NH4OH Wet Etching for Silicon Nano or Sub-Micron Wires

In this work, instead of TMAH (Tetra Methyl Ammonium Hydroxide), ammonium hydroxide (NH
₄
OH) solutions are used to get silicon nano (SiNWs) or sub-micron (SiSMWs) wires, because also these solutions are silicon orientation-dependent wet etching and fully compatible with CMOS (Complementary Metal - Oxide - Semiconductor) technology.These wires were fabricated on Si and SOI (Silicon-On-Insulator) wafers, with (100) crystallographic orientation surfaces. On both wafers, the lateral etch rates under SiO
₂
of <;110> plane Si wire sidewalls between 43 nm/min and 156 nm/min were obtained. Thus, SiNWs and SiSMWs were obtained, indicating that our NH
₄
OH solution is a new alternative to get 3D structures on Si and SOI substrates. To confirm this result, pseudo-MOS (Metal-Oxide-Silicon) transistor on SOI substrate, with conduction channel of n+ Si wire of width of 1.22 μm and height of 100 nm, was fabricated. From drain-source current (I
_DS
) versus back gate - source voltage (V
_BGS
) curve of Pseudo MOS transistor, the threshold voltage (V
_T
) of 1.36 V and the maximum transconductance of 20 μS were extracted.