EP2277191A1

EP2277191A1 - Molybdenum-niobium alloys, sputtering targets containing such alloys, methods of making such targets, thin films prepared therefrom and uses thereof

Info

Publication number: EP2277191A1
Application number: EP09739573A
Authority: EP
Inventors: Shuwei Sun; Prabhat Kumar; Olaf Schmidt-Park; Rong-Chein Richard Wu; Gary Rozak; Mark Gaydos
Original assignee: HC Starck Inc
Current assignee: Materion Newton Inc
Priority date: 2008-04-28
Filing date: 2009-04-28
Publication date: 2011-01-26
Also published as: WO2009134771A1; KR20100135957A; JP2011523978A; TW201006938A

Abstract

Alloys comprising: (a) molybdenum present in a majority portion; (b) niobium present in an alloying amount; and (c) a third metal selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount; along with sputtering targets prepared therewith, films sputtered using such targets and thin film devices containing such films.

Description

TITLE OF THE INVENTION

Molybdenum-Niobium Alloys, Sputtering Targets Containing

Such Alloys, Methods of Making Such Targets, Thin Films

Prepared Therefrom and Uses Thereof

BACKGROUND OF THE INVENTION

[0001] Sputtering is a technique used to produce a metallic layer in various manufacturing processes used in the semiconductor and the photoelectric industries. The properties of films formed during sputtering are related to the properties of the sputtering target itself, such as the size of the respective crystal grain and the formation of secondary phase with distribution characteristics. It is desirable to produce a sputter target that will provide film uniformity, minimal particle generation during sputtering, and the desired electrical and physical properties in the resultant film. [0002] Various sputtering techniques are used in order to effect the deposition of a film over the surface of a substrate. Deposited metal films, such as metal films on a flat panel display device, can be formed by a magnetron sputtering apparatus or other sputtering techniques. The magnetron sputtering apparatus induces plasma ions of a gas to bombard a target, causing surface atoms of the target material to be ejected and deposited as a film or layer on the surface of a substrate. Conventionally, a sputtering source in the form of a planar disc or rectangle is used as the target, and ejected atoms travel along a ljne-of-sight trajectory to deposit on top of a wafer whose deposition face is parallel to the erosion face of the target. Tubular-shaped sputtering targets can also be used, such as described in U.S. Patent Application Publication No. 2007/0042728, the entire contents of which are incorporated herein by reference. [0003] Sputtering targets may be desired which comprise materials or combinations of materials that cannot be fabricated by conventional means such as rolling. In such cases, targets are made by hot isostatic pressing (HIP) powders. Ideally, the target is made in a single step. However, physical limitations of powder packing density and size of HIP equipment make it necessary to join smaller segments in order to produce large sputtering targets. For single-phase targets, conventional processing such as welding may be used; for multi-phase materials or where alloy formation is to be avoided for any reason, solid-state edge to edge bonding is preferred. [0004] Interconnects in semiconductors and TFT-LCDs are evolving from aluminum and toward copper, thus new diffusion barriers are needed. Titanium provides excellent adhesion properties while the molybdenum contributes its dense barrier stability. Integrated circuits (for semiconductors and flat panel displays) use Mo-Ti as an underlayer or capping layer for aluminum, copper, and aluminum alloys to minimize hillocks formation, to control the reflectivity and provide protection from physical and chemical attack during photolithography.

BRIEF SUMMARY OF THE INVENTION

[0005] The present invention relates, in general, to molybdenum alloys, their use in preparing sputtering targets, methods of preparing thin films using such sputtering targets and thin films prepared thereby. More specifically, the present invention relates to molybdenum alloys comprising a majority portion of molybdenum, an alloying amount of niobium and a doping amount of a third metal selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium and/or vanadium. [0006] One embodiment of the present invention includes alloys which comprise

