NOVEL SILICON AND CARBON NANOTUBE ELECTRONIC DEVICES: TECHNOLOGY, STRUCTURE AND PROPERTIES
Originating in an effort to advance electronics into nanometer scale regime and towards higher integration, several novel electronic devices are described here for computation and data storage applications. These include super-self-aligned separately-gated double-gate transistors, a cross-coupled bipolar injection memory (xFET) and top/back-gate carbon nanotube transistors. Hybrid integration of silicon and carbon nanotube electronics are demonstrated for the first time to show a viable direction for future electronics to extend technology reach for new scientific and engineering fields. The Super-self-aligned separately-gated double-gate field-effect transistor (FET), featuring strained silicon channel, thick source-drain region and buried-interconnected gate, have been made for both polarities n- and p-type using a novel approach that helps advance silicon CMOS technology to nanometer scale. All these features help alleviate the power consumption issues for future nanoscale CMOS transistor where performance degrades due to short channel effects and the loss of device threshold voltage control. A novel non-volatile memory device?xFET?is developed with several charge injection mechanisms to allow a variety of operational capabilities and provide significantly faster programming/erasing speed. Nanoseconds programming time has been achieved through hot electron injection. In a crossed nFET/pFET configuration, the new device features a four-terminal bipolar structure with a top floating gate used as the charge storage node. The silicon-on-insulator (SOI) technology in the device development ensures excellent CMOS compatibility. With techniques borrowed from silicon ULSI technology, carbon nanotube field-effect transistor (CNFET) with either back-gate or self-aligned top-gate structure has been developed to improve device performance and integration. For back-gate CNFET, combined analysis of device?s transient and transfer characteristics in contrasting environment (in air or in vacuum) show distinct ambient effects on the device carrier transport properties. High frequency pulse measurement is employed to produce intrinsic device transport properties through elimination of hysteresis and 1/f noise. Integration of carbon nanotubes transistor on top of nMOS transistors can provide compact circuit components. One example?a logic NOT gate is demonstrated in a monolithic integration of p-CNFET on top of nMOSFET. This integration scheme is an example that combine different technologies to make new applications possible on a robust silicon technology platform.
Center for Nanoscale System National Science Foundation
super-self-aligned double-gate; back-gate; strained silicon channel; xFET; threshold voltage tuning; adaptive power control; dual-polarity injection; nanosecond programming time; Field Effect Transistor; nonvolatile memory; carbon nanotube field effect transistor; Hybrid Si/C integrated system; hysteresis; pulse measurement
dissertation or thesis