Systematic DC/AC Performance Benchmarking of Sub-7-nm Node FinFETs and Nanosheet FETs

In this paper, we systematically evaluate dc/ac performances of sub-7-nm node fin field-effect transistors (FinFETs) and nanosheet FETs (NSEETs) using fully calibrated 3-D TCAD. The stress effects of all the devices were carefully considered in terms of carrier mobility and velocity averaged within the active regions. For detailed AC analysis, the parasitic capacitances were extracted and decomposed into several components using TCAD RF simulation platform. FinFETs improved the gate electrostatics by decreasing fin widths to 5 nm, but the fin heights were unable to improve RC delay due to the trade-off between on-state currents and gate capacitances. The NSEETs have better on-state currents than do the FinFETs because of larger effective widths (W-eff) under the same device area. Particularly p-type NSEETs have larger compressive stress within the active regions affected by metal gate encircling all around the channels, thus improving carrier mobility and velocity much. On the other hand, the NSEETs have larger gate capacitances because larger W-eff increase the gate-to-source/drain overlap and outer-fringing capacitances. In spite of that, sub-7-nm node NSEETs attain better RC delay than sub-7-nm node as well as 10-nm node FinFETs for standard and high performance applications, showing better chance for scaling down to sub-7-nm node and beyond.11Ysciescopu

Bottom oxide Bulk FinFETs Without Punch-Through-Stopper for Extending Toward 5-nm Node

Structural advancements of 5-nm node bulk fin-shaped field-effect transistors (FinFETs) without punch-through-stopper (PTS) were introduced using fully calibrated TCAD for the first time. It is challenging to scale down conventional bulk FinFETs into 5-nm technology node due to the sub-fin leakage increase. Meanwhile, bottom oxide deposition after anisotropic etching for source/drain (S/D) epi formation prevents the sub-fin leakage effectively even without the PTS doping, thus achieving better gate-to-channel controllability. Bottom oxide FinFETs also have smaller gate capacitances than do conventional FinFETs because the parasitic capacitances decrease by smaller S/D epi separated from the bottom Si layer, which reduces junction and outer-fringing capacitances. But smaller S/D epi decreases the stresses along the channel direction, and the effective widths decrease by the bottom oxide layer blocking the current paths at the bottom side of fin channels. Furthermore, increase of the interconnect resistance and capacitance parasitics down to 5-nm node diminishes the improvements of total delays as the interconnect wire length increases greatly. In spite of these drawbacks, 5-nm node bottom oxide FinFETs achieve smaller total delays than do the 7-nm node conventional FinFETs, especially for low-power applications, thus promising for the scalability of bulk FinFETs along with simple and reliable process by avoiding PTS step.11Ysciescopu

Force-sensitive resistors to measure the distribution of weight in the pads of sound dogs in static standing position

The purpose of this study was to measure how weight is distributed in the pads of each of the 4 limbs of dogs and evaluate the intra-investigator reproducibility and inter-investigator reliability of the measurement method. Eight dogs were examined 3 times a day by 3 investigators at 1 week intervals for 3 weeks to determine the weight distribution to each of the pads. The force-sensitive resistor was used for measurement and specific software (PetLAB2) was used to calculate the weight applied to each pad. The intra-investigator reproducibility showed moderate to good reliability (ICC range, 0.575-0.873) and the inter-investigator reliability was moderate (ICC range, 0.525-0.746). Based on this study, it can be observed whether the weight distributed to each pad approaches the normal value after treatment in patients with orthopaedic and neurologic diseases. It is expected that this experimental method will be one of the objective indicators to evaluate the degree of recovery in patients with orthopaedic and neurologic diseases

Source/Drain Patterning FinFETs as Solution for Physical Area Scaling Toward 5-nm Node

A novel and feasible process scheme to downsize the source/drain (S/D) epitaxy of 5-nm node bulk fin-shaped field-effect transistors (FinFETs) were introduced by using fully-calibrated TCAD for the first time. The S/D epitaxy formed by selective epitaxial growth was diamond-shaped and occupied a large proportion of the device size irrespective of the active channel area. However, this problem was solved by patterning the low-k regions prior to S/D formation by preventing the lateral overgrowth of S/D epitaxy; the so-called S/D patterning (SDP). Its smaller S/D epitaxy decreased the average longitudinal channel stresses and drive currents for NFETs. However, the small diffusions of the boron dopants into the channel regions improved the short-channel effects and alleviated the drive current reduction for PFETs. Gate capacitances decreased greatly by reducing outer-fringing capacitances between the metal-gate stack and S/D regions. Through SPICE simulation based on the virtual source model, operation frequencies and dynamic powers of 15-stage ring oscillators were studied. SDP FinFETs have better circuit performances than the conventional and bottom oxide bulk FinFETs along with smaller active areas, promising for further area scaling through simple and reliable S/D process.11Ysciescopu

