Junction capacitance reduction due to self-aligned pocketimplantation in elevated source/drain NMOSFETs

A new advantage of an elevated source/drain (S/D) configuration to improve MOSFET characteristics is presented. By adopting pocket implantation into an elevated S/D structure which was formed by Si selective epitaxial growth and gate sidewall removal, we demonstrate that the parasitic junction capacitance as well as the junction leakage was significantly reduced for an NMOSFET while maintaining its good short channel characteristics. These successful results are attributed to the modification of the boron impurity profile in the deep S/D regions. The capacitance reduction rate, furthermore, was more remarkable as the pocket dose was further increased. This means that the present self-aligned pocket implantation is very promising for future MOSFETs with a very short gate length, where high pocket dosage will be required to suppress the short channel effect     

Transmission and attenuation of the dominant mode in uniformly bentcircular hollow waveguides for the infrared: scalar analysis

A numerical evaluation is conducted of electric field distributions, phase constants, and attenuation constants of the lowest eigenmode in the general class of uniformly bent circular hollow waveguides. The analysis is based on a scalar equation, and numerical results are compared with those of existing approximate theories. Normalized forms of attenuation constants are presented for the parallel and perpendicular polarizations to the bending plane by using structural and material parameters. For sharply bent waveguides, useful and simple expressions are derived for the attenuation constants of the TE and TM modes in the corresponding slab geometry with suitable weighting parameters     

Thin oxide films of silicon by high pressure oxidation

High pressure oxidation of silicon was performed at an oxidation temperature range of 650 to 800°C for thin oxide films with about 300 å thickness. The index of refraction was dependent on an oxidation temperature but independent of the oxidation pressure as 1.475 at 750°C. The dielectric breakdown strength of the oxide film was measured by the voltage ramping,method. The fixed oxide charge about 1.0 × 10¹¹ cm^?2 was also measured from the high frequency C-V measurement. The pulse scanning C-V measurement technique was used to measure the minority carrier generation rate in the depleted surface. The surface generation velocity was slightly dependent on the oxidation temperature and indicated that the fast surface states increased with decreasing oxidation temperature.     

Ho arrangement in the Zn6Mg3Ho icosahedral quasicrystal studied by atomic-resolution Z-contrast STEM

The atomic structure of the Zn6Mg3Ho icosahedral quasicrystal has been studied by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) with Z-contrast (Z: atomic number). We demonstrate that in particular Z-contrast imaging is quite powerful for specifying heavy atom positions in the quasicrystalline compound, as shown by a comparison with high-resolution phase-contrast imaging. It is confirmed that the observed Z-contrast images are fairly well explained by the projected potential of only the Ho atomic arrangement, which was recently proposed by X-ray diffraction analysis; Ho occupies an even-body-center site of the 3-dimensional Penrose lattice. Consequently, the present direct structural observation strongly supports the validity of the proposed Ho site.     

Cubic GaN/AlGaN Schottky-barrier devices on 3C-SiC substrates

In this work, we focus on the fabrication of cubic GaN based Schottky-barrier devices (SBDs) and measured current voltage (I-V) characteristics and the critical field for electronic breakdown. Phase-pure cubic GaN and c-Al_xGa_1 − xN/GaN structures were grown by plasma assisted molecular beam epitaxy (MBE) on 200 μm thick free-standing 3C-SiC (1 0 0) substrates, which were produced by HOYA Advanced Semiconductor Technologies Co., Ltd. The thickness of the c-GaN and c-Al_0.3Ga_0.7N epilayers were about 600 and 30 nm, respectively. Ni/In Schottky contacts 300 μm in diameter were produced on c-GaN and c-Al_0.3Ga_0.7N/GaN structures by thermal evaporation using contact lithography. A clear rectifying behavior was measured in our SBDs and the I-V behavior was analyzed in detail, indicating the formation of a thin surface barrier at the Ni-GaN interface. Annealing of the Ni Schottky contacts in air at 200 °C reduces the leakage current by three orders of magnitude. The doping density dependence of breakdown voltages derived from the reverse breakdown voltage characteristics of c-GaN SBDs is investigated. The experimental values of breakdown voltage in c-GaN are in good agreement with theoretical values and show the same dependence on doping level as in hexagonal GaN. From our experimental data, we extrapolate a blocking voltage of 600 V in c-GaN films with a doping level N_D = 5 × 10¹⁵ cm⁻³.     

Ultrahigh-speed HEMT LSI technology for supercomputer

The current status of high electron mobility transistor (HEMT) technology at Fujitsu for high-performance VLSI is presented, focusing on device performance in the submicrometer dimensional range and the HEMT LSIs implemented in supercomputer systems. The HEMT is a very promising device for ultrahigh-speed LSI/VLSI applications because of the high-mobility GaAs/AlGaAs heterojunction structure. A 1.1 K-gate bus-driver logic LSI has been developed to demonstrate the high-speed data transfer in a high-speed parallel processing system at room temperature, operating at 10.92 GFLOPS. A cryogenic 3.3 K-gate random number generator logic LSI with maximum clock frequency of 1.6 GHz has also been developed to demonstrate the high-clock-rate system operations at liquid-nitrogen temperature. For VLSI level complexity, a HEMT 64-kb static RAM with 1.2-ns access operation and a 45 K-gate gate array with 35-ps logic delay have been developed operating at room temperature, demonstrating the high performance required for future high-speed computer systems     

