Patent Description:
Aluminum scandium nitride (AlxSc<NUM>-xN) is of some interest for the fabrication of thin film piezoelectric materials for various applications. A conventional method for manufacturing these piezoelectric thin films is by using reactive sputter deposition. The sputtering target, typically a metal or metallic alloy, is constructed of the material to be sputtered. The sputtering target and the substrate are placed in proximity to one another within the chamber and the target is bombarded with charged particles or ions. The high energy ions cause a portion of the sputtering target to dislodge and be re-deposited on the substrate. Sputtering is advantageous because it allows compositional control of the film, affords control of residual stresses in the film, allows high rate deposition of the thin film, and readily accommodates controlled heating of the substrate. There is already a strong history of using this process in fabricating thin films.

The resulting properties of the thin films depend strongly on uniform deposition of the Al-Sc alloy. This imposes considerable demands on the properties of the sputtering targets and the alloys. The piezoelectric response of the thin film is strongly dependent upon the scandium content of the film, and so the overall chemical stoichiometry and macrodistribution of the scandium in the sputtering target is critical.

Even in view of the known alloys and sputtering targets, the need exists for alloys and sputtering targets that provide for improvements in uniformity of chemical stoichiometry and minimization of porosity. The need further exists for a microstructure that reduces target failure due to cracking and contamination from particle emission during sputtering (particles being ejected from the surface of the sputtering target, rather than individual atoms/ions, and landing on the wafer - often referred to as particulation). These features may contribute to a sputtering target having better performance and lifetime resulting in higher wafer yields and lower cost of ownership.

<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> disclose Al-Sc sputtering targets.

A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.

As discussed above, aluminum-scandium alloys produced using many conventional processes do not meet the demands for a uniform chemical stoichiometry and minimal porosity, and a defect-free microstructure. As a result, the films and substrates formed therefrom have inconsistencies in thin film uniformity. Also, the targets comprising the alloys suffer from deficiencies in physical/mechanical performance such as having defects leading to cracks which can cause arcing or particulation during sputtering, leading to yield losses and reduced target lifetime. The industry desires targets that are defect free, that prevent target cracking, that demonstrate low particle emission during sputtering, and that provide extended target lifetime.

Non-equilibrium composites, e.g., for use as sputtering targets, comprising a ductile, first phase and a brittle second phase are disclosed herein. The use of particular second phases, e.g., (brittle) intermetallic AlxScy phases, (in specific amounts) in the non-equilibrium composites has been found to provide microstructures that maximize the amount of ductile aluminum phase and minimize the amount of brittle intermetallic AlxScy phases, while maintaining the overall composition percentages in the composite. This provides for desirable combinations of the features mentioned above, e.g., uniformity in bulk composition of the aluminum-scandium alloy as well as a defect and porosity-free microstructure, as well as prevention of target cracking and reduction of casting defects and particle emission. In some cases, a desirable increase of the ductile phase content is achieved by employing lower amounts of intermetallic AlxScy phases that have higher scandium content and/or lower amounts of aluminum (outside of the amounts predicted by the equilibrium phase diagram for aluminum-scandium). Thus, because lower amounts of intermetallic AlxScy phases are employed, it is possible to utilize higher amounts of ductile aluminum phase, which provides for the aforementioned benefits.

As noted above, the addition of the metastable ductile phase, e.g., "free aluminum," to the microstructure may reduce particulation and improve the overall performance of the target. In addition, the added ductility offered by the ductile phase facilitates thermomechanical processing of these materials. This allows the healing of casting defects such as solidification pores and inhomogeneous microstructures. It also reduces arcing and improves consistency of the sputter performance over the life of the target. Also, thin films made using the sputtering targets disclosed herein advantageously demonstrate lower particulation during sputtering. The particles that are detrimentally ejected from the particle surface can be considered to be contaminants because these particles affect and reduce overall device yield. In some embodiments, the (uniform) macrodistribution of the brittle second phases provides a composite that has surprisingly been found to have greater compositional uniformity, thus providing sputtering targets that produce higher quality thin films. Also, the composites formed by the disclosed processes, in some cases, advantageously allow the production of larger diameter sputtering targets, which would be prone to cracking if produced by conventional methods.

