摘要:

This paper describes film deposition rates for rf planar magnetron sputtering when the magnetic field parallel to the target surface is varied. Magnetic‐field strength is a key parameter to control deposition rate in rf magnetron sputtering but applying a high magnetic field does not increase the deposition rate. Self‐bias voltage also decreases as the target magnetic field increases and plasma impedance involving the ion sheath region and glow discharge region is inductive. Plasma impedance measurements lead to the conclusion that a deteriorated deposition rate in the high magnetic field occurs due to decreased self‐bias voltage resulting from an increased sheath capacitance.

ISSN:0021-8979    

DOI:10.1063/1.347133

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Resonance‐enhanced multiphoton ionization spectroscopy has been applied to the problem of detection of gas‐phase species in a dense particle‐forming flow. Relative silicon atom profiles in an atmospheric pressure flame reactor producing silica particles have been made using a 2+1 ionization scheme. The results have shown that silicon atoms are confined to a very narrow time window in the reactor (<15 ms). In addition, the nonresonant background indicated the presence of ionizable clusters and could be a valuable tool for observing the presence and location of small clusters. The effect of varying silane loading changed both the location and magnitude of the silicon concentration observed. The results suggest that chain branching chemistry is important in the production of silicon and that enhancement of pyrolytic relative to oxidative processes occurs as the silane loading is increased. Finally, the role of charged particles on electron capture was investigated. It was found that significant attenuation of the electron current can lead to highly erroneous results.

ISSN:0021-8979    

DOI:10.1063/1.347134

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The subject of this paper is the mathematical modeling of a recently proposed class of electron‐beam‐controlled high‐power semiconductor switches that are able to overcome the space‐charge limitation of conventional electron bombarded semiconductor devices by utilizing the secondary ionization effects of cathodoluminiscence and bremsstrahlung. Current densities of several kA/cm2at forward voltages some 10 V can be controlled with an electron beam of 100 keV and 1 A/cm2; holdoff voltages of more than 100 kV/cm and dark currents as small as 10 &mgr;A/cm2are possible. The concept has several possible applications: Its fast and repetitive closing and opening under load makes it suitable for inductive energy storage applications; its linear characteristics suggests a use as a high‐power modulation device.

ISSN:0021-8979    

DOI:10.1063/1.347135

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

One requirement for operating a device in the noninstantaneous multiplication mode is that its response to an incident photon is the generation of a pulse of constant current. This current is allowed to have a fluctuating duration and can exhibit full shot noise. It is shown that a majority of conventional current‐to‐current and voltage‐to‐current converting devices should be operable in the noninstantaneous mode. Ideal photoconductive detectors (current‐to‐current converters) operated in the conventional (temporally deterministic) mode are a factor of 2 below the ideal limit on the signal‐to‐noise ratio set by the shot noise of the input light signal. When operated in the noninstantaneous mode these devices can be made to approach this ideal limit. The issue of resettability, i.e., the guaranteed turn off of each pulse of constant current, is examined with the help of a specific detector structure. Junction field‐effect transistors are presented as an example of voltage‐to‐current converting devices operated in the noninstantaneous mode. The consequent improvement in the noise performance is also quantified.

ISSN:0021-8979    

DOI:10.1063/1.347136

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thermal stress‐induced void formation in aluminum interconnect has become a major reliability problem in the usage of very large scale integration circuits. The purpose of this work is to analytically evaluate stresses in the Al line. By applying Eshelby’s method in micromechanics, the stresses in the Al line were estimated analytically as a function of the aspect ratio of the Al line cross section. The yielding criteria in plasticity were applied to examine whether the calculated stresses can induce relaxation by plastic deformation. The analytically calculated results were compared with previous results of numerical calculation and experimental observation.

