Method for forming a MAMR structure based on a TMR—Spin Torque oscillator (STO) having seed layer and capping layer of metal oxide
A method of forming a MTJ with a tunnel barrier having a high tunneling magnetoresistance ratio, and low resistance x area value is disclosed. The method preserves perpendicular magnetic anisotropy in bottom and top magnetic layers that adjoin bottom and top surfaces of the tunnel barrier. A key feature is a passive oxidation step of a first Mg layer that is deposited on the bottom magnetic layer wherein a maximum oxygen pressure is 10-5 torr. A bottom portion of the first Mg layer remains unoxidized thereby protecting the bottom magnetic layer from substantial oxidation during subsequent oxidation and anneal processes that are employed to complete the fabrication of the tunnel barrier and MTJ. An uppermost Mg layer may be formed as the top layer in the tunnel barrier stack before a top magnetic layer is deposited.
1 . A method, comprising:
providing a MAMR writer including a main pole, a write shield, and a spin torque oscillator (STO) positioned between the main pole and the write shield, wherein providing the STO comprises:
forming a first magnesium layer along a side of the main pole;
performing a passive oxidation process to the first magnesium layer to partially oxidize the first magnesium layer;
forming a second magnesium layer on the partially oxidized portion of the first magnesium layer;
performing a second oxidation process to fully oxidize the second magnesium layer;
after performing a first annealing process during deposition of a third magnesium layer over the fully oxidized second magnesium layer, performing a second annealing process, wherein after the performing the second annealing process, each of the first, second, and third magnesium layers are fully oxidized; and
sequentially forming, adjacent to the third magnesium layer, a magnetic layer, a non-magnetic layer, a high moment magnetic layer, and a metal oxide layer.
2 . The method of claim 1 , wherein the write shield is provided after the sequentially forming the magnetic layer, the non-magnetic layer, the high moment magnetic layer, and the metal oxide layer.
3 . The method of claim 1 , further comprising after the sequentially forming the magnetic layer, the non-magnetic layer, the high moment magnetic layer, and the metal oxide layer, performing a third annealing process.
4 . The method of claim 1 , wherein after forming the second magnesium layer and prior to deposition of the third magnesium layer, performing a third annealing process.
5 . The method of claim 1 , wherein the forming of the metal oxide layer further comprises:
forming a fourth magnesium layer;
performing an oxidation process to partially oxidize the fourth magnesium layer; and
forming a fifth magnesium layer over the partially oxidized fourth magnesium layer.
6 . The method of claim 1 , wherein the method further comprises:
providing a soft underlayer and a medium bit layer disposed on the soft underlayer, wherein the main pole is configured to generate a local magnetic field for interaction with the medium bit layer, and wherein the local magnetic field is configured to flip a magnetization of a medium bit of the medium bit layer with assistance of the STO positioned between the main pole and the write shield.
7 . The method of claim 6 , wherein the high moment magnetic layer includes an oscillation layer configured to generate a radio frequency (RF) field for interaction with the medium bit layer, and wherein the RF field is configured to reduce a coercive field of the medium bit.
8 . The method of claim 1 , wherein the passive oxidation process is performed at a first oxygen pressure, and wherein the second oxidation process is performed at a second oxygen pressure greater than the first oxygen pressure.
9 . A method, comprising:
providing a main pole;
forming a first metal oxide layer adjacent a side of the main pole;
forming a magnetic layer adjacent the first metal oxide layer;
forming a non-magnetic layer adjacent the magnetic layer and opposite the first metal oxide layer;
forming a high moment magnetic layer adjacent the non-magnetic layer and opposite the magnetic layer;
forming a second metal oxide layer adjacent the high moment magnetic layer and opposite the non-magnetic layer, and
forming a write shield adjacent the second metal oxide layer and opposite the high moment magnetic layer;
wherein forming one or both of the first metal oxide layer and the second metal oxide layer comprises:
forming a first magnesium layer;
performing a passive oxidation process that partially oxidizes the first magnesium layer;
forming a second magnesium layer over the partially oxidized first magnesium layer;
performing a second oxidation process to fully oxidize the second magnesium layer;
performing a first annealing process during deposition of a third magnesium layer over the fully oxidized second magnesium layer; and
after performing the first annealing process, performing a second annealing process.
10 . The method of claim 9 , wherein after the performing the second annealing process, each of the first, second, and third magnesium layers are fully oxidized.
11 . A method, comprising:
providing a soft underlayer and a medium bit layer disposed on the soft underlayer;
providing a main pole;
forming a spin torque oscillator (STO) adjacent to the main pole, wherein forming the STO includes:
forming a first non-magnetic layer adjacent a side of the main pole;
forming a magnetic layer adjacent the first non-magnetic layer;
forming a second non-magnetic layer adjacent the magnetic layer and opposite the first non-magnetic layer;
forming a high moment magnetic layer adjacent the second non-magnetic layer and opposite the magnetic layer; and
forming a metal oxide layer adjacent the high moment magnetic layer and opposite the second non-magnetic layer, wherein forming the metal oxide layer includes:
forming a first magnesium layer;
performing a passive oxidation process that partially oxidizes the first magnesium layer;
forming a second magnesium layer over the partially oxidized first magnesium layer;
performing a second oxidation process to fully oxidize the second magnesium layer;
performing a first annealing process during deposition of a third magnesium layer over the fully oxidized second magnesium layer; and
after performing the first annealing process during deposition of the third magnesium layer, performing a second annealing process; and
forming a write shield adjacent the metal oxide layer and opposite the high moment magnetic layer.
12 . The method of claim 11 , wherein the forming of the first non-magnetic layer further comprises:
forming a first metal layer;
performing an oxidation process to oxidize an upper portion of the first metal layer while a bottom portion of the first metal layer remains unoxidized; and
forming a second metal layer over the upper portion of the first metal layer.
13 . The method of claim 12 , wherein the forming of the first non-magnetic layer further comprises forming a third metal layer over the second metal layer.
14 . The method of claim 13 , wherein the forming of the first non-magnetic layer further comprises performing another annealing process during the forming of the third metal layer.
15 . The method of claim 11 , wherein the medium bit layer includes a medium bit having a magnetization.
16 . The method of claim 15 , wherein the main pole is configured to generate a local magnetic field to flip the magnetization of the medium bit with assistance of the STO positioned between the main pole and the write shield.
17 . The method of claim 11 , wherein the high moment magnetic layer includes an oscillation layer.
18 . The method of claim 17 , wherein the oscillation layer is configured to generate a radio frequency (RF) field for interaction with the medium bit layer.
19 . The method of claim 18 , wherein the RF field is configured to reduce a coercive field of a medium bit of the medium bit layer.
20 . The method of claim 11 , wherein the passive oxidation process is performed at a first oxygen pressure, and wherein the second oxidation process is performed at a second oxygen pressure greater than the first oxygen pressure.