(a) molybdenum present in a majority portion; (b) niobium present in an alloying amount; and (c) a third metal selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount; with the proviso that when the third metal is zirconium, the doping amount is less than 0.01% by weight or greater than 1% by weight. [0007] Another embodiment of the present invention includes alloys which comprise (a) molybdenum present in a majority portion; (b) niobium present in an alloying amount; and (c) a third metal selected from the group consisting of nickel, chromium, titanium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount. [0008) Another embodiment of the present invention includes sputtering targets comprising a densified alloy comprising: (a) molybdenum present in a majority portion; (b) niobium present in an alloying amount; and (c) a third metal selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount. In various preferred embodiments, the invention includes sputtering targets comprising a densified alloy comprising: (a) molybdenum present in a majority portion; (b) niobium present in an alloying amount; and (c) a third metal selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount; with the proviso that when the third metal is zirconium, the doping amount is less than 0.01% by weight or greater than 1% by weight. [0009] Still another embodiment of the present invention includes methods comprising providing a blend of a molybdenum powder present in a majority portion, a niobium powder present in an alloying amount and a third metal powder selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount, with the proviso that when the third metal powder is zirconium, the doping amount is less than 0.01% by weight or greater than 1% by weight; and (b) subjecting the blend to heat and pressure to form a densified sputtering target.

[0010] Yet another embodiment of the present invention includes methods comprising: (a) providing a sputtering target comprising a densified alloy comprising: (i) molybdenum present in a majority portion; (ii) niobium present in an alloying amount; and (iii) a third metal selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount; (b) providing a substrate; and (c) subjecting the target to sputtering conditions to form a coating comprised of the target material on the substrate. [0011] Another embodiment of the present invention includes thin film devices comprising a substrate and a thin film disposed above the substrate, the thin film prepared according to any of the sputtering method embodiments of the present invention. [0012] Various embodiments of the present invention can provide sputtering targets which can be used in accordance with other method embodiments of the present invention to provide thin films for use in various devices also embodied by the present invention in which the performance properties of the thin film device are at least comparable to, and in some cases an improvement over, thin film devices known in the art, and wherein the thin films exhibit superior adhesion to the substrate. Thin films according to the present invention and devices containing a thin film in accordance with the invention can also provide advantageous photolithography characteristics which can improve manufacturing productivity. Among the advantages which can be provided by thin films in accordance with the present invention are uniform, rapid and controllable etch rates, which in combination with improved adhesion (both between the substrate and the thin films of the invention, but also between the thin films of the invention and later deposited metallic films, e.g., copper) can greatly improve photolithographic operations.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING [0013] The foregoing summary, as well as the following detailed description of the invention, may be better understood when read in conjunction with the appended drawings. For the purpose of assisting in the explanation of the invention, there are shown in the drawings representative embodiments which are considered illustrative. It should be understood, however, that the invention is not limited in any manner to the precise arrangements and instrumentalities shown. [0014] In the drawings:

[0015] Fig. Ia is a secondary electron image of a comparative Mo-Ti target at a magnification of 100OX;

[0016] Fig. Ib is a backscattering electron image of the comparative Mo-Ti target in Fig. Ia at a magnification of 100OX; [0017] Fig. 2a is a secondary electron image of the comparative Mo-Ti target in

Fig. Ia at a magnification of 100OX;

[0018) Fig. 2b is a backscattering electron image of the comparative Mo-Ti target in Fig. Ia at a magnification of IOOOX ;

(0019J Fig. 3a is a secondary electron image of a MoNbZr target in accordance with one embodiment of the present invention at a magnification of 200X;

[0020] Fig. 3b is a backscattering electron image of the MoNbZr target in Fig. 3a at a magnification of 200X;

[0021] Fig. 4a is a secondary electron image of the MoNbZr target in Fig. 3a at a magnification of IOOOX;

[0022] Fig. 4b is a backscattering electron image of the MoNbZr target in Fig. 3a at a magnification of IOOOX;

[0023] Fig. 5a is a secondary electron image of a film prepared using a comparative Mo-Ti target on an Si substrate at a magnification of IOOOX;

[0024] Fig. 5b is a backscattering electron image of the film in Fig. 5a at a magnification of IOOOX;

[0025] Fig. 6a is a secondary electron image of another film prepared using a comparative Mo-Ti target on an Si substrate at a magnification of 20000X;

[0026] Fig. 6b is a backscattering electron image of the film in Fig. 6a at a magnification of 20000X;

[0027] Fig. 7 is a backscattering electron image of the film in Fig. 7a at a magnification of IOOOX;

[0028] Fig. 8a is a secondary electron image of a film prepared using a comparative Mo-Ti target on a Corning 1737 glass substrate at a magnification of

10000X;

