Search

We present a dark current analysis in waveguide-coupled germanium vertical p-i-n photodetectors. In the analysis, a surface leakage current and a bulk leakage current were separated, and their activation energies were extracted. The surface leakage current originating from the minority carrier generation on the Ge layer sidewalls, governed by the Shockley-Read-Hall process and enhanced by the trap-assisted-tunneling process, was identified as the main contribution to the dark current of vertical p-i-n photodiodes at room temperature. The behavior of this surface leakage current as a function of temperature and reverse bias voltage is well reproduced by using the Hurckx model for trap-assisted-tunneling. [ABSTRACT FROM AUTHOR]

A significant difference in the magnitude of the threshold voltage (Vt) reduction achieved by lanthanum oxide (La2O3) incorporation in ultra-thin dielectrics is observed for TaCx and TaCxNy electrodes. This is explained by dielectric consumption resulting from the thermodynamically unstable TaCx electrode, which gives rise to electrically active oxygen vacancies in the high-permittivity dielectric. We report extensively on the presence and origins of an aberrant negative Vt shift during positive bias temperature instability stressing and, conversely, a positive shift during negative bias temperature instability stressing for La2O3 capped HfSiON dielectrics observed for TaCx electroded films, not seen for the TaCxNy case. Although, oxygen vacancies are inherent due to the differences in electronic configuration between lanthanum and hafnium, this effect is exacerbated by the electrode instability, which is reflected in the Vt dependence. [ABSTRACT FROM AUTHOR]

Carrier lifetimes in Ge-on-Si waveguides are deduced using time-resolved infrared transmission pump-probe spectroscopy. Dynamics of pump-induced excess carriers generated in waveguides with varying Ge thickness and width is probed using a CW laser. The lifetimes of these excess carriers strongly depend on the thickness and width of the waveguide due to defect assisted surface recombination. Interface recombination velocities of 0.975×104 cm/s and 1.45×104 cm/s were extracted for the Ge/Si and the Ge/SiO2 interfaces, respectively. [ABSTRACT FROM AUTHOR]

The mechanism governing threshold voltage (Vt) modulation in NiSi/SiON n-channel metal-oxide-semiconductor field-effect transistors when doping with rare-earth elements (dysprosium or Dy in this work) is studied. In addition to the widely reported interface dipole theory, this letter provides additional evidence that the bulk trapping charges (related to the unintermixed Dy2O3 layer after device fabrication) can play an important role in determining the device Vt for the above-mentioned gate stacks. It is thus suggested that a careful design of the capping layer thickness and the thermal budget for intermixing the capping layer with host dielectrics is necessary to eliminate the impact from bulk trapping charges to the device performance. [ABSTRACT FROM AUTHOR]

The kinetics of Ni3Si2 formation in the Ni2Si–NiSi thin film reaction were determined from simultaneous in situ x-ray diffraction (XRD) measurements, performed using a synchrotron source, and sheet resistance measurements. Samples consisted of 90 nm Ni/100 nm polycrystalline-Si/SiO2 stacks, of interest for fully silicided gate applications, on (100) Si. After initial formation of a Ni2Si/NiSi bilayer, these films reacted to form Ni3Si2. The evolution of sheet resistance and of the intensity of XRD peaks were used to extract the fraction of Ni3Si2 formed during ramp and isothermal annealings. A Kissinger analysis was performed for ramp annealing with ramp rates of 1, 3, 5, 9, and 27 °C/s, obtaining the activation energy of Ni3Si2 formation, Ea=1.92±0.15 eV. A Kolmogorov-Johnson-Mehl-Avrami analysis was performed for isothermal anneals, finding an Avrami exponent of 2.1±0.2, suggesting two-dimensional growth. This is consistent with a nucleation controlled process for Ni3Si2 formation, with nucleation sites at different positions in the thin film, and subsequent lateral two-dimensional propagation of the transformation front parallel to the film surface. Implications for Ni fully silicided gate applications are discussed. [ABSTRACT FROM AUTHOR]