ISSN:0021-8979    

DOI:10.1063/1.347137

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using the previously obtained stress distributions in an Al line after relaxation by plastic deformation, another possible relaxation process by diffusion was analyzed. Even after this relaxation occurs, some stresses still remain in the Al line. If these remaining stresses are large enough, they can be responsible for the growth of voids causing line failure. Using a theory for diffusional growth of grain‐boundary voids, the time to failure of the Al line was estimated analytically. The previous and present papers together constitute a full analysis of the so‐called ‘‘stress migration’’ phenomenon.

ISSN:0021-8979    

DOI:10.1063/1.347198

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The time, voltage, and temperature dependencies of transient polarization currents are reported for two types of varistors (i.e., ZnO and a SiC composite). The current transients exhibit a power‐law time response to a step change in voltage (i.e.,I≊I0/tm, wheremis slightly less than unity) that persists over a time scale exceeding 10−8–104s. The polarization current increases linearly with low applied voltage, but at more than a linear rate for higher voltage. The temperature dependence of the polarization current in medium voltage ZnO varistors is described by an Arrhenius plot with a change of slope near 200 K, which suggests thermal activation energies of about 160 and 10 meV. The time dependence of the polarization currents is confirmed and extended to short times by the ac admittance measured as a function of frequency. Transient changes in the ac admittance accompany the transient polarization currents, and exhibit time and temperature dependencies that reveal their close relationship to the polarization currents. By comparing transient admittance data to predictions of the Mott–Schottky theory of a barrier, it is concluded that the theory gives an inadequate account of the ac conductance, even though the voltage dependence of the capacitance is predicted well. Theoretical explanations of the polarization currents that are based upon a distribution of exponential relaxation times are examined. A reasonable account of the polarization current is provided, but the origin of the distribution is uncertain. Possible origins are a distribution of thermal activation energies or electron hopping among randomly distributed donors.

ISSN:0021-8979    

DOI:10.1063/1.347138

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have examined the growth and device characteristics of In0.53+xGa0.47−xAs/ In0.52Al0.48As (0≤x≤0.27) pseudomorphic modulation‐doped field‐effect transistors on InP substrates.Insitureflection high energy electron diffraction oscillation studies were carried out to study the growth of pseudomorphic InGaAs on GaAs and InP substrates. The data from these measurements and a theoretical formalism based on energy minimization suggest that in the pseudomorphic growth regime increased strain causes growth modes to change from two‐dimensional layer‐by‐layer to a three‐dimensional island mode. The resulting interface roughness is used as a parameter to explain the observed trends in channel mobility and device performance. It is also shown that altered growth techniques, such as migration enhanced epitaxy, in which the surface reconstruction may be changed, can restore the layer‐by‐layer growth mode for large amounts of strain in the pseudomorphic layer.

ISSN:0021-8979    

DOI:10.1063/1.347140

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A simple model for the generation of substrate strain is developed and applied to the fabrication of advanced silicon integrated‐circuit structures. These structures consist of SiO2‐filled isolation trenches residing in a silicon substrate and strain is generated at elevated temperature by thermal oxidation. The high‐stress behavior of the viscosity of SiO2is considered and leads to self‐limiting behavior. During the initial stages of oxidation, the strain rises rapidly and then asymptotically approaches an equilibrium level determined by the oxidation conditions and the trench geometry.

ISSN:0021-8979    

DOI:10.1063/1.347141

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new experimental method was developed in order to estimate the decay of the laser‐generated shock waves and the dynamic spall pressure. Experiments were performed on aluminum, copper, and unidirectional carbon fiber epoxy composites with impact strain rates of the order of 107s−1. The following values for dynamic spall pressure and pressure gradient were obtained (to an accuracy of a factor of two): aluminum [25 kb (kb=kilobars), 60 kb/mm]; copper (20 kb, 180 kb/mm); carbon fiber epoxy composite (0.3 kb, 15 kb/mm) perpendicular to the fiber direction; and (7 kb, 100 kb/mm) when the impact is parallel to the fiber direction.

ISSN:0021-8979    

DOI:10.1063/1.347142

出版商:AIP    

年代:1990

数据来源: AIP