[0029] Fig. 8b is a secondary electron image of the film in Fig. 8a at a magnification of 5000X; [0030] Fig. 9a is a secondary electron image of another film prepared using a comparative Mo-Ti target on a Corning 1737 glass substrate at a magnification of

10000X;

[0031] Fig. 9b is a secondary electron image of the film in Fig. 9a at a magnification of 5000X;

[0032] Fig. 10a is a secondary electron image of another film prepared using a comparative Mo-Ti target on a Corning 1737 glass substrate at a magnification of

10000X;

[0033] Fig. 10b is a secondary electron image of the film in Fig. 10a at a magnification of 5000X;

[0034] Fig. 1 Ia is a secondary electron image of another film prepared using a comparative Mo-Ti target on a Corning 1737 glass substrate at a magnification of

10000X;

[0035] Fig. 1 Ib is a secondary electron image of the film in Fig. 1 Ia at a magnification of 5000X;

[0036] Fig. 12a is a secondary electron image of another film prepared using a comparative Mo-Ti target on a Corning 1737 glass substrate at a magnification of

10000X;

[0037] Fig. 12b is a secondary electron image of the film in Fig. 12a at a magnification of 5000X;

[0038] Fig. 13a is a secondary electron image of a film prepared using a comparative Mo-Ti target on an Si substrate at a magnification of 10000X;

[0039J Fig. 13b is a secondary electron image of the film in Fig. 13a at a magnification of 5000X;

[0040] Fig. 14a is a secondary electron image of another film prepared using a comparative Mo-Ti target on an Si substrate at a magnification of 10000X;

[0041] Fig. 14b is a secondary electron image of the film in Fig. 14a at a magnification of 5000X; [0042] Fig. 15a is a secondary electron image of another film prepared using a comparative Mo-Ti target on an Si substrate at a magnification of 10000X;

[0043] Fig. 15b is a secondary electron image of the film in Fig. 15a at a magnification of 5000X;

[0044] Fig. 16a is a secondary electron image of another film prepared using a comparative Mo-Ti target on an Si substrate at a magnification of 10000X;

[0045] Fig. 16b is a secondary electron image of the film in Fig. 16a at a magnification of 5000X;

[0046] Fig. 17a is a secondary electron image of a film prepared using a MoNbZr target according to one embodiment of the present invention on a Corning 1737 glass substrate at a magnification of 10000X;

[0047] Fig, 17b is a secondary electron image of the film in Fig. 17a at a magnification of 5000X;

[0048] Fig. 18a is a secondary electron image of another film prepared using a

MoNbZr target according to one embodiment of the present invention on a Corning 1737 glass substrate at a magnification of 10000X;

[0049] Fig. 18b is a secondary electron image of the film in Fig. 18a at a magnification of 5000X;

[0050] Fig. 19a is a secondary electron image of another film prepared using a

[0051] Fig. 19b is a secondary electron image of the film in Fig. 19a at a magnification of 5000X;

[0052] Fig. 20a is a secondary electron image of a film prepared using a MoNbZr target according to one embodiment of the present invention on an Si substrate at a magnification of 10000X;

[0053] Fig. 20b is a secondary electron image of the film in Fig. 20a at a magnification of 5000X; [0054] Fig. 21a is a secondary electron image of another film prepared using a

MoNbZr target according to one embodiment of the present invention on an Si substrate at a magnification of 10000X;

[0055] Fig. 23 b is a secondary electron image of the film in Fig. 21 a at a magnification of 5000X;

[0056] Fig. 22a is a secondary electron image of another film prepared using a

[0057] Fig. 22b is a secondary electron image of the film in Fig. 22a at a magnification of 5000X;

[0058] Fig. 23a is a secondary electron image of another film prepared using a

[0059] Fig. 23b is a secondary electron image of the film in Fig. 23a at a magnification of 5000X;

[0060] Fig. 24a is a secondary electron image of another film prepared using a

[0061] Fig. 24b is a secondary electron image of the film in Fig. 24a at a magnification of 5000X;

[0062] Fig. 25 is a schematic representation of sheet resistance measurement point locations on a wafer;

[0063] Fig. 26a is a schematic representation of sheet resistance measurements at the locations identified in Fig. 25 on an Si wafer coated with a thin film prepared using a comparative MoTi target; and

[0064] Fig. 26b is a schematic representation of sheet resistance measurements at the locations identified in Fig. 25 on an Si wafer coated with a thin film prepared using a

