Carbon nanotube switches for memory, RF communications and sensing applications, and methods of making the same

• US 7,446,044 B2
• Filed: 09/19/2006
• Issued: 11/04/2008
• Est. Priority Date: 09/19/2005
• Status: Expired due to Fees

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Wong, Eric W., Kaul, Anupama B., Epp, Larry, Baron, Richard L.
• Primary Examiner(s): Pham; Thanh V
• Application Number:
  US11/523,273
• Publication Number:
  US 20080233744A1
• Time in Patent Office: 777 Days
• Field of Search: 438/684, 438/685, 438/903, 438/FOR.248, 257/382, 257/282, 977/876, 977/938
• US Class Current: 438/684
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G11C 11/56 using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency
• CPC Class Codes: G11C 13/025 using fullerenes, e.g. C60, or nanotubes, e.g. carbon or silicon nanotubes
• CPC Class Codes: G11C 23/00 Digital stores characterised by movement of mechanical parts to effect storage, e.g. using balls; Storage elements therefor
• CPC Class Codes: H01H 1/0094 Switches making use of nanoelectromechanical systems [NEMS]
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: Y10S 438/903 Catalyst aided deposition
• CPC Class Codes: Y10S 977/876 Nanotube tip
• CPC Class Codes: Y10S 977/938 Field effect transistors, FETS, with nanowire- or nanotube-channel region

Abstract

Switches having an in situ grown carbon nanotube as an element thereof, and methods of fabricating such switches. A carbon nanotube is grown in situ in mechanical connection with a conductive substrate, such as a heavily doped silicon wafer or an SOI wafer. The carbon nanotube is electrically connected at one location to a terminal. At another location of the carbon nanotube there is situated a pull electrode that can be used to elecrostatically displace the carbon nanotube so that it selectively makes contact with either the pull electrode or with a contact electrode. Connection to the pull electrode is sufficient to operate the device as a simple switch, while connection to a contact electrode is useful to operate the device in a manner analogous to a relay. In various embodiments, the devices disclosed are useful as at least switches for various signals, multi-state memory, computational devices, and multiplexers.

Claims

1. A method for manufacturing a nanoelectromechanical (NEM) switch comprising the steps of:

providing a conductive substrate;

providing a dielectric material on said conductive substrate;

creating a trench in said dielectric material, said trench having first and second walls extending down to said conductive substrate;

depositing a refractory metal onto said conductive substrate within said trench, said refractory metal forming a first pull electrode;

depositing a catalyst on a surface supported by said dielectric material for in-situ growth of at least one carbon nanotube (CNT) across said trench,

placing said switch in a chemical vapor deposition (CVD) furnace for said in-situ growth;

growing in-situ said at least one CNT that crosses said trench, said at least one CNT at least mechanically connected to said conductive substrate; and

after said growth of said at least one CNT, depositing first and second contact electrodes on said opposite ends of said trench to contact said CNT.

2. The method for manufacturing a NEM switch of claim 1, further comprising the step of:

metallizing a portion of said at least one CNT that is disposed between said first and said second walls of said trench.

3. The method for manufacturing a NEM switch of claim 1, further comprising the steps of:

depositing a dielectric material onto said first and second contact electrodes; and

providing a second pull electrode between said dielectric material deposited onto said first and second metal electrodes, said second pull electrode being disposed on a different side of said at least one CNT from said first pull electrode.

4. The method for manufacturing a NEM switch of claim 1, wherein said conductive substrate is a wafer comprising silicon.

5. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 1, wherein said refractory metal is a selected one of Nb, Mo and Ta.

6. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 1, wherein said growth of said CNT is performed at a temperature above 500°

C.

7. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 1, wherein said growth of said CNT is performed at a temperature at or above 700°

C.

8. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 1, wherein said growth of said CNT is performed at a temperature at or above 850°

C.

9. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 1, wherein said growth of said CNT is performed at a temperature at or above 950°

C.

10. A method for manufacturing a nanoelectromechanical (NEM) switch comprising the steps of:

providing a conductive substrate

defining on a surface of said conductive substrate a location for growing at least one carbon nanotube (CNT);

depositing at said location for growing at least one carbon nanotube (CNT) a growth catalyst;

defining a first plurality of locations on said conductive substrate for a first plurality of pull electrodes, said first plurality of pull electrodes when present defining a cavity therebetween;

depositing a first plurality of pull electrodes, each at one of said first plurality of locations on said conductive substrate, each pull electrode electrically isolated from said conductive substrate; and

growing in-situ at least one CNT at said defined location for growing said CNT, said at least one CNT at least mechanically connected to said conductive substrate.

11. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 10, further comprising the steps of:

depositing a dielectric material onto at least some of said first plurality of pull electrodes;

depositing a second plurality of contact electrodes, each contact electrode being deposited onto a respective one of said dielectric material deposited onto each of said first plurality of pull electrodes; and

providing a second plurality of external terminals, each external terminal electrically connected to a respective one of said second plurality of contact electrodes.

12. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 11, wherein any of said steps of depositing a dielectric material comprises deposition by plasma enhanced chemical vapor deposition.

13. The method for manufacturing a nanoelectroniechanical (NEM) switch of claim 10, wherein said conductive substrate comprises silicon.

14. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 10, wherein said refractory metal is a selected one of Nb, Mo and Ta.

15. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 10, wherein said growth of said CNT is performed at a temperature above 500°

C.

16. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 10, wherein said growth of said CNT is performed at a temperature at or above 700°

C.

17. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 10, wherein said growth of said CNT is performed at a temperature at or above 850°

C.

18. The method for manufacturing a nanoelectromechanical (NEM) switch of claim 10, wherein said growth of said CNT is performed at a temperature at or above 950°

C.

19. A nanoelectromechanical (NEM) switch, comprising:

a conductive substrate;

at least one carbon nanotube (CNT);

a dielectric material on said conductive substrate, said dielectric material defining a trench, said trench having first and second walls;

a refractory metal deposited onto said conductive substrate, said refractory metal situated within said trench and forming a first pull electrode;

said CNT grown across said trench in-situ in a chemical vapor deposition (CVD) furnace, said CNT at least mechanically connected to said conductive substrate; and

a first contact electrode and a second contact electrode located on said opposite ends of said trench contacting said CNT.

20. The NEM switch of claim 19, further comprising:

a plurality of external terminals, each external terminal electrically connected to a respective one of said conductive substrate and said pull electrode.

21. The NEM switch of claim 19, wherein a portion of said CNT situated between said first and second walls of said trench is metallized.

22. The NEM switch of claim 19, further comprising:

a dielectric material deposited onto said first and second contact electrodes; and

a second pull electrode between said dielectric material deposited onto said first and second contact electrodes, said second pull electrode being disposed on a different side of said CNT from said first pull electrode.

23. The NEM switch of claim 19, further comprising:

a plurality of external terminals, each external terminal electrically connected to a respective one of said conductive substrate and said plurality of pull electrodes.

24. The NEM switch of claim 19, wherein said conductive substrate comprises a selected one of a doped silicon wafer and a silicon-on-insulator (SOI) wafer.

25. A nanoelectromechanical (NEM) switch, comprising:

a conductive substrate;

at least one carbon nanotube (CNT), said at least one CNT grown in-situ and at least mechanically connected to said conductive substrate;

a first plurality of pull electrodes deposited on said conductive substrate, each pull electrode electrically isolated from said conductive substrate, said first plurality of pull electrodes defining a cavity therebetween;

said CNT located within said cavity defined by said first plurality of pull electrodes and extending perpendicularly to the conductive substrate, said CNT having been grown in-situ in a chemical vapor deposition (CVD) furnace substantially directly onto said conductive substrate; and

a plurality of external terminals, each external terminal electrically connected to a respective one of said conductive substrate and said first plurality of pull electrodes.

26. The nanoelectromechanical (NEM) switch of claim 25, further comprising:

a dielectric material deposited onto each of said first plurality of pull electrodes;

a second plurality of contact electrodes, each contact electrode deposited onto a respective one of said dielectric material deposited onto each of said first plurality of pull electrodes; and

a plurality of external terminals, each external terminal electrically connected to a respective one of said second plurality of contact electrodes.

27. The NEM switch of claim 25, wherein said plurality of pull electrodes comprises two pull electrodes located substantially diametrically opposed to each other.

28. The NEM switch of claim 25, wherein said plurality of pull electrodes comprises three or more pull electrodes located in a substantially circular pattern.

29. The NEM switch of claim 25, wherein said NEM switch has a unique state associated with each of said plurality of pull electrodes.

30. The NEM switch of claim 29, wherein said NEM switch is configured as a memory having a unique state associated with each of said plurality of pull electrodes.

31. The NEM switch of claim 29, wherein said NEM switch is configured as a computation device having a unique state associated with each of said plurality of pull electrodes.

32. The NEM switch of claim 29, wherein said NEM switch is configured as multiplexer having a unique signal path associated with each of said plurality of pull electrodes.