Title of Invention

A TANTALUM METAL

Abstract

The present invention relates to a tantalum metal obtainable from a tantalum ingot by thermo mechanical processing, said tantalum metal having a purity of at least 99.995% and an average grain size of 150 ~m (microns) or less. The present invention relates to a tantalum metal having a purity of at least 99.995%. Preferably, the tantalum metal has a purity of at least 99.999% and can range in purity from about 99.995% to about 99.999% or more. The tantalum metal has a fine texture. More preferably the texture is such that the (100) peak intensity within any 5% incremental thickness of the tantalum is less than about 15 random, and/or has a natural log (Ln) ratio of(III):(100) center peak intensities within the same increment greater than about -4.0. The present invention also relates to a process for making the tantalum metal of any of claims 1 to 21, comprising reacting a salt containing tan.talum with at least one agent capable of reducing the salt to tantalum and a second salt in a reaction container having an agitator, wherein the reaction container or a liner in the reaction container and the agitator or a liner on the agitator are made from a metal material having the same or higher vapor pressure than tantalum at the melting point of the tantalum.

Full Text

HIGH PURITY TANTALUM AND PRODUCTS CONTAINING THE SAME LIKE SPUTTER TARGETS BA.CKGROUND OF THE INVENTION The present invention relates to metals, in particular tantalum, and products made from tantalum as well as methods of making and processing the tantalum. in industry, there has always been a desire to form higher purity metals for a variety of reasons* With respect to tantalum, higher purity metals are especially desirable due to tantalum's use as a sputtering target and its use in electrical components such as capacitors. Thus, impurities in the metal can have an undesirable effect on the properties of the articles formed from the tantalum. When tantalum is processed, the tantalum is obtained from ore and subsequently crushed and the tantalum separated from the crushed ore throush the use of an acid solution and density separation of the acid solution containing the tantalum from the acid solution containing niobium and other impurities. The acid solution containing the tantalum is then crystallized into a salt and this tantalum containing salt is then reacted with pure sodium in ?. vessel having an agitator ivpicaily consrmc:ed of nickel alloy material, wherein tungsten or molybdenum is pan of the nickel alloy. The vessel will typically be a double walled vessel with pure nickel in the interior surface. The salt is then dissolved in water to obtain tantalum powder. However, curing such processing, the tantalum powder is contaminated bv the various surfaces that it comes in contact with such as the tunssten and/or • ^ molybdenum containing surface, Many contaminants can be volaiized during subsequent melting. except highly soluble refractory metals (e.g., Nb Mo, and W). These impurities can be quite difficult or impossible to remove, thus preventing a very high purity tantaium product, Accordingly, there is a desire to obtain higher purity tantalum produce which substantially avoid the conouninstions obtained during the processing discussed above. Also, there is a desire to have a tantalum product having higher purity, a fine grain size, and/or a uniform texture. Qualities such as fine grain size can be an important property For sputtering targets made from tantalum since fine grain size can lead to improved uniformity of thickness cf the sputtered deposited Film, further- other products containing the tantalum having fine grain size can lead to improved homogeneity or deformation and enhancement of deep drawability and stretchability which are beneficial in making capacitors cans, laboratory crucibles, and increasing the lethality of explosively formed penetrators (EFP's). Uniform texture in tanralum containing products can increase sputtering efficiency (e.g., grea½r sputter rate) and can increase normal anisotropy (e.g., increased deep drawability), in perform products. STIMMA-RV 01 THE PRESENT INVENTION A feature of the present invention is to provide a high purity tantalum product exhibiting a fine grain structure and/or uniform texture. Another feature of the present invention is to provide articles, products, and/or components containing the high purity tantalum. An additional feature of the present invention is to provide processes to make the high purity tantalum product as well as the articles, products, and/or components containing the high puritv Additional features and advantages of the present invention will be set forth in part in the description which follows, and in pan will be apparenr from the description* or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the description and appended claims. To achieve these and other advantages* and in accordance with the purpose of the present invention, as embodied and broadly described herein, the present invention relates to tantalum meta! Having a punty of at least 99.995% and more preferabiy at least 99.999%. The tantalum metal preferably has a fine grain structure andtor uniform texture. The present invention further relates to an alloy or mixture comprising tantalum, wherein the tantaium present in the alloy or mixture has a purity of at least 99.995% and more preferably at least 99.999%. The alloy or mixture (e.g., at least the tantalum present in the alloy or mixture) also preferably has a fine grain structure and/or uniform texture. The present invention also relates to a high purity tantalum, e.g., suitable for use as a Spunering target* having a fully recrysiailized grain size with an average grain size of about 150 µm or less and/or having a primary* (1 i l)-type texture substantially throughout the thickness of the tantalum and preferably throughout the entire thickness of the tantalum metal and/or having an absence of strong (100) texture bands within the thickness of the tantalum. The present invention further relates to manufacturing plate and sheet from the above-mentioned tantalum by flat-forging the tantalum, machining into rolling slabs, annealing rolling stabs, roiling into piste or sheet, then annealing the plate or sheet. Final products such a£ Sputtering targets can be then in;i'.jhit•ed I¾J:) the annealed piate or sheet. The present invention also relates to a sputtering target comprising the above-described tantalum and/or alloy. The soutterins target can also be formed by radial forging ana subsequent round processing to produce billets or slugs, which are thee forged and rol!ed to yield discs, which can then be mKhin‹:d and ^ir^kd. The present invention further relates to resistive films and capacitors comprising the above- described lan&ium and•'ci ailo\. The present invention also relates to articles, components, or products which comprise at teas? in part the 2tav.