摘要:

Electromigration performance of multilevel interconnect vias is investigated using a three-dimensional computer model. The model uses the finite-element method to obtain self-consistently the temperature and current density distributions in order to calculate electromigration fluxes. The model includes the polycrystalline grain structure of the tracks as well as stress-migration and concentration gradient backfluxes. While in single level systems, failure can be analyzed with two-dimensional models because the fluxes are homogeneous, the inclusion of the third dimension along the track thickness is necessary for multilevel systems. In addition to the effects of hot spots, current crowding, and microstructure, it is found that the anisotropy of the grain boundary diffusion plays an important role in determining the locations of void formation. The microstructural details of the track at the interface with the via, including grain boundary geometry, are very important for electromigration studies. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364341

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Large-area (001) oriented epitaxial CeO2films with extremely high crystalline perfection characterized by x-ray diffraction rocking curves of the (002) CeO2reflection with a full width at half maximum (FWHM)&Dgr;&ohgr;⩽0.013°and thickness dependent oscillations in the Bragg-Brentano x-ray diffraction spectra were deposited via rf-magnetron sputtering on (11_02) sapphire. Pole figure measurements of the space symmetry confirmed that the examined sharp reflections belong toCeO2and no other phases like CeAlO3are present. The improvement of the crystalline quality was obtained by optimization of the high-pressure sputter deposition process and the use of large-area substrates. The [100] CeO2axis was slightly tilted with respect to the [11_02] sapphire axis by 0.185°. Subsequently sputter-deposited high-TcYBa2Cu3O7−xthin films revealed structural properties characterized by FWHM<0.06°of the (005)&thgr;-2&thgr;peaks and by FWHM of the (005) peaks rocking curves of&Dgr;&ohgr;=0.3°.©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364342

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effects of the deposition parameters on configurations and stability of hydrogen (deuterium) in amorphous sputtered silicona-Si:Hhave been analyzed using Fourier transformed infrared absorption spectroscopy, deuterium effusion experiments, and x-ray diffractometry. The ratio of monohydride bonds Si–H was calculated from the infrared absorption stretching mode spectrum. This ratio was increased when the substrate temperature was increased. The effusion results ina-Si:D, when deposited with a simple cathode, have shown the presence of clustered deuterium weak bonds in microvoids (400 °C deuterium effusion peak), beside isolated Si–D bonds embedded in the more compact tissue (650 °C deuterium effusion peak). The deconvolutions of the stretching mode infrared absorption spectrum of the as-grown sample and after isothermal annealing at 510 °C have allowed one to conclude that it is not possible to identify the low temperature and high temperature effusion peaks, respectively, with the decomposition ofSi–H2and Si–H centers. The effusion of the less stable hydrogen improved the amorphous structural relaxation. The ratio of monohydride bonds was increased by introducing a magnetron cathode in the deposition chamber. At the same time, the deuterium effusion spectrum was modified, showing a continuous deuterium effusion from 350 °C, instead of two well-defined effusion peaks. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364321

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The heteroepitaxial growth of the new ternary, group-IV, semiconductor material,Si1−x−yGexCyon Si(100), has been investigated. The epitaxial quality ofSi1−x−yGexCyis found to be inferior to that ofSi1−xGexwith similar Si/Ge concentration ratio, grown under identical conditions, and the quality deteriorates with increasing C fraction. Also, the surface roughness, as studied by tapping mode atomic force microscopy, increases with increasing C fraction as well as with increasing Ge fraction, suggesting a transition from Frank–van der Merwe to Stranski–Krastanov type growth. We suggest that the very large mismatch between the average bond length in theSi1−x−yGexCymaterial, as determined by Vegard’s law, and the equilibrium Si&sngbnd;C bond length, weakens the Si&sngbnd;C bonds and reduces the elastic range of the material, thus lowering the barrier for dislocation and stacking fault formation. The change in elasticity may also be responsible for the change in growth morphology, either directly by a lowered barrier for island formation or indirectly through the formation of defects. A decrease in Ge incorporation in theSi1−x−yGexCyfilms with increasing C incorporation suggests a repulsive Ge–C interaction. Moreover, we observe a C-rich, Ge-deficient precursor phase to SiC precipitates at a growth temperature of 560 °C, whereas at 450 °C no such phase can be observed. The temperature dependence of the precursor formation is consistent with C bulk diffusion. Infrared absorption measurements cannot be used to detect the precursor phase. Finally, the onset of epitaxial breakdown is discussed and an accurate and independent determination of the C fraction and its substitutionality is emphasized. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364352

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The parameter space for the heteroepitaxial nucleation of diamond on Si(001) using the bias process was studied by x-ray diffraction texture measurements. It was found that heteroepitaxial orientation can be achieved over a wide range of different parameters provided that the bias time is within a definite time interval. It was observed thattwidth,the width of the time window, andtopt ,the bias time for optimal azimuthal alignment, strongly decrease with the absolute value of the bias voltage. For high bias voltages an extremely low value oftopt(20 s at −300 V) was found. Applying the bias conditions longer thantoptresulted in a strong decrease of the pole density maxima of the heteroepitaxial grains accompanied by a significant broadening of their azimuthal distribution that is interpreted in terms of two different routes for the loss of epitaxy. The different time constants characterizing the process window for a fixed bias voltage are traced back to feedback of the growing film on the plasma and on the electrical field distribution above the substrate. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364319

