K.G. Anil

Highly manufacturable FinFETs with sub-10nm fin width and high aspect ratio fabricated with immersion lithography

We investigate scalability, performance and variability of high aspect ratio trigate FinFETs fabricated with 193 nm immersion lithography and conventional dry etch. FinFETs with fin widths down to 5nm are achieved with record aspect ratios of 13. Excellent nMOS and pMOS performance is demonstrated for narrow fins and short gates. Further improvement in nMOS performance can be achieved by eliminating access resistance that is currently attributed to poor re-crystallization of implantation damage in narrow fins. Fully-depleted FinFETs show strongly improved short channel effect (SCE) control when the fin width is scaled, even without halo-implants. Nearly ideal DIBL and sub-threshold slope (SS) are achieved down to 30nm gate length. Low leakage devices are realized by combining a fully depleted channel, HfSiO high-k dielectric, mid-gap TiN metal electrodes, and aggressive fin width scaling. Symmetrical threshold voltages (±0.35 V) are achieved. It is demonstrated that selective epitaxial growth on source and drain regions is essential to limit parasitic resistance in narrow fin devices. Parametric spread is dominated by gate length variations in short devices but within-die fin width variations are still evident for long devices.

Work function of Ni silicide phases on HfSiON and SiO/sub 2/: NiSi, Ni/sub 2/Si, Ni/sub 31/Si/sub 12/, and Ni/sub 3/Si fully silicided gates

A complete determination of the effective work functions (WF) of NiSi, Ni/sub 2/Si, Ni/sub 31/Si/sub 12/ and Ni/sub 3/Si on HfSiON and on SiO/sub 2/ is presented. Conditions for formation of fully silicided (FUSI) gates for NiSi/sub 2/, NiSi, Ni/sub 3/Si/sub 2/, Ni/sub 2/Si, Ni/sub 31/Si/sub 12/ and Ni/sub 3/Si crystalline phases were identified. A double thickness series (HfSiON/SiO/sub 2/) was used to extract WF on HfSiON accounting for charge effects. A strong effect on WF of Ni content is observed for HfSiON, with higher WF for the Ni-rich silicides suggesting unpinning of the Fermi level. A mild dependence is observed for SiO/sub 2/. While all Ni-rich silicides have adequate WF for pMOS applications, Ni/sub 2/Si is most attractive due to its low formation temperature, lower volume expansion and ease of integration. Similar threshold voltages (-0.3 V) were obtained on Ni/sub 2/Si and Ni/sub 31/Si/sub 12/ FUSI HfSiON pMOSFETS.

Performance improvement of tall triple gate devices with strained SiN layers

In this letter, we investigate the influence of tensile and compressive SiN layers on the device performance of triple-gate devices with 60-nm fin height and fin widths down to 35 nm. It will be shown that even for narrow fin devices, the nMOS performance improvement can be as high as 20% with tensile strained layers. The improvement seen for pMOS is lower, about 10%. Next to that both compressive as well as tensile SiN layers can increase the pMOS on-state current.

A functional 41-stage ring oscillator using scaled FinFET devices with 25-nm gate lengths and 10-nm fin widths applicable for the 45-nm CMOS node

In this letter, we have fabricated a functional FinFET ring oscillator with a physical gate length of 25 nm and a fin width of 10 nm, the smallest ever reported. We demonstrate that these narrow (W/sub fin/ = 10 nm) and tall (H/sub fin/ = 60 - 80 nm) fins can be reliably etched with controlled profiles and that they are required to keep the short-channel effects under control, resulting in drain-induced barrier leakage characteristics of 45 mV/V at V/sub dd/ = 1 V and L/sub g/ = 25 nm for the nFET. For these ultrathin (10 nm) fins, we have succeeded in properly setting the V/sub T/ at 0.2 V without the use of metal gates. In addition to ring oscillators, we also have obtained excellent pFET FinFET devices at wider fin widths (W/sub fin/ = 65 nm) with I/sub dsat/ = 380 /spl mu/A//spl mu/m at I/sub off/ = 60 nA//spl mu/m and V/sub dd/ = -1.2 V.

Layout density analysis of FinFETs

The layout of FinFETs patterned with direct lithography and spacer lithography are analysed from a circuit density perspective. Requirements on the height of the fin to obtain competitive layout density are derived. Spacer lithography will be required to obtain the layout density targets with reasonable values of fin height.

