Ta sputtering target and method for producing the same

Abstract

A method for producing a Ta sputtering target including the following steps: (a) a step of forging a Ta ingot, comprising subjecting the Ta ingot to a forging pattern over at least 3 times, wherein each forging pattern is “a cold forging step comprising stamp-forging and upset-forging operations alternatively repeated over at least 3 times; (b) an in-process vacuum heat-treating step carried out between every successive two forging patterns to thus prepare a Ta billet; (c) a step of rolling the Ta billet to obtain a rolled plate; and (d) a step of vacuum heat-treating the rolled plate to obtain a Ta sputtering target. A sputtering target produced by the above method.

1 . A method for producing a Ta sputtering target comprising:
 (a) a step of forging a Ta ingot, comprising subjecting the Ta ingot to a forging pattern over at least 3 times, wherein each forging pattern is “a cold forging step comprising stamp-forging and upset-forging operations alternatively repeated over at least 3 times;   (b) an in-process vacuum heat-treating step carried out between every successive two forging patterns to thus prepare a Ta billet;   (c) a step of rolling the Ta billet to obtain a rolled plate; and   (d) a step of vacuum heat-treating the rolled plate to obtain a Ta sputtering target.   
     
     
         2 . The method for producing a Ta sputtering target as set forth in  claim 1 , wherein the Ta ingot used is one having an aspect ratio (length/diameter) ranging from 0.7 to 1.5. 
     
     
         3 . The method for producing a Ta sputtering target as set forth in  claim 1 , wherein a change in shape of the ingot during the foregoing stamp-forging and upset-forging operations is performed within an aspect ratio (length/diameter) ranging from 0.7 to 1.5. 
     
     
         4 . The method for producing a Ta sputtering target as set forth in  claim 2 , wherein a change in shape of the ingot during the foregoing stamp-forging and upset-forging operations is performed within an aspect ratio (length/diameter) ranging from 0.7 to 1.5. 
     
     
         5 . The method for producing a Ta sputtering target as set forth in any one of  claims 1  to  4 , wherein the step of rolling of the Ta billet is performed in a cold rolling operation in at least 4 axial directions at a total draft percentage ranging from 65 to 75%, and wherein the step pf vacuum heat-treating the rolled plate is performed at a temperature ranging from 850 to 950° C. 
     
     
         6 . The method for producing a Ta sputtering target as set forth in any one of  claims 1  to  4 , wherein the Ta ingot used is one having a total content of impurities including Al, Cr, Fe, Ni, Ti, Na, Mg, K, Si, Cu, Co, Nb, W, Mo, U and Th on the order of not more than 50 ppm and contents of C, N and O of not more than 50 ppm, respectively. 
     
     
         7 . The method for producing a Ta sputtering target as set forth in any one of  claims 1  to  4 , wherein the Ta sputtering target produced has a crystalline microstructure of an average grain size ranging from 30 to 50 μm with a small dispersion in grain size. 
     
     
         8 . A Ta sputtering target characterized in that it is produced according to the method as set forth in any one of  claims 1  to  4 , that it has a crystalline microstructure of an average grain size ranging from 30 to 50 μm with a small dispersion in grain size. 
     
     
         9 . The Ta sputtering target as set forth in  claim 8 , wherein it has a total content of impurities including Al, Cr, Fe, Ni, Ti, Na, Mg, K, Si, Cu, Co, Nb, W, Mo, U and Th on the order of not more than 50 ppm and contents of C, N and O of not more than 50 ppm, respectively.