NOVEL FABRICATION TECHNIQUES FOR SILICON SINGLE-ELECTRON DEVICES

摘要

We have developed a special method, called pattern-dependent oxidation (PADOX), for fabricating Si single-electron transistors (SETs). This method exploits special phenomena that occur when a laterally modulated Si layer on SiO2 is oxidized. With the method, a one-dimensional Si wire can be converted into a small Si island with a tunneling barrier at each end. Since the size of the resultant Si island is about 10 nm, we can observe the conductance oscillations in the SET even at room temperature. The controllability and reproducibility of this method are excellent, reflecting the stability of the thermal oxidation process. We have been applying this method to the integration of single-electron devices (SEDs) to create sophisticated functions. Several kinds of devices, such as memory and logic devices, have been fabricated and their fundamental operations have been confirmed. We have also found that another type of Si pattern that can be converted into SETs. A thin Si layer under a trench of a Si wire can be converted into two SET islands which are embedded in both edges of the Si layer parallel with the wire. We have demonstrated that the two small Si islands can be operated as individual SETs. Since this method uses a vertically modulated initial pattern, we call it V-PADOX. PADOX and V-PADOX have great flexibility for fabricating various types of SEDs.