Carbon Nanotube Based Memory Using CMOS Production Techniques

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 nanodevices 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 non-volatile memory devices. This unique approach relies on the deposition and lithographic patterning, using standard semiconductor toolsets, of a 1-2 nm thick fabric of 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 non-volatile memory elements are created in an all thin-film process, they are easily integrated directly within existing CMOS circuitry to facilitate addressing and readout. 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