MoNbZr target according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0065] As used herein, the singular terms "a" and "the" are synonymous and used interchangeably with "one or more" and "at least one," unless the language and/or context clearly indicates otherwise. Accordingly, for example, reference to "a metal" herein or in the appended claims can refer to a single metal or more than one metal Other than in the operating examples or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, etc., used in the specification are to be understood as modified in all instances by the term "about." Various numerical ranges are disclosed in this patent application. Because these ranges are continuous, they include every value between the minimum and maximum values. Additionally, all ranges disclosed herein include all narrower ranges disclosed for the same property and any upper or lower range value can serve as an alternate upper or lower value for any other range disclosed for the same property. Accordingly, for example, reference to ranges of 1 to 10 and 4 to 6 for the same property also includes ranges of 1 to 4, 4 to 10, 1 to 6 and 6 to 10 for that property. [0066] Alloys in accordance with the various embodiments of the present invention include molybdenum in a majority portion. As used herein, the term "majority portion" refers to a percent by weight content of greater than 50%. Preferably, a majority portion is 75% or more, and even more preferably, a majority portion is 94 to 99%. In even more preferred embodiments of the alloys of the present invention, molybdenum is present in a majority portion of 95 to 98%, and most preferably 95 to 97%. [0067] Alloys in accordance with the various embodiments of the present invention include niobium in an alloying amount. As used herein, the term "alloying amount" refers to a percent by weight content of about 0.5 to 6%. Preferably, an alloying amount is 1 to 5%, even more preferably, 2 to 4%, and most preferably 3 to 4%. [0068] Alloys in accordance with the various embodiments of the present invention include a third metal in a doping amount. As used herein, the term "doping amount" refers to a percent by weight content generally less than an alloying amount. Preferably, a eloping amount is up to about 2%. In various embodiments, a doping amount can be up to about 1%. In various embodiments, a doping amount can be from 100 ppm to 1%. In various embodiments, a doping amount can be up to 100 ppm. In various embodiments, a doping amount can be any amount greater than 1% up to an amount less than an alloying amount.

[0069] A third metal which is present in alloys in accordance with the various embodiments of the present invention can be selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof. In various preferred embodiments of the present invention, the third metal comprises zirconium. [0070] One embodiment according to the present invention includes alloys which comprise (a) molybdenum present in a majority portion; (b) niobium present in an alloying amount; and (c) zirconium in an amount less than 100 ppm. Another embodiment according to the present invention includes alloys which comprise (a) molybdenum present in a majority portion; (b) niobium present in an alloying amount; and (c) zirconium in an amount greater than 1% by weight.

[0071] Alloys according to the various embodiments of the present invention can be characterized in that the niobium and the third metal are predominantly bound with the molybdenum in a substitutional solid solution, or as a mixture without alloying of the various metals in the crystal structure, or as a mixture with partial alloying. [0072] Alloys according to the various embodiments of the present invention can be prepared by any appropriate melt metallurgical process. Alloys according to the present invention can be further milled and/or ground to produce powders for forming sputtering targets according to the present invention. Powders can also be prepared using an atomization process, e.g., a rotating elctrode process. A suitable melt metallurgy process for preparing an alloy according to the present invention is described in U.S. Patent Application Publication No. US2006/0172454, the entire contents of which are incorporated herein by reference. Alternatively, for example, appropriate amounts of a molybdenum powder, a niobium powder and a third metal powder can be blended, vacuum sintered, vacuum hot pressed or hot isostatically pressed (HIP). Such billets can then subsequently be consolidated by hot deformation processes such as extrusion, forging and/or rolling.

[0073] The present invention also includes sputtering targets comprising a densified alloy according to any of the various alloy embodiments of the invention. Finished sputtering targets of the present invention have a density of greater than about 90% theoretical density, preferably at least 95% of theoretical density, more preferably at least 98% of theoretical density, and most preferably at least 99.5% of theoretical density. [0074] Sputtering targets according to the present invention can be provided through suitable conventional techniques such as a melting process or a powder metallurgy process. Various ingot metallurgy methods are known in the art, including, but not limited to, methods such as electron beam melting process, arc melting, plasma melting and the like. In a suitable electron beam melting process, melting can be performed at a condition of ultimate vacuum equal to or lower than 4 x 10^"5 torr. In a suitable plasma melting process, melting can be done under an atmosphere between 8 x 10^"4 and 4 x lO-³ torr.

