PHASE CHANGE MATERIAL SWITCH AND METHOD OF MAKING THE SAME

• US 20140264230A1
• Filed: 03/14/2013
• Published: 09/18/2014
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Inventors: Young, Robert Miles, Howell, Robert S., BORODULIN, PAVEL, El-Hinnawy, Nabil Abdel-Meguid, Mason, John R., Wagner, Brian Paul, King, Matthew Russell, Jones, Evan B., Lee, Michael J., Sherwin, Mark Eisenzweig
• Granted Patent: US 9,257,647 B2
• Time in Patent Office: Days
• US Class Current: 257/4
• CPC Class Codes: H10N 70/026 by physical vapor deposition, e.g. sputtering
• CPC Class Codes: H10N 70/041 Modification of switching materials after formation, e.g. doping shaping H10N70/061
• CPC Class Codes: H10N 70/061 Shaping switching materials
• 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 70/253 having three or more electrodes, e.g. transistor-like devices
• CPC Class Codes: H10N 70/823 adapted for essentially horizontal current flow, e.g. bridge type devices
• CPC Class Codes: H10N 70/8413 adapted for resistive heating
• CPC Class Codes: H10N 70/8613 Heating or cooling means other than resistive heating electrodes, e.g. heater in parallel
• CPC Class Codes: H10N 70/8828 Tellurides, e.g. GeSbTe

Abstract

A phase change material (PCM) switch is disclosed that includes a resistive heater element, and a PCM element proximate the resistive heater element. A thermally conductive electrical insulating barrier layer positioned between the PCM heating element and the resistive heating element, and conductive lines extend from ends of the PCM element and control lines extend from ends of the resistive heater element

Claims

1. A method for making a switch, the method comprising:

forming an insulating layer over a substrate;

forming a resistive heater element over the insulating layer;

depositing a thermally conductive electrically insulating barrier layer over the heating element;

forming openings in the barrier layer aligned with ends of the resistive heater element;

forming a phase change material (PCM) element over the barrier layer spaced apart and proximate to the resistive heater element; and

forming conductive lines from ends of the PCM element and control lines from ends of the resistive heater element.

2. The method of claim 1, wherein the PCM element being formed in its amorphous state, and further comprising performing an anneal process to change the PCM element from its amorphous state to its crystalline state.

3. The method of claim 2, wherein the performing of an anneal at a pressure between about 1×

10<sup>−

8</sup> Torr to 1000 Torr and a temperature between about 100°

C. to about 900°

C. for about 30 seconds to about 24 hours, such that the PCM element remains above the crystallization temperature during the anneal with oxygen content less than 20% maintained during the anneal.

4. The method of claim 1, wherein the forming a phase change material (PCM) element comprises:

forming a patterned photoresist over the barrier layer with an opening overlying and aligned with the resistive heater device;

depositing PCM to form the PCM element; and

removing the patterned photoresist and excess PCM by applying a chemical solvent lift-off material.

5. The method of claim of 4, wherein the chemical solvent lift-off material is acetone, isopropyl alcohol, and/or 100% pure N-methylpyrrolidone.

6. The method of claim of 4, wherein the depositing PCM comprises sputtering PCM at sputter condition powers ranging from about 0.1 to 5.0 W/cm² and pressures ranging from about 1.0 mTorr to about 50.0 mTorr to provide optimized crystalline resistivity.

7. The method of claim 1, wherein the forming conductive lines from ends of the PCM element and control lines from ends of the resistive heater element comprises:

forming a patterned photoresist over the barrier layer and the PCM element with trenches extending from both ends of the PCM and trenches extending from both openings in the barrier layer aligned with ends of the resistive heater element;

depositing a conductive material to form conductive lines extending from each end of the PCM element and control lines extending from each end of the resistive heater element; and

removing the patterned photoresist and excess conductive material by applying a chemical solvent lift-off material.

8. The method of claim 7, wherein the chemical solvent lift-off material is acetone, isopropyl alcohol, and/or 100% pure N-methylpyrrolidone.

9. The method of claim 1, further comprising forming a passivation layer over a portion of the control lines, the conductive lines, the PCM element and portions of the resistive heater element to protect the active elements from the environment.

10. The method of claim 1, wherein the resistive heater element is formed from a material comprising one of nickel chromium silicon (NiCrSi), nickel chromium (NiCr), Tungsten (W), Titanium-Tungsten (TiW), Platinum (Pt), Tantalum (Ta), Molybdenum (Mo), Niobium (Nb), and Iridium (Ir);

the barrier layer is formed from a material comprising one of Silicon Nitride (SiN), Aluminum Nitride (AlN), Silicon Dioxide (SiO₂), Silicon Carbide (SiC); and

the PCM element is formed from a material that is one of germanium telluride (GeTe), germanium antimony telluride (GeSbTe), and germanium selenium telluride (GeSeTe).

