Schottky barrier height (ΦSBH) tuning from the insertion of dipole providing materials at the TaN/Si and TaN/GaAs interface are investigated using photoelectron spectroscopy and electrical techniques. In-situ processing and characterization of these contact interfaces is utilized to gain understanding of the formation of the dipole at the AlOx/SiO2 interface. Changes in both the band bending and vacuum work function by the insertion of AlOx/SiO2 at the interface are observed on both Si and GaAs substrates and are correlated with a large reduction in the ΦSBH on Si. Applications of this contact scheme for contact resistivity reduction, extremely shallow junctions, and Schottky barrier metal–oxide–semiconductor field effect devices are also discussed.

We have investigated the effect of trimethyl aluminum (TMA) and water (H 2 O) half‐cycle treatments on HF‐treated, and O 3 ‐oxidized GaN surfaces at 300 °C. The in‐situ X‐ray photoelectron spectroscopy results indicate no significant re‐growth of Ga–O–N or self‐cleaning on HF‐treated and O 3 ‐oxidized GaN substrates with exposure to water and TMA. This result is different from the self‐cleaning effect of Ga 2 O 3 seen on sulfur‐treated GaAs or InGaAs substrates. O 3 causes aggressive oxidation of GaN substrate and direct O–N bonding compared to H 2 O. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In this work, nickel germanide Schottky contacts have been fabricated on n-type germanium (n-Ge) with an optimum barrier height of 0.63 eV. For rapid thermal annealing (RTA) temperatures above 300 °C, all phases of nickel and germanium convert to nickel mono-germanide (NiGe). However, higher RTA temperatures are also found to cause agglomeration of the NiGe phase and higher leakage current. So, the optimum temperature for Schottky-based source/drain contact formation on n-Ge is ∼300 °C, where the nickel mono-germanide phase is formed but without phase agglomeration.

Germanium is of unique interest for CMOS technology because of its high electron and hole mobilities compared with those of its counterpart silicon [1]. Significant progress has been in germanium p-MOSFETs, while in n-MOSFETS there are some hindrances. The diffusivity and poor activation of dopants in Ge [2] will not allow the formation of shallow junctions and low resistivity source and drain regions in Ge MOSFETs. Implantless fabrication with nickel germanide Schottky source and drain contacts is an alternative approach to fabricate Ge p-MOSFETs. S. Zhu et al [3] demonstrated the fabrication of nickel germanide based p-MOSFETs. D. R. Gajula et al [4] showed the effect of RTA temperature on the Schottky barrier height (Φbn) of nickel germanides on Ge and observed Φbn of 0.6-0.7 eV for RTA at approximately 300°C. So the barrier height for holes (Φbp = Eg-Φbn) is nearly zero, which is suitable for Schottky based p-MOSFETs. Electrical characterization of NiGe/Ge diodes was used to measure the Schottky barrier height. Surface characterization of these nickel germanides is very important in optimizing the fabrication of germanide based Ge p-MOSFETs. In this work, we show the surface characterization of nickel germanides formed on germanium with different RTA treatments by using SEM, XRD and XPS techniques.

The effects of Trimethyl aluminum (TMA) in atomic-layer-deposition (ALD) of La2O3 film using Tris(N, N'-diisopropylformamidinato) lanthanum and H2O were examined. The behaviors of Si diffusion and the residual C and N-related impurities were observed by in situ x-ray photoelectron spectroscopy. The La-silicate formation by Si out-diffusion from the substrate was suppressed by TMA/H2O pulse (Al2O3), but hardly suppressed the interfacial SiO2 layer growth during ALD. It was confirmed that TMA/H2O pulse (Al2O3) insertion eliminated the residual C-and N-related impurities with low binding energy in the La2O3 film which originated from the incomplete reactions of precursor during ALD. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3545965] All rights reserved.

Effective schemes to address contact resistance between silicide and a highly doped diffused junction are examined. Some of the techniques introduced include (1) metal work function tuning, (2) interfacial dipole engineering, and (3) phase modulation of the nickel silicide. These techniques allow modulation of the Schottky barrier of NiSi to n -Si to less than 0.3 eV, which is crucial to achieve sub 10 −8 Ω cm 2 contact resistivity for the sub-32 nm technology node.

Schottky barrier height tuning is reported from the insertion of thin layers of AlOx and SiO2 at the interface between tantalum nitride and p-type silicon. The magnitude of the change in the barrier height is found to be dependent on the conditions of AlOx and SiO2 formation. The largest change in barrier height is over 350 meV and correlates well with the intrinsic dipole found at this interface. These findings are then interpreted using a model of the dipole formation at the high-kappa and SiO2 interface. The application of these findings for low resistance contacts as well as options to achieve greater performance are discussed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3633117]

Recent experiments have demonstrated the ability to alleviate Fermi-level pinning, resulting in reduced Schottky barrier heights (SBHs) and reduced contact resistivity by inserting thin layers of dielectric at the contact interface. In this letter, FinFETs with dielectric SBH tuning layers are investigated and shown to have reduced contact resistance over the control wafer. The reduced contact resistivity results in an approximate to 25% increase in drive current as well as a reduction of R-S/D by 100 Omega . mu m. Contact chain measurement shows a 10-Omega . mu m(2) reduction in specific contact resistivity over the control wafer associated with a 100-meV reduction in SBH. Routes to further improvements in device performance are discussed, including key material considerations for dielectric tuning layers.

