Nanofabrication toward sub-10 nm and its application to novel nanodevices

The device feature size in Si ULSIs has been reduced over the years, and sooner or later we will probably enter the so-called nanoelectronics era. Two nanofabrication technologies, electron-beam lithography and atomic-beam holography, which are expected to play an important role in the coming era, are discussed first. In order to get finer patterns with electron-beam lithography, improvements in the characteristics of organic resists are crucially important. Organic negative resists with a fine resolution have been developed, and a high-quality resist line pattern with a width as small as 7 nm has been successfully formed. A new atom manipulation technique called atomic-beam holography has been proposed for nanofabrication. It enables direct pattern formation on a substrate by passing laser-cooled atoms through a computer-generated hologram. It is expected to be a technique with a fine resolution, reaching the atomic scale, and a high throughput. Nano-size devices are developed from two standpoints. One pursues the miniaturization limit of MOS transistors: in this context, we discuss the fabrication of MOS transistors with gate length down to 14 nm and their electrical characteristics. The other approach is to explore 'breakthrough devices' that utilize quantum effects: single electron devices are one type of such devices. We discuss the operation of an all-metallic single-electron memory cell along with the electrical characteristics of a single-electron transistor made of aluminium.