# US 8,569,729 B2 · Method and apparatus for reducing programmed volume of phase change memory > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,569,729 B2 - Document ID: US8569729B2 - Status: Granted - Kind: B2 - Application number: 13/163,783 - Filed: 2011-06-20 - Published: 2011-10-06 - Granted: 2013-10-29 - Earliest claimed: 2007-11-06 - Assignees: Ovonyx, Inc. - Applicants: Jim Ricker - Inventors: Jim Ricker - Web page: https://patentgrep.com/patent/US8569729B2 ## CPC - H10N 70/826: {adapted for essentially vertical current flow, e.g. sandwich or pillar type devices} - H10N 70/043: {by implantation} - H10N 70/066: {by filling of openings, e.g. damascene method} - H10N 70/231: {based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect} - H10N 70/828: {Current flow limiting means within the switching material region, e.g. constrictions} - H10N 70/8413: {adapted for resistive heating} - H10N 70/882: {Compounds of sulfur, selenium or tellurium, e.g. chalcogenides} - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR ## Abstract A phase change memory includes a volume of phase change material disposed between, and coupled to, two electrodes, with the composition of a region of at least one of the two electrodes or phase change material having been compositionally altered to reduce the programmed volume of the phase change material. ## Claims ### Claim 1 A phase-change memory, comprising: a first electrode, said first electrode having a first surface; a second electrode disposed over said first electrode, said second electrode having a second surface, said second surface facing said first surface; a phase-change material electrically coupled to said first and second electrodes, said phase-change material being disposed between said first surface of said first electrode and said second surface of said second electrode, said phase-change material having a first cross-section parallel to said first surface, said phase-change material having a non-uniform composition over said first cross-section, said first cross-section including a first region having a first composition and a second region having a second composition, said first composition consisting essentially of the chemical elements present in said second composition, said first composition including said elements in a different proportion than said second composition. ### Claim 2 (depends on 1) The phase-change memory of claim 1, wherein said first surface is parallel to said second surface. ### Claim 3 (depends on 1) The phase-change memory of claim 1, wherein said first cross-section does not directly contact said first surface or said second surface. ### Claim 4 (depends on 1) The phase-change memory of claim 1, wherein said first composition is uniform within said first region and said second composition is uniform within said second region. ### Claim 5 (depends on 4) The phase-change memory of claim 4, wherein said first region is in direct contact with said second region. ### Claim 6 (depends on 4) The phase-change memory of claim 4, wherein said first cross-section includes only said first region and said second region. ### Claim 7 (depends on 1) The phase-change memory of claim 1, wherein said first composition and said second composition comprise Te, said first composition having a higher concentration of Te than said second composition. ### Claim 8 (depends on 1) The phase-change memory of claim 1, wherein said first composition has a greater tendency to crystallize than said second composition. ### Claim 9 (depends on 1) The phase-change memory of claim 1, wherein the threshold voltage of said first composition is lower than the threshold voltage of said second composition. ### Claim 10 (depends on 1) The phase-change memory of claim 1, wherein said first composition is less conductive than said second composition. ### Claim 11 (depends on 1) The phase-change memory of claim 1, further comprising an insulating material, said insulating material having an opening formed therein, said opening exposing said first electrode, said opening having a sidewall, said phase-change material occupying said opening and directly contacting said sidewall. ### Claim 12 (depends on 11) The phase-change memory of claim 11, wherein said first cross-section of said phase-change material fully occupies a first cross-section of said opening. ### Claim 13 (depends on 12) The phase-change memory of claim 12, wherein said first cross-section of said phase-change material includes a first region having a first composition and a second region having a second composition. ### Claim 14 (depends on 13) The phase-change memory of claim 13, wherein said first region and said second region fully occupy said first cross-section of said opening. ### Claim 15 (depends on 14) The phase-change memory of claim 14, wherein said phase-change material has a second cross-section parallel to said first cross-section of said phase-change material, said phase-change material having a non-uniform composition over said second cross-section. ### Claim 16 (depends on 15) The phase-change memory of claim 15, wherein said second cross-section of said phase-change material includes a third region having a third composition and a fourth region having a fourth composition. ### Claim 17 (depends on 16) The phase-change memory of claim 16, wherein said third region of said phase-change material and said fourth region of said phase-change material fully occupy a second cross-section of said opening. ### Claim 18 (depends on 17) The phase-change memory of claim 17, wherein the area of said first region of said first cross-section of said phase-change material differs from the area of said third region of said second cross-section of said phase-change material. ### Claim 19 (depends on 18) The phase-change memory of claim 18, wherein said first composition coincides with said third composition. ### Claim 20 (depends on 19) The phase-change memory of claim 19, wherein said second composition coincides with said fourth composition. ### Claim 21 (depends on 20) The phase-change memory of claim 20, wherein said first cross-section