# US 2008/0185572 A1 · Methods for forming resistive switching memory elements > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0185572 A1 - Document ID: US20080185572A1 - Status: Published application - Kind: A1 - Application number: 11/702,725 - Filed: 2007-02-05 - Published: 2008-08-07 - Earliest claimed: 2007-02-05 - Assignees: Intermolecular, Inc. - Inventors: Tony Chiang; Chi-I Lang; Zhi-wen Sun; Jinhong Tong; Nitin Kumar - Web page: https://patentgrep.com/patent/US20080185572A1 ## CPC - H10N 70/20: Multistable switching devices, e.g. memristors - 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 70/028: {by conversion of electrode material, e.g. oxidation} - 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} - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - H10B: ELECTRONIC MEMORY DEVICES ## Abstract Resistive switching memory elements are provided that may contain electroless metal electrodes and metal oxides formed from electroless metal. The resistive switching memory elements may exhibit bistability and may be used in high-density multi-layer memory integrated circuits. Electroless conductive materials such as nickel-based materials may be selectively deposited on a conductor on a silicon wafer or other suitable substrate. The electroless conductive materials can be oxidized to form a metal oxide for a resistive switching memory element. Multiple layers of conductive materials can be deposited each of which has a different oxidation rate. The differential oxidization rates of the conductive layers can be exploited to ensure that metal oxide layers of desired thicknesses are formed during fabrication. ## Claims ### Claim 1 A method for fabricating a resistive switching memory element on a conducting element that is electrically isolated by laterally adjacent insulating regions, the method comprising: selectively electrolessly depositing conductive material above the conducting element without depositing the conductive material on the insulating regions; oxidizing the conductive material to form a resistive switching metal oxide; and depositing an upper electrode above the resistive switching metal oxide. ### Claim 2 (depends on 1) The method defined in claim 1 wherein selectively electrolessly depositing the conductive material above the conducting element comprises depositing a lower electrode for the resistive switching memory element. ### Claim 3 (depends on 1) The method defined in claim 1 further comprising: forming an electrical device coupled to the resistive switching metal oxide and located between the upper electrode and a lower electrode. ### Claim 4 (depends on 1) The method defined in claim 1 further comprising: forming a current steering element above the resistive switching metal oxide. ### Claim 5 (depends on 1) The method defined in claim 1 further comprising: forming a current steering element below the resistive switching metal oxide. ### Claim 6 (depends on 1) The method defined in claim 1 further comprising: forming a current steering element coupled to the resistive switching metal oxide. ### Claim 7 (depends on 6) The method defined in claim 6 wherein the current steering element is located physically below the resistive switching metal oxide and is coupled to a lower electrode. ### Claim 8 (depends on 6) The method defined in claim 6 wherein the current steering element is not located physically below the resistive switching metal oxide, but is coupled electronically to the resistive switching metal oxide through one of the lower or upper electrodes. ### Claim 9 (depends on 1) The method defined in claim 1 wherein depositing the upper electrode above the resistive switching metal oxide comprises depositing the upper electrode directly on the resistive switching metal oxide. ### Claim 10 (depends on 1) The method defined in claim 1 further comprising forming the resistive switching memory element as part of an array of memory elements on an integrated circuit containing multiple layers of resistive switching memory elements. ### Claim 11 (depends on 1) The method defined in claim 1 wherein the conductive material comprises nickel. ### Claim 12 (depends on 1) The method defined in claim 1 wherein the conductive material is deposited on the conducting element without depositing the conductive material on the insulating regions. ### Claim 13 (depends on 1) The method defined in claim 1, wherein the insulating regions comprise silicon containing oxide and wherein the conductive material is selectively electrolessly deposited on the conducting element without depositing the conductive material on the silicon containing oxide. ### Claim 14 (depends on 1) The method defined in claim 1 further comprising: depositing a lower electrode on the conducting element, wherein the conductive material is selectively electrolessly deposited on the lower electrode without depositing the conductive material on the insulating regions and wherein depositing the upper electrode comprises depositing the upper electrode directly on the resistive switching metal oxide layer. ### Claim 15 (depends on 1) The method defined in claim 1 further comprising: masking the insulating regions with a molecular masking layer; and removing the molecular masking layer, wherein masking the insulating regions with the molecular masking layer and removing the molecular