[0075] In various suitable powder metallurgy processes, the constituent powders

(i.e., molybdenum powder, niobium powder and third metal powder) are blended in lhe proportions described earlier, (or a previously milled and ground alloy powder as described above), and compacted and sintered by various means known in the art. Furthermore, a powdered alloy produced with a predetermined composition through an atomization method or the like may be used in place of or along with elemental powders. The average particle size for the molybdenum powder is preferably between 0.1-25 microns, more preferably less than 5 microns. For the niobium and third metal powders, the desired average particle size is preferably 5-50 microns, more preferably 20-35 microns.

[0076] The powders can be blended in accordance with powder blending techniques that are well known in the art. For example, mixing may occur by placing the molybdenum, niobium and third metal powders in a dry container and rotating the closed container about its central axis. Mixing is continued for a period of time sufficient to result in a completely blended and uniformly distributed powder. A ball mill or similar apparatus may also be used to accomplish the blending step. The invention is not limited to any particular mixing technique, and other mixing techniques may be chosen if they will sufficiently blend the constituent starting powders.

[0077] The powder blend is optionally then consolidated in a preliminary compacting step to a density that is from 60-85% of theoretical density. Consolidation can be accomplished by any means known to one skilled in the art of powder metallurgy, e.g., cold isostatic pressing, rolling or die compaction. The length of time and amount of pressure used will vary depending on the desire degree of consolidation to be achieved in this step. For some types of targets, such as tubular, this step may not be necessary. [0078] Following the preliminary consolidation step, the consolidated powder is encapsulated, e.g., in a mild steel can. Encapsulation can also be accomplished by any method that will provide a compact workpiece that is free of an interconnected surface porosity, such as by sintering, thermal spraying, and the like. As used herein, the term "encapsulation" will refer to any method known to one skilled in the art for providing the compact piece free of interconnected surface porosity. A preferred method of encapsulation is by use of the steel can.

[0079] After encapsulation the encapsulated piece is compacted under heat and pressure. Various compacting methods are known in the art, including, but not limited to, methods such as inert gas uniaxial hot pressing, vacuum hot pressing, and hot isostatic pressing, and rapid omnidirectional compaction, the Ceracon™ process. Preferably, the encapsulated piece is hot isostatically pressed into the desired target shape, as that method is known in the art, under pressure of 75-300 MPa, more preferably 100-175 MPa, at temperatures of 1000°-1500°C, more preferably 1150"-135O⁰C, for a period of 2- 16 hours, more preferably 4-8 hours. Other methods of hot pressing can be used to produce the Mo-Nb-Zr sputtering targets of the present invention, so long as the appropriate temperature, pressure and time conditions are maintained. [0080] Sputtering targets in accordance with the various embodiments of the present invention can be prepared as rectangular plates or other appropriate shapes using the compaction and sintering methods described above, or as tubular sputtering targets. Larger targets can be prepared by bonding multiple plates such as described in U.S. Patent Application Publication No. US2007/0089984, the entire contents of which are incorporated herein by reference. A suitable method for the preparation of tubular targets is described in U.S. Patent Application Publication No. US2006/0172454, which has been incorporated by reference in its entirety. Methods of making tubular sputtering targets which can also be used to prepare targets according to the present invention are disclosed in U.S. Patent Application Publication No. US2006/0042728, the entire contents of which are incorporated herein by reference.

[0081] The present invention also includes thin films prepared by sputtering the targets according to the various embodiments of targets according to the invention described herein. Thin films according to the present invention can be prepared by sputtering a target according to the present invention comprising an alloy of molybdenum, niobium and a third metal. Sputtering a target of the present invention includes subjecting the target to sputtering conditions. Any suitable means of sputtering can be employed. DC magnetron sputtering is preferred.