11. A method for making a phase change material (PCM) switch, the method comprising:

forming an insulating layer over a substrate;

forming a resistive heater element over the insulating layer;

depositing a thermally conductive electrical insulating barrier layer over the heating element;

forming openings in the barrier layer aligned with ends of the resistive heater element;

forming a patterned photoresist over the barrier layer with an opening overlying and aligned with the resistive heater device;

sputtering PCM in its amorphous state to form a PCM element;

removing the patterned photoresist and excess PCM by applying a chemical solvent lift-off material;

performing an anneal process to change the PCM element from its amorphous state to its crystalline state to enhance its immunity to deleterious effects caused by further processing; and

forming conductive lines from ends of the PCM element and control lines from ends of the resistive heater element.

12. The method of claim 11, wherein the performing of an anneal at a pressure between about 1×

10<sup>−

8</sup> Torr to about 1000 Torr and a temperature between about 100°

C. to about 900°

C. for about 30 seconds to about 24 hours, such that the PCM element remains above the crystallization temperature during the anneal with oxygen content less than 20% maintained during the anneal.

13. The method of claim of 11, wherein the chemical solvent lift-off material is acetone, isopropyl alcohol, and/or 100% pure N-methylpyrrolidone.

14. The method of claim of 11, wherein the sputtering PCM comprises sputtering PCM at sputter condition powers ranging from about 0.1 to 5.0 W/cm² and pressures ranging from about 1.0 mTorr to about 50.0 mTorr to provide optimized crystalline resistivity.

15. The method of claim 11, further comprising performing a cleaning on ends of the PCM element and resistive heater element prior to forming conductive lines from ends of the PCM element and control lines from ends of the resistive heater element.

16. The method of claim 15, wherein the forming conductive lines from ends of the PCM element and control lines from ends of the resistive heater element comprises:

forming a patterned photoresist over the barrier layer and the PCM element with trenches extending from both ends of the PCM and trenches extending from both openings in the barrier layer aligned with ends of the resistive heater element comprises;

depositing an ohmic contact on each end of the PCM element and the resistive heater element;

depositing a diffusion barrier on each ohmic contact;

depositing contact material into the trenches and in contact with the diffusion barriers to form the conductive lines and the control lines; and

removing the patterned photoresist and excess conductive material by applying a chemical solvent lift-off material, wherein the depositing a conductive material comprises;

17. The method of claim 16, further comprising forming a passivation layer over a portion of the control lines, the conductive lines, the PCM element and portions of the resistive heater element to protect the active elements from the environment.

18. The method of claim 11, wherein the resistive heater element is formed from a material comprising one of nickel chromium silicon (NiCrSi), nickel chromium (NiCr), Tungsten (W), Titanium-Tungsten (TiW), Platinum (Pt), Tantalum (Ta), Molybdenum (Mo), Niobium (Nb), and Iridium (Ir);

the barrier layer is formed from a material comprising one of Silicon Nitride (SiN), Aluminum Nitride (AlN), Silicon Dioxide (SiO₂), Silicon Carbide (SiC); and

the PCM element is formed from a material that is one of germanium telluride (GeTe), germanium antimony telluride (GeSbTe), and germanium selenium telluride (GeSeTe).

19. A phase change material (PCM) switch comprising:

a resistive heater element;

a PCM element proximate the resistive heater element;

a thermally conductive electrical insulating barrier layer positioned between the PCM heating element and the resistive heating element; and

conductive lines extending from ends of the PCM element and control lines extending from ends of the resistive heater element.

20. The PCM switch of claim 19, wherein the PCM element overlies the resistive heating element.

21. The PCM switch of claim 19, wherein the resistive heating element overlies the PCM element.

22. The PCM switch of claim 19, wherein the resistive heating element comprises a first resistive heating element that overlies the PCM element and a second resistive heating element in which the PCM element overlies the second resistive heating element.

23. The PCM switch of claim 19, wherein the resistive heating element is formed with four sides that substantially surround at least a portion of the PCM element.

24. A method of making a phase change material (PCM) switch, the method comprising:

forming a resistive heater element;

forming a PCM element proximate the resistive heater element;

forming a thermally conductive electrical insulating barrier layer positioned between the PCM heating element and the resistive heating element; and

forming conductive lines extending from ends of the PCM element and control lines extending from ends of the resistive heater element.

25. The method of claim 24, wherein the PCM element is formed over the resistive heating element.

26. The method of claim 24, wherein the resistive heating element is formed over the PCM element.

27. The method of claim 24, wherein the resistive heating element comprises a first resistive heating element and a second resistive heating element, the PCM element being formed over the first resistive heating element and the second resistive heating element being formed over the PCM element.

28. The method of claim 24, wherein the forming the resistive heating element comprises forming four sides of resistive heating material that substantially surrounds at least a portion of the PCM element.

29. The method of claim 24, wherein the forming of the PCM element further comprises depositing PCM in one of an amorphous, semi-crystalline or crystalline state.