Gate-All-Around FETs: Nanowire and Nanosheet Structure

DC/AC performances of 3-nm-node gate-all-around (GAA) FETs having different widths and the number of channels (Nch) from 1 to 5 were investigated thoroughly using fully-calibrated TCAD. There are two types of GAAFETs: nanowire (NW) FETs having the same width (WNW) and thickness of the channels, and nanosheet (NS) FETs having wide width (WNS) but the fixed thickness of the channels as 5 nm. Compared to FinFETs, GAAFETs can maintain good short channel characteristics as the WNW is smaller than 9 nm but irrespective of the WNS. DC performances of the GAAFETs improve as the Nch increases but at decreasing rate because of the parasitic resistances at the source/drain epi. On the other hand, gate capacitances of the GAAFETs increase constantly as the Nch increases. Therefore, the GAAFETs have minimum RC delay at the Nch near 3. For low power applications, NWFETs outperform FinFETs and NSFETs due to their excellent short channel characteristics by 2-D structural confinement. For standard and high performance applications, NSFETs outperform FinFETs and NWFETs by showing superior DC performances arising from larger effective widths per footprint. Overall, GAAFETs are great candidates to substitute FinFETs in the 3-nm technology node for all the applications

Search for the Sagittarius Tidal Stream of Axion Dark Matter around 4.55 μ\mueV

We report the first search for the Sagittarius tidal stream of axion dark matter around 4.55 $\mu$eV using CAPP-12TB haloscope data acquired in March of 2022. Our result excluded the Sagittarius tidal stream of Dine-Fischler-Srednicki-Zhitnitskii and Kim-Shifman-Vainshtein-Zakharov axion dark matter densities of $\rho_a\gtrsim0.184$ and $\gtrsim0.025$ GeV/cm$^{3}$, respectively, over a mass range from 4.51 to 4.59 $\mu$eV at a 90% confidence level.Comment: 6 pages, 7 Figures, PRD Letter accepte

Extensive search for axion dark matter over 1\,GHz with CAPP's Main Axion eXperiment

We report an extensive high-sensitivity search for axion dark matter above 1\,GHz at the Center for Axion and Precision Physics Research (CAPP). The cavity resonant search, exploiting the coupling between axions and photons, explored the frequency (mass) range of 1.025\,GHz (4.24\,$\mu$eV) to 1.185\,GHz (4.91\,$\mu$eV). We have introduced a number of innovations in this field, demonstrating the practical approach of optimizing all the relevant parameters of axion haloscopes, extending presently available technology. The CAPP 12\,T magnet with an aperture of 320\,mm made of Nb$_3$Sn and NbTi superconductors surrounding a 37-liter ultralight-weight copper cavity is expected to convert DFSZ axions into approximately $10^2$ microwave photons per second. A powerful dilution refrigerator, capable of keeping the core system below 40\,mK, combined with quantum-noise limited readout electronics, achieved a total system noise of about 200\,mK or below, which corresponds to a background of roughly $4\times 10^3$ photons per second within the axion bandwidth. The combination of all those improvements provides unprecedented search performance, imposing the most stringent exclusion limits on axion--photon coupling in this frequency range to date. These results also suggest an experimental capability suitable for highly-sensitive searches for axion dark matter above 1\,GHz.Comment: A detailed axion dark matter article with 27 pages, 22 figure

Whole core analysis of Molten Salt Breeder Reactor

The simulation of whole core depletion and continuous reprocessing of Molten Salt Breeder Reactor (MSBR) has been performed. The MSBR model was built using MCNP6 and the depletion and reprocessing simulations were modelled using CINDER90 and PYTHON script. The PYTHON script was introduced to implement online reprocessing of molten-salt fuel and feeding of new fertile material with 3-day depletion intervals during the simulations. The simulation starts with the reference composition from the original ORNL MSBR design [3] and equilibrium compositions are searched through the depletion and reprocessing simulations for 1200 days. The MSBR whole core analysis was performed at the initial and equilibrium core conditions, for various reactor design parameters such as multiplication factors, neutron flux distributions, temperature coefficients, rod worths, and power distributions. The neutronic core characteristics was analyzed using four factor formula applied to the two zones of the core separately