A concept for molecular electronics exploiting carbon nanotubes as both molecular device elements and molecular wires for reading and writing information was developed. Each device element is based on a suspended, crossed nanotube geometry that leads to bistable, electrostatically switchable ON/OFF states. The device elements are naturally addressable in large arrays by the carbon nanotube molecular wires making up the devices. These reversible, bistable device elements could be used to construct nonvolatile random access memory and logic function tables at an integration level approaching 10 12 elements per square centimeter and an element operation frequency in excess of 100 gigahertz. The viability of this concept is demonstrated by detailed calculations and by the experimental realization of a reversible, bistable nanotube-based bit.

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Manufacturability of most electronic devices based on carbon nanotubes depends on the ability to place, manipulate, and control individual structures at the molecular level. This approach is problematic due to the precise placement and registration required thus making large scale manufacturing difficult if not impossible. A novel technique has been developed to overcome this hurdle, allowing CNT based nano-devices to be fabricated directly on existing production CMOS fabrication lines. This technique has been demonstrated in a Class 1 commercial fab and enables the fabrication of CNT nonvolatile memory devices directly onto CMOS substrates. This unique approach relies on the deposition and lithographic patterning, using standard semiconductor toolsets, of a 1-2 nm thick fabric of carbon nanotubes which retain their molecular scale, electro-mechanical characteristics, even when patterned to less than 100 nm feature sizes. The non-volatile CNT switch is turned on using electrostatic forces and remains in the ON state through van der Waals (VDW) attraction. The switch is turned off by overcoming the VDW forces and creating separation of the tubes from a contact.The resulting devices are free from metallic or material contaminants and particulates. Because these nonvolatile memory elements are created through a thin-film process, they are easily integrated with existing CMOS circuitry. Devices fabricated on a commercial line and integrated with transistors have been switched successfully both as single bits and in arrays. Devices have been switched over 50 million times without failure-continued testing is underway. Write and erase voltages can be less than 5 V and can scale downwards with smaller geometries. Additionally, the switch has been tested and shown to switch in less than 3 ns. Design consideration, device structure, testing, and reliability data are presented. 1,2

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