# US 2014/0197504 A1 · Mg Discontinuous Insertion Layer for Improving MTJ Shunt > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0197504 A1 - Document ID: US20140197504A1 - Status: Published application - Kind: A1 - Application number: 13/739,016 - Filed: 2013-01-11 - Published: 2014-07-17 - Earliest claimed: 2013-01-11 - Assignees: Headway Technologies, Inc. - Applicants: Headway Technologies, Inc. - Inventors: Takahiro Moriyama; Yu-Jen Wang; Ru-Ying Tong - Web page: https://patentgrep.com/patent/US20140197504A1 ## CPC - H10N 50/01: Manufacture or treatment - G11C 11/161: {details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell} - H10N 50/10: Magnetoresistive devices - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - G11C: STATIC STORES (semiconductor memory devices H10B) ## Abstract A MTJ is disclosed with a discontinuous Mg or Mg alloy layer having a thickness from 1 to 3 Angstroms between a free layer and a capping layer in a bottom spin valve configuration. It is believed the discontinuous Mg layer serves to block conductive material in the capping layer from diffusing through the free layer and into the tunnel barrier layer thereby preventing the formation of conductive channels that function as electrical shunts within the insulation matrix of the tunnel barrier. As a result, the “low tail” percentage in a plot of magnetoresistive ratio vs Rp is minimized which means the number of high performance MTJ elements in a MTJ array is significantly increased, especially when a high temperature anneal is included in the MTJ fabrication process. The discontinuous layer is formed by a low power physical vapor deposition process. ## Claims ### Claim 1 A magnetic tunnel junction (MTJ), comprising: (a) a free layer having perpendicular magnetic anisotropy (PMA) that contacts a top surface of a tunnel barrier layer; (b) a capping layer as the uppermost layer in the MTJ; and (c) a discontinuous Mg or MgM alloy insertion layer formed between the free layer and the capping layer where M is one of Ta, Ti, V, Mo, Zr, Hf, Pt Pd, W, Nb, Rh, Ru, Cu, Cr, or Ir, and M has a content less than about 5 atomic % in the MgM alloy. ### Claim 2 (depends on 1) The MTJ of claim 1 wherein the discontinuous Mg or MgM alloy insertion layer has a thickness from about 1 to 3 Angstroms. ### Claim 3 (depends on 1) The MTJ of claim 1 further comprised of a reference layer that contacts a bottom surface of the tunnel barrier layer, the reference layer is comprised of one or more ferromagnetic layers wherein a magnetic moment in each ferromagnetic layer is aligned in the plane of each ferromagnetic layer, or the magnetic moment is aligned perpendicular to the plane in each of the ferromagnetic layers. ### Claim 4 (depends on 3) The MTJ of claim 3 wherein the reference layer is comprised of a laminate represented by (A1/A2)n wherein A1 is a first metal or alloy comprising one or more of Co, Ni, and Fe, A2 is a second metal or alloy comprising one or more of Co, Fe, Ni, Pt, and Pd, n is the number of laminates in the (A1/A2)n stack, and A1 is unequal to A2. ### Claim 5 (depends on 4) The MTJ of claim 4 wherein the reference layer has a synthetic antiferromagnetic (SAF) configuration with an AP2/coupling layer/AP1 configuration wherein the AP2 layer contacts a substrate and the AP1 layer contacts a bottom surface of the tunnel barrier layer, and wherein at least one of the AP1 and AP2 layers is comprised of an (A1/A2)n stack. ### Claim 6 (depends on 5) The MTJ of claim 5 wherein the reference layer has an AP2/coupling layer/AP1 configuration, the (A1/A2)n laminate is the AP2 layer and there is a (A1/A2)m laminate as the AP1 layer wherein m and n are each from 1 to 10, and the coupling layer establishes antiferromagnetic coupling between the AP1 and AP2 layers. ### Claim 7 (depends on 6) The MTJ of claim 6 wherein the reference layer is further comprised of a Ta dusting layer that contacts a top surface of the AP1 layer, and a transition layer comprised of CoFeB or CoFeB/Co that contacts a bottom surface of the tunnel barrier layer. ### Claim 8 (depends on 1) The MTJ of claim 1 wherein the free layer is one or more of Fe, Co, and Ni, or is an alloy of one or more of Fe, Co, and Ni that includes boron. ### Claim 9 (depends on 1) The MTJ of claim 1 wherein the free layer is FePt or CoPt, or is a L10 ordered alloy with a DE composition wherein D is Fe, Co, Ni, or an alloy thereof and E is Rh, Pd, Pt, Ir, or an alloy thereof, or the free layer is a rare earth-transition metal (RE-TM) alloy that is TbCo, TbFeCo, or GdFeCo. ### Claim 10 (depends on 1) The MTJ of claim 1 wherein the free layer is a composite that includes a first alloy of one or more of Fe, Co, and Ni with B, and one of a L10 ordered alloy, an alloy of one or more of