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Low Vt Ni fully silicided (FUSI) devices are demonstrated making use of Al implantation for pMOS and Yb or Yb+P implantation for nMOS combined with Ni-silicide phase engineering. When Yb(+P) and Al implantation are followed by a high temperature anneal, significant segregation of Yb or Al toward the Ni-FUSI/SiON interface is observed and large Vt shifts of 450 mV (330 mV) and 200 mV are obtained for nMOS NiSi FUSI/SiON devices and pMOS Ni-rich FUSI/SiON devices, respectively, as compared to the undoped reference devices. The Vt shifts are preserved down to the shortest gate lengths. For both Al and Yb, the Vt shifts are explained by the dopants reacting with and modifying the dielectric. Thus, the low Vt dual implantation approach proposed achieves a low-cost "dual dielectric" implementation without the need of dual deposition of dielectrics or capping layers. In the case of Yb implantation followed by a high temperature anneal, a significant reduction in the inversion dielectric thickness is observed, indicating that the reaction between Yb and SiON results in the formation of a high-κ dielectric. The Yb diffusion and reaction at the interface can be engineered using a P complaint. [ABSTRACT FROM AUTHOR]

Metal-insulator-metal capacitors with SrxTiyOz (STO) dielectric films on TiN, Ru, and RuOx bottom electrodes with TiN top electrodes were studied. Metastable perovskite STO films with compositions in the Sr/(Sr+Ti)∼54-64 at. % range were obtained by crystallization at 600 °C in N2 of dielectric stacks grown by atomic layer deposition consisting of Sr-rich STO films [Sr/(Sr+Ti)∼64 at. %] on thin interfacial TiOx layers. The significant decrease in equivalent oxide thickness (EOT) and STO lattice parameter observed with increasing TiOx thickness indicates full intermixing of the TiOx and STO layers during the crystallization anneal, which results in the formation of an STO layer with higher Ti content and higher dielectric constant. The Sr-rich STO on TiOx stacks crystallize with small grain size, favorable for low leakage (JG). A significant improvement in JG for e-injection from the bottom electrode is obtained when using RuOx, as compared to TiN or Ru. A milder JG improvement with RuOx bottom electrode is also seen for e-injection from the top TiN electrode, indicating that higher quality perovskite STO films are formed on RuOx, or equivalently, that their trap density is lower. We propose oxygen scavenging from the STO by TiN or Ru electrodes, eliminated or reversed when using RuOx, as an explanation for the improvement. Using an optimized RuOx/TiOx/STO/TiN stack we obtained leakage of 10-7 A/cm2 (at 0.8 V) and 0.4 nm EOT. [ABSTRACT FROM AUTHOR]

Metastable perovskite SrxTiyOz (STO) films were formed over a wide composition range by crystallization of layers grown by atomic layer deposition. An expansion of the lattice, decrease in permittivity and mild increase in band gap are observed with increasing Sr content. Sr-rich films [Sr/(Sr+Ti)∼62 at. %] show significant improvement in leakage current at low equivalent oxide thicknesses (EOT) as compared to stoichiometric films (Sr/(Sr+Ti) ∼50 at. %). TiN/STO/TiN capacitors with leakage ∼10-6 A/cm2 at 1 V were obtained at 0.6 nm EOT for crystalline Sr-rich STO. The difference in leakage behavior was found to correlate with different microstructures developed during crystallization. [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 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]

