Two-terminal nanotube devices and systems and methods of making same

• US 20080012047A1
• Filed: 11/15/2005
• Published: 01/17/2008
• Est. Priority Date: 05/09/2005
• Status: Active Grant

• Current Assignee: Nantero Incorporated
• Original Assignee: Nantero Incorporated
• Inventors: Konsek, Steven, Huang, X. M., Bertin, Claude, Sivarajan, Ramesh, Guo, Frank, Strasburg, Max, Meinhold, Mitchell, Ruckes, Thomas
• Granted Patent: US 7,781,862 B2
• Time in Patent Office: Days
• US Class Current: 257/213
• 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 13/0002 using resistive RAM [RRAM] elements
• CPC Class Codes: G11C 13/025 using fullerenes, e.g. C60, or nanotubes, e.g. carbon or silicon nanotubes
• CPC Class Codes: G11C 17/16 using electrically-fusible links
• CPC Class Codes: G11C 17/165 Memory cells which are electrically programmed to cause a change in resistance, e.g. to permit multiple resistance steps to be programmed rather than conduct to or from non-conduct change of fuses and antifuses digital stores using resistance random access memory elements G11C13/0002
• CPC Class Codes: G11C 2213/19 Memory cell comprising at least a nanowire and only two terminals
• CPC Class Codes: G11C 2213/77 Array wherein the memory element being directly connected to the bit lines and word lines without any access device being used
• CPC Class Codes: G11C 2213/79 Array wherein the access device being a transistor
• CPC Class Codes: H10B 20/00 Read-only memory [ROM] devices
• CPC Class Codes: Y10S 977/943 Information storage or retrieval using nanostructure

Abstract

A two terminal switching device includes first and second conductive terminals and a nanotube article. The article has at least one nanotube, and overlaps at least a portion of each of the first and second terminals. The device also includes a stimulus circuit in electrical communication with at least one of the first and second terminals. The circuit is capable of applying first and second electrical stimuli to at least one of the first and second terminal(s) to change the relative resistance of the device between the first and second terminals between a relatively high resistance and a relatively low resistance. The relatively high resistance between the first and second terminals corresponds to a first state of the device, and the relatively low resistance between the first and second terminals corresponds to a second state of the device.

Claims

1. A two terminal switching device, comprising:

a first conductive terminal;

a second conductive terminal in spaced relation to the first terminal;

a nanotube article having at least one nanotube, said article being arranged to overlap at least a portion of each of the first and second terminals; and

a stimulus circuit in electrical communication with at least one of the first and second terminals,

said stimulus circuit capable of applying a first electrical stimulus to at least one of the first and second terminals to change the resistance of the device between the first and second terminals from a relatively low resistance to a relatively high resistance,

said stimulus circuit capable of applying a second electrical stimulus to at least one of the first and second terminals to change the resistance of the device between the first and second terminals from a relatively high resistance to a relatively low resistance,

wherein the relatively high resistance between the first and second terminals corresponds to a first state of the device, and wherein the relatively low resistance between the first and second terminals corresponds to a second state of the device.

2. The device of claim 1, wherein the first and second states of the device are nonvolatile.

3. The device of claim 1, wherein one or more thermal characteristics of the device are selected to minimize a flow of heat out of the nanotube element.

4. The device of claim 1, wherein the nanotube article overlaps at least a portion of the first terminal with a controlled geometrical relationship.

5. The device of claim 4, wherein the controlled geometrical relationship allows electrical current to flow relatively well between the first terminal to the nanotube article, and allows heat to flow relatively poorly between the first terminal and the nanotube article.

6. The device of claim 4, wherein the controlled geometrical relationship is a predetermined extent of overlap.

7. The device of claim 6, wherein the predetermined extent of overlap is within the range of 1 to 150 nm.

8. The device of claim 6, wherein the predetermined extent of overlap is within the range of 15 to 50 nm.

9. The device of claim 6, wherein the predetermined extent of overlap is defined by a dimension of the first terminal.

10. The device of claim 1, wherein the first conductive element comprises a material that conducts electricity relatively well and conducts heat relatively poorly.

11. The device of claim 1, further comprising a passivation layer disposed on the nanotube element.

12. The device of claim 11, wherein the passivation layer comprises a material that conducts heat relatively poorly.

13. The device of claim 12, wherein the passivation layer traps heat in the nanotube element.

14. The device of claim 1, wherein the resistance of the first state is at least about ten times larger than the resistance of the second state.

