Kyoung Hwan Yeo

High performance 5nm radius Twin Silicon Nanowire MOSFET (TSNWFET) : fabrication on bulk si wafer, characteristics, and reliability

For the first time, we have successfully fabricated gate-all-around twin silicon nanowire transistor (TSNWFET) on bulk Si wafer using self-aligned damascene-gate process. With 10nm diameter nanowire, saturation currents through twin nanowires of 2.64 mA/mum, 1.11 mA/mum for n-channel TSNWFET and p-channel TSNWFET are obtained, respectively. No roll-off of threshold voltages, ~70 mV/dec. of substhreshold swing (SS), and ~20 mV/V of drain induced barrier lowering(DIBL) down to 30 nm gate length are observed for both n-ch and p-ch TSNWFETs

Gate-All-Around (GAA) Twin Silicon Nanowire MOSFET (TSNWFET) with 15 nm Length Gate and 4 nm Radius Nanowires

GAA TSNWFET with 15 nm gate length and 4 nm radius nanowires is demonstrated and shows excellent short channel immunity. p-TSNWFET shows high driving current of 1.94 mA/mum while n-TSNWFET shows on-current of 1.44 mA/mum. Merits of TSNWFET and performance enhancement of p-TSNWFET are explored using 3D and quantum simulation

Investigation of nanowire size dependency on TSNWFET

Nanowire size (dNW) dependency of various electrical characteristics on gate all around twin silicon nanowire MOSFET (TSNWFET) is investigated to understand overall performance of nanowire transistor deeply. When dNW decreases, current drivability (Ion) normalized by circumference at the same VG-VTH improves and maximizes at dNW of 4 nm. And mobility is also estimated with capacitance and series resistance. All the experimental investigation shows that dNW of 4 nm is the best point to maximize the volume inversion effect on gate all around nanowire MOSFET.

A novel multi-channel field effect transistor (McFET) on bulk Si for high performance sub-80nm application

We demonstrate highly manufacturable double FinFET on bulk Si wafer, named multi-channel field effect transistor (McFET) for the high performance 80nm 144M SRAM. Twin fins are formed for each transistor using our newly developed simple process scheme. McFET with L/sub G/=80nm shows several excellent transistor characteristics, such as /spl sim/5 times higher drive current than planar MOSFET, ideal subthreshold swing of 60mV/dec, drain induced barrier lowering (DIBL) of 15mV/V without pocket implantation, and negligible body bias dependency, maintaining the same source/drain resistance as planar transistor due to the unique feature of McFET.

High-Performance Twin Silicon Nanowire MOSFET (TSNWFET) on Bulk Si Wafer

Gate-all-around twin silicon nanowire MOSFET (TSNWFET) with 5-nm-radius channels on bulk Si wafer is successfully fabricated to achieve extremely high drive currents of 2.37 mA/mum for n-channel and 1.30 mA/mum for p-channel TSNWFETs with mid-gap TiN metal gate. It also shows good short channel effects immunity down to 30 nm gate length due to GAA structure and nanowire channel. The effect of bottom parasitic transistor in TSNWFET is also investigated.

A partially insulated field-effect transistor (PiFET) as a candidate for scaled transistors

Highly manufacturable partially insulated field-effect transistors (PiFETs) were fabricated by using Si-SiGe epitaxial growth and selective SiGe etch process. Owing to these technologies, pseudo-silicon-on-insulator (SOI) structures, partially insulating oxide (PiOX) under source/drain (PUSD) and PiOX under channel (PUC), could be easily realized with excellent structural and process advantages. We are demonstrating their preliminary characteristics and properties. Especially, in the PUSD PiFET, junction capacitance, leakage current, and DIBL in bulk devices could be reduced and the floating body problem in SOI devices was also cleared without any area penalty. Thus, this PiFET structure can be a promising candidate for the future DRAM cell transistor.

80 nm 512M DRAM with enhanced data retention time using partially-insulated cell array transistor (PiCAT)

An 80 nm 512M DDR DRAM with partially-insulated cell array transistor (PiCAT) was fabricated. Si/SiGe epitaxial growth and selective SiGe etch process were used to form PiOX (Partially-Insulating OXide) under source and drain of the cell transistor. Using these technologies, partial-SOI (Silicon-On-Insulator) structure could be realized with excellent structural and electrical advantages on bulk Si wafer. Self-limited shallow junction under source/drain and halo doping effect at the channel region were formed by PiOX. With PiCAT, junction leakage current and SCE (Short Channel Effect) were reduced, and excellent data retention time was obtained.

Observation of Single Electron Tunneling and Ballistic Transport in Twin Silicon Nanowire MOSFETs (TSNWFETs) Fabricated by Top-Down CMOS Process

the authors report transport experiments on gate-all-around (GAA) TSNWFETs fabricated by top-down CMOS processes. The nanowire with 45 nm gate length exhibits single electron tunneling, and the total capacitance extracted from the measured data is in good agreement with the self-capacitance of an ideal cylinder. The nanowire with 125 nm gate length shows conductance quantization suggesting ballistic transport. The temperature dependence of the conductance steps is consistent with the crossover from classical to ballistic

Damascene gate FinFET SONOS memory implemented on bulk silicon wafer

We successfully demonstrate highly scaled damascene gate FinFET SONOS memory implemented on bulk silicon wafer. The FinFET SONOS devices show extremely high program/erase speed, large threshold voltage shifts over 4V at 1/spl mu/s/12V for program and 50/spl mu/s/-12V for erase, good retention time, and acceptable endurance. Thus, in sub-50nm regimes, ultra high speed operation becomes possible by using FinFET SONOS structure without sacrificing retention time.

Temperature-Dependent Characteristics of Cylindrical Gate-All-Around Twin Silicon Nanowire MOSFETs (TSNWFETs)

The characteristics of cylindrical gate-all-around twin silicon nanowire field-effect transistors with a radius of 5 nm have been measured in temperatures T ranging from 4 to 300 K. The dependence of the off-current suggests that thermal generation in the channel is the main leakage mechanism. The dependence of the subthreshold swing exhibits no body effects but shows degradations due to slight differences in the threshold voltages and in the body effect constants of the twin nanowires. The T dependence of the peak normalized transconductance gm /VDS gives a clue of 1-D phonon scattering and suggests that surface roughness scattering at the nanowire wall is dominant at low values.