3-D device modeling for SRAM soft-error immunity and tolerance analysis

Soft-error tolerance of static random-access memory (SRAM) devices has been predicted by using three-dimensional (3-D) and time-dependent device simulation in conjunction with circuit simulation. An inverter model developed for 3-D device simulation is described, along with the analysis of the inverters device response as a function of time. The output thus obtained was applied as an input voltage source in circuit simulation of unit SRAM cell and the stability of this bistable circuit is studied on that basis. The effects on soft-error immunity of changes in alpha-particle injection conditions and in load resistance and capacitance are described. The validity of the presented model is examined through comparison of the bit-error-rate dependence on incident angle of alpha particles to that of measured rates. To simulate the angular dependence, we introduce statistical distribution models for alpha-particle energy, position of incidence on the device surface, and angle of incident. Results of device/circuit simulation carried out with many sets of energy, position, and angle are presented. Reasonable agreement between results of simulation and experimental data without the use of adjustment parameters is demonstrated. A map of soft-error tolerance on the CR plane with critical charge Q/sub c/ as a parameter is presented and its derivation explained. An analytic expression for the tolerance is clarified by proposing an equivalent circuit model for the simulation of alpha-particle injection at the output node in an inverter circuit. Inverter modeling is shown to be essential to obtaining SRAM soft-error tolerance to high degrees of accuracy.     

High-efficiency drive due to power factor control of a permanentmagnet synchronous motor

A drive system of a permanent magnet motor without a magnetic position detector is described. Generally, the position data of a magnet is obtained from the terminal voltage of the motor. In the newly developed method, the inverter DC-link current waveform provides the control signal for driving a permanent magnet motor without a detector. Since the power factor of the motor is controlled around 1.0, the motor runs at a higher efficiency than one controlled by the conventional method. Therefore, this control method saves energy. Current pulsation induced by sudden load fluctuations has been studied and its stabilization has been achieved. This paper provides the principle and operation of the new control method, simulated characteristics, and experimental results     

A new self-alignment technology using bridged base electrode forsmall-scaled AlGaAs/GaAs HBT's

The fabrication and characterization of a new self-aligned HBT utilizing bridged base-electrode technology (BBT) are presented. This new technology simplifies the fabrication process and relaxes the limitations in device size scaling, thus decreasing the emitter size to 1 μm×1 μm. In spite of a large junction periphery area ratio, a good current gain of more than 10 is obtained in an HBT with an emitter size of 1 μm×1 μm. A series of fabricated HBTs shows excellent high-speed performance. The highest values of f_T =90 GHz and f_max=63 GHz are obtained in an HBT with an emitter size of 1 μm×5 μm. The realization of HBTs with small emitters and excellent high-frequency characteristics demonstrates the effectiveness of this new technology     

Chemicals influencing maturation, activation, and degeneration of bovine oocytes in culture

The effects of the dibutyryl cyclic adenosine 3',5'-monophosphate, calmodulin antagonist W7, and ovarian glycosaminoglycans on polar body extrusion, "nucleus" formation, and segmentation of bovine oocytes were examined in vitro. Dibutyryl cyclic adenosine 3',5'-monophosphate (100 microM) accelerated the extrusion of first polar body; however, W7 (20 microM) suppressed the formation of the first polar body. Spontaneous "nucleus" formation resembling pronucleus formation in oocytes was accelerated in the presence of dibutyryl cyclic adenosine 3',5'-monophosphate at concentrations of greater than 20 microM. The spontaneous segmentation, which is a degenerative change, was suppressed in the presence of bovine follicular fluid-glycosaminoglycans at concentrations of 250 micrograms/ml or greater. These results may indicate that maturation, activation, and degeneration of bovine oocytes in culture are modulated by dibutyryl cyclic adenosine 3',5'-monophosphate, W7, and ovarian glycosaminoglycans.     