15. The device of claim 1, wherein an impedance of the first state is at least about ten times larger than an impedance of the second state.

16. The device of claim 1, wherein the first state is characterized by a resistance above about 1 megaohm.

17. The device of claim 1, wherein the second state is characterized by a resistance below about 100 kilaohm.

18. The device of claim 1, wherein the first electrical stimulus is an erase operation.

19. The device of claim 18, wherein the erase operation comprises the stimulus circuit applying a relatively high voltage across the first and second terminals.

20. The device of claim 19, wherein the relatively high voltage is within the range of 3 to 10 V.

21. The device of claim 18, wherein the erase operation comprises the stimulus circuit applying one or more voltage pulses across the first and second terminals, wherein an amplitude of the pulses, a waveform of the pulses, and a number of the pulses together are sufficient to change the device to the first state.

22. The device of claim 1, wherein the second electrical stimulus is a program operation.

23. The device of claim 22, wherein the program operation comprises the stimulus circuit applying a relatively low voltage and a relatively low current across the first and second terminals.

24. The device of claim 23, wherein the relatively low voltage is within the range of 1 to 5 V and the relatively low current is within the range of 100 to 1000 nA.

25. The device of claim 22, wherein the program operation comprises the stimulus circuit applying one or more voltage pulses across the first and second terminals, wherein an amplitude of the pulses, a waveform of the pulses, and a number of the pulses together are sufficient to change the device to the second state.

26. The device of claim 1, wherein the stimulus circuit is capable of applying a third electrical stimulus to at least one of the first and second terminals to determine the state of the device.

27. The device of claim 26, wherein the third electrical stimulus is a non-destructive read-out operation.

28. The device of claim 27, wherein the non-destructive read-out operation comprises the stimulus circuit applying a voltage across the first and second terminals and sensing the resistance between the first and second terminals, the voltage being sufficiently low that it does not change the state of the device.

29. The device of claim 28, wherein the voltage is smaller than about 2 V.

30. The device of claim 1, wherein at least one of the first and second terminals overlaps an edge of the nanotube article.

31. The device of claim 1, wherein opposing ends of the nanotube article respectively overlap at least a portion of each of the first and second terminals.

32. The device of claim 1, wherein one of the first and second terminals is a picture frame structure that overlaps a periphery of the nanotube article, and does not overlap a central region of the nanotube article.

33. The device of claim 32, wherein the other of the first and second terminals overlaps a central region of the nanotube article.

34. The device of claim 1, wherein the first terminal has a plurality of surfaces, wherein the nanotube article substantially conforms to and overlaps at least a portion of more than one surface.

35. The element of claim 1, wherein at least one of the first and second terminals has a vertically oriented feature, and wherein the nanotube article substantially conforms to at least a portion of the vertically oriented feature.

36. The device of claim 1, wherein the nanotube article comprises a region of nanotube fabric of defined orientation.

37. The device of claim 1, wherein the nanotube article comprises double walled nanotubes.

38. The device of claim 1, wherein the nanotube article comprises single walled nanotubes.

39. The device of claim 1, wherein the nanotube article comprises multiwalled nanotubes.

40. The device of claim 1, wherein the nanotube article comprises bundles of nanotubes.

41. The device of claim 1, wherein one or more nanotubes in the nanotube article are selected to have a particularly strong radial breathing mode.

42. The device of claim 41, wherein the particularly strong radial breathing mode behaves as a thermal bottleneck.

43. The device of claim 41, wherein the particularly strong radial breathing mode couples to a mode that causes a connection between a nanotube and a conductor in the device to break, wherein a conductor in the device comprises one or more of the first terminal, the second terminal, a nanotube, and a nanotube segment.

44. The device of claim 1, wherein the first and second terminals are metal.

45. The device of claim 44, wherein the metal comprises at least one of Ru, Ti, Cr, Al, Au, Pd, Ni, W, Cu, Mo, Ag, In, Ir, Pb, Sn, TiAu, TiCu, TiPd, PbIn, and TiW.