Fe, Co, and Ni, or a second alloy of one or more of Fe, Co, and Ni with B wherein at least two elements in the second alloy have a different atomic % content than in the first alloy. ### Claim 11 (depends on 1) The MTJ of claim 1 wherein the capping layer is a dielectric layer or non-magnetic layer that is one or more of Ta, Ti, V, Mo, Zr, Hf, Pt, Pd, W, Nb, Rh, Ru, Cu, Cr, or Ir. ### Claim 12 A magnetic tunnel junction (MTJ), comprising: (a) a seed layer formed on a substrate; (b) a free layer formed on the seed layer; and (c) a discontinuous Mg or MgM alloy layer formed between the free layer and the seed layer where M is one of Ta, Ti, V, Mo, Zr, Hf, Pt Pd, W, Nb, Rh, Ru, Cu, Cr, or Ir, and M has a content less than about 5 atomic % in the MgM alloy. ### Claim 13 (depends on 12) The MTJ of claim 12 wherein the discontinuous Mg or MgM alloy layer has a thickness from about 1 to 3 Angstroms. ### Claim 14 (depends on 12) The MTJ of claim 12 further comprised of a tunnel barrier layer, reference layer, and capping layer that are sequentially formed on a top surface of the free layer. ### Claim 15 (depends on 12) The MTJ of claim 12 wherein the free layer is one or more of Fe, Co, and Ni, or is an alloy of one or more of Fe, Co, and Ni that includes boron. ### Claim 16 (depends on 12) The MTJ of claim 12 wherein the free layer is FePt or CoPt, or is a L10 ordered alloy with a DE composition wherein D is Fe, Co, Ni, or an alloy thereof and E is Rh, Pd, Pt, Ir, or an alloy thereof, or the free layer is a rare earth-transition metal (RE-TM) alloy that is TbCo, TbFeCo, or GdFeCo. ### Claim 17 (depends on 14) The MTJ of claim 14 wherein the capping layer is a dielectric layer or non-magnetic layer that is one or more of Ta, Ti, V, Mo, Zr, Hf, Pt, Pd, W, Nb, Rh, Ru, Cu, Cr, or Ir. ### Claim 18 A method of forming a MTJ on a substrate, comprising: (a) forming a MTJ stack of layers wherein a seed layer, reference layer, tunnel barrier layer, free layer with perpendicular magnetic anisotropy, discontinuous Mg or MgM layer where M is one of Ta, Ti, V, Mo, Zr, Hf, Pt Pd, W, Nb, Rh, Ru, Cu, Cr, or Ir, and M has a content less than about 5 atomic %, and a capping layer are sequentially formed on a substrate; (b) annealing the MTJ stack of layers; and (c) patterning the MTJ stack of layers with a photolithography process and an etch process to give a plurality of MTJ nanopillars. ### Claim 19 (depends on 18) The method of claim 18 wherein the substrate is a bottom electrode in a spin transfer MRAM (STT-RAM) device, or is a bottom shield in a magnetic sensor. ### Claim 20 (depends on 18) The method of claim 18 wherein the discontinuous Mg or MgM layer has a thickness from about 1 to 3 Angstroms. ### Claim 21 (depends on 18) The method of claim 18 wherein the reference layer is a synthetic antiferromagnetic (SAF) reference layer with an AP2/coupling layer/AP1 configuration wherein the AP2 layer is formed on the seed layer and the AP1 layer contacts a bottom surface of the tunnel barrier layer. ### Claim 22 (depends on 18) The method of claim 18 wherein the reference layer is comprised of a laminate represented by (A1/A2)n wherein A1 is a first metal or alloy comprising one or more of Co, Ni, and Fe, A2 is a second metal or alloy comprising one or more of Co, Fe, Ni, Pt, and Pd, n is the number of laminates in the (A1/A2)n stack, and A1 is unequal to A2. ### Claim 23 (depends on 18) The method of claim 18 wherein the free layer is one or more of Fe, Co, and Ni, or is an alloy of one or more of Fe, Co, and Ni with boron. ### Claim 24 (depends on 18) The method of claim 18 wherein the free layer free layer is FePt or CoPt, or is a L10 ordered alloy with a DE composition wherein D is Fe, Co, Ni, or an alloy thereof and E is Rh, Pd, Pt, Ir, or an alloy thereof, or the free layer is a rare earth-transition metal (RE-TM) alloy that is TbCo, TbFeCo, or GdFeCo. ### Claim 25 (depends on 18) The method of claim 18 wherein the free layer is a composite that includes a first alloy of one or more of Fe, Co, and Ni with B, and one of a L10 ordered alloy, an alloy of one or more of Fe, Co, and Ni, or a second alloy of one or more of Fe, Co, and Ni with B wherein at least two elements in the second FeCoNiB alloy have a different atomic % content than in the first FeCoNiB alloy. ### Claim 26 (depends on 18) The method of claim 18 wherein the capping layer is a dielectric layer or non-magnetic layer that is one or more of Ta, Ti, V, Mo, Zr, Hf, Pt, Pd, W, Nb, Rh, Ru, Cu, Cr, or Ir. ### Claim 27 (depends on 18) The method of claim 18 wherein the discontinuous Mg or MgM alloy layer is deposited by a physical vapor deposition (PVD) process at a power of about 20 to 500 Watts to give a deposition rate that is substantially less than 1 Angstrom per second.