masking layer enhance selectivity of the deposition of the conductive material on the conducting element. ### Claim 16 (depends on 1) The method defined in claim 1 further comprising: depositing a lower electrode on the conducting element, wherein the conductive material oxidizes more readily than the lower electrode. ### Claim 17 (depends on 1) The method defined in claim 1 further comprising: forming a lower electrode on the conducting element by depositing a lower electrode conductor that contains nickel on the conducting element, wherein the lower electrode conductor oxidizes less readily than the conductive material. ### Claim 18 A method for forming a resistive switching memory element, comprising: depositing a first conductive material that serves as at least part of a lower electrode for the resistive switching memory element; depositing a second conductive material on the first conductive material, wherein the second conductive material oxidizes more readily than the first conductive material; and oxidizing the second conductive material to form the resistive switching metal oxide. ### Claim 19 (depends on 18) The method defined in claim 18 wherein substantially no portion of the first conductive material is oxidized during the oxidization of the second conductive material. ### Claim 20 (depends on 18) The method defined in claim 18 further comprising oxidizing part of the first conductive material. ### Claim 21 (depends on 18) The method defined in claim 18 further comprising selecting oxidation parameters to use when oxidizing the second conductive material so that substantially no portion of the first conductive material is oxidized during the oxidization of the second conductive material. ### Claim 22 (depends on 18) The method defined in claim 18 further comprising selecting oxidation parameters to use when oxidizing the second conductive material so that part of the first conductive material is oxidized when forming the resistive switching memory element. ### Claim 23 (depends on 18) The method defined in claim 18 further comprising forming an upper electrode for the resistive switching memory element that is above the resistive switching metal oxide. ### Claim 24 (depends on 18) The method defined in claim 18 wherein depositing the first conductive material comprises depositing a first material using physical vapor deposition, wherein depositing the second conductive material comprises depositing a second material using electroless deposition, and wherein the first material oxidizes less readily than the second material. ### Claim 25 (depends on 18) The method defined in claim 18 wherein the first conductive material comprises at least one material selected from the group consisting of: platinum, nickel containing boron, and nickel containing chromium and wherein the second conductive material comprises at least one material selected from the group consisting of: nickel, nickel containing phosphorous, and nickel containing cobalt. ### Claim 26 (depends on 18) The method defined in claim 18 wherein the first conductive material comprises at least one material selected from the group consisting of: platinum, nickel containing boron, and nickel containing chromium, wherein the second conductive material comprises at least one material selected from the group consisting of: nickel and nickel containing phosphorous, wherein depositing the first conductive material comprises depositing the first conductive material with physical vapor deposition, and wherein depositing the second conductive material comprises depositing the second conductive material with physical vapor deposition. ### Claim 27 (depends on 18) The method defined in claim 18 wherein the first conductive material comprises at least one material selected from the group consisting of: platinum, nickel containing boron, and nickel containing chromium, wherein the second conductive material comprises at least one material selected from the group consisting of: nickel and nickel containing phosphorous, wherein depositing the first conductive material comprises depositing the first conductive material with physical vapor deposition, and wherein depositing the second conductive material comprises depositing the second conductive material with electroless deposition. ### Claim 28 (depends on 18) The method defined in claim 18 wherein the first conductive material comprises at least one material selected from the group consisting of: platinum, nickel containing boron, and nickel containing chromium, wherein the second conductive material comprises at least one material selected from the group consisting of: nickel and nickel containing phosphorous, wherein depositing the first conductive material comprises depositing the first conductive material with electroless deposition, and wherein depositing the second conductive material comprises depositing the second conductive material with electroless deposition. ### Claim 29 (depends on 18) The method defined in claim 18 wherein the first conductive material comprises at least one material selected from the group consisting of: platinum, nickel containing boron, and nickel containing chromium, wherein the second conductive material comprises at least one material selected from the group consisting of: nickel and nickel containing phosphorous, wherein depositing the