Recombination effects with high-pressure Langmuir probes

With increasing ion density, the ion current collected by a negatively biased electric probe is eventually dominated by ions produced by reactive processes in the vicinity of the probe. Here, we derive an expression for the probe current to a cylindrical probe when all the ions collected to the probe are assumed to be generated within the sheath which surrounds the probe. Measurements of probe current in a seeded atmospheric-pressure flame are in good agreement with the theory. The significance of reaction processes is reinforced by the fact that the maximum probe current is found to be approximately three times the total current that the flame would produce with frozen chemistry, i.e. the saturation current.     

Nonlinear Dynamics of a Passively Mode-Locked Fiber Laser Containing a Long-Period Fiber Grating

We report on a numerical investigation of the nonlinear dynamics of a passively mode-locked fiber laser containing a long period fiber grating. The model is based on the normalized complex Ginzburg-Landau equation and the nonlinear coupled mode equations of the grating. The numerical results indicate the existence of passive mode-locking and autosoliton generation in the cavity of the laser. Both single and bound soliton pulse trains exhibit period doubling bifurcations and a route to chaos as the normalized saturated gain is increased. Furthermore, we show the presence of long period pulsation, soliton sidebands and possible coexisting attractors excited by multisoliton formation and soliton energy quantization.     

A lateral magnetotransistor structure with a linear response to themagnetic field

An experimental study and analytical model of a novel magnetotransistor are presented. This device displays some very promising features. A linear response to the magnetic field is experimentally demonstrated and very high sensitivities are measured, on the order of 3000%/T. Previous comparable magnetotransistors have reported sensitivities on the order of 150%/T. A theoretical explanation of the very high sensitivity is proposed, involving carrier deflection as the dominant operating principle     

A simulation study of long throw sputtering for diffusion barrierdeposition into high aspect vias and contacts

Modified sputtering techniques, such as long throw sputtering, collimation, and ionized sputtering, have been proposed to improve VLSI topography bottom coverage by narrowing the angular distribution of the sputter flux at the substrate and reducing subsequent flux shadowing at the bottom of topography. This paper first investigates a number of unique aspects involved in the simulation of long throw sputter systems. In particular, time importance of inhomogeneous film density and nonunity sticking coefficients are addressed. The second part of the paper presents a simulation study of long throw sputtering, providing a comparison to collimated and standard sputtering systems. The simulations are performed using the SIMSPUD/SIMBAD ballistic deposition tool. SIMSPUD is used to study film uniformity over a 300-mm wafer and to generate angular distributions at the center and edge of the wafer. The ability of SIMBAD to simulate directed sputtering systems is verified by direct comparison to Ti films deposited into oxide trenches. The importance of modeling the film microstructure is demonstrated by comparison between cross-sectional SEM's micrograph for evaporation and modeling results, such as long throw sputtering with a variety of substrate/target spacings, typical “standard” as well as “collimated” systems. SEM's of overhang structures and simulations are also presented to demonstrate nonunity sticking during the co-sputtering of TiW     

Algorithmic Approach for Thermal Port Definition

An algorithmic technique is presented that allows estimation of maximum temperature rise in a thermal model with component-board thermal interaction. The technique is based on a generalized thermal port grouping to estimate the interface temperature profile derived from coarse port assignments. By using a very simple environment, it takes a library-type thermal component model with many thermal ports included and transforms it by grouping thermal ports based on a temperature profile, allowing a minimal number of port groups to provide the same accuracy as the original model in a shorter time. The usefulness of this technique is illustrated through simulation of two thermal models with extreme nonuniform temperature distribution on the interface surface. The prediction accuracy is evaluated by comparison with the final solutions to numerical simulation.     

Breakdown voltage of a plasma-filled gap

The letter reports a series of measurements on the breakdown voltage of a two-electrode gap immersed in an arc plasma.     

Langmuir-probe measurement of electron temperature in a flowing high-density plasma

Measurements with cooled double probes in a propane-air flame show that the measured electron temperature and the floating voltage of the probes can be strongly affected by variation of the probe temperature. Simple theoretical considerations indicate that these effects arise from cooling of the plasma electrons by collisions with cold molecules in the hydrodynamic boundary layer surrounding the probe.     

The use of Langmuir probes in the study of high pressure plasmas

The theory of d.c. and transient probes in stationary and moving plasmas is discussed. The success (or otherwise) of theory in explaining experimental results obtained by many researchers working over a wide range of conditions is noted with the aim of enabling some assessment to be made of the feasibility of carrying out a given probe measurement.     

Simulation of elevated temperature aluminum metallization usingSIMBAD

A ballistic deposition model, SIMBAD, has been extended to simulate physical vapor deposition onto substrates at elevated temperatures. The model has been expanded to account for the effect of film curvature on surface diffusion. The effects on via coverage and filling have been simulated for aluminum films, and complete planarization of a 1:1 aspect ratio via is predicted for a temperature of 550°C. Via aspect ratio and sidewall taper can also strongly affect coverage and filling. Biased sputtering has also been incorporated into the model and shows that a primary effect is a substantial reduction in the temperature required to achieve full planarization. However, void formation and substrate damage are problems predicted to occur under some bias sputter conditions