£•ifc;^:bi¾J lar.taiijut and/or alloy Also, the present invention relates to a process of making the above-described tantrum which involves reacting a salt-containing tantalum with pure sodium or other suitable salt in a tractive container or pot and an agitator which both are made from or have a liner comprising a metal or alloy-thereof which has the same or higher vapor pressure as tantalum at the melting point of tantaium. The present invention further relates to processing tantaium powder by melting the tantalum powder in a high vacuum of 10" torr or more. The pressure above the mclr is lower than the vapor pressures of the impurities existing in the tantalum. Preferably, the melting of the tantalum powder is accomplished by eiectran beam melting. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed, BRIEF DESCRIPTION OF THE DRAWINGS imrni iiu in ■ • ■■■■■■ ■--- ..^u•m•w^„^^„ Figures l(A-B)-ll(A•B) are graphs and corresponding data relating to texture gradient (incremental thickness vs. random) and log ratio (11 l):(lOO) gradients (incremental thickness vs. Ln (111/100)) of high purity tantalum plates of the present invention. DETAILED DESCRIPTION OF THE PRESENT INVENTION The present invention relates to a tantalum metal having a purity of at least 99.995%. Preferably, the tantalum metal has a purity of at least 99.999% and can range in purity from about 99.995% to about 99.999% or more. Other ranges include about 99.998% to about 99.999% and from aoout 99.999% to about 99.9992% and from about 99.999% to about 99.9995% The present invention further relates to a meal alloy which comprises the high purity tantalum metal, such as a tantalum based alloy or other alloy which contains the high purity tantalum as one of the components of the ailcy. The impurities that may be present in the high purity tantalum metal are less than or equal to .005% and typically comprise other body-centered cubic (bcc) refractory metals of infinite solubility in tantalum. 3uch as niobium, molybdenum, and turtfc›ran. The tantalum metal and alloys thereof containing the tantalum metal preferably have a texture which is advantageous for particular end uses, such as sputtering. In other words, when the tantalum metal or alloy thereof is formed into a sputtering target having a surface and then sputtered, the texture of the tantalum metal in the present invention leads to a sputtering target "which is easily sputtered and. very few if any areas in the sputtering target resist sputtering; Further, with the texrure of the tantalum metal of the present invention, the sputtering of the sputtering target leads 10 a very uniform sputtering erosion thus leading to a sputtered fum which is therefore uniform as well It is preferred that the tantaium having any purity, but preferably a purity of at least about 99.995%, has a grain size of about 150 microns or less- Preferably, the tantalum mecai is at least partially recrystailized, and more preferably at least about 80% of the tantaium metal is recrystailized and even more preferably at least about 98% of the tantalum metal is recrystailized. Most preferably, the tantalum metal is fully recrvstalfec, Aiso. it is preferred that tne tantaium metal have a fine texture. More preferably the texture ts such that the (100) peak intensity within any 5% incremental thickness of the tantalum is less than about 15 random, and/or has a natural log (In) ratio of (111);(IOO) center peak intensities within the same increment greater than about-4.0 (i.e.. meaning, •4.O, -3.0, -2.0, -1,5, -1.0 and so on) or has both the (100) centroid intensity and the ratio. The center peak intensity is preferably from about 0 random to about !O random, and more preferably is from about 0 random to about 5 random. Other (100) centroid intensity ranges include, but are not limited to, from about 1 random to about 10 random and from about ! random to about 5 random. Further, the log ratio of (111):(lOO) center peak intensities is from about - 4,0 to about 15 and more preferably from about -1.5 to about 7.0. Other suitable ranges of log ratios, include, but are not limited to. about -4,0 to about 10, and from about -3,0 to about 5.0. Most preferably, the tantalum metal has the desired purity of at least about 99.995% and the preferred gram size and preferred texture with regard to the (100) incremental intensity and the (111):(lOO) ratio of incremental centroid intensities. The method and equipment thai can be used to characterize the texture are described in Adams et aL9 Materials Science Forum. Voi. 157-162 (1994), pp. 3:-42; Adams et a!.. Metallurgical Transactions A7 Vol. 24A. April J993•N'o. 4, pp. 819-831: Wright ei aL International Academic Publishers, 137 Chaonei Dajie. Beijing, 1996 ("Textures of Material: Proceedings of the Eleventh International Conference on Textures of Materials); Wright Journal of Computer-Assisted Microscopy. Vol. 5, No. 3 (1993). all incorporated in their entirety by reference he: sin. The high purity tantalum metal of the present invention can be used in a number of areas. For instance, the high purity tantalum metal can be made into a sputtering target or into chemical energy (CE) munitions warhead liner which comprises the high purity metal. The high purity metal can also be used and formed into a capacitor anode or into a resistive film layer. The tantalum metal of the present invention can be used in any article or component which conventional tantalum is used and the methods and means of making the various articles or components containing the conventional tantalum can be used equaiiy here in incorporating the high purity tantalum metal into the various articles or components. For instance, the subsequent processing used in making sputtering targets, such as the backing plate,, described in U.S. Patent Nos. 5.753,090,5,687,600, and 5,522,535 can be used here and these patents are incorporated in their entirety by reference herein. Generally, a process that can be used to make die high purity tantalum metal of the present invention involves a refining process, a vacuum meitinz process, and a thermal mechanical process. In this process or operation* the refining process involves the steps of extracting tantalum metal preferat›iy in the form a powder from ore containing tantalum and preferably the ore-containing tantalum selected has low amounts of impurities, especially, low amounts of niobium, molybdenum, and tungsten- More preferably, the amount of niobium, molybdenum, and tungsten is betow about 10 ppai, and most preferably is oeiow about 8 pprn. Such a selection leads to a purer tantalum metal. After the refining process, the vacuum melting process is used to purge low melting point impurities, such as Jilkyde and transition metais from the tantalum while consolidating the tantalum material into i fully dense, malleable ingot Then, after