46. A two-terminal memory device, comprising:

a first conductive terminal;

a second conductive terminal in spaced relation to the first conductive terminal;

a nanotube article having at least one nanotube, said article being arranged to overlap at least a portion of each of the first and second terminals; and

a stimulus circuit in electrical communication with at least one of the first and second terminals,

said stimulus circuit capable of applying a first electrical stimulus to at least one of the first and second terminals to open one or more gaps between one or more nanotubes and one or more conductors in the device, said opening of one or more gaps changing the resistance of the device between the first and second terminals from a relatively low resistance to a relatively high resistance,

said stimulus circuit capable of applying a second electrical stimulus to at least one of the first and second terminals to close one or more gaps between one or more nanotubes and one or more conductors in the device, said closing of one or more gaps changing the resistance of the device between the first and second terminals from a relatively high resistance to a relatively low resistance,

wherein a conductor in the device comprises one or more of the first terminal, the second terminal, a nanotube, and a nanotube segment,

wherein the relatively high resistance between the first and second terminals corresponds to a first state of the device, and wherein the relatively low resistance between the first and second terminals corresponds to a second state of the device.

47. The device of claim 46, wherein the first and second states of the device are nonvolatile.

48. The device of claim 46, wherein the first electrical stimulus overheats at least a portion of the nanotube article to open one or more gaps.

49. The device of claim 48, wherein the first electrical stimulus overheats at least a portion of the nanotube article by Joule heating.

50. The device of claim 46, wherein one or more thermal characteristics of the device are selected to minimize a flow of heat out of the nanotube element.

51. The device of claim 50, wherein the flow of heat out of the nanotube element is minimized by arranging the nanotube article and the first terminal with a controlled geometrical relationship that limits heat flow out of the nanotube article and into the first terminals.

52. The device of claim 51, wherein the controlled geometrical relationship is a predetermined extent of overlap.

53. The device of claim 52, wherein the predetermined extent of overlap is less than 50 nm.

54. The device of claim 50, wherein the flow of heat out of the nanotube element is minimized by selecting a material for the first terminal that conducts electricity relatively well and conducts heat relatively poorly.

55. The device of claim 54, wherein the material has a relatively high electrical conductivity and a relatively low thermal conductivity.

56. The device of claim 54, wherein the material is selected from the group of conductive polymers and doped semiconductors.

57. The device of claim 46, wherein the first electrical stimulus opens one or more gaps by forming a gap between one or more nanotubes and one or more of the first and second terminals.

58. The device of claim 46, wherein the first electrical stimulus opens one or more gaps by separating one or more nanotubes from one or more other nanotubes in an electrical network of nanotubes.

59. The device of claim 46, wherein the first electrical stimulus opens one or more gaps by breaking one or more nanotubes into two or more nanotube segments.

60. The device of claim 46, wherein the first electrical stimulus comprises a voltage that exceeds a threshold voltage of the nanotube article.

61. The device of claim 46, wherein the first electrical stimulus opens one or more gaps by exciting one or more phonon modes of one or more nanotubes in the nanotube article.

62. The device of claim 61, wherein the one or more phonon modes behave as a thermal bottleneck.

63. The device of claim 61, wherein the one or more phonon modes are optical phonon modes.

64. The device of claim 61, wherein one or more nanotubes in the nanotube article are selected to have a particularly strong radial breathing mode.

65. The device of claim 61, wherein one or more nanotubes in the nanotube article are selected to have a defect mode.

66. The device of claim 46, wherein the second electrical stimulus closes one or more gaps by attracting one or more nanotubes to one or more conductors.

67. The device of claim 66, wherein the second electrical stimulus attracts one or more nanotubes to one or more conductors by generating an electrostatic attraction.

68. The device of claim 46, wherein the first electrical stimulus opens one or more gaps characterized by a gap size, and wherein the second electrical stimulus has sufficient amplitude to close one or more gaps characterized by that size.

69. The device of claim 46, further comprising a passivation layer disposed on the nanotube element.

70. The device of claim 69, wherein the passivation layer traps heat in the nanotube element.

71. The device of claim 46, wherein the device can be repeatedly switched between the first and second states over one million times.