Conventionally, it has been difficult to achieve a desirable (high) amount, if any, of ductile aluminum phase in higher scandium-containing alloys. This is because conventional production (casting) processes produce equilibrium microstructures with lower aluminum content and phase volume ratios predicted by the equilibrium phase diagram for aluminum-scandium. In contrast, by employing a non-equilibrium phase distribution as noted herein, the composites produced by processes disclosed herein achieve the desired amounts of ductile aluminum phase in the overall composition.

By judicious design of the phases present in the composite targets, the amount of ductile phase present relative to conventional equilibrium alloys, which either possess a small amount, if any, of free aluminum (alloys with less than <NUM>% Sc) or no equilibrium aluminum (alloys with Sc contents greater than or equal to <NUM>% Sc), can be beneficially increased, thereby increasing the ductility and strength of the material, improve the chemical uniformity, and reduce the amount of particulation that occurs during sputtering.

The present disclosure relates to composites comprising aluminum and scandium - Al-Sc composites. The Al-Sc composites can be used to produce articles, such as sputtering targets, having, among other benefits, high compositional uniformity with a uniform distribution of second phase(s). In some embodiments, the Al-Sc composites contain from <NUM> at% to <NUM> at% scandium and from <NUM> at% to <NUM>% aluminum (optionally along with other elements). Further compositional details are provided below.

Overall, the disclosed composite, in some embodiments, comprises from <NUM> at% to <NUM> at% scandium, e.g., from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, or from <NUM> at% to <NUM> at%.

In terms of lower limits, the composite may comprise greater than <NUM> at% scandium, e.g., greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, or greater than <NUM> at%. In terms of upper limits, the composite may comprise less than <NUM> at% scandium, e.g., less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, or less than <NUM> at%.

As used herein, "greater than" and "less than" limits may also include the number associated therewith. Stated another way, "greater than" and "less than" may be interpreted as "greater than or equal to" and "less than or equal to. " It is contemplated that this language may be subsequently modified in the claims to include "or equal to. " For example, "greater than <NUM>" may be interpreted as, and subsequently modified in the claims as "greater than or equal to <NUM>.

In some embodiments, the composite comprises from <NUM> at% to <NUM> at% aluminum, e.g., from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, from <NUM> at% to <NUM> at%, or from <NUM> at% to <NUM> at%. These amounts account for aluminum present in the first phase (as free aluminum) and as a component in the intermetallic second phase.

In terms of lower limits, the composite may comprise greater than <NUM> at% aluminum, e.g., greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, or greater than <NUM> at%. In terms of upper limits, the composite may comprise less than <NUM> at% aluminum, e.g., less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, or less than <NUM> at%.

In some embodiments, the composite comprises from <NUM> mol% to <NUM> mol% scandium nitride, e.g., from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, or from <NUM> mol% to <NUM> mol%. In terms of lower limits, the alloy may comprise greater than <NUM> mol% scandium nitride, e.g., greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, or greater than <NUM> mol%. In terms of upper limits, the alloy may comprise less than <NUM> mol% scandium nitride, e.g., less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, or less than <NUM> mol%.

Nitrided powders may be useful in controlling oxygen uptake and passivate the powder components to stabilize with the molten aluminum during processing.

In some cases, the composite is of high purity, and contains as few contaminants as possible. For example, oxygen is extremely deleterious to the properties of piezoelectric films, both by preferentially binding into the matrix and by stabilizing other, non piezoelectric phases. Thus, the composite or sputtering target should contain as little oxygen as possible. In some embodiments, the composite comprises less than <NUM> ppm oxygen, e.g., less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, or less than <NUM> ppm. The presence of transition metal elements, for example iron, should also be minimized.

In some embodiments, the uniformity of scandium across a surface of the composite, e.g., a sputtering target formed therefrom, varies by less than +/- <NUM> at% scandium, e.g., less than +/-<NUM> at%, less than +/- <NUM> at%, less than +/- <NUM> at%, less than +/- <NUM> at% , or less than +/- <NUM> at%, over the surface. In some embodiments, a sputtering target formed from the composites and having a central axis and a diameter intersecting the central axis through a thickness of the sputtering target, has a uniformity of scandium across the central axis and the diameter that varies by less than +/- <NUM> at% scandium, e.g., less than +/- <NUM> at%, less than +/- <NUM> at%, less than +/- <NUM> at%, less than +/- <NUM> at% , or less than +/- <NUM> at%.