this process, a thermal mechanical process can be used which can involve a combination of cold working and annealing of a tantalum which further ensures that the preferred grain size and/or preferred texwre and uniformity are achieved, !f desired. The high purity tantalum merai preferably may be made by reacting a salt-containing Tantalum with at least one agent (e.g., compound or element) capable of reducing this salt to the tantalum metal and further results in the fonnation of a second salt in a reaction container. The reaction container ran be any container typically used for the reaction of metais and should withstand hi¾h temperatures or the order of about 8Q0*C to about I‚2OO°C For purposes of the preseni invention, the reaction container or the liner in the reaction container, which comes in contact with the salt-containing tantalum and the agent capable of reducing the salt to tantalum, is made from a material having the same or higher vapor pressure as tantalum at the melting point of the tantalum. The agitator in the reaction container can be made of the same material or can be lined as well The liner can exist only in the portions of the reaction container and agitator that come in contact with the salt and tantalum. Examoies of such metal materials which can form the liner or reaction container include, but are not limited to, metal-based materials made from nickel, chromium, iron- manganese, titanium, zirconium, hafnium, vanadium* ruthenium, cobalt, rhodium* palladium, platinum, or any combination thereof or alloy thereof as long as the alloy material has the same or higher vapor pressure as the meiiing point of tantalum metal Preferably, the metal is a nickel or a nickel-based alloy, a chromium or a chromium-based alloy, or an iron or an iro.›based alloy. The liner, on the reaction container and/or agitator, if present, typically will have a thickness of from about ,5 cm to about 3 cm. Other thicknesses can he. used. It ia within the bounds of the present invention to have multiple layers of liners made of the same or di"f¾(‹j:nt :ri£&ii i:Uton:iis das.;* :L-eci above. The salt-containing tantalum can be any salt capable of having rantalum contained therein such as a potassium-fluoride tantalum. Wirh respect to the agent capable of reducing the salt to tantalum and a second sait ir; the reaction container, the agent which is capable of doing this reduction is any agent which has the anility to result in reducing the salt-containing tantalum to just tantalum metal and other ingredients (e.g. sak(s)) which can be separated from the tantalum metal, for example by dissolving the salts with water or other aqueous sources. Preferably, this agent is sodium. Other 3Kample3 include, but are not limited to, lithium, magnesium, calcium, potassium, carbon, carbon monoxide, ionic hydrogen, and the like. Typically, the second salt which also is formed during the reduction of the salt-containing tantalum is sodium fluoride. Details of the reduction proem which can be appiiea to the present invention in view of the present application are s«t forth in Kirk-Othmer Encyclopedia of Chemical Technology, 1* Edition, Vol. 22, pp. 541-564. U.S. Patent No*. 2.950;i$5; 3,829,310; 4,149,876; and 3,767,456. Further details of the processing of tantalum can be found in U.S. Patent Nos. 5,234,491; 5,242,481; and 4,684,399. All of these patents and publication* are incorporated in their entirety by reference herein. The above-described process can be included in a multi-step process which can begin with low purity tantalum, such as ore-containing tantalum. One of the impurities that can be substantially present with the tantalum is niobium. Other impurities at this stage are tungsten, silicon, calcium, iron, manganese, etc. In mare detail, low purity tantalum can be purified by mixing the low purity tantalum which has tantaium and impurities with an acid solution. The low purity tantalum, if present as an ore, should first be crushed before being combined with an acid solution. The acid solution should be capable of dissolving substantially all of the tantalum and imourities. especially when the mixing is occurring at hign temperature*;. Once ttie acid solution has had sufficient time to dissolve substantially, if not all. of the solids containing the tantalum and impurities, a liquid solid separation can occur which will generally remove any of the undissoived impurities. The solution is further nurified by liquid-liquid extraction Methyl isobutyi ketone (MIBK) can be used to contact the tantalum rich solution, and deioni¾d water can be added to create a tantalum fraction. At this point, the amount of niobium present in the liquid combining tantalum k general below about 25 ppm. Then, with the liquid containing at least tantalum, the liquid is permitted to crystallize into a salt with the use of vats. Typically, this salt will be a potassium tantalum fluoride salt. More preferably, this salt is Ki i aR This salt is then reacted with an agent capable of reducing the salt into I) tantaium and 2) a second sait as described above. This compound will typically be pure sodium an?. the reaction will occur in a reaction container described above. As stated above, the second sale byproducts can be separated from the tantalum by dissolving the salt in an aqueous source and washing away the dissolved salt. At this stage, the purity of the tantalum is typically 99.50 to 99.99% Ta. Once the tantaium powder is extracted from this reaction, any impurities remaining, including any contamination from the reaction container, can be removed through melting of the tantalum powder. The tantaium powder can be melted a number of ways such as a vacuum arc rcmelt or an electron beam meiring› Generally, me vacuum during the melt will be sufficient to remove substantially any existing impurities from the recovered tantalum so as to obtain high purity tantalum. Prefeiablvj me melting occurs in a high vacuum such as 104 torr or more. Preferably, the pressure above the meited tantaium is lower than the vapor pressures of the metal impurities in order for these impurities, such as nickel ana iron to be vaporized. The diameter of the cast ingot should be as large as possible, preferably greater than S ½ inches. The large diameter assures a greater meit surface to vacuum interface which enhances purification rates. In addition, the large ingot diameter allows for a greater amount of cold work, to be imparted to the metal during processing which improves the attributes of the final products. Once the mass of meited tantalum consolidates, the ingot formed will have a µwicy ot 9939h¼ or higher and preferably 99.999% or higher. The electron beam processing preferably occurs at a melt rate of from about 300 to about 800 lbs. per hour using 20:000 to 3,8,000 volts and 15 to 40 amps, and under a vacuum of from about 1 X 10"3 to about 1 X 10* Tnrr. Mare preferably, the