D. Mocuta

Strained germanium quantum well p-FinFETs fabricated on 45nm Fin pitch using replacement channel, replacement metal gate and germanide-free local interconnect

Strained Ge p-channel FinFETs on Strain Relaxed SiGe are integrated for the first time on high density 45nm Fin pitch using a replacement channel approach on Si substrate. In comparison to our previous work on isolated sGe FinFETs [1], 14/16nm technology node compatible modules such as replacement metal gate and germanide-free local interconnect were implemented. The ION/IOFF benchmark shows the high density strained Ge p-FinFETs in this work outperform the best published isolated strained Ge on SiGe devices.

Gate-all-around MOSFETs based on vertically stacked horizontal Si nanowires in a replacement metal gate process on bulk Si substrates

We report on gate-all-around (GAA) n- and p-MOSFETs made of 8-nm-diameter vertically stacked horizontal Si nanowires (NWs). We show that these devices, which were fabricated on bulk Si substrates using an industry-relevant replacement metal gate (RMG) process, have excellent short-channel characteristics (SS = 65 mV/dec, DIBL = 42 mV/V for LG = 24 nm) at performance levels comparable to finFET reference devices. The parasitic channels below the Si NWs were effectively suppressed by ground plane (GP) engineering.

Impact of Wire Geometry on Interconnect RC and Circuit Delay

We investigate the impact of wire geometry on the resistance, capacitance, and RC delay of Cu/low-k damascene interconnects for fixed line-to-line pitch. The resistance is computed by applying a semiempirical resistivity model, calibrated to Cu damascene wires, integrated with a Ru-based liner, currently investigated for the 7 nm logic technology node. The capacitance is simulated by means of a 2D field solver (Raphael) by Synopsys. The impact of line dimensions is analyzed for the case of 32 nm pitch interconnects, which are representative of the 7 nm logic technology node. We show that for aspect ratios greater than 1, the resistance is more sensitive to variations of the line width rather than of the line height, because of the higher surface scattering induced by the sidewall interfaces, which are closer to each other compared with the top and bottom interfaces. For capacitance, low-k sidewall damage exacerbates capacitance sensitivity to line dimensions and, for typical interconnect schemes, the impact of line width variations dominates over variations of the line height. We demonstrate that for a given pitch and dielectric stack height, the RC delay can be significantly reduced by targeting wider and deeper damascene trenches, that is, by trading capacitance for resistance, and that an optimal wire geometry for RC delay minimization exists. In addition, we show that a given RC delay can be achieved with several geometries and, therefore, R and C pairs, which represents a useful degree of freedom for designers to optimize system-level performance. As an application, we analyze a possible 7 nm technology scenario and show that wide and deep damascene trenches can mitigate the impact of the increased wire resistance on circuit delay.

Vertically stacked gate-all-around Si nanowire CMOS transistors with dual work function metal gates

We report on the CMOS integration of vertically stacked gate-all-around (GAA) silicon nanowire MOSFETs, with matched threshold voltages (Vt, sat ∼ 0.35 V) for N- and P-type devices. The Vt setting is enabled by nanowire-compatible dual-work-function metal integration in a high-k last replacement metal gate process. Furthermore, we demonstrate that N- and P-type junction formation can influence nanowire release differently due to both implantation-induced SiGe/Si intermixing and doping effects. These findings underline that junction formation and nanowire release require co-optimization in GAA CMOS technologies.

InGaAs tunnel FET with sub-nanometer EOT and sub-60 mV/dec sub-threshold swing at room temperature

InGaAs homojunction Tunnel FET devices are demonstrated with sub-60 mV/dec Sub-threshold Swing (SS) measured in DC. A 54 mV/dec SS is achieved at 100 pA/μm over a drain voltage range of 0.2–0.5 V. The SS remains sub-60 mV/dec over 1.5 orders of magnitude of current at room temperature. Trap-Assisted Tunneling (TAT) is found to be negligible in the device evidenced by low temperature dependence of the transfer characteristics. Equivalent Oxide Thickness (EOT) is found to play the major role in achieving sub-60 mV/dec performance. The EOT of the demonstrated devices is 0.8 nm.

