IBM Reveals Nanoelectromechanical Transistors Using Carbon Nanotubes for Integrated Circuit Chips

In U.S. Patent 7,701,013, International Business Machines Corporation (Armonk, NY) reveals methods for forming nanoelectromechanical transistors (NEMTs) using carbon nanotubes for application in computer chips.

According to IBM  inventor Huilong Zhu, nanoelectromechanical transistors (NEMTs) include a substrate including a gate adjacent thereto, a source region and a drain region; an electromechanically deflectable nanotube member; and a channel member electrically insulatively coupled to the nanotube member so as to be aligned with the source region and the drain region, wherein electromechanical deflection of the nanotube member is controllable, in response to an electrical potential applied to the gate and the nanotube member, between an off state and an on state, the on state placing the channel member in electrical connection with the source region and the drain region to form a current path.

In the integrated circuit (IC) chip fabrication industry, interest is growing regarding the use of nanoelectromechanical transistors (NEMT) or switches. NEMTs use carbon nanotubes to form switch structures. In this switch, the carbon nanotube is drawn downwardly by a potential applied to a gate and acts as a contact between the source and drain of the switch. Hence, the carbon nanotube constitutes an integral part of the switch and must be conductive.

One issue limiting the use of NEMTs is that it is difficult to control the resistance of the nanotube. In particular, current techniques for growing carbon nanotubes typically result in some nanotubes having metal-like characteristics and some having semiconductor characteristics. Unfortunately, the unpredictability prevents the necessary amount of manufacturing control over the ratio of the on-current to off-current. Hence, use of carbon nanotubes for massive manufacturing of nanoelectromechanical switches or transistors is currently impracticable.

The NEMTs and methods as described by Zhu in U.S. Patent 7,701,013  may be used in the fabrication of integrated circuit chips that overcome prior limitations to the use of carbon nanotube NEMTs. The resulting integrated circuit chips can be distributed by the fabricator in raw wafer form (that is, as a single wafer that has multiple unpackaged chips), as a bare die, or in a packaged form. In the latter case, the chip is mounted in a single chip package (such as a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (such as a ceramic carrier that has either or both surface interconnections or buried interconnections).

 In any case, the chip is then integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either (a) an intermediate product, such as a motherboard, or (b) an end product. The end product can be any product that includes integrated circuit chips, ranging from toys and other low-end applications to advanced computer products having a display, a keyboard or other input device, and a central processor.