meh rate is from about 400 to about 600 lbs. per hour wins from 24,000 to 26.000 volts and 17 to 36 amps, and under a vacuum ot from about 1 X 10- to 1 X 10*J Torr. With respect to the VAR processing, the meit rate is preferably of 500 to 2f000 !bs. per hour using 2545 volts and 12,000 to 22,000 amps under a vacuum of 2-X i0'r to 1 X Iff* Tom and more preferably 800 to 1200 lbs. per hour at from 30 to 60 volts and 16,000 to 18,000 amps, and under a vacuum of from 2 X 10½" to 1 X Hr*Torr. Tks high purity tantalum ingor can then be thermomechanicaliy processed to produce the hi3h purity tantalum containing product. The fine, and preferably fully recrystallized, grain structure and/or uniform texture is imparted to the product through a combination of cold and/or warm working and in-procesb annealing. The high purity tantalum product preferably exhibits a uniform texture of mixed or primary (111) throughout its thickness as measured by orientation imaging microscopy (OlM) or other acceptable means. With respea 10 thermomechanical processing, the ingot can be subjected to rolling and/or forging processes and a fine, uniform microstnicture having high purity can be obtained. The high purity tantalum has an excellent fine .grain size and/or a uniform distribution. The high purity tantalum preferably has an average reciystaliized grain size of about ISO microns or less, more preferably about 100 microns or less, and even more preferably about 50 microns or less. Ranges of suitable average grain sizes include from about 25 to about 150 microns; from about 30 to about 125 r microns, and from about 30 to about 100 microns. The resuiring high purity metal of the present invention, preferably has 10 ppm or less merallic impurities and preferably 50 ppm or less O:, 25 ppm or less Na, and 25 ppm or less carbon. If a purity level of about 99.995 is desired, than the resulting high purity metal preferably has metallic impurities of about 50 ppm or less, and preferably 50 ppm or less O?, 25 ppm or less N2, and 25 ppm or less carbon. With respect to taking this ingot and forming a sputtering target, the following process can be used. In one embodiment, the sputtering targei made from the high purity tantalum metal can be made by mechanically or chemically cleaning the surfaces of the tantalum metal, wherein the tantalum metal has a sufficient starring cross-sectional area to permit the subsequent processing steps described below. Preferably the tantalum metal has a cross*sectional area of at least 9 ½ inches or more. The next step involves flat forging the tantalum metal into one or more rolling slabs. The rolling siab(s') has a sufficient deformation to achieve substantially uniform recrystalli¾Kion after the annealing step immediately following this step as described below. The roiling siab(s) is then annealed in vacuum and at a sufficient temperature to achieve at least partial recystailization of the rolling siab(s). Preferred annealing temperatures and times are set forth below and in the examples. The rolling siab(s) is then subjected to cold or warm roiling in both the perpendicular and parallel directions to the axis of the starting tantalum metal (e.g., the tantalum ingot) to form at least one plate. The plate is then subjected tc flattening (e.g., level rolling). The plate is then annealed a final time at a sufficient temperature and for a sufficient time to have an average £rain size of equal to or less than about 150 microns and a texture substantially void of (100) texture! bands. Preferably, no (100) textural bands exist The plate can then be mechanically or chemically cleaned again and formed into the sputtering target having any desired dimension. Typically, the flat forging will occur after the tantalum metal is placed in air for at least about 4 hours at temperatures ranging from ambient to about 370eC Also, preferably before cold rolling, the rolling slabs are anneated at a temperature (e‚g., from about 9SO°C to about I5OO°C) and for a time (e.g., from about ½ hour to about 8 hours) to achieve at least partial reciystallization of the tantalum metal. Preferably the coid rolling is transverse rolling at ambient temperatures and the warm rolling is at temperatures of less than about 37O°C. With respect to annealing of the tantalum plate, preferably this annealing is in a vacuum annealing at a temperature and for a time sufficient to achieve complete recryytallizaiion of the tantalum metal. The examples in this application set forth further preferred details with respect to this processing. Another way to process the tantalum metal into sputterina targets involves mechanically or chemicallv clean surfaces of the tantalum metal (e.«., the tantalum ineot), wherein the tantalum jneia! has a sufficient starting cross-sectional area to permit the subsequent processing as described above. The nexL step involves round ibrging the tantalum meta! into at least one rod. wherein the rod has Sufficient deformation to achieve substantially uniform recrystaiiizaiion either after the annealing step which occurs immediately after this step or the annealing step prior to coid rolling. The tantalum rod U th‹Mi cut into billets and the surfaces mechanically or chemically cleaned. An optional anneal:nr sttp can occur afterwards to achieve at least partial recrystallizauon. The billets are then axi:illy forged into performs. Again, an optional annealing step can occur afterwards to achieve at least pani.¾i recrysiallization. However, at least one of the optional annealing steps or both are done. The perform* are then 3ubjecied to cold roiling into at least one plate. Afterwards, the surfaces of the piate{s) can be optionally mechanically or chemically cl&an. Then, the final annealing step occurs to result in an average grain size of about 150 microns or less and a texture substantially void of (100) lextural bonds if not totally void of (100) textui¾l bands. The round forging typically occurs after subjecting the tantalum metal to temperatures of about 3709C or lower. Higher temperatures can be used which results in increased oxidation of the surface. Preferably, prior to forging the billets, the billets are annealed. Also, the performs, prior to cold rolling can be annealed. Typically, these annealing temperarures will be from about 9OQ°C to about I2OO°C, AUo, any annealing is preferably vacuum annealing at a sufficient temperature and for a sufficient time to achieve recrystailization of the tantalum metal. Preferably, the sputtering targets made from the high purity tantalum have the following dimensions; a thickness of from about O.C8O to about 1.50", and a surface area from about 7.0 to about !225 square inches. The high purity tantalum preferably has a primary or mixed (111) texture, and a minimum (100) texture throughout the thickness of the sputtering target, and is sufficiently void of (100) texrur¾i binds. The tantalum metal of the present invention can be used in any application or product that uses conventional tantalum metal as a component or as pan of a component. For Instance, the tantalum metal can be a component or pan of a componenr in integrated circuits, such as semiconductors and :he like. The designs described in U.S. Patent Nos,: 5,987,635; 5‚9S7‚56O: 5,986,961; 5,986,960; 5,986,940; 5,986,496; 5‚9SM69. 