Method for making a current-perpendicular-to-the-plane (CPP) magnetoresistive sensor containing a ferromagnetic alloy requiring post-deposition annealing
A method for making a current-perpendicular-to the-plane giant magnetoresistance (CPP-GMR) sensor with a Heusler alloy pinned layer on the sensor's Mn-containing antiferromagnetic pinning layer uses two annealing steps. A layer of a crystalline non-Heusler alloy ferromagnetic material, like Co or CoFe, is deposited on the antiferromagnetic pinning layer and a layer of an amorphous X-containing ferromagnetic alloy, like a CoFeBTa layer, is deposited on the Co or CoFe crystalline layer. After a first in-situ annealing of the amorphous X-containing ferromagnetic alloy, the Heusler alloy pinned layer is deposited on the amorphous X-containing ferromagnetic layer and a second high-temperature annealing step is performed to improve the microstructure of the Heusler alloy pinned layer.
1. A method for making a current-perpendicular-to-the-plane (CPP) magnetoresistive sensor having a pinned layer comprising:
providing a substrate in a vacuum chamber;
depositing on the substrate a pinning layer of a Mn alloy capable of becoming antiferromagnetic; and
forming on the pinning layer a multilayer pinned layer comprising the steps of:
depositing on the Mn alloy layer a non-Heusler alloy ferromagnetic layer;
depositing on the non-Heusler alloy ferromagnetic layer a layer of a ferromagnetic alloy comprising B and one or more of Ta, Ti, Zr, Nb, Si and W;
after depositing said ferromagnetic alloy comprising B and one or more of Ta, Ti, Zr, Nb, Si and W, performing a first annealing in the vacuum chamber by subjecting the deposited layers to a temperature between 250-400° C for between 1-60 minutes;
after said first annealing, depositing at least one layer of material selected from a Heusler alloy material and a non-Heusler alloy material of the form (Co y Fe (100-y) ) (100-z) X z (where X is one or more of Ge, Al, Si or Ga, y is between about 45 and 55 atomic percent, and z is between about 20 and 40 atomic percent); and
performing a second annealing in the vacuum chamber by subjecting the deposited layers to a temperature between 300-550° C for between 1-60 minutes to thereby form said multilayer pinned layer;
after said second annealing step, depositing a nonmagnetic spacer layer on said layer of material selected from a Heusler alloy material and a non-Heusler alloy material of the form Co y Fe (100-y) ) (100-z) X z (where X is one or more of Ge, Al, Si or Ga, y is between about 45 and 55 atomic percent, and z is between about 20 and 40 atomic percent), and a non-Heusler alloy ferromagnetic free layer on the nonmagnetic spacer layer.
2. The method of claim 1 wherein depositing a non-Heusler alloy ferromagnetic layer comprises depositing a first non-Heusler alloy ferromagnetic layer, and further comprising, after said first annealing and prior to depositing said at least one layer of material selected from a Heusler alloy material and a non-Heusler alloy of the form (Co y Fe (100-y) ) (100-z) X z , depositing a second non-Heusler alloy ferromagnetic layer.
3. The method of claim 1 wherein depositing said at least one layer of material selected from a Heusler alloy material and a non-Heusler alloy of the form (Co y Fe (100-y) ) (100-z) X z comprises depositing said at least one layer of material selected from a Heusler alloy material and a non-Heusler alloy of the form (Co y Fe (100-y) ) (100-z) X z directly on and in contact with said layer of a ferromagnetic alloy comprising B and one or more of Ta, Ti, Zr, Nb, Si and W.
4. The method of claim 1 wherein said layer of a ferromagnetic alloy comprising B and one or more of Ta, Ti, Zr, Nb, Si and W consists essentially of a layer of an alloy having the composition (CoFe) (100-x-y) B x Ta y , where the subscripts are in atomic percent, 10≦x≦30 and 5≦y≦10.
5. The method of claim 1 wherein said Mn alloy consists essentially of IrMn.
6. The method of claim 1 wherein said Heusler alloy material is selected from Co 2 MnX (where X is one or more of Ge, Si, or Al), Co 2 FeZ (where Z is one or more of Ge, Si, Al or Ga) and CoFe x Cr (1-x) Al(where x is between 0 and 1).
7. The method of claim 1 wherein X is Ge in said non-Heusler alloy material of the form (Co y Fe (100-y) ) (100-z) X z (where X is one of more of Ge, Al, Si or Ga, y is between about 45 and 55 atomic percent, and z is between about 20 and 40 atomic percent).
8. The method of claim 1 , further comprising depositing a capping layer on the non-Heusler alloy ferromagnetic free layer and thereafter performing a third annealing in the presence of a magnetic field by subjecting the deposited layers to a temperature between 200-400° C for between 0.5-50 hours to thereby increase the exchange coupling between the antiferromagnetic layer and the non-Heusler alloy ferromagnetic layer.
9. A method for making a current-perpendicular-to-the-plane (CPP) magnetoresistive sensor having an antiparallel (AP) pinned structure comprising a first AP-pinned (AP 1 ) ferromagnetic layer, a second AP-pinned (AP 2 ) ferromagnetic layer, and an AP coupling (APC) layer between and in contact with the AP 1 and AP 2 layers, wherein said AP 1 layer comprises a Heusler alloy ferromagnetic layer, the method comprising:
providing a substrate in a vacuum chamber;
depositing on the substrate a Mn-containing layer capable of becoming antiferromagnetic;
depositing on and in contact with the Mn-containing layer a first ferromagnetic layer selected from Co and a non-Heusler alloy comprising Co and Fe;
depositing on and in contact with said first ferromagnetic layer a ferromagnetic diffusion blocking layer comprising Co, B and one or more of Ta, Ti, Zr, Nb, Si and W;
performing a first annealing in the vacuum chamber by subjecting the deposited layers to a temperature between 250-400° C. for between 1-60 minutes;
after said first annealing, depositing on said diffusion blocking layer said AP 1 layer Heusler alloy material selected from Co 2 MnX (where X is one or more of Ge, Si, or Al), Co 2 FeZ (where Z is one or more of Ge, Si, Al or Ga) and CoFe x Cr (1-x) Al (where x is between 0 and 1);
performing a second annealing in the vacuum chamber by subjecting the deposited layers to a temperature between 300-550° C. for between 1-60 minutes; and
after said second annealing, depositing said APC layer on said Heusler alloy AP 1 layer and said AP 2 layer on said APC layer.
10. The method of claim 9 wherein depositing said AP 1 Heusler alloy layer comprises depositing said Heusler alloy layer on and in contact with said diffusion blocking layer.
11. The method of claim 9 further comprising, after said first annealing and before depositing said AP 1 Heusler alloy layer, depositing on and in contact with said diffusion blocking layer a second ferromagnetic layer selected from Co and a non-Heusler alloy comprising Co and Fe; and wherein depositing said AP 1 Heusler alloy layer comprises depositing said AP 1 Heusler alloy layer on and in contact with said second ferromagnetic layer.
12. The method of claim 9 wherein said diffusion blocking layer consists essentially of a layer of an alloy having the composition (CoFe) (100-x-y) B x Ta y , where the subscripts are in atomic percent, 10≦x≦30 and 5≦y≦10.
13. The method of claim 9 wherein the Mn-containing layer consists essentially of IrMn.