Novel junction design for NMOS Si Bulk-FinFETs with extension doping by PEALD phosphorus doped silicate glass

We demonstrate a NMOS Si Bulk-FinFET with extension doped by Phosphorus doped Silicate Glass (PSG). Highly doped PSG (6e21 cm^-3) was used as a diffusion source. SiO₂ cap on PSG decreased sheet resistance (Rs) due to less out diffusion of P. Even when thin SiO₂ exists at the interface between Si and PSG, P diffused from PSG into Si. Thanks to the high etch rate of the PSG/SiO₂ cap stack after drive-in anneal, the PSG/SiO₂ cap was successfully removed by HF with minimum removal of STI and gate hard mask oxide. PSG provides damage free and uniform sidewall doping to fin. On current I_ON is improved by 20% for L_G in the 30-24 nm range, with similar I_OFF and better DIBL compared to P ion implanted reference.

Epitaxial diamond-hexagonal silicon nano-ribbon growth on (001) silicon.

Silicon crystallizes in the diamond-cubic phase and shows only a weak emission at 1.1 eV. Diamond-hexagonal silicon however has an indirect bandgap at 1.5 eV and has therefore potential for application in opto-electronic devices. Here we discuss a method based on advanced silicon device processing to form diamond-hexagonal silicon nano-ribbons. With an appropriate temperature anneal applied to densify the oxide fillings between silicon fins, the lateral outward stress exerted on fins sandwiched between wide and narrow oxide windows can result in a phase transition from diamond-cubic to diamond-hexagonal Si at the base of these fins. The diamond-hexagonal slabs are generally 5–8 nm thick and can extend over the full width and length of the fins, i.e. have a nano-ribbon shape along the fins. Although hexagonal silicon is a metastable phase, once formed it is found being stable during subsequent high temperature treatments even during process steps up to 1050 ºC.

A 2nd Generation of 14/16nm-node compatible strained-Ge pFINFET with improved performance with respect to advanced Si-channel FinFETs

Sub-30nm LG Fin-replacement strained-Germanium pFinFETs at state-of-art device dimensions are reported with optimized S/D junctions and RMG stack. Competitive performance is shown for the first time when comparing the sGe devices with counterparts from the same 14-16nm R&D platform (Ge vs Si channel, FinFET vs lateral Gate All around). Improvement in channel passivation efficiency at scaled device features is seen to be an important knob to further boost the performance of scaled Ge channel FINFETs.

Extreme scaling enabled by 5 tracks cells: Holistic design-device co-optimization for FinFETs and lateral nanowires

By optimizing design rules, layout, devices and parasitics, we show how 5 Tracks standard cells with one fin can be enabled. This reduces area by 16% without pitch scaling and provides 34% energy gain from 6T cells. The loss in speed of 15% can be recovered by different front-end solutions. Air gap spacers are the most efficient booster and provide an extra 16% gain in energy. Lateral Nanowires can compete in speed with FinFETs with an extra energy gain of 12% if tight vertical pitch of 10 nm between wires can be achieved.

A comparison of arsenic and phosphorus extension by Room Temperature and hot ion implantation for NMOS Si bulk-FinFET at N7 (7nm) technology relevant fin dimensions

We compare As and P extension implants for NMOS Si bulk FinFETs with 5nm wide fins. P implanted FinFETs shows improved ION, +15% with Room Temperature (RT) ion implantation (I/I) and +9% with hot I/I, keeping matched Short Channel Effects (SCE) for gate length (LG) of 30nm compared with As implanted FinFETs. Based on TCAD work, P increases activated dopant concentration in extension compared with As and 5nm fin suppresses off state leakage current under the gate efficiently even in P extension case though P diffusion is faster than As.