# US 10,312,433 B2 · Reduction of capping layer resistance area product for magnetic device applications > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,312,433 B2 - Document ID: US10312433B2 - Status: Granted - Kind: B2 - Application number: 13/441,158 - Filed: 2012-04-06 - Published: 2013-10-10 - Granted: 2019-06-04 - Earliest claimed: 2012-04-06 - Assignees: Taiwan Semiconductor Manufacturing Company, Ltd. - Applicants: Guenole Jan; Ru-Ying Tong - Inventors: Guenole Jan; Ru-Ying Tong - Web page: https://patentgrep.com/patent/US10312433B2 ## CPC - H10N 50/01: Manufacture or treatment - H01F 10/3286: {Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy} - H01F 41/308: {lift-off processes, e.g. ion milling, for trimming or patterning} - H10N 50/10: Magnetoresistive devices - G11C 11/161: {details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell} - H01F 10/329: {Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect} - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - G11C: STATIC STORES (semiconductor memory devices H10B) ## Abstract A ferromagnetic layer is capped with a metallic oxide (or nitride) layer that provides a perpendicular-to-plane magnetic anisotropy to the layer. The surface of the ferromagnetic layer is treated with a plasma to prevent diffusion of oxygen (or nitrogen) into the layer interior. An exemplary metallic oxide layer is formed as a layer of metallic Mg that is plasma treated to reduce its grain size and enhance the diffusivity of oxygen into its interior. Then the plasma treated Mg layer is naturally oxidized and, optionally, is again plasma treated to reduce its thickness and remove the oxygen rich upper surface. ## Claims ### Claim 1 A capped ferromagnetic layer having perpendicular-to-plane magnetic anisotropy, comprising: a ferromagnetic layer having an upper surface in a plane of its deposition; wherein a first plasma treatment has been applied to smooth said upper surface and make it resistant to oxygen or nitrogen diffusion; and wherein an oxide layer or a nitride layer is formed as a cap on said plasma-treated upper surface to promote a perpendicular-to-plane interfacial magnetic anisotropy in said ferromagnetic layer; and wherein a region extending from an upper surface of said oxide layer or said nitride layer to an interface with said upper surface of said ferromagnetic layer is characterized by an oxygen concentration profile or a nitrogen concentration profile; and wherein an annealing process has been applied to said capped ferromagnetic layer to sharply reduce said oxygen or said nitrogen profile to approximately zero at said upper surface interface with said ferromagnetic layer and thereby provide higher perpendicular-to-plane interfacial magnetic anisotropy as evidenced by an enhanced Hk and Hc and, in addition, to provide an improved value of a resistance and surface area product, RA. ### Claim 2 (depends on 1) The capped ferromagnetic layer of claim 1 wherein an upper surface of said oxide layer or said nitride layer has been etched back, thinned and made smooth by a third plasma treatment thereby removing an over-oxidized or over-nitrided upper portion and eliminating a source of excess oxygen or nitrogen that would be adversely distributed during said anneal. ### Claim 3 (depends on 1) The capped ferromagnetic layer of claim 1 wherein said oxygen concentration profile or said nitrogen concentration profile is smoothly reduced from its maximum value at an upper surface of said oxide layer or said nitride layer, respectively, to an approximately zero value at an interface between said oxide layer or said nitride layer, respectively, and said ferromagnetic layer. ### Claim 4 (depends on 1) The capped ferromagnetic layer of claim 1 wherein said ferromagnetic layer is a free magnetic layer. ### Claim 5 (depends on 1) The capped ferromagnetic layer of claim 1 wherein said cap is an oxide layer that is a native oxide layer of the ferromagnetic material. ### Claim 6 (depends on 5) The capped ferromagnetic layer of claim 5 wherein an upper surface of said native oxide layer has been made smooth by a third plasma treatment. ### Claim 7 (depends on 5) The capped ferromagnetic layer of claim 5 wherein said native oxide layer has been thinned by a third plasma treatment. ### Claim 8 (depends on 7) The capped ferromagnetic layer of claim 7 where a metal layer of Mg is formed over said thinned oxide layer. ### Claim 9 (depends on 1) The capped ferromagnetic layer of claim 1 wherein said ferromagnetic layer is a tri-layer comprising two layers of CoFeB of approximately 10 angstroms thickness separated by a layer of Ta of approximately 1.5 angstroms thickness. ### Claim 10 (depends on 9) The capped ferromagnetic layer of claim 9 wherein said capping layer is an oxide layer that is a first metallic layer of Mg of thickness approximately 6 angstroms that is oxidized and plasma treated and over which a second layer of metallic Mg of thickness 3 angstroms is formed. ### Claim 11 (depends on 1) The capped ferromagnetic layer of claim 1 wherein said cap is an oxide layer that is a deposited metallic layer that is subsequently oxidized. ### Claim 12 (depends on 11) The capped ferromagnetic layer of claim 11 including a second plasma treatment applied to an upper surface of said deposited metal layer prior to said oxidation process whereby a grain size of said deposited metal layer is reduced, resulting in a reduced metallic grain size, and a uniform oxidation is subsequently achieved. ### Claim 13 (depends on 12) The capped ferromagnetic layer of claim 12 wherein said deposited metal layer is a layer of Mg. ### Claim 14 (depends on 12) The capped ferromagnetic layer of claim 12 wherein said deposited metal layer is a layer of Si, Ba, Ca, La, Mn, Zn, Hf, Ta, Ti, B, Cu, Cr, V or Al. ### Claim 15 (depends on 12) The capped ferromagnetic layer of claim 12 wherein said second plasma treatment produces a smooth upper surface of said deposited metal layer. ### Claim 16 (depends on 12) The capped ferromagnetic layer of claim 12 wherein said reduced metallic grain size promotes a more uniform oxygen diffusion through said metal layer and thereby produces a more uniform oxide layer. ### Claim 17 A TMJ spin torque transfer cell comprising: a reference layer having a perpendicular-to-plane component of magnetic anisotropy; a tunneling barrier layer formed on said reference layer; a free layer having a perpendicular-to-plane component of magnetic anisotropy; a capping layer formed as a metallic oxide or nitride layer on said free layer by the oxidation or nitrogenation of a metal layer first deposited on an upper surface of said free layer, wherein said capping layer maintains a perpendicular-to-plane component of magnetic anisotropy of said free layer while providing a low value of RA, by means of a combined sequence of plasma treatments that, in a first plasma treatment, smooths said upper surface of said free layer to prevent diffusion of oxygen or nitrogen from said capping layer into said free layer, then, in a second plasma treatment by reducing the grain size of said first deposited metal layer, then oxidizing said metal layer and then, in a third plasma treatment removing an overoxidized or overnitrogenized portion of said oxidized or nitrogenized metal layer and, finally, by a magnetic anneal that produces an oxygen or nitrogen concentration profile in said capping layer that goes to zero at the interface of said free layer.