Takashi Ando

Physical origins of mobility degradation in extremely scaled SiO2/HfO2 gate stacks with La and Al induced dipoles

We demonstrate metal-gate-induced interfacial layer (IL) scaling using a HfO2 dielectric and clarify the kinetics underlying this process. The intrinsic IL scaling effect on electron mobility is separated from La and Al-induced dipole effects. We find that the mobility degradation for La-containing high-κ dielectrics is not due to the La-induced dipole but due to the intrinsic IL scaling effect, whereas the Al-induced dipole brings about additional mobility degradation. This unique nature of the La-induced dipole enables aggressive equivalent oxide thickness scaling down to 0.42 nm without extrinsic mobility degradation when combined with IL scaling.

Temperature-dependent La- and Al-induced dipole behavior monitored by femtosecond pump/probe photoelectron spectroscopy

The impact of thermal budget on La- and Al-induced dipoles is systematically investigated by femtosecond pump/probe photoelectron spectroscopy. We find that the La-induced dipole requires annealing at 300u2009°C for complete activation, whereas the Al-induced dipole is activated at the lower temperature but requires annealing at 300u2009°C to eliminate a counteracting sheet charge. When La and Al atoms coexist on a SiO2 surface, the La-induced dipole becomes dominative after a silicate-forming reaction at the temperature above 600u2009°C. This phenomenon is attributed to the different natures of the La- and Al-induced dipoles, i.e., long-range and short-range.

A simple preparation of 1,3,5-triazine derivatives from 4-pyridones

Abstract The reaction of 4-pyridone or 4-quinolone with methyl or benzyl isocyanate in the presence of triethylamine or 1,1,3,3-tetramethylguanidine base gave the corresponding 1,3,5-triazine derivative (e. g., II) in a good yield via stepwise additions.

Total reactivity of pyridine and quinoline via the reactions of arylbenzoates with hydroxide ion. Apparent substituent constants for some N-heteroaromatic groups

Abstract A new set of apparent σ values was evaluated for the aza substitution of all positions in pyridyl and quinolyl groups on the basis of the alkaline hydrolysis of aryl benzoates. The enhanced reactivities of 4-pyridyloxy- and 4-quinolyloxy- groups were first estimated quantitatively.

Oxygen Transport in High-k Metal Gate Stacks and Physical Characterization by SIMS Using Isotopic Labeled Oxygen