Demonstration of fully Ni-silicided metal gates on HfO/sub 2/ based high-k gate dielectrics as a candidate for low power applications

We have fabricated fully Ni-silicided metal gate (FUSI) CMOS devices with HfO2-based gate dielectrics for the first time. We demonstrate that full silicidation eliminates the Fermi level pinning at the polySi-HfO2 dielectric interface in pFETs. For nMOS devices, a 5 orders of magnitude reduction in short channel sub-threshold leakage is obtained with similar drive current compared to the poly gate devices. In addition, the FUSI process does not degrade the hysterisis nor the dielectric breakdown. This result makes FUSI on high-K a strong candidate for scaled low power technologies.

Impact of Stochastic Mismatch on Measured SRAM Performance of FinFETs with Resist/Spacer-Defined Fins: Role of Line-Edge-Roughness

Spacer-defined fin-patterning results in double/quadruple fin density and hence is attractive for high performance 32-nm CMOS applications. For the first time 55-nm gate-length FinFET SRAMs with resist- and spacer-defined fins are electrically compared. Due to short-range process variations, SRAM bit-cells with spacer-defined fins show approximately 2.5 times higher variability in static-noise-margin than resist-defined fins at VDD=1.2V. These SRAM test-cells achieve 130-nm planar-bulk comparable intra-bit-cell stochastic-mismatch and static noise margins

Scalability of Ni FUSI gate processes: phase and Vt control to 30 nm gate lengths

We demonstrate for the first time the scalability of NiSi and Ni/sub 3/Si FUSI gate processes down to 30 nm gate lengths, with linewidth independent phase and V/sub t/ control. We show that 1-step FUSI is inadequate for NiSi FUSI gates, because it results in incomplete silicidation at low thermal budgets or in a linewidth dependent Ni silicide phase - inducing V/sub t/ shifts - at higher thermal budgets. We show that V/sub t/ and WF shifts are larger on high-K (HfO/sub 2/ (250 mV) or HfSiON (330mV)) than on SiON (110mV) and report Fermi level unpinning for Ni-rich FUSI on high-K. In contrast, we demonstrate the scalability of Ni/sub 3/Si FUSI, with no phase control issues, and report HfSiON Ni/sub 3/Si FUSI PMOS devices with V/sub t/= -0.33 V. Lastly, we show that, for NiSi, phase control down to narrow gate lengths can be obtained with a 2-step FUSI process.

Enhanced Performance of PMOS MUGFET via Integration of Conformal Plasma-Doped Source/Drain Extensions

For the first time, scaled PMOS MUGFET devices with TiCN/HfO2 gate stack is doped with specific pulsed plasma doping processes. This paper first highlights the key benefit brought by conformal source/drain extensions, demonstrates how pulsed plasma doping process can be tuned to conformal dope very dense fin structures and finally shows that high performance (+24% vs. ion implant reference) multi-gate pMOS device (720 muA/mum @ Ioff 20nA/mum, at Vds = -1.2V) is achieved with extensions formed by optimized PLAD process

CMOS integration of dual work function phase controlled Ni FUSI with simultaneous silicidation of NMOS (NiSi) and PMOS (Ni-rich silicide) gates on HfSiON

We demonstrate for the first time CMOS integration of dual WF (work function) metal gates on HfSiON using Ni-phase controlled FUSI. The novel integration scheme that we demonstrate uses our optimized 2-step Ni FUSI process (1) for simultaneous full silicidation of nMOS and pMOS, achieving different Ni/Si ratios on nMOS and pMOS by reduction of the pMOS poly height through a selective and controlled poly etch back prior to gate silicidation. This novel integration scheme offers the advantages of 1) simplicity (same Ni deposition and silicidation process on nMOS and pMOS), 2) large process window for poly etch-back process (same pMOS characteristics for poly thickness variation of 50%), 3) WF and Vt tuning on HfSiON by phase control, with 4) scalable, linewidth independent suitable Vts for nMOS (0.5 V) and pMOS (-0.3 V), and 5) solves process yield issues of Ni-rich silicides related to volume expansion, stress, filaments and voiding, resulting in a continuous silicide that is nicely confined between the sidewall spacers. Ring oscillator operation was also demonstrated