Search

Thin film metallizations are one of the most important interconnects in large-scale integrated circuits. They are covered by substrates and passivation films. Large hydrostatic (mean) tension develops due to the constraint and thermal mismatch, and voiding is identified as the failure mechanism. This phenomenon of rapid nucleation and growth of voids is called cavitation instability and it can lead to the failure of ductile components in electronic packages such as metallizations. A micromechanics model is developed to provide the critical mean stress level that will trigger the cavitation instability. It is found that this critical mean stress level, the cavitation stress, not only depends on the material properties but also is very sensitive to defects in the material. For example, the cavitation stress decreases drastically as the void volume fraction increases. The stress-based design criterion for ductile components in electronic packages should then be: (1) Von Mises effective stress < yield stress; and (2) mean stress < cavitation stress, which is particularly important to the constrained ductile components in electronic packages such as vias and conductive adhesives. An analytical expression of cavitation stress for elastic-perfectly plastic solids is obtained, and numerical results for elastic-power law hardening solids are presented.

The equivalence between monotonic and cyclic loading for multiple cracking is the same as that for a single crack in the matrix of a fiber-reinforced composite having multiple cracks. The interactions among cracks and slip zones reduce the crack tip stress intensity factor in multiple cracking. The growth of the fatigue crack is slower than that for a single bridged crack or for multiple nonbridged cracks. This significantly delays the onset of steady-state crack growth.

An angle-dependent wavelength-modulated differential-photovoltage spectroscopy (DPVS) investigation has been performed at room temperature on a bare as-grown wafer of GaAs/ GaAlAs-based vertical-cavity surface-emitting laser (VCSEL) structure, designed for emitting at a wavelength near 850 nm. The differential-photovoltage (DPV) spectra exhibit both the fundamental conduction to heavy-hole excitonic transition and cavity mode plus an interference pattern related to the mirror stacks. By changing the angle of incidence in the DPV measurements the energy positions of the cavity mode and distributed Bragg reflector features show a blueshift while the excitonic transition remains unchanged. The energies of the excitonic transition and cavity mode are accurately determined from the DPV spectra. The advantages of DPVS in relation to other methods of characterizing VCSEL structures, such as surface photovoltage, photoreflectance, photocurrent, and differential photocurrent spectroscopy, are discussed. The results demonstrate considerable potential of DPVS for the nondestructive characterization of these structures at room temperature. [ABSTRACT FROM AUTHOR]

We have characterized an InGaP/InGaAsN/GaAs NpN double-heterojunction bipolar transistor structure using polarized photoreflectance (PR) spectroscopy. The ordering parameter of the InGaP is deduced from the polarization {[110] and [11¯0]} dependence of the PR signals from the emitter region. The ordering related piezoelectric field is also found to influence the electric field, as evaluated from observed Franz–Keldysh oscillations, in the InGaP emitter region. The field in the emitter region is found to be about 25 kV/cm smaller than the theoretical value that does not take into account the possible ordering induced screening effect, while the field in the collector region agrees well with the theoretical value. In addition, the InGaAsN band gap is also determined by analyzing the PR spectrum of the base region. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the effects of trimethylantimonide/triethylgallium ratios on epilayer properties of gallium antimonide grown by low-pressure metalorganic chemical vapor deposition. Characteristics of gallium-antimonide-based compound semiconductors; Details on the experiment; Discussion on the results of the study.

Presents information on a study which analyzed the thermal stability for palladium (Pd)/n-GaSb Schottky contacts. Fabrication of Schottky diodes; Analysis of the interface transition between Pd and GaSb using Rutherford backscattering spectroscopy; Information on the current-voltage characteristics for Pd/n-GaSb Schottky diodes.