Scaled-Down Phase Change Memory Cell in Recessed Heater

• US 20080164452A1
• Filed: 01/05/2007
• Published: 07/10/2008
• Est. Priority Date: 01/05/2007
• Status: Active Grant

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Lam, Chung Hon, Schrott, Alejandro Gabriel, Joseph, Eric Andrew
• Granted Patent: US 8,426,967 B2
• Time in Patent Office: Days
• US Class Current: 257/3
• CPC Class Codes: H10B 63/30 comprising selection components having three or more electrodes, e.g. transistors
• CPC Class Codes: H10N 70/068 by processes specially adapted for achieving sub-lithographic dimensions, e.g. using spacers
• CPC Class Codes: H10N 70/231 based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect
• CPC Class Codes: H10N 70/826 adapted for essentially vertical current flow, e.g. sandwich or pillar type devices
• CPC Class Codes: H10N 70/828 Current flow limiting means within the switching material region, e.g. constrictions
• CPC Class Codes: H10N 70/8413 adapted for resistive heating
• CPC Class Codes: H10N 70/8828 Tellurides, e.g. GeSbTe
• CPC Class Codes: H10N 70/884 Other compounds of groups 13-15, e.g. elemental or compound semiconductors

Abstract

A semiconductor structure configurable for use as a nonvolatile storage element includes a first electrode, an insulating layer formed on at least a portion of an upper surface of the first electrode, and a pillar traversing the insulating layer and being recessed relative to an upper surface of the insulating layer. The pillar includes a heater formed on at least a portion of the upper surface of the first electrode and a collar formed on sidewalls of the insulating layer proximate the heater and on at least a portion of an upper surface of the heater. The structure further includes a PCM layer formed on at least a portion of the upper surface of the insulating layer and substantially filling a volume defined by the upper surface of the heater and at least a portion of an upper surface of the collar. A second electrode is formed on at least a portion of an upper surface of the phase change material layer.

Claims

1. A semiconductor structure configurable for use as a nonvolatile storage element, the semiconductor structure comprising:

a first electrode;

an insulating layer formed on at least a portion of an upper surface of the first electrode;

a pillar traversing the insulating layer and being recessed relative to an upper surface of the insulating layer, the pillar comprising a heater formed on at least a portion of the upper surface of the first electrode and a collar formed on sidewalls of the insulating layer proximate the heater and on at least a portion of an upper surface of the heater;

a phase change material layer formed on at least a portion of the upper surface of the insulating layer and substantially filling a volume defined by the upper surface of the heater and at least a portion of an upper surface of the collar; and

at least a second electrode formed on at least a portion of an upper surface of the phase change material layer.

2. The structure of claim 1, further comprising a conductive barrier layer formed between the second electrode and the phase change material layer.

3. The structure of claim 2, wherein the conductive barrier layer comprises an electrical conductive material that is substantially inert with respect to materials used to form at least one of the phase change material layer and the second electrode.

4. The structure of claim 1, wherein the collar is configured so as to constrict a flow of current in at least a portion of the phase change material layer proximate the heater to thereby create a region of localized heating in at least a portion of the phase change material layer when a switching current signal is applied between the first and second electrodes.

5. The structure of claim 4, wherein the region of localized heating is substantially confined to a portion of the phase change material substantially filling the volume defined by the upper surface of the heater and at least a portion of the upper surface of the collar.

6. The structure of claim 1, wherein the phase change material layer comprises at least one of a chalcogenide material and a transition metal oxide.

7. The structure of claim 1, wherein the heater comprises an electrically conductive material which is substantially chemically inert when in contact with materials used to form at least one of the phase change material layer, the insulating layer, the first electrode and the collar.

8. The structure of claim 1, wherein the heater comprises at least one of titanium nitride and tantalum nitride.

9. The structure of claim 1, wherein the collar is shaped substantially as a toroid.

10. An integrated circuit including at least one semiconductor structure, the at least one semiconductor structure comprising:

a first electrode;

an insulating layer formed on at least a portion of an upper surface of the first electrode;

a pillar traversing the insulating layer and being recessed relative to an upper surface of the insulating layer, the pillar comprising a heater formed on at least a portion of the upper surface of the first electrode and a collar formed on sidewalls of the insulating layer proximate the heater and on at least a portion of an upper surface of the heater;

a phase change material layer formed on at least a portion of the upper surface of the insulating layer and substantially filling a volume defined by the upper surface of the heater and at least a portion of an upper surface of the collar; and

at least a second electrode formed on at least a portion of an upper surface of the phase change material layer.

11. A memory circuit, comprising:

a plurality of nonvolatile memory cells; and

a plurality of bit lines and word lines operatively coupled to the memory cells for selectively accessing one or more of the memory cells;

wherein at least a given one of the memory cells comprises;

a first electrode;

an insulating layer formed on at least a portion of an upper surface of the first electrode;

a pillar traversing the insulating layer and being recessed relative to an upper surface of the insulating layer, the pillar comprising a heater formed on at least a portion of the upper surface of the first electrode and a collar formed on sidewalls of the insulating layer proximate the heater and on at least a portion of an upper surface of the heater;

a phase change material layer formed on at least a portion of the upper surface of the insulating layer and substantially filling a volume defined by the upper surface of the heater and at least a portion of an upper surface of the collar; and

at least a second electrode formed on at least a portion of an upper surface of the phase change material layer.

12. The circuit of claim 11, wherein the collar is configured so as to constrict a flow of current in at least a portion of the phase change material layer proximate the heater to thereby create a region of localized heating in at least a portion of the phase change material layer when a switching current signal is applied between the first and second electrodes.

13. The circuit of claim 12, wherein the region of localized heating is substantially confined to a portion of the phase change material substantially filling the volume defined by the upper surface of the heater and at least a portion of the upper surface of the collar.

14. The circuit of claim 11, wherein the heater comprises an electrically conductive material which is substantially chemically inert when in contact with materials used to form at least one of the phase change material layer, the insulating layer, the first electrode and the collar.

15. The circuit of claim 11, wherein the given memory cell further comprises a conductive barrier layer formed between the second electrode and the phase change material layer.

16. A method of forming a semiconductor structure configurable for use as a nonvolatile storage element, the method comprising the steps of:

forming a first electrode;

forming an insulating layer on at least a portion of an upper surface of the first electrode;

forming a pillar traversing the insulating layer and being recessed relative to an upper surface of the insulating layer, the pillar comprising a heater formed on at least a portion of the upper surface of the first electrode and a collar formed on sidewalls of the insulating layer proximate the heater and on at least a portion of an upper surface of the heater;

forming a phase change material layer on at least a portion of the upper surface of the insulating layer and substantially filling a volume defined by the upper surface of the heater and at least a portion of an upper surface of the collar; and

forming at least a second electrode on at least a portion of an upper surface of the phase change material layer.

17. The method of claim 16, wherein the collar is configured so as to constrict a flow of current in at least a portion of the phase change material layer proximate the heater to thereby create a region of localized heating in at least a portion of the phase change material layer when a switching current signal is applied between the first and second electrodes.

18. The method of claim 17, wherein the region of localized heating is substantially confined to a portion of the phase change material substantially filling the volume defined by the upper surface of the heater and at least a portion of the upper surface of the collar.

19. The method of claim 16, further comprising the step of forming a conductive barrier layer between the second electrode and the phase change material layer.

20. The method of claim 16, wherein the heater comprises an electrically conductive material which is substantially chemically inert when in contact with materials used to form at least one of the phase change material layer, the insulating layer, the first electrode and the collar.