5,986,410; 5,986 J2Q; 5‚9S6‚29S, 5,986.294; :›‚985•697; and 5‚9S2‚2IS can be used as well as other conventional designs and each of thsse patents are incorporated herein in their entireties by reference. The tantalum metal can be present in any device which typically uses sputtering techniques to deposit metal to form a component or part of n component flfl a device The present invention will be further clarified by the following examples, which are intended it.) be purely exemplary of the prc:^iTt invention. EXAMPLES Kumerous sublets of sodium-reduced commercial-grade tantalum powder, each weighing about 200-800 lbs., were chemically analyzed for suitability as 99*999% Ta feedstock for electron beam melting. Representative samples from each powder lot were analyzed by Glow Discharge Mass Spectrometry (GDMS): powder sublets having combined niobium (Nb), molybdenum (Mo), and tungsten (W) impurity content less than 3 ppm were selected for melting. The selected la powder sublots were then blended in a V-oone blender to produce a homogeneous 4000 pound powder master lot, which was again analyzed by GDMS to confirm purity. Next, the powder was cold isostaiica!!y pressed (CIP'ed) into green logs approximately 5.5"-6.5" in diameter, each weighing nominally 300 pounds. The pressed logs were then degassed by heating at l45OºC for 2 hours ai a vacuum level of about 10""-10'5 torr. For this operation, the logs were covered with tantalum sheets to prevent contamination from the furnace elsments- The degassed logs were then side fed into a 1200KW EB furnace and drip melted a: s. rate of 400 ibs./hr, into a 10" water-cooled copper crucible under a vacuum less than I0"J torr. Once cooled- the resulting first-meit ingot was inverted, hung in the same furnace, and reme!ted using the same EB melting parameters. The V* melt ingot wss again inverted and remelted a third time, but into ‹i !2" crucible u a melt fiUv of 800 !bs./hr. A sample was taken from the sidewall of the resulting ingot for chemical analysis by Glow Discharge Mass Spectrometry (GDMS). Results confirmed that the Ta ingot was 99.9992% pure. A potassium fiuo:antalate (K3TaF7) was obtained and upon spark source mass spec anaivsis, me KyfaF7 exhibited 5 ppm or less niobium. Levels of Mo and W were also analyzed by spectrographic detection and Icvcis were below 5 ppm for Mo and beiow 100 ppm for W. In particular, the KjTaF? had levels of Nb of 2 ppm or less, of Mo of less than I ppm and of W of less than or equal to 2 ppm. In each sample, the total recorded amount of Nb, Mo, and W was below 5 ppm. rw tors of 2.200 lbs. eacii were ana!vzed. One of the lots was transferred to KDEL reactor which used a pure nickel vessel anca Hastdloy X agitator. The Hasxelloy X agitator contained 9% Mo and 0.6% W. The shaft and paddles cf the agitator were then shielded with 1/16" nickel sheet using welding to clad all surfaces exposed to *he reaction. A standard sodium reduction process was used except as noted beiow. The lot was subjected to the agitator in the presence of pure sodium to form tantalum powder. The tantaium powder was then washed with water and subjected to acid treating and then sieam drying and then screening to - iQCtnesh. A sample from each batch was then submitted for glow discharge mass spec analysis. The two tables (Tables I and 2) below show the starting analysis for the KiTaF? and the final analysis of rhe liinralum recovered As can be seen in the above tables, a high purity tantalum powder suitable for electron beam melting into an ingot can be obtained and purities on the Order of 99,999% purity can be obtained by the processing shown in Exampie 1. Examp.'e ;, Two distinct process methodologies were used. First, a 99,998% pure tantalum ingot was used which was subjected to three eiecrron beams melts to produce a 12 inch nominal diameter ingot- The ingor was machined clean to about 1! ½ inch diameter and then heated in air to about 26O°C for 4-S hours. The ingot was then flat forged, cut, and machined into slabs (approximately 4 inch by 10 inch with a length of approximately 28 inch to 32 inch) and then acid cleaned with KF/HNO3 /water solution. The slabs were annealed at 1050, 1 ISO, and l3OOºC under vacuum of ? X i0"4 Terr for 2 hours, then cold rolled into plate stock of G‚5OO and 0.250" gauge, This cold rolling was accomplished by taking a 4 inch thick by 10 inch wide by 30 inch long siab and rolling it perpendicular to the ingot axis at 0.200 inch per pass to 31 inches wide. The piate was then rolled parallel to the ingot axis at 0.100 inch per pass to 0,650 inch thick or O‚5OO inch thick. Both rollings wtre done on a 2-High breakdown rolling mill. Each of the plates were roiled by multiples passes or 0.050 inch per pass and then 0.025 inch per pass with final adjustments to meet a finish gauge of O‚5OO inch plate or 0.250 inch plate, using a four high finishing rolling mill. The plates were then subjected to a final annealing at temperatures of from 950 -115O°C. The alternative process began with a 99.95 % pure Ta which was subjected to three electron beam melts to produce an ingot as described above prior to being forged. The ingo* was then round forged using a GFM rotary forge to 4'1 diameter after multiples passes of about 70% reduction in area per pass. From this intermediate stock, 4 billets M75"0 x T long) were machined, and 2 billets (iabeied A and ß) were annealed at 10506C while billets C and D remained unannealed. Next, the billets wers upset forged to performs of height of 2.5", after which performs A and C were annealed ar 1050VC. The performs were then clock roiled to a thickness of about 0.400" to yield discs of a diameter of approximately 14". This was accomplished bv taking muiripte passes of 0,200 inch per pass to about 0.5250 inch thick. The discs were then rolled to about 0.5 inch thick by multiple passes of 0.100 inch per pass. Then, the discs were clocked rolled on a four high finishing mill in three passes of 0.050 inch, 0,025 inch, › and 0.015 inch reductions per pass to yta!d a disc of about 0.400 incn thick by about 14 inch diameter. A quarter of the disc was cut into four wedges and final annealed at temperatures of 950-1100*C Tabla 4 below summarizes this processing. Meiallograpbic and texture analysis was conducted on longitudinal sections of the plate material (measurement face parallel to the final rolling direction) and on radial sections of the forged and rolled discs (measurement face parallel to the radius of the discs). METAL IURG1CAL