The CMOS integration of dual work function (WF) phase-controlled Ni fully silicided (FUSI) gates on HfSiON was investigated. For the first time, the integration of NiSi FUSI gates on n-channel MOS (NMOS) and Ni31Si12 FUSI gates on p-channel MOS (PMOS) with good Vt control to short gate lengths (LG = 50 nm, linear Vt of 0.49 V for NMOS, and -0.37 V for PMOS) is demonstrated. A poly-Si etch-back step was used to reduce the poly-Si height on PMOS devices, allowing for the linewidth-independent formation of NISi on NMOS and Ni-rich silicides on PMOS with a two-step rapid thermal processing (RTP) silicidation process. The process space for the scalable formation of NiSi on NMOS and Ni2Si or Ni31Si12 on PMOS devices was investigated. It was found that within the process window for linewidth-independent NiSi FUSI formation on 100-nm poly-Si NMOS devices, it is possible to control the silicide formation on PMOS devices by adjusting the poly-Si etch-back and RTP1 conditions to obtain either Ni2Si or Ni31Si12 FUSI gates. A reduction in the PMOS threshold voltage of 90 mV and improved device performance (18% Ion improvement at Ioff = 100 nA/µm) was obtained for Ni31Si12 compared to Ni2Si FUSI gates, as well as a Vt reduction of 350 mV when compared to a single WF flow using NiSi FUSI gates on PMOS. [ABSTRACT FROM AUTHOR]

Short gate-length Pt full-silicidation (FUSI) (PtSi and Pt2Si) pMOSFETs were fabricated for the first time using a self-aligned Pt-FUSI process, demonstrating scalability (with no linewidth effects) down to ∼ 60-nm gate lengths. The electrical results are compared to the Ni-FUSI (NiSi and Ni31Si12) pMOSFET devices. A low threshold voltage ≤ ∣ -0.29 V∣ was obtained for the Pt2Si-FUSI pMOSFETs on SiON and HfSiON indicating that the Pt2Si FUSI does not suffer from the Fermi-level pinning or gate-dielectric-charge effects on the HfSiON. [ABSTRACT FROM AUTHOR]

A complete determination of the effective work functions (WF) of NiSi Ni2Si, Ni31Si12 and Ni3Si on HfSiON and on SiO2 is presented. Conditions for formation of fully silicided (FUSI) gates for NiSi2, NiSi, Ni3Si2, Ni2Si, Ni31Si12 and Ni3Si crystalline phases were identified. A double thickness series (HfSiON/SiO2) 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 SiO2. While all Ni-rich silicides have adequate WF for pMOS applications, Ni2Si 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 Ni2Si and Ni31Si12 FUSI HfSiON pMOSFETS. [ABSTRACT FROM AUTHOR]

The presence of Ni can significantly promote the CoSi–CoSi2 transformation process reducing the transformation temperature and, in consequence, the thermal budget of silicidation. In this work, silicidation of the Si/Co0.95Ni0.05/Ti system was investigated. Four point probe (4PP), Auger electron spectroscopy (AES), X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), and transmission electron microscopy (TEM) were used to characterise the silicide films. It was found that Co–Ni silicide can be formed at lower temperatures compared to the pure Co/Ti process, at the same time keeping important properties such as sheet resistance and roughness close to those of pure CoSi2. [Copyright &y& Elsevier]

The present investigation was designed to assess the effects of strips made of different materials on the recovery of enzymes in gingival crevicular fluid (GCF) (Experiment 1), and to examine a possible relationship between lysosomal enzyme activities and number of crevicular polymorphonuclear leukocytes (PMNs) (Experiment 2). In Experiment 1, GCF was collected with capillaries from 14 patients with periodontal disease, and applied on various test strips in microcentrifuged tubes or directly into tubes (controls). Strips were then shaken and centrifuged to elute GCF enzymes. The supernate was used for determinations of alkaline phosphatase (ALP), beta-glucuronidase (BG) and aspartate aminotransferase (AST) activities. The % recoveries were calculated as relative percentages to controls. When using saline as eluent, 90% or more ALP, BG and AST were found to be recovered from strips of durapore and papers. More than 35% of ALP and BG was found to remain on paper points. However, the % recoveries from paper points were improved using eluent with 0.1% (w/v) cetyl pyridinium chloride. In Experiment 2, 54 GCF samples were collected from 3 periodontitis patients by using durapore strips, in order to measure both PMN numbers and BG activities in the same samples. The 2 parameters showed strong and positive correlation with 0.847 (p < 0.001) of the Pearson's correlation coefficient. These findings suggest that durapore is a useful material not only for counting PMNs but also for measuring activities of GCF enzymes. Elevation of BG activities in GCF can be due to increasing numbers of PMNs.