[0082] Suitable sputtering conditions which can be used in accordance with the methods of the present invention can include a preliminary burn in procedure which can comprise power application to a target, with ramping of the wattage, e.g., from 0 to 100 W, and maintaining a constant power for 10 minutes, ramping to 1000 W over a period of 50 minutes and then maintaining constant power at 1000 W for 2 hours. Following a burn in procedure, and any optional substrate cleaning, sputtering can be carried out. Prior to deposition, a substrate can be subjected to chemical cleaning by successive rinsing in ultrasonic baths of acetone and ethyl alcohol. The substrates can then be blown dry in nitrogen and loaded into the deposition chamber for sputtering. [0083] Deposition in the sputtering chamber can be carried under various parameters or power applied to the target and gas pressure in the chamber. Suitable power levels applied to the target can be 500 to 2000W and are preferably about 100OW. The substrate is preferably grounded at OV, and a substrate source spacing (SSS) is maintained at about 5 inches. The gas pressure is generally about 1 to 10 mTorr, and more preferably 1 to 5 mTorr.

[0084] The present invention also includes thin film devices incorporating a thin film made in accordance with the above-described methods of sputtering targets according to the present invention. As used herein, "thin film devices" include electronic components such as semiconductor devices, thin film transistors, TFT-LCD devices, black matrix devices that enhance image contrast in Flat Panel Displays, solar cells, sensors, and gate devices for CMOS (complementary metal oxide semiconductor) with tunable work functions.

[0085] Thin films prepared in accordance with the methods of the present invention by sputtering a target according to the invention can be used in any of the aforementioned thin film devices in any suitable manner. Accordingly, for example, a Mo_xNb_xM³ _Z; thin film (M³ represents a third metal and x+y+z preferably equals 100%) prepared from a target of the present invention can serve as a barrier layer, a conductive wiring after etching, a gate, source and/or drain electrode, etc. Thin films according to the various embodiments of the present invention are preferably used in flat panel displays and solar cells. Any suitable processes for etching, photolithography and other electronic device architecture manufacturing can be used to form the appropriate wirings, electrodes or transistor elements from thin films deposited according to the present invention. As a barrier layer, a thin film in accordance with the various embodiments of the present invention can serve as a diffusion barrier layer (e.g., between an Si substrate and a metallic layer disposed above), or as a protective layer disposed above an underlying layer within a device, or both. The use of molybdenum layers as barrier layers is described, for example, in U.S. Pat. No. 7,352,417, the entire contents of which are incorporated herein by reference.

[0086] Thin films of the present invention can be deposited on any suitable substrate upon which materials can be sputtered. In various preferred embodiments of the present invention, a substrate upon which a thin film according to the present invention is sputtered comprises glass, silicon, steel or a polymeric material. Additionally, a thin film according to the invention can be deposited onto other thin film silicon/silicon alloy layers. In various preferred embodiments, the substrate can comprise glass, silicon and/or stainless steel. In various particularly preferred embodiments, the substrate can comprise low sodium glass, other non-alkaline LCD substrates glasses (e.g., Coming® 1737), or combinations thereof.

[0087] MoNbM³ thin films prepared in accordance with the present invention can be advantageously used in various thin film devices, particularly preferably in flat panel displays as wiring. The MoNbM³ thin films exhibit minimal particle generation, good substrate adhesion and low resistivity. As discussed below, uniformity of the MoNbM³ thin films is comparable to, or even better than, known Mo and MoTi films. [0088] The invention will now be described in further detail with reference to the following non-limiting examples.

EXAMPLES

[0089] Comparative sputtering targets 1, 2, 3 A and 3B were prepared based on known high purity molybdenum alloys where molybdenum comprises substantially the entire target. An additional comparative target based on a known molybdenum-titanium alloy was also prepared. Finally, a target comprising molybdenum, niobium and zirconium was prepared for preparation of a thin films in accordance with an embodiment of the invention. Thin films were then deposited on various substrates under various conditions and evaluated for morphology, particle generation, accumulation rate, microstructure, adhesion, etch rate, resistivity, and uniformity. [0090] Target preparation:

[0091] Each of the targets were prepared by combining the appropriate metals and conventional melting with electron beam radiation, annealing, extrusion, annealing, forging and annealing. All annealing steps were carried out under a protective atmosphere or in vacuum. Each of the targets used were circular with a thickness of 0.25 inches.

[0092] Substrates and Substrate Preparation:

[0093] Prior to the deposition of the thin films on the substrates, each of the silicon, stainless steel (AlSI 304), soda lime glass, and Corning 1737 glass substrates were subjected to chemical cleaning by successive rinsing in ultrasonic baths of acetone and ethyl alcohol, Each of the substrates were then dried with nitrogen and loaded into the deposition chamber.