The Ni/polycrystalline-Si thin film reaction was monitored by in situ x-ray diffraction during ramp annealings, obtaining a detailed view of the formation and evolution of silicide phases in stacks of interest for fully silicided gate applications. Samples consisted of Ni (30–170 nm)/polycrystalline-Si (100 nm)/SiO2 (10–30 nm) stacks deposited on (100) Si. The dominant end phase (after full silicidation) was found to be well controlled by the deposited Ni to polycrystalline-Si thickness ratio (tNi/tSi), with formation of NiSi2 (∼600 °C), NiSi (∼400 °C), Ni3Si2 (∼500 °C), Ni2Si, Ni31Si12 (∼420 °C), and Ni3Si (∼600 °C) in stacks with tNi/tSi of 0.3, 0.6, 0.9, 1.2, 1.4, and 1.7, respectively. NiSi and Ni31Si12 were observed to precede formation of NiSi2 and Ni3Si, respectively, as expected for the phase sequence conventionally reported. Formation of Ni2Si was observed at early stages of the reaction. These studies revealed, in addition, the formation of transient phases that appeared and disappeared in narrow temperature ranges, competing with formation of the phases expected in the conventional phase sequence. These included the transient formation of NiSi and Ni31Si12 in stacks in which these phases are not expected to form (e.g., tNi/tSi of 1.7 and 0.9, respectively), at temperatures similar to those in which these phases normally grow. [ABSTRACT FROM AUTHOR]

The Ni silicidation of polycrystalline-Si/SiO2 gates with 25 nm linewidth was studied by x-ray diffraction and compared to that of blanket films. The authors found direct evidence of a linewidth effect in Ni full silicidation (FUSI), with formation of Ni-richer silicides at short gate lengths, and attribute it to the excess availability of Ni from regions surrounding the gate. On blanket films, the end silicide phase can be controlled by the deposited Ni (tNi) and polycrystalline-Si (tSi) thicknesses (e.g., tNi/tSi∼0.55, 1.09, 1.37, and 1.64 for stoichiometric NiSi, Ni2Si, Ni31Si12, and Ni3Si, respectively). In contrast, they demonstrate that on 25 nm lines, the resulting films can contain Ni31Si12 and Ni3Si even for deposited tNi/tSi as low as 0.6. They found, however, that the phase formation sequence and required thermal budgets were similar on 25 nm lines (tNi/tSi∼0.6 and 1.2) to those on blanket films with thicker Ni (tNi/tSi∼1.7). This suggests that the nucleation and phase formation kinetics of Ni silicides, including Ni31Si12 and Ni3Si, are not significantly affected by the small dimensions. They also demonstrated NiSi FUSI phase control down to 25 nm, by controlling the reacted Ni to Si ratio through the reaction thermal budget. These results indicate that Ni FUSI is an attractive option for future nodes. [ABSTRACT FROM AUTHOR]

The effective work function (WF) of Ni3Si2 was evaluated on HfSixOy and SiO2 dielectrics. Ni3Si2 forms, in thin film Ni–Si diffusion couples with Ni to Si composition ratios between 1 and 2, after formation of a Ni2Si/NiSi stack and by its reaction at moderate thermal budgets (comparable to those used in back end processing of complementary metal-oxide-semiconductor circuits). Ni3Si2 formation limits, on the Ni-rich side, the process window for NiSi fully silicided (FUSI) gates (NiSi at interface with dielectric) to reacted Ni–Si ratios <1.5. The WF of Ni3Si2 was found to have similar values and behavior to that of NiSi, both on SiO2 (showing similar modulation with dopants) and on HfSixOy, in contrast to Ni-richer silicides such as Ni2Si and Ni31Si12 which do not exhibit significant WF modulation with dopants on SiO2 and have considerably higher WF on HfSixOy. This suggests that the chemistry and structure of the original NiSi/dielectric interface are not modified significantly by the subsequent growth of Ni3Si2 and implies that its formation may be tolerable when targeting NiSi FUSI gates, thereby expanding the process window for this application. [ABSTRACT FROM AUTHOR]

Co-implantation schemes for sub-65 nm n-type extension formation have been explored. These included phosphorous (P) and arsenic (As) implants into crystalline Si as well as combinations using higher energy silicon pre-amorphization implant (PAI) steps together with low energy carbon (C) implantation. Dopant energies were varied between 500 eV and 1 keV, with C dose of1×1015 cm-2 and P and As doses of 7×1014 cm-2. The anneal step was a fast ramp-up and ramp-down spike at 1050 °C. Comparisons with dopant-only implants or with PAI and dopant only showed these two schemes to give deeper, more gradual and less well activated junctions than when combined with C. The best result was obtained using a 25 keV Si PAI, 6 keV C and 1 keV P, resulting in a junction depth of 20.5 nm at 1×1019 cm-3, and Rs=318 Ω/□ and a 3 nm/dec trailing slope. [ABSTRACT FROM AUTHOR]

We show how Newton's rings manifest themselves in near-field scanning optical microscopy and discuss how this effect can be used with topographic imaging to measure correlated roughness of thin films. In conventional optics, transmission through a thin nonabsorbing film depends on film thickness when multiple reflections from the film boundaries are coherent. Measurements and modeling of the transmission through thin films illuminated by a near-field probe show that these oscillations are present despite the large distribution of transverse wave vectors needed to describe light from the probe. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]