Analysis of electron range versus energy relationship of insulators in low-voltage scanning electron microscopy

A theoretical analysis is made concerning the question of whether or not an insulator's surface is observable without the unstable disturbance due to negative charge-up in the secondary electron mode of a low-voltage scanning electron microscope. Introducing a simple modification into the elementary theory of secondary electron emission from solid materials, the threshold condition as to observability is formulated as a function of the energy E_p and the incident angle ?_p of the primary beam. It is shown that for insulators the material's constant n, which appears in the standard formula of the electron range (R) versus energy (E_p) relationship R Φ E, can be determined through experimental investigations into observability of the surface. Careful consideration is also given to the effectiveness of the present theoretical analysis.     

Calculations of positron states in BEDT-TTF based organic superconductors

We have calculated positron distributions on a series of BEDT-TTF based organic conductors, whose anion species are I₃, Cu(NCS)₂, Cu(CN)[N(CN)₂], Cu[N(CN)₂]Br and KHg(SCN)₄. The results are discussed in connection with Fermiological studies by the positron annihilation method. Lifetimes and band masses of positrons have been calculated also.     

Levels of thermostable direct hemolysin production by Vibrio parahaemolyticus strains carrying both tdh and trh genes

One hundred and twenty-five strains of Vibrio parahaemolyticus carrying both the tdh and trh genes were selected from the strains isolated from the travelers with diarrhea by an hybridization test using polynucleotide probes. The levels of TDH produced by these strains and the association between the TDH levels and related characteristics in these strains were analyzed. The TDH level varied greatly from strain to strain, but none of the levels was as high as that of the typical Kanagawa phenomenon-positive strains. The strains were classified into "TDH producer" (18 strains), "Low-level TDH producer" (85 strains), and "No TDH producer" (22 strains) based on the results of a modified Elek test and the hemolysis assay on Wagatsuma agar. The highest TDH level achieved by the "TDH producer" was twofold lower than that of the Kanagawa phenomenon-positive strains as assayed by the RPLA method. All strains possessed the toxR gene. The trh1 and trh2 genes were detected in, respectively, 105 and 20 strains, and no correlation existed between the type of the trh gene and the levels of TDH produced. Considerable restriction fragment length polymorphism was observed with the tdh gene-bearing HindIII DNA fragment in different strains, but it was not related with the TDH level.     

Rapid Crystallization of Levitated and Undercooled Semiconducting Material Melts

Using a CO₂ laser-equipped electromagnetic levitator, we carried out the containerless crystallization of Si and Ge. From the point of interface morphologies, the relation between growth velocities and undercoolings was classified into three regions. In regions I and II, although the morphologies of growing crystals are different: plate-like needle crystals in region I and facetted dendrite at region II, the growth velocities in these two regions are fundamentally scaled by the thermal diffusivities and the temperature increase caused by the release of the latent heat. This result means that the growth velocity can be expressed by the product of the thermal diffusivity and the growth kinetics. An analysis of the dendrite morphologies revealed that the kinetics of crystal growth in regions I and II represent two-dimensional nucleation at the reentrant corner formed at the edge of the two parallel twins. In region III, thermal diffusion-controlled interface attachment kinetics control as described by a modified Wilson?CFrenkel model.     

Universal-Vdd 0.65-2.0-V 32-kB cache using avoltage-adapted timing-generation scheme and a lithographicallysymmetrical cell

A universal-V_dd 32-kB four-way-set-associative embedded cache has been developed. A test cache chip was fabricated by using 0.18-μm enhanced CMOS technology, and it was found to continuously operate from 0.65 to 2.0 V. Its operating frequency and power are from 120 MHz and 1.7 mW at 0.65 V to 1.04 GHz and 530 mW at 2.0 V. The cache is based on two new circuit techniques: a voltage-adapted timing-generation scheme with plural dummy cells for the wider voltage-range operation, and use of a lithographically symmetrical cell for lower voltage operation