Volume 92, Issue 9, 01 November 2002
Index of content:
- DEVICE PHYSICS (PACS 85)
92(2002); http://dx.doi.org/10.1063/1.1510564View Description Hide Description
A model is developed to describe the light-induced restoration of the drain current from current collapse in AlGaN/GaN high electron mobility transistors. The model assumes that the collapse results from a transfer at large drain bias of hot carriers from the gate–drain region of the two-dimensional electron gas to deep traps in the high-resistivity GaN layer. Application of the model provides a means of determining the photoionization cross sections and the areal densities of the responsible traps. Where multiple trapping species are involved, it is shown that photoinduced transitions between trapping sites can significantly alter the response of the drain current to light illumination, and must therefore be taken into account.
Dopant deactivation in heavily Sb doped Si (001): A high-resolution x-ray diffraction and transmission electron microscopy study92(2002); http://dx.doi.org/10.1063/1.1510953View Description Hide Description
Laser annealing is being studied as an alternative dopant activation technique to form the ultrashallow, low resistivity junctions required in future generations of integrated circuits. This method benefits from the ability to create uniform, box-shaped dopant profiles with concentrations that can exceed equilibrium solubility values. These supersaturated dopant concentrations, however, exist in a metastable state and deactivate upon subsequent thermal processing. Electrical measurements show that antimony deactivation becomes increasingly severe as the concentration increases. High-resolution x-ray diffraction (HR-XRD), secondary ion mass spectroscopy and transmission electron microscopy were used to study the deactivation process. Under most conditions, Sb deactivation occurs through the precipitate mechanism in which the inactive dopant forms precipitates, leading to a decrease in the substitutional dopant concentration. However, the HR-XRD data reveal that at high concentrations above during low temperature anneals, the inactive dopant forms a type of inactive structure that resides on a substitutional site within the Si matrix.
Improved diffusion barriers for copper metallization obtained by passivation of grain boundaries in electroless deposited cobalt-based films92(2002); http://dx.doi.org/10.1063/1.1512321View Description Hide Description
The mechanism for improved barrier properties against copperdiffusion in electroless deposited and thin films compared to physical vapor deposition(PVD) of cobalt is quantitatively explained. Secondary ion mass spectrometry depth profile measurements were performed on the filmsdeposited on copper substrates after subjecting them to thermal anneals at approximately half the melting temperature of cobalt. A steady-state mode was observed in the form of concentration plateaus which originate from a combined contribution of grain-boundaries’ saturation and coppersolubility in the grains. The difference in plateau heights between the samples is assigned to the varying degrees of grain-boundaries’ passivation. For the copper concentration in the grain boundaries is negligible and the solubility in the temperature region between 550 and may be described as at. %. The higher-copper concentration plateaus in the films are a result of a low, non-negligible copper concentration at the grain boundaries, estimated at less than 10 at. %. The copper concentration plateaus in PVDcobalt were significantly larger due to saturation of the grain boundaries.
92(2002); http://dx.doi.org/10.1063/1.1509102View Description Hide Description
The improvement of the diffusion barrier performance for Cumetallization, by inserting a thin Al layer between two TiN layers, has been clearly demonstrated and reported by us. The key idea behind our scheme is “stuffing” of grain boundaries of columnar TiN films by It has been also found that the barrier property is at its best when the Al thickness is 1 nm, but above this value, the barrier performance degrades drastically when the upper TiN film is not preannealed. In this study, why the barrier breaks down at above 1 nm of Al interlayer thickness is investigated. High-resolution transmission electron microscopy,scanning transmission electron microscopy, and energy dispersive spectroscopy analyses revealed that the fast diffusion of Cu in the presence of the free Al is the main reason for the failure of the present diffusion barrier scheme. These results are discussed on the basis of the differences between the movements of Al and Cu through TiN film, and the differences between the solid solubilities of Al in Cu and in Si. Our results show that both Al interlayer thickness and the oxygen content in TiN film should be properly controlled to take full advantage of the present multilayerdiffusion barrier scheme.