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EXECUTIVE OVERVIEW In highly-scaled MOS devices, performance might be affected by individual atomic-scale features of the device structure, such as the position of the dopant atoms in the transistor channel [...]

EXECUTIVE OVERVIEW Recent advancement in high-k and metal gate (HK+MG) technology has allowed improvements in gate control owing to the aggressive scaling of equivalent oxide thickness (EOT), which has not […]

The information on the subtle local structural modifications around the Hf atom in HfO2high‐kdielectric stacks has been demonstrated to be crucial in determining the resulting electronic properties of the complementary metal oxide (CMOS) devices. In this work, using extended X‐ray‐absorption fine structure (EXAFS) spectroscopy, the local structural characterization of Hf‐based advanced gate stacks thin films were investigated. The thin film stacks used in this project are Al2O3capped HfO2thin films deposited on silicon substrates. EXAFS simulations and fits were applied to the data in order to extract crucial structural modifications on these films upon postdeposition annealing (PDA). The local crystal symmetry and coordination around the Hf atom were investigated under various annealing conditions. Specifically, in Hf‐based dielectric thin films on silicon substrates capped with Al2O3layers, the local crystal symmetry, and coordination around the Hf atom were investigated under various annealing conditions. The questions addressed are the effects of various annealing mechanisms to the diffusion mechanisms in the cap layers and modifications on the emerging local structures around the Hf atom. The diffusion of Al into HfO2films were monitored through the EXAFS simulations. The non‐linear least‐squares fitting to the EXAFS data revealed that the PDA in NH3(or N2) ambient after HfO2deposition had prevented Al diffusion to the HfO2layers.

Scaling of complementary metal oxide semiconductor devices is critical to enhancing performance and reducing the production cost of transistors. Conventional gate stack film systems consisting of a SiO2dielectric layer between the Si substrate channel and a doped polycrystalline silicon (poly-Si) gate electrode exhibited excessively high gate current leakage when the physical thickness of this traditional dielectric was scaled to Tphys?=?~2?nm. The rate of scaling was initially preserved by incorporating nitrogen to form an SiOxNyinsulator layer; however, this material soon experienced unacceptable levels of direct tunneling leakage current, which launched an industry-wide investigation of potential high dielectric constant (high-k) metal oxides as replacement materials for the SiO2based gate dielectric layer. Thermal stability requirements for the introduction of high-k dielectric materials necessitated the simultaneous replacement of poly-Si with a metal gate electrode due to several performance factors including unscalable threshold voltage. Although high-k/metal gate thermal stability has been demonstrated, significant challenges remain to be resolved for future technology nodes. This paper reviews the progress and challenges associated with the introduction of high-k/metal gate transistors, including threshold voltage tuning and gate dielectric thickness scaling, from a materials and process integration perspective.

Abstract: Long lengths of mono-and multifilament Ag-clad BSCCO superconductors were fabricated by the powder-in-tube technique. Critical current density (Jc) up to 12,000 A/cm2 has been achieved in an 850 m long multicore conductor. Long length conductors were formed into pancake-shaped coils by the wind-and-react approach. Test magnets were then fabricated by stacking the pancake coils and connecting them in series. The magnets were characterized as a function of applied magnetic field at various temperatures. A test magnet, fabricated with ≈770 m of BSCCO tape, generated fields of ≈1 T at 4.2K and ≈ 0.6 T at 27K, both in an applied background field of 20 T. Additionally, the strain tolerance of both mono-and multifilament conductors at 77K in 0.5 T applied field has been studied. We observed that multifilament conductors have better strain tolerance than monofilament tapes, retaining more than 90% of the initial critical current (at 0.5 T) with strain ≥1%.

Abstract: The advent of high-Tc superconducting tapes for a variety of applications has resulted in the need for superconducting joints. Although long-length tapes can be custom-made for some applications, interconnections between subcoils of a magnet or shorter-length conductors for coil winding and current leads, make the development of such joints imperative. Additionally, high-quality short-or medium-length conductors, which are easier to make, can be joined for improved performance. Employing a novel chemical etching technique, we have fabricated lap joints between short lengths of silver-clad BSCCO tapes. Each joint was formed by etching the silver away and bringing together the exposed superconductor cores of two tapes together. The joined tapes were then subjected to a series of thermomechanical treatments. Detailed microstructural and electrical characterization within and across the joint was performed. Critical currents of up to 37 A within the joint region and 10 A through the joint region(at 77K) have been achieved.

AbstractPb(Zr0.5Ti0.5)O3/RuO2thin film heterostructures were successfully grown on SiO2/Si(001) substrates using metal-organic chemical vapor deposition with a maximum processing temperature of 525°C. To form the heterostructures, (110)-textured RuO2electrode layers were first deposited on SiO2/Si(001) substrates at temperatures as low as 350°C at a typical grow rate of μΩ40Å/min. The resistivity of the RuO2films was 30–40 μΩ-cm. Plan-view transmission electron microscopy (TEM) and atomic force microscopy (AFM) showed that typical RuO2films had a grain size of 800–1000Å with surface roughness of 3–25 nm, respectively. Perovskite phase Pb(Zr0.5Ti0.5)O3(PZT) was then deposited at 525°C. The as-deposited films exhibited a dense, randomly-oriented crystal structure with a grain size of ∼800–1000Å. Using capacitors defined with Ag top electrodes, the film showed a remanent polarization of 21.5 μC/cm2and a coercive field of 39.0 kV/cm. The capacitors showed little fatigue up to ∼1010cycles. The as-deposited films exhibited high resistivity (1012-1013Ω-cm at 100 kV/cm). The current versus voltage characteristics show that the films have typical dielectric breakdown strengths of ∼60 V/μm with a sub-breakdown leakage current density of 5×10−5A/cm2.

Concerted physical and electrical characterization of the gate stacks, which includes high dielectric constant materials and metal electrodes, has been performed in order to link atomic defects to the specific device electrical characteristics. It has been shown that defects in the SiO2 layer formed at the interface of the dielectric stack and the substrate plays a critical role in defining both performance and reliability of the high-k devices.

An interface dipole model explaining threshold voltage (Vt) tuning in HfSiON gated n-channel field effect transistors (nFETs) is proposed. Vt tuning depends on rare earth (RE) type and diffusion in Si/SiOx/HfSiON/REOx/metal gated nFETs as follows: Sr < Er < Sc+Er < La < Sc < none. This Vt ordering is very similar to the trends in dopant electronegativity (EN, dipole charge transfer) and ionic radius (r, dipole separation) expected for a interfacial dipole mechanism. The resulting Vt dependence on RE dopant allows distinction between a dipole model (dependent on EN and r) and an oxygen vacancy model (dependent on valence).