ANALYSIS Grain size and texture were measured along the longitudinal or radial directions of samples liken from rolled plate and forgeu and rolled discs, respectiveIv. Grain size was measured using ASTM pioceduie £-il2. Results from the annealing studies on products produced via the flat and round processes are given in Ya&les 3 and 4, respectively. Intermediate annealing treatments h:id no noricaubie inxiuttice on the grain size of the finished product. Also, for plate, the final grain sizes of 0,300 and O.25Q"1 thick tantalum were comomble. The only variable found to significantly effect thv grain site of the materials was the final anneal cemperacure; the higher the final anneal Uiinoerrvrure. the iaiaer me resulting grain 2i2e. in plate, grain sizes of ASTM o.i - 7.0 were measured in samples from product annealed at 1000 and 95O°C. However, each of these samples showed evidence of elongated and/or uiircciy3tallized regions at or near the surface, •and reeryst2!Hz2tion values were reported to be 98-99%. for plates annealed at 1050, 1100, and 115O°C ASTM grain sizes ranged from 5.3 to 3.7, with ail samples being 100% re.;rystalii‹ied. Forme round-processed discs, ail samples were reported to be 100% recrystallized. with the exception of Disc C annealed at 95O°C which was 99% recrystaHized. Grain sizes of ASTM 7,1 - 7.2, 6,1-6.S› and 5.9-5.9 were measured in the disc samples annealed at 950, 1000, and 1050CC, respectively. Annealing at 1 lOO•C produced grain sizes of ASTM 4.0-4,5. For both processes, these findings demonstrate that a fully recrysrallized grain size of 50 µjfrt or finer is achievable using either the plate roiling or the billet forging process at a preferred final anneal temperature of from about 950 to about !O5O°C, Should the unrecrysta!lized areas be limited to only the surface regions of the plate, then they can be removed by machining. tgxrure Measurement Technique: A limited number of samples (chosen based on metallurgical results) were used for texture analysis. Mounted and polished samples, previously prepared for metallurgical analysis, were employed as texture samples* after being given a heavy acid etch prior to texture measurement. Orientation Imaging Microscopy (OIM) was chosen as the method of texture analysis because of its unique ability to determine the orientation of individual grains within a polycrystalline sample. Established techniques such as X-ray or neutron diffraction would have been unable to resolve any localized texture variations within the thickness of the tantalum maieriab. For the analysis, each texture sample was increm¾nta!ly scanned by an electron beam (within an SEM) across its entire thickness: the bacfc¾atter Kikuchi patter? generated fcr ¾ach measurement point was then indexed using a computer fo determine the crystal orieittatiori. From each sample, a raw-data i¾ containing the orienrations for each data poinr within the measurement grid iiray was created. These fries served as the input data for subsequently producing gr:i::‹ orientation maps &A calculating pole figures and orientation distribution functions (ODFs). By convention, texture orientations are described in rcfer2i;ce to the lampift-nunrni coordinate system. That is, pole figures are "standardized" such that the origin h normal to the plate surface, ana (he reference direction is the rolling (or radial') direction; likewise, ODFs are always defined with rested ^o the sample-normal coordinate system: Terminology such as i;a (1! 1) icxninv" means thai cue (II1; atomic pianes are preierenually oriented to be parallel (and the (111) pole onented to be normal) with the surface of the plate, In the analyse;, the crystal orientations were measured with respect to the sample longitudinal direction. Therefore, it was necessary to transpose the orientation data from the longitudinal to sample-normal coordinate system as part of the subsequent texture analysis. These tasks were conducted through use of computer algorithms. Grain Orientation Maos: Derived from principles of presenting texture information in the form of inverse pole figures, orientation maps are images of the microstructure within the sample where each individual grain is "color-coded * based on its crystallographic orientation relative to the normal direction of the plate of disc from which it was taken. To produce these images, the crystal axes for each grain (determined along the longiiudinal direction of the texture sample by OIM) were tilted 90d about the transverse direction so to align the crystal axes to the ncrmni direction of the sample. Orientation maps serve to reveal the presence of texture bancs or gradients through the thickness on the product; in tantalum, orientation maps have shown that large, elongated giains identified by optical microscopy can be composed of several small grains with low-angle grain boundaries. Analysts of the Texture Results: OIM scans were taken along the thickness of each sample provided; lor the Q.5G(T piate samples, separate measurements were made for the top and the bottom portions of the plate md ;epcrted separately. The orientation maps were visually examined to qualitatively characterize the texture uTiifOiiiiity tiu'ougu the sample thickness. To attain a quantifiable description of the texture gradienrs and texture bands in the example materials, the measured EBSD data was partitioned into 20 sublets, with each representing a 5% increment of depth through the thickness of the sample For each incremental da:a set, an OUF was first calculated, then (100) and (1!!) cemroid intensities determined numerically using techniques reporxed elsewhere. The equipment and procedures described m S. Matthies et aL Materials Science Forum, Vol. 157-162 (1994), pp. 1647-1652 and S. Matthies et aL, Materials Science Forum, Vol. 157-162 (1994), pp. 1641-1646 were applied, and thesi publications ate incorporated in their entiretv herein by reference. The texture gradient? wars then described graphically by plotting the (100) and (111) intensities, as well as the log ratio of the (iOO);(l; I), as a function depth of the sample. These results are set forth in Ffgures 1 (A and B) throu¾h Fi£iite½ II ('A and B). The heavy-gauge tantalum piate exhibited the most uniform through-thickness texture; the oniy sample containing texture bands was that processed with a slab anneal of 1300*C and a final anneal of 1000*C, in addition, the 0.500" plate materials also had a relative weak {most random) texture base on pale figure and CDF analysis. Compared to the heavy plate, the 0.250' sheets contained a slight to moderate texture gradient and some evidence of texture banding. Alsot the thin-gauge plates showed a more defined {111) texture in the ODFs and an increased prominence of (100). The greatest variability in terms of texture uniformity and banding was found in the forged and roiled discs. Unlike the metallurgical