of said phase-change material makes direct contact with said first electrode. ### Claim 22 (depends on 21) The phase-change memory of claim 21, wherein said second cross-section of said phase-change material makes direct contact with said second electrode. ### Claim 23 (depends on 21) The phase-change memory of claim 21, wherein said first composition extends continuously from said first cross-section of said phase-change material to said second cross-section of said phase-change material. ### Claim 24 (depends on 23) The phase-change memory of claim 23, wherein said second composition extends continuously from said first cross-section of said phase-change material to said second cross-section of said phase-change material. ### Claim 25 (depends on 23) The phase-change memory of claim 23, wherein said first cross-section of said phase-change material makes direct contact with said first electrode. ### Claim 26 (depends on 25) The phase-change memory of claim 25, wherein said second cross-section of said phase-change material makes direct contact with said second electrode. ### Claim 27 A phase-change memory, comprising: a first electrode, said first electrode having a first surface; a second electrode disposed over said first electrode, said second electrode having a second surface, said second surface facing said first surface; a phase-change material electrically coupled to said first and second electrodes, said phase-change material being disposed between said first surface of said first electrode and said second surface of said second electrode, said phase-change material having a first cross-section directly contacting said first electrode and parallel to said first surface, said first cross-section including a first region having a first composition and a second region having a second composition, said phase-change material having a second cross-section directly contacting said second electrode and parallel to said first cross-section, said second cross-section including a third region having said first composition and a fourth region having said second composition, the area of said third region differing from the area of said first region and the area of said fourth region differing from the area of said second region, said phase-change material having a non-uniform composition over said first and second cross-sections of said phase change material; and an insulating material, said insulating material having an opening formed therein, said opening exposing said first electrode, said opening having a sidewall, said phase-change material occupying said opening and directly contacting said sidewall, said first region and said second region of said first cross-section of said phase change material fully occupying said first cross-section of said opening, said third region and said fourth region of said second cross-section of said phase-change material fully occupying a second cross-section of said opening; wherein said first and fourth regions have a composition materially different from said second and third regions. ### Claim 28 A phase-change memory, comprising: a first electrode, said first electrode having a first surface; a second electrode disposed over said first electrode, said second electrode having a second surface, said second surface facing said first surface; a phase-change material electrically coupled to said first and second electrodes, said phase-change material being disposed between said first surface of said first electrode and said second surface of said second electrode, said phase-change material having a first cross-section directly contacting said first electrode and parallel to said first surface, said first cross-section of said phase-change material including a first region having a first composition and a second region having a second composition, said phase-change material having a second cross-section parallel to said first cross-section of said phase-change material, said second cross-section of said phase-change material including a third region having a third composition and a fourth region having a fourth composition, said first composition extending continuously from said first cross-section of said phase-change material to said second cross-section of said phase-change material, said second composition extending continuously from said first cross-section of said phase-change material to said second cross-section of said phase-change material, said phase-change material having a non-uniform composition over said first and second cross-sections of said phase change material; and an insulating material, said insulating material having an opening formed therein, said opening exposing said first electrode, said opening having a sidewall, said phase-change material occupying said opening and directly contacting said sidewall, said first and second regions of said first cross-section of said phase-change material fully occupying a first cross-section of said opening; wherein said first composition is materially different from said second composition. ### Claim 29 A phase-change memory, comprising: a first electrode, said first electrode having a first surface; a second electrode disposed over said first electrode, said second electrode having a second surface, said second surface facing said first surface; a phase-change material electrically coupled to said first and second electrodes, said phase-change material being disposed between said first surface of said first electrode and said second surface of said second electrode, said phase-change material having a first cross-section parallel to said first surface, said phase-change material having a non-uniform composition over said first cross-section, said first cross-section including a first region having a first composition and a second region having a second composition, said first composition being uniform within said first region and said second composition being uniform within said second region, said first and said second compositions including a chalcogen element; wherein said first composition is materially different from said second composition.