Fabrication of Silicon Nano-Devices with High Controllability beyond Lithography Limit

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The purpose of this study is to develop a highly controllable method for fabricating ultra-small silicon nano-devices beyond the lithography limit without using fine lithography techniques such as electron beam lithography. We have proposed a new method that makes use of anisotropic etching and multiple layers of silicon oxide and silicon nitride. Fine point contact channel was successfully fabricated by selective oxidation and two anisotropic etching steps on silicon-on-insulator (SOI) substrate. The fabricated MOSFET shows good uniformity. The distribution of drain current is less than 10%. Moreover, Coulomb blockade oscillations due to single electron tunneling are observed at low temperatures. Using this technique, the integration of single electron transistors is also performed. By combining the single electron transistor and a memory device with silicon nano-crystal floating dots, the characteristics of single electron transistors are precisely controlled and the peak positions of Coulomb blockade oscillations are adjusted to the desired positions. Then, two single electron transistors are integrated to form a directional current switch. The fabrication process and device control are very effective for the practical integration of single electron transistors.