[0094] The chamber was then evacuated to a pressure below 5 x 10^~6 Torr, and subsequently filled with argon to a pressure of 65 x 10^"3 Torr. The substrates were then sputter etched by applying a negative voltage of 400 V, pulsing at 100 kHz for 30 minutes, and accelerating argon ions to the substrate. After the substrates were sputter cleaned, the argon gas flow was reduced to 2 mTorr and the target was sputter cleaned at

500 W (DC) for 5 minutes. During the sputter cleaning of the target, a shutter was positioned in front of the target to prevent deposition on the substrates.

[0095] Deposition on the substrates was performed with fixed power applied to the target and under varying conditions of gas pressure and time. The conditions are shown below in Table 1.

Table 1. Parameters for deposition at 1000 W, w/ substrate at 0 V (grounded)

[0096] The substrate source spacing was maintained at 5". The power applied to the target was 1000 W and the substrate was maintained at 0 V. The deposition chamber employed was a cylindrical vessel with a base pressure of 1 x 10^"6 Torr, manufactured by ACSEL powered by an Advanced Energy-manufactured, Pinnacle power supply having dual channel DC 6 kW power. [0097J Thin Film Evaluation:

[0098] Each of the different substrates was provided with a thin film using each of the prepared sputtering targets. The coaled substrates were then evaluated as follows. [0099] Morphology of the Targets:

[00100] Some pores were observed in the erosion track of the comparative molybdenum-titanium films. Based on backscattering electron images, it appears that some molybdenum grains and titanium grains are segregated and most of the pores were present in the brighter area (consisting of molybdenum grains with larger atom number). In contrast, no pores or segregation of molybdenum, niobium and zirconium grains were observed in the film prepared from the MoNbZr sputtering target. Moreover, the grain size in the MoNbZr sputtering target was much larger than in the comparative targets. Referring to Figs Ia, Ib, 2a, and 2b, pores can be discerned in the MoTi target, particularly at 500Ox magnification, such as shown in Fig. 2a. Backscattering electron imaging of the MoTi target at 500x magnification shows that most of the pores were between Mo grains. Referring to Figs 3a, 3b, 4a and 4b, no pores are discernible in the MoNbZr targets. [00101] Particle Generation: [00102] Referring to Figs. 5a, 5b, 6a, 6b, and 7, macroparticles were also observed in the thin films produced with the comparative MoTi target. The particles encountered had measurements between 2 and 5 μm in diameter. An estimation of the macro particle density is about 4 macro particles in a 50 μm x 50 μm area. In contrast, no macroparticles were observed in the films prepared using the MoNbZr target at 5 mTorr, 3 mTorr or 1 mTorr on the silicon substrates. [00103) Accumulation Rate:

[00104] Accumulation rates for the coatings prepared using each of the targets on both silicon and the Coming 1737 glass substrates were measured using scanning electron microscopy (SEM). The data is presented below in Table 2.

[00105] Microstructure:

[00106] The microstructure of the films prepared using the MoTi and the MoNbZr sputtering targets on the silicon and Corning 1737 glass substrates were also observed using SEM. With decreasing deposition pressure, the coatings prepared using both targets became denser. The coatings on the 1737 glass substrates were denser than the coatings on the silicon substrates. Referring to Fig. 8a through Fig. 24b, similar density of the films is shown.

[00107] Adhesion (Tape Test):

[00108] The adhesion of the coatings prepared using the MoTi and the MoNbZr sputtering targets were measured using a tape test. The coatings prepared on the Corning

1737 glass having a thickness around 200 nm demonstrated much better adhesion than the coatings prepared on stainless steel and soda lime glass substrates with thicknesses of about 5 μm. The results are shown below in Table 3a and Table 3b.

Table 3a. Ta e test: Mo-Ti and Mo-NbZr coatin s; thickness ~ 200 nm on Cornin 1737

Table 3b. Ta e test: Mo-Ti and Mo-NbZr coatin s; thickness ~ 5 m.

[00109] Etch Rate:

[0011OJ The etch rate of the coatings on silicon substrates prepared using the MoTi sputtering targets were measured by immersing the coatings in a ferricyanide solution at 25 ⁰C for 30 minutes. The etch rate of the coatings prepared using the MoNbZr target on silicon substrates were measured by immersing the coatings in a ferricyanide solution at 25 ⁰C for 5 minutes. The etch rates of the coatings prepared using the MoTi target were much lower than those of the coatings prepared using the MoNbZr targets and the coatings prepared from pure molybdenum targets. The results are shown below in Table 4.