properties, the texture of forged and roiled discs was effected by the use of intermediate anneahne. For discs A, B, and C. each of which were processed with one or two intermediate annealing steps, the texture gradients ranged from negligible to strong (dtpenuing to processing parameters) with slight ~ if any - banding. However, for disc D, which was worked from ingot to final discs without intermediate annealing the resultant product contained le¾s uesuauie strong texture gradients and sharp texture bands. Similarly* disc C. which was alto ftugtd fiom unanneaisd billet but then annealed prior to cc!ri rolling, al¾o showed a strong texture gradient and banding in the sample final annealed at 95O°C. For disc C, increasing *he find anneal temperature to 1 i0C-C acted to dimmish the gradient, eliminated the bands, but strengthening the intensity of (100) texture component. These effects from increasing final annealing temperatures were also evident, but to a lesser degree, in bo›h the other disc materta-s *'n* the neaw cause 9late. From the microsiructural and texturai observations, the following conclusions could bt* marie regarding the optimum processing for fabricating tantalum sputtering targets: * For flat products, slab anneal temperatures preferably do not exceed I l5OºC (lO5OºC is more preferred) and the final anneal temperature is preferably kept at 950-1000ºC, more preferably 1000CC The resulting product is characterized as having a rccrystallized average grain size of less 50 µrn, and a (100) incremental intensity of less than i 5 random and a iog ratio of f 111 ):(IOO) of less than -4 0, * For round processing, billets preferably are annealed prior to forging and rolling into disc without use of an intermediate anneal at perform level. Final anneal temperature is preferably 950-1 !OO°C, and more preferably is IQ5O°C The resulting product is characterized as having a recrystallized average grain size below 50 µm, and a(lOO¾ incremental intensity of less than 15 random and a log ratio of (11 l);(lOO) of less than -4.0. Other embodiments of the present invention *ill be apparent to those skilled in the art from consideration of the present specification and practice of the present invention disclosed herein. It is intended th¾r The present specification wd example?, be considered as exemplary only with a. true scope and spirit of die invention being indicated by the following claims. WE CLAMS 1. Tantalum metal having a purity of at least about 99.995%, and an average grain size of abou-150 microns or less* 2. The tantalum metal of claim I, wherein said metal is fully ^crystallized. 3. The tantalum meta) of claim 1, wherein said metal is at least partially recrystallyzed. 4. The tantalum metal of claim U wherein about 98% or more of said metal is recrystallyzed. 5. The tantalum metal of cteim 1, wherein about 80% or more of said metal is recrystatly/ed 6. The tantalum metal of claim 1, wherein said metai has; a) a texture in which a (100) noic fii/u has a center peak intensity less than about 15 random or b) a log ratio of (1! 1):(100 7. The tantalum metal of ciaim 6, wherem said center peak intensity is from about 0 nndoir. TO about 15 random. 8. The tantalum metal of claim 6, wherein said center peak intensity is from about 0 random r : about 10 random. 9. The tantalum metal of claim 6, wherem said log ratio is from about -4,0 to about 15. 10. The tantalum metai of claim 6, wnerein said log ratio is from about -1.5 to ahmir 7.0 11. The tantalum metal of claim 6, wherein said center peak intensity is from about 0 -incioir; u: about IS random, and said log ratio is from about ~4.0 to about 15. 12. The tantalum metai of ciaim 1 having a purity of from 99.995?/Q to about 99,999% 13. A metal alloy eompnsingttie tantalum mewl of claim 1. 14. A metal alloy comprising the tantalum metal of claim 6. 15. A metal aiioy comprising the tantalum met,*! of claim 3. 16. A sputtering target comprising the tantalum metal of claim 1. 1". A sputtering target comprising the tantalum metal of ciaim 6. 18, A sputtering target comprising the tantalum metal of claim 3. 19- A capacitor cart comprising the tantalum metal of claim 1- 20. A capacitor can comprising the tantalum metal of claim 6. 21. A capacitor can comprising the tantalum metal of claim 3. 22. A resistive film layer comprising the tantalum metal of claim 1. 23. A resistive film layer comprising the tantalum metsl of claim 6. 24. A resistive film layer comprising the tantalum metal of claim 3. 25. An article comprising at least as a component the tantalum metal of claim 1, 26. An article comprising at least as a component the tantalum metal of claim 6. 27. An article comprising at least as a component the tantalum metal of claim 3. 28. Tantalum metal having a) an average grain size of about 50 microns or less, or b) a texrur* ; which a (100) pole figure ha* a center peak intensity equal to or less than about 15 random 'f ^ log ratio of (131):(100) center peak intensities of greater than about -4.0, or combinations rhw - 29. The taiuaium nietai of claim 28 having an average grain size of from about 25 to about ':0 microns. 30. The tantalum metai of claim 2S having a ratio of (111):(100) center peak intensities of _^UM: thaft about -4 0. 31. The tantalum meui of ciaim 28, having both a) and b). 32. Tlic tantalum mewl of ciaim 28, wherein said metal has purity of ai iea&t 99/>y5?'o t^nt;,iur»i 3:-. The tantalum iftetai of ciaim 28, wherein said metal has a puriiy ox 99.909% [HUIAIUW. 34. The tauuiucn metai of claim 28, wlietein said meial is fullv recrvstaihscd. 35. The tantalum mers! of claim 32, whercic said meiai is fully recn-'SUllizr.J. 36. The tantalum mctai of claim *3, wherein said metal is fully rec:y$taii;Zfd j7. The tantalum metal of claim 28, wherein about $0% or more of said metal is fully rcervstallized. 38. The tantalum metal of claim 28, wherein said center peak intensity is from about 0 random u-. about 15 random. 39* The tantalum metal of claim 23, wherein said log ratio is from about -4.0 to about 15 40. An article comprising the tantalum metal of claim 28. 41. An article comprising the tantalum metal of claim 33. 42. A spurtering target comprising the tantalum metal of claim 28. 43. A sputtering target comprising the tantalum metal of claim 33. 44. A process for making the tantalum metal of claim I. comprising reacting 3 salt containing tantalum with at least one agent capable of reducing the salt to tantalum and a second salt in a reaction container having an agitator, wherein the reaction container • ^ liner in the reaction container and the agitator or a iiner on the agirator are made from a m^:-' material having the same or higher vapor pressure of tantalum at the melting point of the ranralum. 45. The process of claim 44, wherrin the salt containing tantalum comprises a potassium*fluoride tantalum and the agent comprise? sodium. 