Ta sputtering target and method for producing the same
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 having a length and a diameter, 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 during the foregoing stamp-forging and upset-forging operations, the ingot maintains 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 during the foregoing stamp-forging and upset-forging operations, the ingot maintains 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 of 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 on the order of not more than 50 ppm, the impurities being selected from the group consisting of Al, Cr, Fe, Ni, Ti, Na, Mg, K, Si, Cu, Co, Nb, W, Mo, U, Th, and combinations thereof, and
wherein a content of each C, N and O in the Ta ingot is not more than 50 ppm.
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.
8. The method for producing a Ta sputtering target as set forth in claim 7 , wherein the average grain size of the crystalline microstructure has a standard deviation of about 12 μm to about 30 μm.