Table 4. Etch rate; Mo coatings produced at IkW for 1 hr, OV bias (grounded) in ferricyanide solution at 25⁰C,

[00111] Resistivity:

[00112] Sheet resistance of selected molybdenum films was measured using a four-point probe. The results are presented below in Table 5. As shown in Table 5, the resistivity of the coatings prepared using the MoTi targets was much higher than that of the coatings prepared using the MoNbZr sputtering targets.

Table S. Sheet resistance & Resistivit .

[00113] Uniformity:

[00114] The uniformity of the thin films was determined through sheet resistance measurements of 37 points of a coating produced on a 4" wafer positioned at 5" from the target. The uniformity of the coatings prepared using each of the targets are comparable. The uniformity evaluation results are shown below in Table 6 and graphically with reference to Figs. 25, 26a and 26b.

[00115] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

CLAIMS What is claimed is:

1. An alloy comprising: (a) molybdenum present in a majority portion; (b) niobium present in an alloying amount; and (c) a third metal selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount; with the proviso that when the third metal is zirconium, the doping amount is less than 0.01% by weight or greater than 1% by weight.

2. The alloy according to claim 1, wherein the third metal is selected from the group consisting of nickel, chromium, titanium, hafnium, vanadium and mixtures thereof.

3. The alloy according to claim 1 , wherein the doping amount is less than 0.01% by weight

4. The alloy according to claim 1 , wherein the doping amount is greater than 1% by weight.

5. The alloy according to claim 2, wherein the doping amount is less than 0.01% by weight.

6. The alloy according to claim 2, wherein the doping amount is greater than 1% by weight.

7. The alloy according to claim 2, wherein the doping amount is 0.01 to 1 % by weight.

8. The alloy according to claim 1, wherein the alloying amount is 0.5 to 10% by weight.

9. The alloy according to claim 2, wherein the alloying amount is 0.5 to 10% by weight.

10. A sputtering target comprising a densifieci alloy according to claim 1.

11. A sputtering target comprising a densified alloy according to claim

2.

12. A method comprising: (a) providing a blend of a molybdenum powder present in a majority portion, a niobium powder present in an alloying amount and a third metal powder selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount, with the proviso that when the third metal powder is zirconium, the doping amount is less than 0.01% by weight or greater than 1% by weight; and (b) subjecting the blend to heat and pressure to form a densified sputtering target.

13. A method comprising: (a) providing a sputtering target comprising a densified alloy comprising: (i) molybdenum present in a majority portion; (ii) niobium present in an alloying amount; and (iii) a third metal selected from the group consisting of nickel, chromium, titanium, zirconium, hafnium, vanadium and mixtures thereof, wherein the third metal is present in a doping amount; (b) providing a substrate; and (c) subjecting the target to sputtering conditions to form a coating comprised of the target material on the substrate.

14. A method comprising: (a) providing a sputtering target according to claim 10; (b) providing a substrate; and (c) subjecting the target to sputtering conditions to form a coating comprised of the target material on the substrate.

15. A thin film device comprising a substrate and a thin film disposed above the substrate and prepared according to the method of claim 13.

16. A thin film device comprising a substrate and a thin film disposed above the substrate and prepared according to the method of claim 14.

17. The thin film device according to claim 15, wherein the substrate is transparent.

18. The thin film device according to claim 17, wherein the transparent substrate comprises glass and the thin film device is a flat panel display.

19. The thin film device according to claim 15, wherein the substrate comprises one or more selected from the group consisting of glass, steel, polymers and combinations thereof, and the thin film device is a solar cell.

20. The thin film device according to claim 16, wherein the substrate is transparent.

21. The thin film device according to claim 20, wherein the transparent substrate comprises glass and the thin film device is a flat panel display.

22. The thin film device according to claim 16, wherein the substrate comprises one or more selected from the group consisting of glass, steel, polymers and combinations thereof, and the thin film device is a solar cell.

23. The thin film device according to claim 15, wherein the substrate comprises silicon.

24. The thin film device according to claim 16, wherein the substrate comprises silicon.