72. The device of claim 46, wherein the nanotube article comprises a region of nanotube fabric of defined orientation.

73. The device of claim 46, wherein the nanotube article comprises double walled nanotubes.

74. The device of claim 46, wherein the nanotube article comprises single walled nanotubes.

75. The device of claim 46, wherein the nanotube article comprises multiwalled nanotubes.

76. The device of claim 46, wherein the nanotube article comprises bundles of nanotubes.

77. The device of claim 46, wherein the first and second terminals are metal.

78. A selectable memory cell, comprising:

a cell selection transistor including a gate, a source, and a drain, with the gate in electrical contact with one of a word line and a bit line, and a drain in electrical contact with the other of the word line and the bit line;

a two-terminal switching device comprising a first conductive terminal, a second conductive terminal, and a nanotube article having at least one nanotube and overlapping at least a portion of each of the first and second terminals, wherein the first terminal is in electrical contact with the source of the cell selection transistor and the second terminal is in electrical contact with a program/erase/read line; and

a memory operation circuit in electrical communication with the word line, bit line, and program/erase/read line,

said memory operation circuit capable of applying a select signal on the word line to select the cell and an erase signal on the program/erase/read line to change the resistance of the device between the first and second terminals from a relatively low resistance to a relatively high resistance,

said memory operation circuit capable of applying a select signal on the word line to select the cell and a program signal on the program/erase/read line to change the resistance of the device between the first and second terminals from a relatively high resistance to a relatively low resistance,

wherein the relatively high resistance between the first and second terminals corresponds to a first informational state of the memory cell, and wherein the relatively high resistance between the first and second conductive elements corresponds to a second informational state of the memory cell.

79. The selectable memory cell of claim 78, wherein the first and second informational states are nonvolatile.

80. The selectable memory cell of claim 78, wherein said memory operation circuit applies a select signal on the word line to select the cell and a read signal on the program/erase/read line to determine the informational state of the memory cell.

81. The selectable memory cell of claim 80, wherein determining the informational state of the memory cell does not change the state of the memory cell.

82. The selectable memory cell of claim 78, further comprising a plurality of selectable memory cells connected to the program/erase/read line.

83. The selectable memory cell of claim 78, wherein one or more thermal characteristics of the device are selected to minimize a flow of heat out of the nanotube element.

84. The selectable memory cell of claim 78, wherein the nanotube article overlaps at least a portion of the second terminal with a controlled geometrical relationship.

85. The selectable memory cell of claim 84, wherein the controlled geometrical relationship allows electrical current to flow relatively well between the second terminal and the nanotube article, and allows heat to flow relatively poorly between the second terminal and the nanotube article.

86. The selectable memory cell of claim 84, wherein the controlled geometrical relationship is a predetermined extent of overlap.

87. The selectable memory cell of claim 86, wherein the predetermined extent of overlap is defined by a dimension of the first terminal.

88. The selectable memory cell of claim 86, wherein the predetermined extent of overlap is within the range of 1 to 150 nm.

89. The selectable memory cell of claim 78, wherein one of the first and second terminals is a picture frame structure that overlaps a periphery of the nanotube article, and does not overlap a central region of the nanotube article, and wherein the other of the first and second terminals overlaps a central region of the nanotube article.

90. The selectable memory cell of claim 78, wherein the second terminal has a plurality of surfaces, and wherein the nanotube article substantially conforms to and overlaps at least a portion of more than one surface.

91. The selectable memory cell of claim 78, wherein the second terminal has a vertically oriented feature, and wherein the nanotube article substantially conforms to at least a portion of the vertically oriented figure.

92. The selectable memory cell of claim 78, wherein the cell has an area less than about 10F².

93. The selectable memory cell of claim 78, wherein the nanotube article comprises a region of nanotube fabric of defined orientation.

94. The selectable memory cell of claim 78, wherein the nanotube article comprises double walled nanotubes.

95. The selectable memory cell of claim 78, wherein the nanotube article comprises multiwalled nanotubes.

96. The selectable memory cell of claim 78, wherein the nanotube article comprises bundles of nanotubes.

97. The selectable memory cell of claim 78, wherein the first and second terminals are metal.

98. A reprogrammable two-terminal fuse-antifuse device, comprising:

a first conductor;

a second conductor in spaced relation to the first conductor;

a nanotube element having at least one nanotube and overlapping at least a portion of each of the first and second conductors,

the nanotube element capable of opening an electrical connection between the first and second conductors in response to a first threshold voltage across the first and second conductors to form a first device state, and capable of closing an electrical connection between the first and second conductors in response to a second threshold voltage across the first and second conductors to form a second device state.

99. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the device can be switched between the first and second device states repeatedly for at least one million cycles.

100. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the device is a cross-point switch.

101. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the first and second device states are nonvolatile.

102. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the nanotube article overlaps at least a portion of the first conductor with a controlled geometrical relationship.

103. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the controlled geometrical relationship allows electrical current to flow relatively well between the first conductor and the nanotube article, and allows heat to flow relatively poorly between the first conductor and the nanotube article.

104. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the controlled geometrical relationship is a predetermined extent of overlap.

105. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein one of the first and second conductors is a picture frame structure that overlaps a periphery of the nanotube article, and does not overlap a central region of the nanotube article, and wherein the other of the first and second terminals overlaps a second region of the nanotube article.

106. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the nanotube article comprises a region of nanotube fabric of defined orientation.

107. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the nanotube article comprises single walled nanotubes.

108. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the nanotube article comprises multiwalled nanotubes.

109. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the nanotube article comprises double walled nanotubes.

110. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the nanotube article comprises bundles of nanotubes.

111. The reprogrammable two-terminal fuse-antifuse device of claim 98, wherein the first and second conductors are metal.

112. A reprogrammable interconnection between a plurality of wiring layers, the interconnection comprising:

a first conductive terminal;

a plurality of wiring layers, each wiring layer comprising a wiring layer conductive terminal;

a stimulus circuit in electrical communication with the first conductive terminal and with each wiring layer conductive terminal;

a nanotube article having at least one nanotube, said nanotube article being arranged to overlap at least a portion of the first conductive terminal and at least a portion of each wiring layer conductive terminal,

said stimulus circuit capable of applying a first electrical stimulus to cause the nanotube article to form an interconnection between two wiring layers of the plurality of wiring layers,

said stimulus circuit capable of applying a second electrical stimulus to cause the nanotube article to break an interconnection between two wiring layers of the plurality of wiring layers.

113. The reprogrammable interconnection of claim 112, wherein the stimulus circuit breaks all interconnections in response to a security concern.

114. The reprogrammable interconnection of claim 112, wherein one or more thermal characteristics of the device are selected to minimize a flow of heat out of the nanotube element.

115. The reprogrammable interconnection of claim 112, wherein the nanotube article overlaps at least a portion of each wiring layer conductive terminal with a controlled geometrical relationship.

116. The reprogrammable interconnection of claim 115, wherein the controlled geometrical relationship allows electrical current to flow relatively well between each wiring layer conductive terminal and the nanotube article, and allows heat to flow relatively poorly between each wiring layer conductive terminal and the nanotube article.

117. The reprogrammable interconnection of claim 115, wherein the controlled geometrical relationship is a predetermined extent of overlap.

118. The reprogrammable interconnection of claim 117, wherein the predetermined extent of overlap is defined by a dimension of each of the wiring layer conductive terminals.

119. The reprogrammable interconnection of claim 117, wherein the predetermined extent of overlap is within the range of 1 to 150 nm.

120. The reprogrammable interconnection of claim 112, wherein the nanotube article comprises a region of nanotube fabric of defined orientation.

121. The reprogrammable interconnection of claim 112, wherein the nanotube article comprises double walled nanotubes.

122. The reprogrammable interconnection of claim 112, wherein the nanotube article comprises multiwalled nanotubes.

123. The reprogrammable interconnection of claim 112, wherein the nanotube article comprises bundles of nanotubes.

124. The reprogrammable interconnection of claim 112, wherein the wiring layer conductive terminals comprise metal.

125. A method of making a two terminal memory device, the method comprising:

providing a first conductive terminal;

providing a second conductive terminal in spaced relation to the first terminal;

providing a stimulus circuit in electrical communication with at least one of the first and second terminals;

providing a nanotube article comprising at least one nanotube, the nanotube article overlapping by a predetermined extent at least a portion of at least one of the first and second terminals, the device response being a function of the predetermined extent of overlap between the nanotube article and the at least one of the first and second terminals.

126. The method of claim 125, wherein the predetermined extent of overlap is determined by a timed isotropic etch procedure.

127. The method of claim 125, wherein the predetermined extent of overlap is determined by a directional etch procedure.

128. The method of claim 125, wherein the predetermined extent of overlap is determined by a thickness of a sacrificial film.

129. The method of claim 125, wherein the predetermined extent of overlap is determined by a thickness of the at least one of the first and second terminals.

130. The method of claim 125, further comprising fabricating a second memory device, the device having a structure that is a mirror image of a structure of the two terminal memory device.

131. The method of claim 125, wherein providing the nanotube article includes selecting one or more nanotubes to use in forming the nanotube article in which the nanotubes exhibit a particularly strong radial breathing mode.