Parallel Fabrication Of Nano-electromechanical Structures By Spacer Technology

The research in this thesis is focused on the parallel fabrication of nano-electromechanical structure by spacer technology. As the IC industry enters nano-scale era, the nano-fabrication depends more and more on expensive photolithography apparatus, or other serial nanofabrication equipments. The spacer technology mentioned in this thesis originates from IC industry, with the intrinsic feature of batch fabrication. The line width defined by spacer technology is well beyond the photolithography limit. So first of all, we demonstrate the spacer masks and ploy-Si nanowires by spacer technology. The poly-Si film stress and two kinds of release methods are investigated to ensure the final suspension of nano-beams. The maskless thermal oxidization is also introduced for further size reduction as well as profile improvement. Finally suspended Si nano-beams with a width of 23 nm are obtained. Furthermore, by extending single spacer to periodical multi-spacers, nano-grating and nano-grid become possible. Based on the process that has been proved, two crossed or overlapped SiO2 spacers are proposed to fabricate nano-needle array. SiO2 nano-needles will only be left at the cross or overlapping points by controlling anisotropic dry etching. In the thesis both double crossed and overlapped spacers are performed. By double crossed spacers, we obtain quadplex device density with a high aspect ratio and hybridized nano-needles. Moreover, overlapped spacers have proved the feasibility for ultra-high density, even overcoming the lithography-feature-size limitation. By overlapped spacers, the diameter of the nano-needle is as small as 24 nm and the minimum tip radius is 11 nm.Some experiments are performed to characterize the samples including nanowires, nano-beam and nano-needle. I-V characteristics and temperature-dependent conductance of the nanowires are investigated. Actuated by mechanical vibration and electrostatic forces, vibrations of the cantilever beams and fixed-fixed beams are observed in SEM. Nano water droplets with a diameter of 270 nm are condensed at the SiO2 tip of the obtained stacked SiO2/Si nano-needle, and fluorescent test also proved nano-extraction by the SiO2 tip, which validates the hydrophilic/hydrophobic selectivity between the tip and body of the needle.We also designed and developed some applications of the fabricated nano-structures. We designed a nano-resonator system including signal processing circuit and simulated it by lumped parameter method, which takes the parasitic effects into account. In addition, a nano-nozzle, a nano-pipe and nano-imprint are established separately with Si nano-beam and nanowire served as a template or mold. Based on the hydrophilic/hydrophobic selectivity between the tips and bodies of the stacked SiO2/Si nano-needles, the SiO2 tips are chemically decorated and finally used to localize proteins. For future nano-electromechanical system (NEMS) application, we also proposed the process integration of nano-electromechanical beam and FinFET. This may enable the monolithic integration of advanced circuits and NEMS devices, and solve the bottleneck of signal detection in NEMS.