Sputtering targets made from the composites may be used to deposit thin films onto a substrate. The piezoelectric properties of an individual device on the substrate are critically dependent upon the local stoichiometry of the film contained within an individual device. Hence the distribution of the scandium through an Al-Sc sputtering target should be as uniform as possible, both in-plane (e.g., on a surface) and through the thickness of the sputtering target. This chemical uniformity across both the surface and through the thickness is necessary because if the amount of scandium being sputtered from the target varies over the life of the target, the piezoelectric properties of the deposited film will change over the life of the target, resulting in device performance inconsistencies and resulting product yield loss. Properties and characteristics of the composite are discussed below.

In some embodiments, the composite comprises a ductile, first phase and a brittle, second phase dispersed throughout the matrix, and the second phase may comprise aluminum and scandium. The scandium present in the overall composite, in some cases, is provided by the second phase. In some cases, the second phase may include one or more compounds corresponding to the formula AlxScy, where x is from <NUM> to <NUM> and y is from <NUM> to <NUM>. The second phase may comprise Al<NUM>Sc, AhSc, AlSc, Sc<NUM>Al, or Sc, or combinations thereof.

In some embodiments, the composite comprises from <NUM> vol% to <NUM> vol%, e.g., from <NUM> vol% to <NUM> vol%, first phase (free aluminum) and from <NUM> vol% to <NUM> vol % second phase, based on the total volume of the composite. For example, the composite may comprise from <NUM> vol% to <NUM> vol% first phase, e.g., from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, or from <NUM> vol% to <NUM> vol%. In terms of lower limits, the composite may comprise greater than <NUM> vol% first phase, e.g., greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, or greater than <NUM> vol%. In terms of upper limits, the composite may comprise less than <NUM> vol% first phase, e.g., less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, or less than <NUM> vol%.

The amount of first phase and second phases present may be quantitatively determined optical and SEM/EDS microscopy, EBSD, or other known techniques.

In some cases, the first phase may comprise a small amount of scandium, e.g., less than <NUM> wt%, less than <NUM> wt%, less than <NUM> wt%, or less than <NUM> wt%.

In some embodiments, the composite comprises from <NUM> vol% to <NUM> vol% second phase, e.g., from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, from <NUM> vol% to <NUM> vol%, or from <NUM> vol% to <NUM> vol%. In terms of lower limits, the composite may comprise greater than <NUM> vol% second phase, e.g., greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, greater than <NUM> vol%, or greater than <NUM> vol%. In terms of upper limits, the composite may comprise less than <NUM> vol% first phase, e.g., less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, less than <NUM> vol%, or less than <NUM> vol%. These amounts are generally lower than amounts used in conventional alloys because the disclosed second phases have higher scandium content than conventional alloys that use an equilibrium phase distribution, as determined by the equilibrium phase diagram. Thus, the lower amounts can be used to achieve the overall scandium level. Because lower amounts of second phases are employed, it is possible to advantageously utilize higher amounts of ductile aluminum phase.

<FIG> is the phase diagram <NUM> for aluminum and scandium. The x-axis indicates the amount of scandium in atomic percent (at%), with zero scandium / <NUM> at% aluminum at the far left of the phase diagram. Examination of the Al-Sc phase diagram reveals that from <NUM> to <NUM> at% scandium, the equilibrium alloy may include an intermetallic Al<NUM>Sc phase in a metallic aluminum matrix. At higher scandium content, the composite may include one or more intermetallic phases selected from Al<NUM>Sc, AhSc, AlSc, Al Sc<NUM>, or may include scandium, or may include any combination of intermetallic phases and scandium.

The second phase in the composite comprises high amounts/concentrations of scandium, e.g., amounts/concentrations that are outside of, e.g., greater than, the amounts/concentrations predicted by the equilibrium phase diagram for aluminum-scandium. For example, the second phase may comprise greater than (or equal to) <NUM> at%, based on the total of the second phase e.g., greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, greater than <NUM> at%, or greater than <NUM> at%.

The second phase comprises specific intermetallic phases, e.g., Al<NUM>Sc, Al<NUM>Sc, AlSc, Al Sc<NUM>, e.g., in amounts that are outside of the amounts/concentrations predicted by the equilibrium phase diagram for aluminum-scandium. For example, the second phase may comprise these intermetallic phases in an amount greater than <NUM> mol%, based on the total of the second phase e.g., greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, or greater than <NUM> mol%. In terms of upper limits, the second phase may comprise these intermetallic phases in an amount less than <NUM> mol%, e.g., less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, or less than <NUM> mol%.

