摘要:

The nucleation of an intermediate phase at the planar boundary of two other phases in a diffusion couple is considered. An extension of classical nucleation theory is presented which yields the shape of the critical intermediate phase nucleus and the critical work of formation. With the use of a simple example it is demonstrated that the work of formation decreases, and hence the nucleation rate increases, with increasing interdiffusion time. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360252

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The diffusion of Be in GaAs is studied in samples which are molecular beam epitaxy GaAs with grown‐in Be. The Be diffusion profiles of samples annealed under various conditions are obtained using secondary ion mass spectrometry. SUPREM‐IV.GS, a simulator for GaAs and Si processing technology, is used to compare the experimental results with our models and to extract parameters. The Be diffusion profiles show a kink feature and a time‐dependent Be diffusivity which are successfully simulated. The intrinsic Be diffusivity, the Ga interstitial diffusivity, and the equilibrium concentration of Ga interstitials, all as a function of temperature, are obtained from this study:D+1Be=0.17 exp(−3.39 eV/kBT) cm2 s−1,DI=6.4×10−5 exp(−1.28 eV/kBT) cm2 s−1, andCI*int=4.7×1028 exp(−3.25 eV/kBT) cm−3. The role of nonequilibrium Ga point defects in the anomalous Be diffusion behavior is addressed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360253

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The diffusion of implanted Be in liquid‐encapsulated Czochralski GaAs samples is modeled using SUPREM‐IV.GS, a simulator for GaAs and Si processing technology. The ‘‘plus one’’ approach for defect generation after implantation, as well as an assumption of local Ga interstitial sinks, are used to successfully simulate the high Be diffusivity, the uphill diffusion and the time‐dependent Be diffusivity. The fast diffusion of implanted Be can be simulated using the same intrinsic Be diffusivity as that used in the simulation of the slow diffusion of molecular beam epitaxy grown‐in Be. The roles of extended defects and nonequilibrium Ga point defects in the implanted Be anomalous diffusion behavior are taken into account. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360254

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Large tensile stresses usually exist in metallic interconnect lines on silicon substrates as a result of thermal mismatch. When a current is subsequently passed any divergence of atomic flux can create superimposed stress variations along the line. Together, these stresses can significantly influence the growth of voids and therefore affect interconnect reliability. In this work, a high‐resolution (∼2 &mgr;m) optical spectroscopy method has been used to measure the localized stresses around passivated aluminum lines on a silicon wafer, both as‐fabricated and after electromigration testing. The method is based on the piezospectroscopic properties of silicon, specifically the frequency shift of the Raman line at 520 R cm−1. By focusing a laser beam at points adjacent to the aluminum lines, the Raman signal was excited and collected. The stresses in the aluminum lines can then be derived from the stresses in the silicon using finite element methods. Large variations of stress along an electromigration‐tested line were observed and compared to a theoretical model based on differences in effective diffusivities from grain to grain in a polycrystalline interconnect line. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360255

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In a series of experiments, the influence of phosphorus diffusion at high concentrations on the diffusion of an antimony marker layer was investigated. The marker layer was separated from the surface by a 4 &mgr;m layer of epitaxially grown silicon. To reduce the effects of implantation enhancement and phosphorus precipitation on the diffusion of the antimony marker layer, the phosphorus was implanted into a polysilicon layer deposited on top of the single‐crystalline substrate. It was found that the diffusion of the antimony marker layer is already reduced by the epilayer. From these diffusion coefficients, upper limits for the fractional diffusivity of antimony were derived. In contrast to previous investigations, the diffusion of the antimony marker layer was found to be enhanced below regions where phosphorus was implanted. A comparison of diffusion in FZ and CZ samples shows that this enhanced diffusion of antimony can be explained only by an injection of self‐interstitials from the phosphorus‐doped region. Since the polysilicon layer was found to recrystallize, this self‐interstitial injection can be the result of phosphorus diffusing mainly via self‐interstitials, phosphorus precipitation, or both. Using Boltzmann–Matano analysis and antimony diffusivity data, the fractional diffusivity of phosphorus via self‐interstitials was estimated to be lower than 0.71 at 950 °C. Possible sources of error in this estimation are discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360256

