Cobalt, iron, boron, and/or nickel alloy-containing articles and methods for making same
Methods for making a high purity (>99.99%) and low oxygen (<40 ppm) sputtering target containing Co, CoFe, CoNi, CoMn, CoFeX (X═B, C, Al), Fe, FeNi, or Ni alloys with a column microstructure framed by boron intermetallics are disclosed. The sputtering target is made by directional casting a molten mixture of the metal alloy, annealing to remove residual stresses, slicing, and optional annealing and finishing to obtain the sputtering target.
1. A method for making a sputtering target,
comprising:
forming a molten alloy mixture, wherein the molten alloy mixture comprises (i) a composition including at least one of Co, Fe, or B, as a primary constituent, or (ii) a composition including Co and at least one of Fe, and Ni, or (iii) a composition of the formula CoFeX, wherein X is one of B, C, or Al;
pouring the molten mixture into a mold to form a directional casting ingot;
annealing the casting ingot; and
slicing the casting ingot to form the sputtering target,
wherein the sputtering target has a purity of greater than 99.99% and a low oxygen content of 40 ppm or less, and has a column microstructure framed by borides.
2. The method of claim 1 , wherein the molten alloy mixture
comprises a composition including 15% or more of boron (B).
3. The method of claim 1 , further comprising (i) shaping the casting ingot prior to slicing the casting ingot, or (ii) annealing the sputtering target after slicing the casting ingot, or (iii) finishing the sputtering target after slicing the casting ingot.
4. The method of claim 3 , wherein the finishing comprises grinding at least one surface of the sputtering target.
5. The method of claim 1 , wherein the annealing is performed at a temperature of less than 700° C. for a minimum of about 8 hours.
6. The method of claim 1 , further comprising pouring the molten mixture into a funnel above the mold, wherein the funnel comprises a conical top portion and a cylindrical bottom portion.
7. The method of claim 1 , wherein the sputtering target comprises an alloy of the formula Co x Fe y B (1-x-y) .
8. The method of claim 1 , wherein the sputtering target comprises an alloy of the formula (CoFe) 1-x B x , wherein 0.2≤x≤0.4.
9. The method of claim 1 , wherein the sputtering target has a diameter of up to 250 mm.
10. The method of claim 1 , wherein the sputtering target has a pass through flux of at least 30% at a thickness of 3 mm.
11. The method of claim 1 , wherein the sputtering target has a purity of 99.99%.
12. The method of claim 1 , wherein the sputtering target has an oxygen content less than 40 ppm.
13. The method of claim 1 , wherein the sputtering target has a B content of greater than 15%.
14. The method of claim 1 , wherein the annealing is performed under vacuum or under gas protection using an inert gas.
15. The method of claim 1 , wherein the sputtering target has a uniform microstructure.
16. A sputtering target for production of a magnetoresistive RAM (MRAM) prepared by a process comprising the steps of:
forming a molten alloy mixture comprising Co, Fe, B, or Ni and at least one of Ni, Mn, B, C, and/or Al;
pouring the molten mixture into a funnel located above a mold to form a directional casting ingot;
annealing the casting ingot; and
EDM slicing the casting ingot to form the sputtering target,
wherein the sputtering target has a purity of greater than 99.99%, and has a column microstructure framed by borides.
17. The sputtering target formed by the process of claim 16 , wherein the sputtering target has a B content of greater than 15%.