High purity refractory metal powders and their use in sputtering targets which may have random texture

Abstract

A method for making a sputtering target including steps of encapsulating and hot isostatically pressing at least one mass of metal powder (e.g., tantalum), having a particle size ranging from about 10 to about 1000 μm, with at least about 10 percent by weight of particles having a particle size greater than about 150 μm (for example, about 29 to about 56 percent (e.g., about 35 to about 47 percent) by weight of the particles in the at least one mass of metal powder having a particle size that is larger than 150 microns, but below about 250 μm), for defining at least a portion of a sputtering target body, having an essentially theoretical random and substantially uniform crystallographic texture.

1 .- 20 . (canceled) 
     
     
         21 . A method for making a sputtering target comprising the steps of:
 a. encapsulating a mass of metal powder that has at least about 95% by weight of particles exhibiting a particle size ranging from about 10 to about 1000 μm, with at least about 10 percent by weight of particles having a particle size greater than about 150 μm, in a container configured for defining at least a portion of a sputtering target body, wherein at least some of the particles of the mass of metal powder are non-spherical; and   b. hot isostatically pressing the mass of metal powder to form a resulting densified mass having an initial crystallographic texture, while the mass of metal powder is in the container, wherein the hot isostatically pressing step is performed under conditions so that the initial crystallographic texture achieved in the resulting densified mass is an essentially theoretically random and generally uniform crystallographic texture, wherein the method is devoid of any step of altering the initial crystallographic texture substantially throughout the resulting densified mass after the step of hot isostatically pressing and prior to sputtering.   
     
     
         22 . The method of  claim 21 , wherein the mass of metal powder comprises one or more refractory metals. 
     
     
         23 . The method of  claim 21 , wherein the mass of metal powder contains oxygen at a concentration less than about 150 ppm. 
     
     
         24 . The method of  claim 23 , wherein the mass of metal powder contains oxygen at a concentration ranging from about 10 ppm to about 125 ppm. 
     
     
         25 . The method of  claim 21 , wherein the mass of metal powder contains one or more alkaline earth metals at a concentration less than about 15 ppm. 
     
     
         26 . The method of  claim 21 , wherein the mass of metal powder contains one or more alkaline earth metals at a concentration ranging from about 0.5 ppm to about 10 ppm. 
     
     
         27 . The method of  claim 21 , wherein at least 50 percent by weight of the particles of the mass of metal powder have a particle size greater than about 150 μm. 
     
     
         28 . The method of  claim 21 , wherein none of the particles of the mass of metal powder have a particle size greater than about 250 μm. 
     
     
         29 . The method of  claim 21 , wherein between about 29 percent and about 56 percent of the particles of the mass of metal powder have a particle size ranging from 150 μm to 250 μm. 
     
     
         30 . The method of  claim 21 , wherein at least about 95 percent of the particles of the mass of metal powder have a particle size ranging from 45 μm to 250 μm. 
     
     
         31 . The method of  claim 21 , wherein the hot isostatically pressing step takes place at a temperature between about 1000° C. and below 1200° C., and wherein the hot isostatically pressing step takes place at a pressure between 100 and 250 MPa and for a period sufficient to achieve a density of at least 98% of theoretical density. 
     
     
         32 . The method of  claim 21 , wherein the resulting densified mass is a sputtering target body that has grains that are generally uniformly distributed throughout the sputtering target body and the grains have an average grain size of about 40 to about 100 μm. 
     
     
         33 . The method of  claim 21 , further comprising making the mass of metal powder using a method comprising:
 a. locating an initial mass of metal powder having an initial content of oxygen in a reactor;   b. locating within the reactor, spaced apart from the initial mass of metal powder, a mass of a scavenging metal, wherein the mass of the scavenging metal and the initial mass of metal powder are not blended together;   c. heating within the reactor to a scavenging temperature for causing at least a portion of the scavenging metal to at least partially vaporize and react with at least a portion of the initial content of oxygen to form a scavenging metal oxide with at least a portion of the scavenging metal; and   d. separating the scavenging metal oxide from the initial mass of metal powder so the mass of metal powder thereby formed has a resulting content of oxygen that is less than the initial content of oxygen.   
     
     
         34 . The method of  claim 33 , wherein the initial content of oxygen is greater than about 300 ppm by weight. 
     
     
         35 . The method of  claim 33 , wherein the initial mass of metal powder is in a bed having a depth ranging from about 0.3 cm to about 3.5 cm. 
     
     
         36 . The method of  claim 33 , wherein the scavenging metal comprises magnesium. 
     
     
         37 . The method of  claim 33 , wherein the scavenging metal is present in the reactor in the form of flakes. 
     
     
         38 . The method of  claim 33 , wherein (i) the scavenging temperature ranges from about 800° C. to about 1000° C., and (ii) the heating within the reactor is performed for a time of about 30 minutes to about 2 hours. 
     
     
         39 . The method of  claim 21 , wherein the resulting densified mass is a sputtering target body that has a substantially uniform crystallographic texture throughout the sputtering target body and is essentially devoid of any crystallographic texture banding and/or crystallographic texture gradients. 
     
     
         40 . The method of  claim 21 , wherein the mass of metal powder comprises tantalum.