In some embodiments, these amounts/concentrations are outside of, e.g., greater than, the amounts/concentrations predicted by the equilibrium phase diagram for aluminum-scandium.

In some embodiments, intermetallic phases having greater amounts/concentrations of scandium and/or lesser amounts of aluminum may be utilized. For example, the second phase may comprise Al<NUM>Sc, Al<NUM>Sc, AlSc, Al Sc<NUM>, or Sc or combinations thereof in an amount greater than <NUM> mol%, based on the total moles of the second phase, e.g., greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, greater than <NUM> mol%, or greater than <NUM> mol%. In some embodiments, these amounts/concentrations are outside of, e.g., greater than, the amounts/concentrations predicted by the equilibrium phase diagram for aluminum-scandium. These ranges and limits are applicable to the intermetallic phases collectively and to each of the intermetallic phases individually.

It has been discovered that some second phase components are particularly brittle, which may be an overall detriment to the compositions. In some embodiments, the second phase comprises specific amounts of intermetallic phases, e.g., AhSc. For example, the second phase may comprise less than <NUM> mol% AhSc, based on the total moles of the second phase, e.g., less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, less than <NUM> mol%, or less than <NUM> mol%. In some embodiments, the second phase is devoid of or substantially devoid of AhSc.

The second phase comprises low amounts/concentrations, if any, of aluminum, e.g., amounts/concentrations that are outside of the amounts/concentrations predicted by the equilibrium phase diagram for aluminum-scandium. For example, the second phase may comprise less than (or equal to) <NUM> at%, based on the total of the second phase e.g., less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, less than <NUM> at%, or less than <NUM> at%.

In some cases, the amount of scandium in the second phase is greater than the amount predicted by the equilibrium phase diagram for aluminum-scandium, e.g., at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, or at least <NUM>%.

<FIG> represent schematic cross-sections of Al-Sc alloy microstructures, while <FIG> represents a conventional aluminum alloy <NUM> having an aluminum rich metal matrix <NUM> with no second phases present. <FIG> represents an Al-Sc alloy <NUM> according to the present disclosure that may include a second phase <NUM> dispersed uniformly throughout the aluminum matrix <NUM>. In some cases, the second phase as described above may be distributed at a spatial distance d<NUM> apart, which may include a range of values.

The second phase, in some embodiments, may comprise multiple individual phases, e.g., a second phase and a third phase and a fourth phase. It is intended that phases higher than the second phase, e.g., the third phase, the fourth phase, etc., shall have the same description and properties as mentioned above with regard to the second phase. For example the third phase may have high amounts scandium content, e.g., amounts that are outside of the amounts predicted by the equilibrium phase diagram for aluminum-scandium.

For example, <FIG> shows another Al-Sc composite <NUM> according to the present disclosure that includes second phase <NUM> and third phase <NUM> dispersed uniformly throughout the first phase <NUM>. Phases <NUM> and <NUM> may be as described herein. Not shown, composites according to the present disclosure may include more than four phases, e.g., five phases or six phases, with each phase being dispersed throughout the first phase.

In some embodiments, the first phase grains and the second phase grains each have an average particle size, which may be measured in accordance with ASTM E112 (current year).

In some embodiments, the first phase is characterized as having an average particle size ranging from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>.

In terms of lower limits, the first phase may be characterized as having an average particle size greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM> or greater than <NUM>. In terms of upper limits, the first phase is characterized as having an average particle size less than <NUM>, e.g., less than <NUM>, less than <NUM>, or less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>,.

In some embodiments, the grains of the first aluminum matrix phase are characterized as having a crystallographic orientation of (<NUM>). In other embodiments, the grains of the first aluminum matrix phase are characterized as having no preferred crystallographic orientation, or as having random texture. In some cases, texture may be quantified via XRD peak height ratios, EBSD volume ratios, EBSD texture analysis MRD values, and/or XRD pole-figure MRD values.

In some embodiments, the grains of the first phase are characterized as having a random crystallographic orientation.