Changes in the surface structure of the hamster sperm head associated with maturation, in vitro capacitation and acrosome reaction: an atomic force microscopic study

Structural changes of the hamster sperm head surface associated with maturation, capacitation and acrosome reaction were examined by atomic force microscopy. Spermatozoa were taken from the initial segment and distal cauda of the epididymis, washed in a modified Tyrode solution and fixed by glutaraldehyde. Some sperms taken from distal cauda epididymides were incubated with the capacitation medium before fixation. All samples were attached on the glass slide, dried in a critical point drier and observed by atomic force microscopy. The sperm head surface was characterized by the presence of numerous round particles, approximately 40 and 60 nm in diameter. The distribution and density of these particles on the sperm surface were significantly different between the equatorial segment and post-acrosomal region in each sperm, and also between sperms under different conditions. The surface of the equatorial segment was rather smooth in sperms from the initial segment of the epididymis, but had many large (60 nm) particles in sperms from the distal cauda epididymides, suggesting that the large particles were glycoproteins which were secreted from the epididymis and attached to the sperm surface during maturation. The number of these particles dramatically decreased in both capacitated acrosome-unreacted and acrosome-reacted sperms. This finding supports the idea that glycoproteins are removed from the sperm surface during capacitation. Atomic force microscopic studies of the sperm head surface are expected to be used for future molecular studies on the cell surface components involved in the mechanism of maturation, capacitation and acrosome reaction.     

Spectroscopic and Photoluminescent Properties of Indium Zinc Oxide (IZO) and IZO/Ag/IZO Sandwiched Film

We report the ellipsometric and photoluminescence (PL) properties of Indium zinc oxide (IZO) films, which were grown by radio frequency sputtering under Ar and O₂ atmospheres. IZO films grown under an O₂ atmosphere (IZO (O₂)) showed enhanced PL properties when compared to the films grown under an Ar atmosphere (IZO (Ar)), particularly with respect to the band-edge emission. The enhancement of band-edge emission can be attributed to the reduction in the non-emissive defect states related to oxygen vacancies, which were repaired by sputtering under O₂ atmosphere, whereas the PL enhancement in green region is probably due to the formation of the different types of defects under the excess oxygen environment. This was also supported by the results of time-resolved PL measurements, where the band-edge emission of IZO (Ar) showed rapid decay with a 50 ps lifetime, which indicates the dominance of the relaxation pathway to underlying defect states. In contrast, the PL decay profiles of IZO (O₂) for band-edge and emissive defect states showed moderate decay with time-constants of 2.3 ns and 5.7 ns, respectively. The exciton relaxation dynamics were sensitive to the presence and its kinds of defect states, which were controlled by the growth conditions.     

Ferroelectric and Magnetic Properties in Room‐Temperature Multiferroic GaxFe2−xO3 Epitaxial Thin Films

GaFeO₃‐type iron oxide is a promising room‐temperature multiferroic material due to its large magnetization. To expand its usability, controlling the ferroelectric and magnetic properties is crucial. In this study, high‐quality Ga_xFe_2–xO₃ (x = 0–1) epitaxial films are fabricated and their properties are systematically investigated. All films exhibit room‐temperature out‐of‐plane ferroelectricity, showing that the coercive electric field (E_c) decreases monotonically with x. Additionally, the films show in‐plane ferrimagnetism with a Curie temperature (T_C) >350 K at x = 0–0.6. The coercive magnetic field (H_c) decreases with x at x ≤ 0.6, but shows a constant value at x > 0.6, whereas the saturated magnetization (M_s) increases with x at x ≤ 0.6, but decreases with x at x > 0.6. X‐ray magnetic circular dichroism reveals that the large magnetization at x = 0.6 is derived from Fe³⁺ (3d⁵) at octahedral sites. The controllable range of the E_c, H_c, and M_s values at room temperature (400–800 kV cm^?1, 1–8 kOe, and 0.2–0.6 µ_B/f.u.) is very wide and differs from those of well‐known multiferroic BiFeO₃. Furthermore, the Ga_xFe_2?xO₃ films exhibit room‐temperature magnetocapacitance effects, indicating that adjusting T_C near room temperature is useful to achieve large room‐temperature magnetocapacitance behavior.     

A 146-mm/sup 2/ 8-gb multi-level NAND flash memory with 70-nm CMOS technology

An 8-Gb multi-level NAND Flash memory with 4-level programmed cells has been developed successfully. The cost-effective small chip has been fabricated in 70-nm CMOS technology. To decrease the chip size, a one-sided pad arrangement with compacted core architecture and a block address expansion scheme without block redundancy replacement have been introduced. With these methods, the chip size has been reduced to 146 mm/sup 2/, which is 4.9% smaller than the conventional chip. In terms of performance, the program throughput reaches 6 MB/s at 4-KB page operation, which is significantly faster than previously reported and very competitive with binary Flash memories. This high performance has been achieved by the combination of the multi-level cell (MLC) programming with write caches and with the program voltage compensation technique for neighboring select transistors. The read throughput reaches 60 MB/s using 16I/O configuration.