The effect of H2O and O3 oxidants on the behavior of residual C and N-related impurities as well as Si out-diffusion and interfacial layer formation in atomic-layer-deposited La2O3 films grown at 250 °C were examined using in situ x-ray photoelectron spectroscopy. The silicate formation was suppressed in a La2O3 film grown using O3 compared to that deposited using H2O, but interfacial layer growth was enhanced. The accumulation of C and N-related residues with low binding energy, which originated from incomplete reactions, was suppressed in La2O3 films grown using O3. However, the use of O3 resulted in La-carbonate phase in film.

For the first time, we demonstrate stressor contact etch stop liner (sCESL) modulation of parasitics/external resistance in nonplanar devices. We report 17% saturation drive current enhancement in underlap doped cMOS FinFETs attributed to simultaneous lowering of RS/D via biaxial S/D stress and μo increase via effective uniaxial channel stress. Our observations imply that biaxial strain engineering for reduction of RS/D offers a significant opportunity to realize non-planar CMOSFET performance metrics for the 22nm node and beyond.

We demonstrate for the first time contact resistance reduction using dielectric dipole mitigated Schottky barrier height (SBH) tuning on a FinFET source/drain. Different techniques for forming a SiO 2 /AlO x dipole layer are investigated using diodes. FinFETs, with contacts containing a SBH tuning dipole layer, are also presented. Reduction of the SBH by 100meV from the AlO x /SiO 2 dipole results in a 10Ω-μm 2 reduction in specific contact resistivity (ρ CO ) and a 100Ω-μm reduction in FinFET source/drain resistance (R S/D ). Larger reductions of ρ CO should be possible if chemically formed or atomic-layer deposited SiO 2 is used in the dipole layer instead of interfacial SiO 2 due to the larger SBH reduction (ΔSBH ~300meV) obtained from these oxidation methods. Contact formation without the need for silicide makes this technique very promising for emerging devices, alternative channel materials, and sub-22nm CMOSFETS.

We demonstrate for the first time Schottky barrier height (SBH) tuning using interfacial SiO2/high-kappa dipoles resulting in SBH <= 0.1 eV from the conduction band-edge (CBE) and SBH <= 0.2 eV from the valence band-edge (VBE). The near band-edge electron and hole SBHs have been obtained using a dielectric-dipole mitigated (DDM) scheme with single metal on Si junction. By optimizing the dielectric thickness, we obtained effective dipole modulation to the SBH of +0.5 and -0.3 eV for AlOx/SiO2 and LaOx/SiO2, respectively, demonstrating reductions in SBH and contact resistance that arc necessary for continued enhanced performance in future technology nodes.

Schottky barrier height tuning using high-κ/SiO2 interfacial dipoles is reported. Schottky barrier heights of 1.0 and 0.2 eV are observed in a TaN/p-Si diode by insertion of thin layers of high-κ (LaOx,AlOx) and SiO2 at the metal-semiconductor interface. The dipole tunes the effective work function of TaN/p-Si by more than 0.8 eV to achieve effective Schottky barrier heights near conduction and valence band edge. LaOx (n-type) and AlOx (p-type) have a dipole potential offsets estimated to be 0.3 and 0.5 V, respectively. Applications to lowering contact resistivity are discussed, as well as a comparison of other dipole offsets.

We examine the characteristics of TaLaN metal gates in direct contact with HfO2 dielectric, in particular focusing on the effect of La in the gate stack for NMOS applications. Effective work functions (EWF) and vacuum work functions (WF) are measured as a function of lanthanum content in TaLaN without any intentional heating using X-ray photoelectron spectroscopy, U-V photoelectron spectroscopy, and electrical C–V measurements. We find that the addition of lanthanum to tantalum nitride lowered both the EWF and the WF of the metal gate by ∼0.2eV and ∼0.9eV, respectively. Furthermore, XPS indicates that lanthanum in TaLaN at the interface with HfO2 is primarily bonded to nitrogen rather than oxygen and not reacting with the dielectric.

Omega gate type pFETs with SiGe shell-Si core are demonstrated that show 30% mobility enhancement for (110) oriented fins and 46% mobility enhancement for (100) oriented fins compared to Si omega gate devices. Performance improvement is demonstrated because of higher mobility and inherent epitaxial strain, while the external resistance in the two SiGe and Si omega FETs is comparable. Performance can further be improved by uniaxial compressive stress.

Using a presilicide implantation approach, we demonstrate that the Schottky barrier height (SBH) of NiSi/n-Si(100) can be modulated by doping a Si substrate with a halogen species such as chlorine. Activation energy measurements indicate that an ultralow barrier of 0.08 eV for NiS/n-Si can be achieved when a high dose (~1 times 10 15 cm 2 ) of chlorine is implanted prior to Ni silicidation. A secondary ion mass spectroscopy analysis on the presilicide Cl-implanted NiSi shows chlorine segregates at the interface with SBH tuning from 0.68 to 0.08 eV on n-Si and a corresponding increase in hole SBH on p-Si(100). The presilicide Cl-implanted NiSi film also demonstrates an enhanced thermal stability with a low sheet resistively of < 28 muOmega even up to 850degC.

We report the results of a systematic study to understand low drive current of Ge-based nMOSFET. The poor electron transport property is primarily attributed to the intrinsically low density of state and high conductivity effective masses. Results are supported by interface trap density (Dit) and specific contact resistivity (rhoc), which are comparable (or symmetric) for both n- and p-MOSFETs. Effective masses of electrons, which populate L valleys are large for conductivity and small for the density of states in conventional (100) [110] channel directions, resulting in low electron mobility and carrier concentration in Ge-based nMOSFETs.