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In order to clarify the mechanisms that limit the alignment for diamond heteroepitaxy on Si(001) the influence of different process parameters during the bias enhanced nucleation step on the misorientation of diamond on Si(001) was evaluated using x-ray diffraction texture measurements. It is shown that the azimuthal width of the {220} pole density maxima in the substrate plane measured in transmission is a quantity that allows a systematic study of the parameter space for oriented nucleation. From the negligible influence of the substrate surface roughness and of the substrate temperature between 675 and 905 °C it is concluded that the migration, rotation, and rearrangement processes of nucleated diamond clusters do not control alignment in the temperature range studied. In contrast, the duration of the biasing procedure, the process pressure, and the absolute value of the bias voltage can strongly vary the azimuthal distribution between a full width at half-maximum of 3.9° and more than 15°. Low bias voltages favor narrow distributions whereas high bias voltages are accompanied by extremely low biasing times (down to 20 s). When the optimum biasing time is exceeded, the orientation is lost via two different routes. Several models for the underlying mechanisms are proposed with those that are most probable pointing to a detrimental influence by ion bombardment. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364343

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A continuous buriedGdSi1.7layer is formed by channelled implantation of 90 keV Gd ions into Si(111). In the case of (001) oriented silicon substrates, the silicide film is formed on the silicon surface. Its worse crystalline quality is due to the epitaxy occurring relative to all four{111}Siplanes resulting in a texturedGdSi1.7layer. Annealing at a temperature of ⩾850 °C for 30 min results in the presence of only the orthorhombicGdSi2phase on the silicon surface for both (111) and (001) silicon substrates. However, the precipitates embedded in the silicon substrate are still hexagonalGdSi1.7.The phase transformation temperature is higher for (111) than for (001) silicon. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364344

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The defect structure in relaxed gradedGe/GexSi1−x/Sistructures grown on (001) exact and (001) off-cut substrates using ultra-high vacuum chemical vapor deposition was characterized using transmission electron microscopy (TEM), atomic force microscopy, and electron beam induced current. The samples grown on off-cut (001) substrates showed a remarkable improvement in surface roughness and dislocation pile-up densities. By applying both a dislocation blocking criterion and surface roughness to graded Si-Ge/Si(001) structures, we can predict the formation of dislocation pile-ups in graded structures. Nonparallel misfit dislocation networks in off-cut wafer samples are not as efficient at blocking perpendicular dislocation motion, leading to a large reduction in dislocation pile-up density. The lower pile-up density on layers grown on off-cut wafers results in less stress-induced surface instability during growth, leading to surfaces with much lower roughness. TEM studies revealed that the array of 60° dislocations, that usually forms to relieve the misfit stress, transforms into a lower energy hexagonal dislocation network consisting of edge dislocations with Burgers vectors of the type 1/2⟨110⟩, 1/2⟨1¯10⟩, and ⟨100⟩. Such reactions were found to be more prevalent in the samples grown on off-cut substrates. Favorable intersections of {111} type planes on the off-cut substrates were found to aid such reactions. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364345

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The driving force of ⟨100⟩ dark-line defect (DLD) climbing growth based on vacancy unsaturation is discussed. InInxGa1−xAs/GaAsstrained structures, it is found that compressive strain can reduce the osmotic (climb) force and can suppress the climb of DLDs in ⟨100⟩ direction. The percentage of indium inInxGa1−xAs/GaAsstrained heterostructures for the suppression of ⟨100⟩ DLD propagation is calculated under different material growth temperatures and doping levels. For ann-type doping level higher than 5×1016 cm−3, an indium percentage less than approximately 9&percent; inInxGa1−xAs/GaAsheterostructures is sufficient to stop the ⟨100⟩ DLDs growth and agrees well with the experimental observation. These results are useful for the design and fabrication of high reliability strained heterostructure devices. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364353

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We examined the role of substrate quality on the epitaxial microstructure and performance of pseudomorphic InGaAs/AlGaAs/GaAs high electron mobility transistors (HEMTs). High resolution x-ray diffraction, high resolution x-ray topography, and transmission electron microscopy indicate that, for a given channel layer thickness, the misfit dislocation density is always lower for HEMT structures grown on substrates having lower threading dislocation densities. Furthermore, the onset of misfit dislocation formation occurs at higher channel layer thicknesses for HEMTs grown on substrates having a lower threading dislocation density when compared to those grown on substrates with a higher threading dislocation density. However, the ratio of the density of misfit dislocations to threading dislocations is greater than one on the low dislocation density substrates, which demonstrates that other misfit dislocation nucleation sources (i.e., surface particulates) are significant when there is an insufficient density of threading dislocations. The Hall conductivity measurements show that the performance of HEMT structures improves with higher substrate quality, showing that the range of epitaxial layer metastability increases with improved substrate quality. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364346

出版商:AIP    

年代:1997

数据来源: AIP