46. The process of claim 45, wherein the second salt comprises sodium fluoride and/or sodium chloride, 47. The process of claim 44, wherein prior to reacting said salt conrair.ine tantalum saia process comprising forming an acid solution comprising tantalum and impurities and conducting a aensitv separation of the acid solution containing tantalum from the acid solution containing the impurities: and crystallizing the acid solution cemtaininc: :hc tantalum to form the salt oontiiininst tuiitaium. 48. The process of claim 47, wherein the tantalum and impurities are crushed ore. comprising rantalum and impurities. 49. The process of claim 47, wherein the acid solution comprising unraium and impurities are formed by combining acid solution with crushed ore comprising tantalum. 50. The process of claim 44, wherein the reaction occurs at about 800°C to about i 100°C while -stirring. 51. The process of claim 44, wherem the reaction container or litter and the agitator or liw on the agitator are rnetai-based, wherein said metal is nickel, chromium, iron, manganese, titanium, zirconium, hafnium, vanadium, technerium, ruthenium, cobalt, rhodium. paii.-Wium. platinum, or any combination Thereof. 52. The process of claim 51, wherein the metal is nickel or a nickel-based alloy. 53. The process of claim 5 U wherein the metai is chromium or a chromium-based alloy. 54. Thfe process or claim i 1, wherein tha metal is iron or an iron-bas.ed alloy. 55. The process of claim 44, further comprising recovering tantalum by dissolving the second salt in S'.i aqueous wludop., 56. The process of claim 55* furtfter comprising melting said recovered tantalum in :\ sufficient vacuum to remove substantially any existing impurities in said rooovere-.i tOTTaii/m und obtain high pmity tantalum. 37. The process of claim 56, wherein the vacuum is !(T* torr or more. 53* The process of claim 56, wherein the pressure above the melted recovered tantalum is lower than the vapor pressures of substantial ly all of the impuri^. 59. The process of claim 36, wherein the impurities are removed by vaporization of the impurities. 60. The process of claim 56, wherein said melting is accomplished by electron bean meitiiig. 61. The process of claim 56, wtiercin said melting is accomplished by vacuum arc remek processing 62. The process of claim i6, wherein the high purity tantalum is allowed to form a solid and subjected to a railing process, a forging process, or both. 62. The tantaluni metal of ciaim i, wherein the tantalum metal has a substantially fine and uniform mierosirucntre, 64. The tantalum metai of claim U wherein the tantalum metal has an average £ram size of from about 25 to about 150 microns, 65. The tantaluni meul of claim 64, wherein the tamaium metal has an average gran sizit of from about 25 to dtout 100 microns. 66. The tantalum memi of claim 65, wherein the tantalum metal has an avciage grain size of from about 25 to about 75 microns 67. A process of uiaking a sputtering target from tantalum metal having a purity of 2: least 99 V95%, comprising: a) mechanically or chemically clean surfaces of the tantalum meal whem/i thv ^-Li'*::v m*tal has a sufficient surfing cross-sectional area to permit steps b) through gV. b) flat forging the tamaium metal into &t least one roiling slab, wherein the at l?a.cr ov.:.: rH! i:iv slab has sufficient deformation to achieve substantially uniform recrystaKization sf ?r inn ; -in 5:ep;!); c) mechanically or chemically clean surfaces cf the at least om? rolling ;,Lib; d) annealing the at least one rolling slab at a sufficient temperature and for a sufncieni time ro achieve ar least partial recryscailization of the at least one rolling slab; e) cold or warm rolling the at least o.ie rolling slab in both the perpendicular and parallel directions to the axis of the starting tantalum metal to form at least one plate; f) flattening the at least one plate; and g) annealing the at. least one plate to have an average grain size equal to or less thrm zh^u !c 0 microns and a texiure substantially void of (100) textural bands; 68- The process of claim 67, wherein the tantalum metal has a purity of at least 99.9^9% 69, The process of claim 67, wherein the flat forging occurs after the tantalum metal r placed in air for at ieast about 4 hours and from temperatures ranging from ambient to about 1200°C. 70. The process of claim 67, wherein the cold rolling is transverse rolling at ambient temperatures and the warm rolling is at temperatures of less than about 370°C. 71, The process of claim 67, wherein the annealing of the plate is vacuum annealing .IT a temperature and for a time sufficient to achieve recrystaltization of the tantalum metal. 72. A process of making a sputtering target from tantalum metal having a purity of :u least 99,99-:QA, cornorisins: a) mcchanicaiiy or chemically clean surfaces of the tantalum metal, wherein the nnrahrr metal has a sufficient starting cross-sectional area to permir steps b) through i); b) round forging the tantalum metal into at least one rod, wherein rhe at least one vr h. sufficient deformation to achieve substantially uniform renrystallizanon after annealin;; r d) or c) cutting the rod into billets and mechanically or chemically clean the surface?, of n.? b d) optionally annealing the billets to achieve at least partial recrysrallizarion: e) axiaily forging billets iruc performs; 0 optionally annealing the performs to achieve at least partial rectyttallization; g) cold roiling the performs into at least one plate; and h) optionally mechanically or chemically clean the surfaces of the at least one plate; ar.c! i) anneaiing the at least one plate to have an average grain size equal to or {ess than aboii 150 mkrons and a texture substantially void of (100) texturai bands, wherein annealmp ocwm at least in stop d) or f) or both. 73. The process of claim 72* wherein the tantalum metal has a purity of at least 99.995%. 74. The process of claim 72, wherein the round forging occurs after subjecting the tantalum metal to tempeatures uf about 170°C or lower. 75. The process of claim 72 wherein prior to forging the billets, the billets nrc annealed. 76. The piocess of claim 72, wherein prior to cold roiling of the performs, the performs a*e annealed. 77. Tiie process of claim 72. wherem the anneaiine of the performs is vncnym annealing at a sufficient temperature and for a time to achieve; recrvstaitization. 78. Tantalum metal, substantially as hereinabove described and illustrated with reference to the accompanying drawings. 79. A process of making a sputtering target from tantalum metal, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

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in-pct-2001-735-che-abstract.pdf

in-pct-2001-735-che-claims filed.pdf

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in-pct-2001-735-che-description(complete)filed.pdf

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