The second phase may be desirably as fine as possible, and more specifically with an average particle size of less than <NUM> microns (µm). In some embodiments, the second phase(s) is characterized as having an average particle size ranging from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of lower limits, the second phase(s) is characterized as having an average particle size greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. In terms of upper limits, the second phase(s) is characterized as having an average particle size less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>.

In some cases, the microstructure of the sputtering target is uniform over the entire surface area of the target (typically a disk that is <NUM> inches to <NUM> inches in diameter, or about <NUM> to about <NUM>) and through its full thickness (typically approximately one-quarter inch, or <NUM>/<NUM> inch, or about <NUM> to about <NUM>). The scale of the microstructure in the sputtering target is also significant. Defects such as microcracks and fissures, pores, refractory or dielectric inclusions, oxide inclusions, and large intermetallic phase grains are typically associated with undesirable events such as micro-arcing and particulation, and are extremely deleterious to the properties of the films and should be avoided.

In some embodiments, the aluminum-scandium composites have a microstructure devoid of or substantially devoid of microcracks and fissures. The microcracks and fissures may be determined using optical/SEM metallography.

In some embodiments, the aluminum-scandium composites have a microstructure devoid of or substantially devoid of porosity. As measured, the composite comprises less than <NUM>% porosity, e.g., less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, or less than <NUM>%.

In some embodiments, the aluminum-scandium alloys have a microstructure devoid of or substantially devoid of oxide inclusions.

Microscopy may be employed to quantify the aforementioned measurements.

In some embodiments, the aluminum-scandium composite sputtering target has a diameter or cross measurement of greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>.

The aluminum-scandium composite sputtering target may have a thickness, e.g., height, ranging from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to about <NUM>.

A process for producing a (non-equilibrium) aluminum-scandium composite as disclosed herein. In some embodiments, the process comprises the steps of providing a second phase powder comprising a compound corresponding to the formula AlxScy, where x is from <NUM> to <NUM> and y is from <NUM> to <NUM>; and mixing the powder with a first phase (powder) comprising aluminum to form a composite precursor. The process may further comprise the step of applying at least one of heat or pressure to the composite precursor to consolidate the materials, e.g., the first and second phase powders. The process further comprises the step of cooling the consolidated composite precursor to form the non-equilibrium composite.

In some cases, temperatures in the range of from <NUM> to <NUM> are employed, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of lower limits, temperatures of greater than <NUM> may be employed, e.g., greater than <NUM>, greater than <NUM>, or greater than <NUM>. In terms of upper limits, temperatures of less than <NUM> may be employed, e.g., less than <NUM>, less than <NUM>, or less than <NUM>.

In some cases, pressures in the range of from <NUM> kPa to <NUM> kPa are employed, e.g., from <NUM> kPa to <NUM> kPa, from <NUM> kPa to <NUM> kPa, or from <NUM> kPa to <NUM> kPa. In terms of lower limits, pressures of greater than <NUM> kPa may be employed, e.g., greater than <NUM> kPa, greater than <NUM> kPa, or greater than <NUM> kPa. In terms of upper limits, pressures of less than <NUM> kPa may be employed, e.g., less than <NUM> kPa, less than <NUM> kPa, or less than <NUM> kPa.

In some embodiments, e.g., when rapid cooling is employed for example in a squeeze casting process, the cooling of the composite may be at a rate of greater than <NUM>/per minute, e.g., greater than <NUM>/per minute, greater than <NUM>/per minute, greater than <NUM>/per minute, greater than <NUM>/per minute, or greater than <NUM>/per minute.

In some cases, by using a cooling step, the amount of the non-phase diagram intermetallic phases in the second phase is kept in the first phase matrix, without having a chance to revert back to equilibrium phases and/or amounts. In some embodiments, by using a cooling step, the non-equilibrium phase mixture is maintained, without having a chance to revert back to the equilibrium phase mixture.

In some embodiments, the scandium-aluminum composites described herein can be formed via casting processes, preferably employing aluminum (first phase) powder and intermetallic (second phase) powder. Melt processing, e.g. via a casting route, also produces composites with much lower oxygen contents than powder processing, e.g., less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, or less than <NUM> ppm. Thus, casting of aluminum-scandium alloys is suitable for fabrication of the disclosed composites. In some cases, e.g., when using casting techniques, free aluminum is increased/maintained by keeping the temperatures below a certain lever. By keeping temperatures within these ranges and limits, formation of unwanted metallic phase components is advantageously avoided/minimized.

