摘要:

Thermal stresses that develop in aluminum interconnects upon cooling from an annealing temperature are investigated using crystal plasticity theory. The crystal plasticity model is implemented assuming either isotropic hardening or a physically based hardening model developed for single crystals. The dependence of the predicted thermal stresses on crystal orientation and on interconnect aspect ratio is examined. The results are compared with recent observations of electromigration‐induced transgranular voids to ascertain the contribution of the thermal stresses in the failure of aluminum interconnects. The analysis clearly demonstrates the necessity of accounting for all slip systems when modeling the effects of texture in single‐crystal thin films. In addition, the calculations suggest that proper consideration of the hardening description is necessary for accurate predictions of thermal stresses. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359044

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The crystallization process in SbxGe1−xalloy films has been observed duringinsituannealing in a transmission electron microscope. Results are presented for two films withx=0.89 (89 at. % Sb) andx=0.71 (71 at. % Sb), which lie on either side of the eutectic composition (x=0.85). In the former films radial crystals are observed to grow rapidly from discrete nuclei, whereas in the latter films the crystallization process occurs through a near‐planar front. In addition, quantitative data obtained from these experiments show that the Sb0.89Ge0.11films have a higher activation energy for crystal growth and a lower temperature for the nucleation of crystals. Significant differences are observed between the crystallization processes for the two films studied, with the Sb0.89Ge0.11film showing better potential for development as an ultrafast optical phase‐change storage medium. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359045

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The activation energies,Ea’s, for CoSi and CoSi2formation were determined usinginsituresistance measurements during rapid thermal annealing. Co films were evaporated on undoped polycrystalline Si (poly‐Si) and single‐crystal Si on sapphire (SOS) substrates. The resistance was monitored for heating rates from 1 to 60 °C/s up to 900 °C. There was significant thermal lag between the samples and thermocouple embedded in the susceptor wafer for heating rates greater than 20 °C/s. The thermal lag was quantified by melting Au‐Si, Al‐Si, and Ag‐Si eutectics, and shown to be consistent with finite element modeling. TheEa’s determined from Kissinger plots for heating rates ≤20 °C/s were 2.09±0.11 and 2.03±0.08 eV for CoSi formation and 2.91±0.22 and 2.81±0.23 eV for CoSi2formation, for Co/poly‐Si and Co/SOS samples, respectively. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359046

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electrical characterization has been carried out on electron irradiated InP grown by metal‐organic chemical‐vapor deposition (MOCVD) and liquid encapsulated Czochralski (LEC), throughI–V(–T),C–V, deep level transient spectroscopy (DLTS) and admittance spectroscopy measurements and the resistance to electron radiation for these two materials has been compared. It was found that MOCVD‐InP was more resistant to electron radiation than LEC‐InP, as demonstrated by the lower carrier removal rate and change of series resistance in the MOCVD‐InP diodes as a result of electron radiation. The introduction rates for the dominant hole defectsH3 andH4 and for additional electron defect states were found to be similar for both materials, but were insufficient to explain the degree of degradation of solar cell efficiency incurred by these known defects. A new defect,HD1, has been found to be responsible for the high carrier removal rate and the introduction of a large series resistance which accounts for the difference of radiation hardness between these two materials. The results again show that the dominant irradiation defects in InP are not the defectsH3 andH4 as is usually accepted, but the new found defectHD1, which was undetected by the DLTS technique. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359047

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Detailed characteristics of photoinduced surface deposition (PSD) of metallic Ag have been studied using Ag‐As‐S bulk glasses to reveal the mechanism. The composition dependence of PSD in the AgxAs60−xS40(25≤x≤45) system shows that the photosensitivity decreases with a decrease in the Ag content and becomes negligible atx&bartil;25. All the related crystalline materials hardly exhibit the PSD, even if the Ag content is greater than 45 at. %. The size of photodeposited Ag particles and the number per unit area depend on the Ag content and illumination conditions (light intensity, photon energy, and temperature). The PSD phenomenon is induced by light with photon energy higher than the optical band gap, and the photosensitivity shows a maximum at room temperature. PSD can be suppressed by coating over the surface with thin Au film. From these results and other observations it can be suggested that the PSD phenomenon is characteristic of thermodynamically unstable glasses containing excess Ag+ions and is a kind of photoelectro‐ionic chemical reaction. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.359048

