Limits of nano-gate fabrication

The authors review the limits of nanometer-scale gate electrode (nano-gate) fabrication. The technology to fabricate nano-gates has become increasingly important in recent years as the scaling limits of conventional electronic devices and the quantum effects of novel devices are investigated. Consistent with the technology used to fabricate virtually all of the smallest devices to date, the emphasis is on the resolution limits of electron beam lithography and associated ultrahigh resolution resists. Recent results of directly patterning SiO₂ with nanometer-scale resolution by e-beam exposure through a sacrificial layer are also presented. Because the high resistance normally associated with nanometer-scale electrodes seriously limits the performance of high-frequency devices, various techniques to reduce the gate resistance are compared