In a typical casting process, the composite constituents are melted together in a crucible at an elevated temperature and then poured into a mold where the molten composite solidifies into an ingot. Solidification typically proceeds from the bottom and walls of the mold towards the center, therefore it would be expected that the outermost regions would cool much faster than the central portions of the casting.

In some cases, a high cooling rate of a casting with large intermetallic loading will cause the buildup of large internal stresses, which can cause the casting to crack. In addition, many cast composites are subjected to subsequent thermomechanical processing (e.g. plastic deformation and/or heat treatment) to break down the characteristic structures associated with casting and yield a uniform microstructure through the target thickness. Brittle castings generally do not withstand such thermomechanical processing steps very well. However, the disclosed composites may be able to withstand this processing due to the composition thereof.

To produce a composite sputtering target of Example <NUM>, an intermetallic (second phase) Al<NUM>Sc<NUM> powder comprising multiple intermetallic aluminum-scandium phases was prepared. AlSc and Sc were blended in a Turbula® mixer for <NUM> minutes to form a precursor. The precursor was loaded into a <NUM> (<NUM> inch) graphite die and hot pressed to consolidate. The consolidated precursor was heated and pressed at <NUM> and <NUM> MPa (<NUM> psi), respectively, for approximately <NUM> hours. The formed precursor was removed at room temperature and cooled. <NUM> grams of the cooled precursor were crushed together with <NUM> grams of (free) aluminum powder to form the sputtering target composition precursor, which was processed further to yield the sputtering target composition. The overall (free) aluminum content was approximately over <NUM> at%, and the overall scandium content was approximately <NUM> at%. These percentages are outside the amounts predicted by the equilibrium phase diagram for aluminum-scandium.

A comparative intermetallic powder of Comparative Example A was prepared by alloying <NUM> grams of aluminum and <NUM> grams of scandium. These components were alloyed at approximately <NUM> under vacuum to form a precursor. The precursor was cast using a mold in a conventional casting process, then cooled to room temperature.

The overall alloyed aluminum content and the overall alloyed scandium content were consistent with the amounts predicted by the equilibrium phase diagram for aluminum-scandium.

As shown in Table <NUM>, the target of Example <NUM> showed a high content of (free) aluminum and a low content of intermetallic phase, e.g., AhSc. Because of the high free aluminum/low ScAh content, the sputtering target should demonstrate superior ductility.

<FIG> are exemplary representations showing the microstructure of an Al-Sc alloy (with multiple phases indicated). The circular dots indicate the second intermetallic phase, which contains scandium, e.g., ScAl<NUM>, ScAh, ScAl, Sc<NUM>Al, Sc, or combinations thereof, and the remaining area represents the (first) free aluminum phase. Representations for <NUM> at%, <NUM> at%, <NUM> at%, <NUM> at% and <NUM> at% scandium in the overall composition are shown.

<FIG> are representations of SEM photographs that show the microstructure of an Al-Sc alloy. <FIG> shows the microstructure that has been EDS mapped to indicate aluminum content, e.g., free aluminum and/or aluminum-containing intermetallic, see flecked area. <FIG> shows the microstructure that has been EDS mapped to indicate scandium content, e.g., scandium-containing intermetallic phase(s), see diagonally-lined area. <FIG> shows the microstructure that has been EDS mapped to indicate free aluminum content. Area that shows both aluminum presence and scandium presence indicates intermetallic (second phase) content. Free aluminum content (first phase) is represented by the area in <FIG> that contains aluminum, but does not contain scandium (scandium presence is indicated shown in <FIG>), see flecked areas in <FIG>. The areas of free aluminum (first phase) were analyzed and calculated to represent approximately <NUM> vol% to <NUM> vol% of the total alloy.

Claim 1:
An Al-Sc composite comprising from <NUM> at% to <NUM> at% scandium (Sc) and from <NUM> at% to <NUM> at% aluminum (Al), having a microstructure including a first aluminum matrix phase and a second phase dispersed therethrough, the second phase comprising a compound corresponding to the formula AlxScy, where x is from <NUM> to <NUM> and y is from <NUM> to <NUM>,
wherein the second phase further comprises from <NUM> mol% to <NUM> mol% scandium nitride (ScN).