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

PbTiO3thin films have been deposited by a sol‐gel method onto various crystalline substrates and their texture has been investigated. The perovskite phase crystallizes directly from an amorphous mixture above 350 °C. Films have preferential orientation along the (001) axis on (100) MgO, are strongly oriented along both the (110) and (101) axis on (1102) sapphire, and along the (001) axis on (100) SrTiO3. High texturing is only observed on this last substrate as evidenced by rocking curves and channeling effects in Rutherford backscattering spectrometry. The origin of the strain observed along thecaxis is also discussed. The thickness of the films has a strong effect on the texturing. Thin films crystallize as well textured, whereas orientation appears in thick films only after heating at high temperatures. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359049

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Homoepitaxial diamond films were grown at temperatures between 1000 and 1400 °C with an oxy‐acetylene torch. The growth rates of the {100} and {111} faces were observed to increase through 1400 °C, while the {110} face did not grow above 1400 °C. The quality of all faces deteriorated significantly between 1300 and 1400 °C, as shown by scanning electron microscopy and Raman spectroscopy. The transparency of a film as measured by Fourier‐transform infrared spectroscopy was type‐IIa quality with very little C–H absorption.

ISSN:0021-8979    

DOI:10.1063/1.359518

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A model for the low‐temperature growth of poly‐Si by plasma‐enhanced chemical‐vapor deposition using SiF4/SiH4/H2gases is presented. The model is based on the existing so‐called etching model in which growth and etching take place simultaneously. In this model a set of chemical reactions are postulated. The crucial factors to obtain high‐quality poly‐Si films are (1) the flux of precursors, (2) the concentration of F radicals in the vicinity of the growing surface which determines the etching rate, and (3) the H‐covered surface which ensures long diffusion length of precursors. The flow rate of SiH4[factor (1)] determines whether the film becomes crystalline or amorphous, and variation in the other gas flow rates and plasma parameters affect factors (2) and (3). According to the model the electrode spacing and rf power predominantly determine the concentration of F radicals diffused to the growing surface, while the gas pressure changes the residence time of radicals which predominantly affects the etching reaction. Natural consequences of the model are that an excess supply of F radicals will in turn deteriorate the crystallinity by stripping the hydrogen covering the surface and increasing nucleation sites. The crystallinity of poly‐Si films prepared by changing the above plasma parameters are characterized by x‐ray diffraction, and their dependence on the above parameters are found to be consistent with the model. A high degree of hydrogen exchange between the growing surface and the plasma is observed by secondary‐ion‐mass spectroscopy for the film prepared with SiF4/SiH4/D2gases. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.359586

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This paper reports on resistance and capacity measurements of ohmic contacts which were deposited on heteroepitaxially grown, Si‐doped GaAs layers on Si substrates. It is observed that the process of rapid thermal annealing (RTA) considerably affects the ohmic properties of subsequently deposited contacts. With rising annealing temperature, the electrical resistivity in the GaAs layer and thus, the contact resistance increased essentially. Although the chemical concentration profile of Si dopants is not changed by RTA, the number of electrically active carriers is lowered. Photoluminescence measurements confirm that Si donors on Ga sites perform a site exchange to As vacancies, thereby forming Si acceptors. The extent of this exchange process is considerably enhanced by the presence of a high dislocation density in the heteroepitaxial GaAs films. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359050

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The concept of the polar optical momentum relaxation time for phonon energies larger than the thermal energy is applied to the analytical calculations of the electron mobility in bulk GaAs and in a two‐dimensional (2D) electron gas. The theory also accounts for nonparabolicity. For the bulk material, the analytical formula is in good agreement with experimental data even at elevated temperatures where it can be used as an extrapolation formula. The comparison with numerical simulations for the 2D gas shows that the analytical formula for the 2D case applies when intersubband scattering is unimportant. When many subbands are involved in scattering processes, the polar optical mobility can be estimated using the analytical formula for the bulk case. Hence the results provide convenient analytical equations for polar optical mobility which can be used in device simulators. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359051

出版商:AIP    

年代:1995

数据来源: AIP