# US 2019/0378973 A1 · Heusler-alloy and ferrimagnet based magnetic domain-wall devices for artificial neural network applications > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0378973 A1 - Document ID: US20190378973A1 - Status: Published application - Kind: A1 - Application number: 16/002,543 - Filed: 2018-06-07 - Published: 2019-12-12 - Earliest claimed: 2018-06-07 - Assignees: International Business Machines Corporation - Applicants: International Business Machines Corporation - Inventors: Ching-Tzu Chen; See-Hun Yang - Web page: https://patentgrep.com/patent/US20190378973A1 ## CPC - H01F 10/1936: {Half-metallic, e.g. epitaxial CrO2 or NiMnSb films} - H10N 50/10: Magnetoresistive devices - G06N 3/065: Analogue means - G11C 11/161: {details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell} - G11C 11/54: using elements simulating biological cells, e.g. neuron - H01F 10/3254: {the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]} - H01F 10/3272: {by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets} - H01F 10/3286: {Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy} - H01F 41/307: {insulating or semiconductive spacer} - H10B 61/00: Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices - H10B 61/20: {comprising components having three or more electrodes, e.g. transistors} - H10N 50/85: Materials of the active region - G06N 3/084: Backpropagation, e.g. using gradient descent - H10N 50/01: Manufacture or treatment - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - G06N: COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS - G11C: STATIC STORES (semiconductor memory devices H10B) - H10B: ELECTRONIC MEMORY DEVICES ## Abstract A synapse device includes a perpendicularly magnetized ferrimagnetic racetrack layer, a tunneling barrier layer disposed on the racetrack layer and a reference layer including a perpendicular magnetic alloy. The racetrack layer, the tunneling layer and the reference layer have a channel portion and contact pad portions. First and second contacts are provided over the contact pad portions, and a third contact is provided over the channel portion, wherein the first and second contacts are electrically isolated from the third contact. ## Claims ### Claim 1 A synapse device, comprising: a perpendicularly magnetized ferrimagnet racetrack layer; a tunneling barrier layer disposed on the racetrack layer; a reference layer including a perpendicular magnetic alloy; the racetrack layer, the tunneling layer and the reference layer having a channel portion and contact pad portions; first and second contacts provided over the contact pad portions; and a third contact provided over the channel portion, wherein the first and second contacts are electrically isolated from the third contact. ### Claim 2 (depends on 1) The device as recited in claim 1, wherein the ferrimagnet racetrack layer includes a Heusler alloy of a Mn3Z material where Z is selected from the group consisting of Sn, Ge, Sb, Al, Bi, As, and Se. ### Claim 3 (depends on 1) The device as recited in claim 1, wherein the ferrimagnet racetrack layer includes an alloy selected from the group consisting of CoTb, CoGd, FeTb, FeGd and combinations thereof. ### Claim 4 (depends on 1) The device as recited in claim 1, wherein the ferrimagnet racetrack layer includes a multilayer ferrimagnet structure having one or more layers of material pairs selected from the group consisting of Co/Tb, Co/Gd, Fe/Tb and Fe/Gd. ### Claim 5 (depends on 1) The device as recited in claim 1, wherein the contact pad portions include a width at least three times a width of the channel portion and an area of each of the contact pad portions is at least ten times the channel portion area. ### Claim 6 (depends on 1) The device as recited in claim 1, further comprising a weight that is inversely proportional to a tunneling magnetoresistance of the device. ### Claim 7 (depends on 1) The device as recited in claim 1, wherein the first, second and third contacts are configured to control domain wall motion and magnetization direction of the racetrack layer to provide a plurality of states for the device. ### Claim 8 A neural network device, comprising: a conductive grid having first conductive lines, second conductive lines and third conductive lines wherein the first conductive lines are disposed transversely to the second conductive lines and third conductive lines; and crosspoint synapse devices coupled to the first, second and third conductive lines at conductive line intersection points, the crosspoint synapse devices, each including: a perpendicularly magnetized ferrimagnet racetrack layer; a tunneling barrier layer disposed on the racetrack layer; and a reference layer including a perpendicular magnetic alloy; the racetrack layer, the tunneling layer and the reference layer of each crosspoint synapse device having a channel portion contact coupled to a third conductive line and contact pad contacts coupled to a respective first and second conductive lines, wherein the contact pad contacts are electrically isolated from the channel portion contact. ### Claim 9 (depends on 8) The device as recited in claim 8, wherein the ferrimagnet racetrack layer includes a Heusler alloy of a Mn3Z material where Z is selected from the group consisting of Sn, Ge, Sb, Al, Bi, As, and Se. ### Claim 10 (depends on 8) The device as recited in claim 8, wherein the ferrimagnet racetrack layer includes an alloy selected from the group consisting of CoTb, CoGd, FeTb, FeGd and combinations thereof. ### Claim 11 (depends on 8) The device as recited in claim 8, wherein the ferrimagnet racetrack layer includes a multilayer ferrimagnet structure having one or more layers of material pairs selected from the group consisting of Co/Tb, Co/Gd, Fe/Tb and Fe/Gd. ### Claim 12 (depends on 8) The device as recited in claim 8, wherein the contact pad portions include a width at least three times a width of the channel portion and an area of each of the contact pad portions is at least ten times the channel portion area. ### Claim 13 (depends on 8) The device as recited in claim 8, further comprising a weight that is inversely proportional to a tunneling magnetoresistance of the device. ### Claim 14 (depends on 8) The device as recited in claim 8, wherein the first, second and third contacts are configured to control domain wall motion and magnetization direction of the racetrack layer to provide a plurality of states for the device. ### Claim 15 A method for forming a synapse device, comprising: blanket depositing a stack of layers, on a substrate, including a perpendicularly magnetized ferrimagnet racetrack layer, a tunneling barrier layer on the racetrack layer and a reference layer including a perpendicular magnetic alloy; defining a mesa structure from the stack of layers having a channel portion and contact portions on opposing ends, by a patterning process, wherein the contact pad portions include a width at least three times a width of the channel portion; forming a sidewall spacer around the mesa structure; depositing a conductive material to form first, second and third contacts where the first and second contacts are formed over the contact pad portions and the third contact is formed over the channel portion; and patterning the conductive material and the reference layer such that the reference layer of the contact pad portions is isolated from the reference layer of the channel portion. ### Claim 16 (depends on 15) The method as recited in claim 15, wherein the racetrack layer includes a perpendicularly magnetized Heusler alloy that includes a Mn3Z material where Z is selected from the group consisting of Sn, Ge, Sb, Al, Bi, As, and Se. ### Claim 17 (depends on 15) The method as recited in claim 15, wherein the racetrack layer includes an alloy or alloys selected from the group consisting of CoTb, CoGd, FeTb, FeGd and combinations thereof. ### Claim 18 (depends on 15) The method as recited in claim 15, wherein the racetrack layer includes a multilayer structure including an alloy or alloys selected from the group consisting of CoTb, CoGd, FeTb, FeGd and combinations thereof. ### Claim 19 (depends on 15) The method as recited in claim 15, further comprising a weight that is inversely proportional to a tunneling magnetoresistance of the device, and the first, second and third contacts are configured to control domain wall motion and magnetic direction of the racetrack layer to provide a plurality of states for the device. ### Claim 20 (depends on 15) The method as recited in claim 15, wherein an area of each of the contact pad portions is at least ten times the channel portion area.