M.Sc Thesis

M.Sc StudentShirak Oren
SubjectSilicon Nanowire Field Effect Transistors
DepartmentDepartment of Electrical and Computer Engineering
Supervisors DR. Yuval Yaish


One-dimensional (1D) semi-conducting nanowires, especially silicon nanowires  (SiNWs) are of both scientific and technological interest. SiNWs have been pointed out as one of the most promising building blocks for submicron electrical applications, not only because of their interesting electronic, optical and mechanical properties but also as a result of their high compatibility to the existent semiconductor industry and their flexible engineering capabilities.

In this work systematic research on electrical properties of SiNWs was conducted. The wires were synthesized at the IBM T. J. Watson Research Center (New York) and included three types of undoped, p-doped and n-doped nanowires with typical diameters in between 30 to 60 nm. A process to fabricate back-gate SiNW- FETs (Field Effect Transistors) based on the 'bottom-up' approach was developed, the devices contacts were studied and optimized, and transfer measurements were taken in order to extract their primary electrical properties. In total, more than 50 devices were fabricated, optimized and measured with the aim of giving a general picture of their electrical capabilities.

Furthermore, a new design and fabrication method was examined and successfully implemented in creating high performance, horizontal, gate-all-around (HGAA) SiNW-FETs, (the NW is fully enveloped by the gate electrode from all directions).  The electrical properties of this firstly fabricated device were measured and compared to those of other state-of-the-art FET devices.

From the results of this study, the new HGAA device exhibits some of the most promising electrical characteristics, including more than a 107 on/off current ratio, a relatively low subthreshold swing (107 mV/decade), low contact resistance (< 50 kΩ), and high transconductance (0.40 mS/µm).  This last characteristic, to the best of our knowledge, demonstrates the best transconductance result of a single SiNW-FET published to date.

Finally, a transport model for a long-channel, cylindrical surrounding-gate FET was adapted, and found to be in good agreement with the HGAA-SiNWFETs empirical data.