first conductive material comprises depositing the first conductive material with electroless deposition, and wherein depositing the second conductive material comprises depositing the second conductive material with physical vapor deposition. ### Claim 30 (depends on 18) The method defined in claim 18 wherein depositing the first conductive material comprises depositing a first nickel-containing material using physical vapor deposition, wherein depositing the second conductive material comprises depositing a second nickel-containing material using electroless deposition, and wherein the first nickel-containing material oxidizes less readily than the second nickel-containing material. ### Claim 31 (depends on 18) The method defined in claim 18 wherein depositing the first conductive material comprises depositing the first conductive material using electroless deposition, wherein the first conductive material contains nickel and contains at least one element selected from the group consisting of: boron, phosphorous, and chromium, wherein depositing the second conductive material comprises depositing a nickel-containing material on the first conductive material, and wherein oxidizing the second conductive material comprises thermally oxidizing the second conductive material. ### Claim 32 (depends on 18) The method defined in claim 18 wherein depositing the first conductive material comprises depositing the first conductive material using electroless deposition, wherein the first conductive material contains nickel and contains at least one element selected from the group consisting of: boron, phosphorous, and chromium, wherein depositing the second conductive material comprises depositing a nickel-containing material on the first conductive material, and wherein oxidizing the second conductive material comprises thermally oxidizing the second conductive material using rapid thermal oxidation (RTO). ### Claim 33 (depends on 18) The method defined in claim 18 wherein depositing the first conductive material comprises electrolessly depositing a material containing nickel and boron, wherein depositing the second conductive material comprises depositing a material containing nickel and phosphorous, wherein the second conductive material oxidizes more readily than the first conductive material, and wherein oxidizing the second conductive material comprises thermally oxidizing the second conductive material. ### Claim 34 (depends on 18) The method defined in claim 18 wherein depositing the first conductive material comprises electrolessly depositing a material containing nickel and boron, wherein depositing the second conductive material comprises depositing a material containing nickel and phosphorous, wherein the second conductive material oxidizes more readily than the first conductive material, and wherein oxidizing the second conductive material comprises thermally oxidizing the second conductive material using rapid thermal oxidation (RTO). ### Claim 35 (depends on 18) The method defined in claim 18 wherein insulating regions that are laterally adjacent to the lower electrode are used to electrically isolate the lower electrode and wherein depositing the second material comprises selectively electrolessly depositing a conductive material on the lower electrode without depositing the conductive electrode material on the insulating regions. ### Claim 36 (depends on 18) The method defined in claim 18 further comprising forming an upper electrode on the resistive switching metal oxide by forming a seed layer of conductor on the resistive switching metal oxide and depositing an electroless layer on the seed layer from an electroless solution. ### Claim 37 An integrated circuit resistive switching memory element structure comprising: a lower electrode formed of a conductive material; a resistive switching metal oxide on the lower electrode that is formed from electroless metal that oxidizes more readily than the conductive material; and an upper electrode, wherein the resistive switching metal oxide is formed above the lower electrode and wherein the upper electrode is formed above the resistive switching metal oxide. ### Claim 38 (depends on 37) The integrated circuit resistive switching memory element structure defined in claim 37 further comprising an electrical device that is located below the lower electrode and that is electrically connected to the lower electrode. ### Claim 39 (depends on 37) The integrated circuit resistive switching memory element structure defined in claim 37 further comprising a current steering element that is located below the lower electrode and that is electrically connected to the lower electrode. ### Claim 40 (depends on 37) The integrated circuit resistive switching memory element structure defined in claim 37 further comprising an electrical device that is located above the upper electrode and that is electrically connected to the upper electrode. ### Claim 41 (depends on 37) The integrated circuit resistive switching memory element structure defined in claim 37 further comprising a current steering element that is located above the upper electrode and that is electrically connected to the upper electrode. ### Claim 42 (depends on 37) The integrated circuit resistive switching element structure defined in claim 37 wherein the metal comprises nickel.