Two step annealing process for TMR device with amorphous free layer

摘要

An annealing process for a TMR or GMR sensor having an amorphous free layer is disclosed and employs at least two annealing steps. A first anneal at a temperature T1 of 200° C. to 270° C. and for a t1 of 0.5 to 15 hours is employed to develop the pinning in the AFM and pinned layers. A second anneal at a temperature T2 of 260° C. to 400° C. where T2>T1 and t1>t2 is used to crystallize the amorphous free layer and complete the pinning. An applied magnetic field of about 8000 Oe is used during both anneal steps. The mechanism for forming a sensor with high MR and robust pinning may involve structural change in the tunnel barrier or at an interface between two of the layers in the spin valve stack. A MgO tunnel barrier and a CoFe/CoB free layer are preferred.

主权项

1. An annealing process for a spin valve in a magnetic read head, said spin valve is comprised of a plurality of layers including at least one AFM layer and at least one pinned layer, and has a ferromagnetic free layer consisting of one or more of CoFe, CoB, CoFeB, FeB, CoFeNi, and CoNiFeB that includes at least one amorphous layer, comprising:
(a) a first anneal step comprised of applying a first temperature and a magnetic field along a desired pinning direction for a first period of time to pin a magnetization in the at least one AFM layer and at least one pinned layer; (b) a second anneal step comprised of applying a second temperature and a magnetic field along said desired pinning direction for a second period of time to crystallize the at least one amorphous layer and further develop pinning of the AFM layer and at least one pinned layer in the desired pinning direction and wherein said second temperature is greater than said first temperature and said first period of time is longer than said second period of time; and (c) a third step between the first anneal step and the second anneal step which is a heat treatment of the magnetic read head wherein the first temperature is ramped to the second temperature during a period of 5 to 10 minutes in a chamber that is used for the first and second anneal steps.