Distribution and migration of oxygen in the highk/metal gate stack has a strong impact on the CMOS transistor electrical characteristics. Excess O can cause interlayer (IL) growth and subsequent increase of Equivalent Oxide Thickness (EOT), whereas O-vacancies induced by the metal gate contact may lead to unpredictable and feature size dependent shifts in threshold voltage (Vt). In addition to these phenomena, we have recently described a new migration pathway for O in poly-Si/TiN/TiO2-based high-k/stacks [1]. Besides re-growth of the bottom IL, excess O –released by the thermal decomposition of TiO2-based high-k stacks upon annealing– was observed to diffuse upwards, resulting in SiO2 growth at the TiN/poly-Si interface, as evidenced by regular SIMS analysis following the O main isotope. Here, we have employed SIMS depth profiling in combination with isotopic labeling –using minority Oisotope– to characterize the migration and/or redistribution of O in the high-k metal gate stack (HK/MG) at different stages of processing. Firstly, the creation of vacancy defects in high-k dielectrics –induced by the TiN-based metal gate contact upon high temperature annealing– is the most probable cause for large (~500 meV) Vt shifts, which is especially problematic for pFET devices. We have demonstrated that these shifts can be largely recovered after a lowtemperature low-pressure top-down oxygenation step on TiN metal gate exposed by poly-Si removal, while preventing excessive oxidation of TiN and parasitic IL regrowth [2]. Using SIMS, we have systematically investigated the incorporation of O by SIMS for different temperatures and TiN thicknesses on TiN-gated high-k films, subjected to top-down oxygenation with isotopic labeled O2, see Figure 1. We have thus established that incorporated O-doses –needed to remove the defects created in a metal-HfO2 contact– amount 1.4e14 to 3.9e14 at.cm. In addition, O-profiles after top-down oxidation show a small but significant shift with respect to pre-existing O towards the TiN-interface (see inset Figure 1). This implies that passivation of vacancies preferentially occurs in the top portion of the high-k layer, consistent with negligibly small oxide (IL) re-growth. Secondly, remote O-scavenging from the SiO2 interlayer (IL) using a poly-Si/doped TiN metal gate stack is a promising technique to achieve aggressive EOT scaling in a gate-first flow, compliant with 16 nm technology node requirements [3]. The remote scavenging mechanism is based on the presence of a metallic element M, inserted in the TiN metal gate at a certain separation from the high-k interface. This scavenging element is capable of scavenging O from the SiO2 IL upon poly activation anneal, as evidenced by TEM and conventional O-SIMS. Here, we have employed SIMS to determine the kinetics of O-scavenging from Hf-based high-k dielectric –enriched in O by isotopic exchange after high-k deposition upon low-temperature O2 exposure– towards M-TiN alloy for different annealing temperatures and IL’s. Use of an O-isotope enriched high-k layer allows following of O-redistribution through scavenging and isotopic exchange for different annealing temperatures, see Figure 2. This approach has revealed a subtle effect of IL composition on remote O-scavenging kinetics. In addition, rapid isotopic exchange between the different interfaces through the TiN metal gate is seen to occur upon high temperature anneal, indicating rapid Odiffusion in these stacks. These examples demonstrate the benefits of using O isotope labeling for SIMS analysis to resolve small quantities of O and to obtain fundamental knowledge on oxygen transport in high-k metal gate stacks.

Tinv Scaling and Gate Leakage Reduction for n-Type Metal Oxide Semiconductor Field Effect Transistor with HfSix/HfO2 Gate Stack by Interfacial Layer Formation Using Ozone?Water-Last Treatment

In this paper, we demonstrate a wet treatment for the HfSix/HfO2 gate stack of n-type metal oxide semiconductor field effect transistor (nMOSFET) fabricated by a gate-last process in order to scale down the electrical thickness at inversion state Tinv value and reduce the gate leakage Jg. As a result, we succeeded in scaling down Tinv to 1.41 nm without mobility or Jg degradation by ozone–water-last treatment. We found that a high-density interfacial layer (IFL) is formed owing to the ozone–water-last treatment, and Hf diffusion to the IFL is suppressed, which was analyzed by high-resolution angle-resolved spectroscopy.

α-tritium isotope effects in the menschutkin-type reaction with variable transition states

Abstract Secondary α-tritium isotope effects in the series of the Menschutkin-type reaction of benzyl benzenesulfonates with N,N -dimethylanilines were all small and varied only slightly; it was concluded that the transition states vary mainly in the parallel direction to the reaction coordinate.

Electronic nature of the aza substituent of pyridyl and quinolyl groups for reactivities in an insulated system

Abstract A new set of σ o values was determined for all positions of pyridyl and quinolyl groups, reliably excluding steric effect by perihydrogen, on the basis of the rates of the alkaline hydrolysis of substituted 2-methylbenzoates and pyridylmethyl and quinolylmethyl 2-methylbenzoates in 70% aq acetone.

Band-Edge High-Performance Metal-Gate/High-

A record high electron mobility (248 cm²/V middots at <i>E</i> _eff of 1 MV/cm) was obtained at <i>T</i> _inv of 1.47 nm, with a band-edge effective work function, by a Hf-Si/HfO₂ stack using gate-last process, resulting in <i>I</i> _ON of 1178 muA/mum (<i>I</i> _OFF of 100 nA/ mum ) at <i>V</i> _dd of 1.0 V for a 45-nm gate nMOSFET without strain-enhanced technology.

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Abstract The behavior of ion pairs in the trifluoroacetolysis of 2-arylethyl arenesulfonates was studied by means of tracer techniques with deuterium and oxygen-18.