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Finite element calculations of stresses and strains in substrates and stripe films of thicknesshand width 2lare reported. Both variation of the stress in the vertical direction (away from the interface) in the film and distortion of the substrate are taken into account. The calculations show that both the horizontal and vertical lattice planes are curved in the film as well as in the substrate. If the thickness of the substrate is infinite, the curvature in the substrate is maximum near the interface and decays rapidly with depth. Furthermore, the edges near the top are over‐relaxed, i.e., if the film is originally under compression, the stress becomes tensile because the free edge surfaces affect the relaxation. For a film withh/l=1 or greater, the stress is reversed throughout the top layer. The change from compression to tension takes place partly because of the Poisson effect and partly due to the bending of the lattice planes. The approximations made in the existing analytical models were examined and the conditions under which the models describe the stresses in the film or in the substrate were determined to a good approximation. Our finite element calculations agree with the available experimental data. Ours are the only theoretical results with which measured substrate stresses agree qualitatively. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360257

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The solid‐state reaction between a nickel (7 at. % gold) film and a silicon substrate at temperature lower than the gold‐silicon eutectic temperature (370 °C) is examined by transmission and scanning electron microscopy and by Rutherford backscattering spectrometry. Epitaxial NiSi and preferentially oriented Ni2Si are present and gold precipitation occurs at the inner interface. This gold precipitation leads to a peculiar backscattering spectrum which is analyzed taking into account morphological information. The driving forces leading to gold redistribution are interpreted in terms of surface energies and chemical interactions with silicon. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360258

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A study is described of the impact process and the corresponding surface damage to PMMA (polymethylmethacrylate) targets impacted by ice and nylon spheres. A gas gun system was used to project the spheres and the impacts were recorded using a high‐speed image converter camera (Imacon 792). Special attention was paid to the conditions causing projectile failure and the surface damage to the target. The experimental results show that although the deformation and failure modes for ice and nylon are different, the surface damage to the PMMA target has a similar failure pattern, i.e., a central, circular undamaged region surrounded by an annular damaged region containing many short circumferential cracks. Analysis shows that the diameterdof the central undamaged region and the annular damaged areaAmcan be used to characterize the surface damage which depends on the projectile material, sphere radiusR, as well as the impact velocityV0. For a given projectile, two critical impact velocities exist: One is the threshold velocity (V0)th, below which no visible surface damage is observed, and another is the fracture velocity (V0)f, above which a plate target is broken. Damage in the annular region is caused by the Rayleigh surface wave in the present experiments. The conditions for the Rayleigh surface wave to pass ahead of the expanding edge contact velocity are analyzed. Comparisons between the theoretical predictions and experimental results, including the present study and earlier data, are made for PMMA plates impacted by projectiles of different materials (ice, nylon spheres, and water drops) and at different impact angles. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360259

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The mechanism of silicon stock removal in chemomechanical polishing (CMP) is studied by characterizing surface chemical species with infrared‐absorption measurements and the corresponding degree of hydrophobicity with contact angle measurements immediately after CMP. Surface properties and stock removal rates are found to depend strongly on thepH of the silica slurry used in this ‘‘syton polishing’’ technique. At the peak of the removal rate [pH∼11 for both Si(100) and Si(111)], the surfaces have the highest hydrophobicity and the highest hydrogen coverage. Si(111) has an ideal monohydride termination, while Si(100) is characterized by a variety of hydrides (mono‐, di‐, and trihydrides), suggesting different morphologies for the surfaces: atomically flat domains on Si(111) and rougher areas on Si(100). Away from the optimum slurrypH (at lower stock removal rates), a higher concentration of hydroxyl groups is observed, increasing the surface hydrophilicity. At allpH, some oxidation occurs beneath the H‐terminated Si surface, as evidenced by a characteristic frequency shift of oxygen‐backbonded hydrides. The mechanisms of stock removal are considered in view of these observations for the different ranges of slurrypH. In particular, at the highest removal rates, an interplay of surface oxidation, removal of oxidized silicon, and subsequent H termination is suggested. Based on the spectroscopic characterization of surface morphologies, the relevance of CMP to prepare atomically smooth silicon surfaces is discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360721

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We determine the evolution of Si–H and C–H bonding during the growth of hydrogenated amorphous silicon carbide films by reactive magnetron sputtering of a Si target in (Ar+H2+CH4). Si–H and C–H modes are observed by infrared reflectance spectroscopy. An optical cavity substrate is used to enhance the sensitivity. We identify Si–H stretching modes at 2110 and 2145 cm−1due to Si–H clusters in microvoids and Si–H back‐bonded to carbon, respectively. C–H stretching modes are identified at 2870, 2900, and 2950 cm−1. These indicate dominantsp3bonding configuration for C. During initial growth, a transition layer rich in H and C is observed. Steady state growth is not achieved until ≳250 A˚ on SiO2substrates, and ∼70 A˚ ona‐Si:H substrates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360260

出版商:AIP    

年代:1995

数据来源: AIP