Fabrication of field effect transistor using combined nanoimprint and soft lithography

Abstract

FET is the most attractive scheme for an integrated system. Formation of short channel for FET is one of the most important issues in microelectronics. Although previously reported lithographic techniques are interesting and often effective, most of those methods are expensive, time consuming and not easily amenable to mass production. Therefore, low cost and high throughput patterning with large area is essential to the fabrication and commercialization of a variety of nano-sensors or nano device. In this thesis, a simple method combining nanoimprint and soft lithography is developed to fabricate short channel field effect transistor. Precise nano patterning with spatial control on a large area is achieved by combined lithographic techniques. Large numbers of short devices with 500 nm channel length can be obtained without the need of complex tools. In other words, this combined lithography has the enormous benefit of being able to fabricate transistors with significantly shorter gate lengths than those feasible with the resolution of the available photolithography. Semiconducting single walled carbon nanotube FET (CNT FET) device is produced to achieve quasi-ballistic operations for molecular transistors. The output characteristic of CNT FET shows clear unipolar p-type behavior, high on-current value ($10^{-3}$A), and high on/off-current ratio ($10^5$). The highly length-scaled FET can deliver nearly ballistic currents for transistor operations in the on state. Compared with the device fabricated by photolithography, the device represents higher saturation drain current ($10^4$ fold increase), higher on/off-current ratio value (10 fold increase), and lower power consumption (0.5V of gate bias). These improved characteristics results from high aspect ratio channel (W/L=20). Combined lithographic technique would provide significant advantages of low cost and high efficiency to fabricate short channel. By controlling size of the nano patterns from etc...