# US 2014/0151625 A1 · Nonvolatile memory device using a varistor as a current limiter element > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0151625 A1 - Document ID: US20140151625A1 - Status: Published application - Kind: A1 - Application number: 14/176,882 - Filed: 2014-02-10 - Published: 2014-06-05 - Earliest claimed: 2012-02-17 - Assignees: Kabushiki Kaisha Toshiba; SanDisk 3D LLC - Applicants: Kabushiki Kaisha Toshiba; Sandisk 3D LLC - Inventors: Mihir Tendulkar; Imran Hashim; Yun Wang - Web page: https://patentgrep.com/patent/US20140151625A1 ## CPC - H10N 70/021: {Formation of switching materials, e.g. deposition of layers} - H10N 70/023: {by chemical vapor deposition, e.g. MOCVD, ALD} - H10N 70/24: {based on migration or redistribution of ionic species, e.g. anions, vacancies} - H10N 70/801: {Constructional details of multistable switching devices} - H10N 70/826: {adapted for essentially vertical current flow, e.g. sandwich or pillar type devices} - H10N 70/8833: {Binary metal oxides, e.g. TaOx} - H10B 63/20: {comprising selection components having two electrodes, e.g. diodes} - H10B 63/80: {Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays} - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - H10B: ELECTRONIC MEMORY DEVICES ## Abstract Embodiments of the invention include a method of forming a nonvolatile memory device that contains a resistive switching memory element that has improved device switching performance and lifetime, due to the addition of a current limiting component disposed therein. The electrical properties of the current limiting component are configured to lower the current flow through the variable resistance layer during the logic state programming steps by adding a fixed series resistance in the resistive switching memory element of the nonvolatile memory device. In some embodiments, the current limiting component comprises a varistor that is a current limiting material disposed within a resistive switching memory element in a nonvolatile resistive switching memory device. Typically, resistive switching memory elements may be formed as part of a high-capacity nonvolatile memory integrated circuit, which can be used in various electronic devices, such as digital cameras, mobile telephones, handheld computers, and music players. ## Claims ### Claim 1 A nonvolatile memory element, comprising: a first electrode; a second electrode; a variable resistance layer disposed between the first electrode and the second electrode, the variable resistance layer comprising a metal oxide; a current limiting layer disposed between the variable resistance layer and the first electrode, wherein the current limiting layer comprises a varistor layer; and an oxygen deficient material layer disposed between the current limiting layer and the variable resistance layer. ### Claim 2 (depends on 1) The nonvolatile memory element of claim 1, wherein the variable resistance layer comprises a material selected from the group of hafnium oxide, zirconium oxide, lanthanum oxide, and aluminum oxide. ### Claim 3 (depends on 1) The nonvolatile memory element of claim 1, wherein the variable resistance layer has a thickness of between 20 angstroms and 100 angstroms. ### Claim 4 (depends on 1) The nonvolatile memory element of claim 1, wherein the current limiting layer comprises a material comprised of zinc oxide doped with one or more of bismuth, cobalt, or manganese. ### Claim 5 (depends on 1) The nonvolatile memory element of claim 1, wherein the current limiting layer has a thickness of between 50 angstroms and 500 angstroms. ### Claim 6 (depends on 1) The nonvolatile memory element of claim 1, wherein the oxygen deficient material layer comprises a material selected from the group of tantalum nitride, titanium nitride and tungsten nitride, silicon oxy-nitride, aluminum oxy-nitride, aluminum nitride, hafnium nitride zirconium nitride, boron nitride, calcium nitride, ruthenium titanium nitride, gold, zirconium platinum and platinum beryllium. ### Claim 7 (depends on 1) The nonvolatile memory element of claim 1, wherein the current limiting layer has a thickness of between 50 angstroms and 100 angstroms. ### Claim 8 A nonvolatile memory element, comprising: a first electrode; a second electrode; a variable resistance layer disposed between the first electrode and the second electrode, the variable resistance layer comprising a metal oxide; a current limiting layer disposed between the first electrode and the variable resistance layer, the current limiting layer comprising a varistor layer; an oxygen deficient material layer disposed between the current limiting layer and the variable resistance layer, the oxygen deficient material layer operable to inhibit oxygen from the variable resistance layer; a first stabilizing layer; and a second stabilizing layer, wherein the current limiting layer is disposed between the first stabilizing layer and the second stabilizing layer, and the first stabilizing layer and second stabilizing layer are operable to provide oxygen to the current limiting layer. ### Claim 9 (depends on 8) The nonvolatile memory element of claim 8, wherein the variable resistance layer comprises a material selected from the group of hafnium oxide, zirconium oxide, lanthanum oxide and aluminum oxide. ### Claim 10 (depends on 8) The nonvolatile memory element of claim 8, wherein the variable resistance layer has a thickness of between 20 angstroms and 100 angstroms. ### Claim 11 (depends on 8) The nonvolatile memory element of claim 8, wherein the current limiting layer comprises a material comprised of zinc oxide doped with one or more of bismuth, cobalt, or manganese. ### Claim 12 (depends on 8) The nonvolatile memory element of claim 8, wherein the current limiting layer has a thickness of between 50 angstroms and 500 angstroms. ### Claim 13 (depends on 8) The nonvolatile memory element of claim 8, wherein the oxygen deficient material layer comprises a material selected from the group of tantalum nitride, titanium nitride, tungsten nitride, silicon oxy nitride, aluminum oxy-nitride, aluminum nitride, hafnium nitride zirconium nitride, gold, zirconium, platinum and platinum beryllium. ### Claim 14 (depends on 8) The nonvolatile memory element of claim 8, wherein the oxygen deficient material layer has a thickness of between 30 angstroms and 1000 angstroms. ### Claim 15 (depends on 8) The nonvolatile memory element of claim 8, wherein the first stabilizing layer and the second stabilizing layer each comprise a material selected from the group consisting of indium tin oxide and iridium oxide and indium zinc oxide. ### Claim 16 (depends on 8) The nonvolatile memory element of claim 8, wherein the first stabilizing layer and second stabilizing layer each have a thickness of between 50 angstroms and 1000 angstroms. ### Claim 17 (depends on 15) The nonvolatile memory element of claim 15, wherein each of the first stabilizing layer and the second stabilizing layer comprise a material selected from the group of indium tin oxide and iridium oxide, and wherein the materials selected for each first stabilizing layer and second stabilizing layer are not the same. ### Claim 18 A method of forming a nonvolatile memory element, comprising: forming a first electrode over a substrate; forming a second electrode over the substrate; forming a variable resistance layer between the first electrode and the second electrode, the variable resistance layer comprising a metal oxide; forming a current limiting layer between the first electrode and the variable resistance layer; and forming a separation layer between the current limiting layer and the variable resistance layer, the separation layer comprising an oxygen deficient material. ### Claim 19 (depends on 18) The method of claim 18, wherein the separation layer comprises a material selected from the group of tantalum nitride, titanium nitride and tungsten nitride, silicon oxy-nitride, aluminum oxy-nitride, aluminum nitride, hafnium nitride zirconium nitride, gold, zirconium platinum and platinum beryllium. ### Claim 20 (depends on 18) The method of claim 18, wherein the current limiting layer comprises a material comprised of zinc oxide doped with one or more of bismuth, cobalt, or manganese.