic press ram and cooling and releasing the vacuum level of the hot press vacuum furnace chamber,

(j) removing the compacted die assembly and ram from the vacuum hot press furnace,

(k) removing a composite sputtering target pre-form from the graphite die to form a composite sputtering target,

using the used composite sputtering target as a backing plate to form a new composite sputtering target.

30. The method of claim 29 including the further step of machining the surface of the composite sputtering target pre-form to obtain specified physical dimensions of the composite sputtering target.

31. The method of claim 30 wherein the machining step includes one or more of diamond grinding and electrodynamic machining.

32. The method of claim 30, wherein the backing plate comprises a material that is the sputtering material or Mo, Ta, or Nb.

33. The method of claim 30, wherein said sputtering material is composed of pure Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals, or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals, and oxides such as TiO2 or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt with oxides.

34. A composite sputtering target comprised of a backing plate which is one or more of Mo, Ta, and Nb, and a sputtering zone which is composed of pure Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals, or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt, with transition metals and oxides or mixtures of Ru, Rh, Pd, Re, Os, Ir, Pt with oxides, the sputtering zone being a densified area of sputtering material chemically, thermally and electrically consolidated with the backing target, and the sputtering target having a suitable geometry for use in a sputtering process.

35. The composite sputtering target of claim 34, wherein a barrier material comprised of Nb, Ta, Mo, is inserted between the sputtering material and backing plate so as to prevent adverse reactions between the precious metal containing material and the machined backing plate material.

36. The composite sputtering target of claim 34 wherein the configuration of the sputtering zone is formed by calculating the erosion pattern of a used sputtering target having a geometry which corresponds to the geometry of the composite sputtering target and using that erosion pattern to calculate the sputtering zone.