Methods for manufacturing a perpendicular magnetic tunnel junction (p-MTJ) MRAM having a precessional spin current injection (PSC) structure
A method for manufacturing a magnetic memory element for use in a magnetic random access memory device to form a MgO spin current coupling layer with improved spin current coupling and reduced device area resistance (RA). The method involves depositing a magnetic free layer structure, and then depositing a MgO spin current coupling layer over the magnetic free layer. The magnetic spin current coupling layer is deposited in a sputter deposition chamber using radio frequency (RF) power. The sputter deposition of the spin current coupling layer can be performed using a MgO target without intervening oxidation steps to form a continuous layer of MgO that is not a multilayer structure of Mg and intermittent oxidation layers. Because the MgO spin transport layer deposited by this RF sputtering does not affect RA of the device, the thickness of the MgO spin transport layer can be adjusted to optimize spin transport performance.
1. A method for manufacturing a magnetic memory element,
the method comprising:
forming a magnetic reference layer structure;
forming a non-magnetic barrier layer over the magnetic reference layer structure;
forming a magnetic free layer structure over the non-magnetic barrier layer;
depositing a MgO spin current coupling layer over the magnetic free layer structure, the MgO spin current coupling layer being deposited in a sputter deposition chamber using a radio frequency sputtering method;
after depositing the MgO spin current coupling layer:
depositing a magnetic spin transport coupling layer over the MgO spin current coupling layer;
depositing a non-magnetic exchange coupling layer comprising Ru over the magnetic spin transport coupling layer; and
depositing a magnetic spin current layer over the non-magnetic exchange coupling layer.
2. The method as in claim 1 , wherein the MgO spin current coupling layer is deposited in the sputter deposition chamber using a MgO target.
3. The method as in claim 1 , wherein the MgO spin current coupling layer is deposited as a continuous layer of MgO from a MgO target without intervening oxidation steps.
4. The method as in claim 1 , wherein the MgO spin current coupling layer is deposited to a thickness of 0.5-1.5 nm.
5. The method as in claim 1 , wherein the magnetic spin current layer comprises a magnetic material having a magnetic anisotropy in a direction parallel to the plane of the magnetic spin current layer.
6. The method as in claim 1 , wherein the magnetic spin current layer comprises CoFeB.
7. The method as in claim 1 , wherein the MgO spin current coupling layer is deposited so as to have a resistance area product of not greater than 5 Ωμm 2 .
8. A method for manufacturing a magnetic memory element, the method comprising:
forming a magnetic reference layer structure;
forming a non-magnetic barrier layer over the magnetic reference layer structure;
forming a magnetic free layer structure over the non-magnetic barrier layer;
depositing a MgO spin current coupling layer over the magnetic free layer structure, the MgO spin current coupling layer being deposited in a sputter deposition chamber using a radio frequency sputtering method;
after depositing the MgO spin current coupling layer:
depositing a magnetic spin transport coupling layer over the MgO spin current coupling layer;
depositing a non-magnetic exchange coupling layer over the magnetic spin transport coupling layer; and
depositing a magnetic spin current layer over the non-magnetic exchange coupling layer wherein the magnetic spin current layer comprises CoFeB.
9. The method as in claim 1 , further comprising, adjusting a thickness of the MgO spin current coupling layer to achieve a spin polarization of at least 15-30%.