摘要:

A ternary compound ofCo3Ti2Siis suggested as a reaction barrier for the formation of epitaxialCoSi2in the Co/Ti/Si system when adopting the rapid thermal annealing process. It controls Co diffusion to the Si substrate, followed by formation of epitaxialCoSi2. After the epitaxialCoSi2was formed, the interfacial morphology of the upper layer/CoSi2interface was very different according to silicidation temperature, that is, the interface was planar at 800 °C, but rough at 900 °C. This was attributed to the reaction between the upper layer consisting of Co–Ti–Si and theCoSi2layer at 900 °C, which resulted in Ti-rich precipitates at the surface. The Ti-rich precipitates acted as a diffusion sink of dopant, thus, the leakage current density for the silicidation temperature of 900 °C was much higher than that for the temperature of 800 °C. These results suggest that the silicidation temperature is one of the most critical factors in determining the leakage current of thep+njunction diode. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366040

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The surface structures of C60films, epitaxially grown on the GeS(001) surface, were investigated from 90 to 350 K by helium atom scattering (HAS) diffraction. The present HAS results indicate a step-flow growth mode that is consistent with the results of previous x-ray scattering studies. By monitoring the diffraction intensities, the orientational-disordering phase transition is found to be completed at Tc=235K, which is about 25 K lower than the bulk transition temperature. This surface phase transition appears to be preempted by rotational disordering of C60molecules at defect sites, already initiated at Ts=130K. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366041

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Detailed characterization using x-ray diffractometry, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, and Auger infrared and focused ion-beam spectroscopy, was carried out on cubic SiC films grown on single-crystal (100) Si substrates by reactive hydrogen plasma sputtering over a range of growth temperatures between 700 and 1000 °C. It was found that the first few deposited atomic layers were always amorphous. The subsequent SiC films showed well-defined (111) growth at the lowest temperatures, becoming randomly oriented by 1000 °C. The measured C:Si ratio was always >1, and varied with depth inside a film and also with temperature. At higher temperatures, the presence of “hollow voids” was observed, our data being consistent with their formation by outdiffusion of Si atoms from the substrate through the SiC layer. Associated with the hollow voids we observed the presence of a porous, highly C-rich region at the Si–SiC interface. We propose that this was due to diffusion of C from the SiC film into the voids themselves. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366042

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effects of alloy composition on the electrical and structural properties of zirconium germanosilicide (Zr–Si–Ge) films formed during theZr/Si1−xGexsolid state reaction were investigated. Thin films ofZr(Si1−yGey)and C49Zr(Si1−yGey)2were formed from the solid phase reaction of Zr andSi1−xGexbilayer structures. The thicknesses of the Zr andSi1−xGexlayers were 100 and 500 Å, respectively. It was observed that Zr reacts uniformly with theSi1−xGexalloy and that C49Zr(Si1−yGey)2withy=xis the final phase of theZr/Si1−xGexsolid phase reaction for all compositions examined. The sheet resistance of theZr(Si1−yGey)2thin films was higher than the sheet resistance of similarly preparedZrSi2films. The stability ofZr(Si1−yGey)2in contact withSi1−xGexwas investigated and compared to the stability ofTi(Si1−yGey)2in contact withSi1−xGex.TheTi(Si1−yGey)2/Si1−xGexstructure is unstable when annealed for 10 min at 700 °C, with Ge segregating fromTi(Si1−yGey)2and forming Ge-richSi1−zGezprecipitates at grain boundaries. In contrast, no Ge segregation was detected in theZr(Si1−yGey)2/Si1−xGexstructures. We attribute the stability of the Zr-based structure to a smaller thermodynamic driving force for germanium segregation and stronger atomic bonding in C49Zr(Si1−yGey)2.Classical thermodynamics were used to calculateZr(Si1−yGey)2–Si1−xGextie lines in the Zr–Si–Ge ternary phase diagram. The calculations were compared with previously calculatedTi(Si1−yGey)2–Si1−xGextie lines. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366043

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A microscopic analysis of current and voltage fluctuations in GaAs Schottky barrier diodes under forward-bias conditions in the absence of1/fcontributions is presented. Calculations are performed by coupling self-consistently an ensemble Monte Carlo simulator with a one-dimensional Poisson solver. By using current- and voltage-operation modes the microscopic origin and the spatial location of the noise sources, respectively, is provided. At different voltages the device exhibits different types of noise (shot, thermal, and excess), which are explained as a result of the coupling between fluctuations in carrier velocity and self-consistent field. The essential role of the field fluctuations to correctly determine the noise properties in these diodes is demonstrated. The results obtained for the equivalent noise temperature are found to reproduce the typical behavior of experimental measurements. An equivalent circuit is proposed to predict and explain the noise spectra of the device under thermionic emission-based operation. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366044

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

(Ba,Sr)TiO3(BST) thin films grown by chemical vapor deposition and with platinum (Pt) top and bottom electrodes have been characterized with respect to the leakage current as a function of temperature and applied voltage. The data can be interpreted via a thermionic emission model. The Schottky approximation accounts for superohmic behavior at higher fields, but the barrier lowering is stronger than expected from this theory. While the leakage mechanism is comparable toSrTiO3thin films prepared by chemical solution deposition, the absolute values of the leakage current are significantly lower for the metalorganic chemical vapor deposition (MOCVD) prepared BST film. This is presumably due to a more homogeneous microstructure of the latter and may also be due to different electrode processing. The influence of the film thickness on the leakage in combination with additional findings is used to discuss the field distribution in the films under a dc voltage stress. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366045

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Hall-effect and space-charge-limited-current (SCLC) measurements were performed on Cl-doped GaSe single crystals grown by the Bridgmann–Stockbarger method. The temperature dependence of the free electron density shows the characteristics of a partially compensatedn-type semiconductor. The electrical properties are dominated by a deep donor level at about 0.57 eV below the conduction band. An electron trapping level between 0.56 and 0.62 eV below the conduction band has been observed by SCLC measurements. The trapping level concentration depends on the amount of dopant. Finally, the conduction band density-of-states effective mass was estimated to be1.1 m0.©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366046

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Stability of contacts in shallow junction devices against high current density is a reliability issue for very large scale integration technology. We have observed a strong polarity effect on failure at nickel and nickel silicide contacts on bothn-andp-type Si under high stress conditions. In a pair of cathode and anode contacts theNi/n+-Sicontact pair fails at the anode, while theNi/p+-Sipair fails at the cathode. TheNi/Ni2Si/n+-Si andNi/Ni2Si/p+-Siwere found to fail preferentially at the cathode. Microbeam Rutherford backscattering spectrometry and Auger electron spectroscopy depth profiles show that a silicide reaction occurs between Ni and Si during current stressing, especially at the failed contacts.In situresistance data indicate that the resistance of the failed contact increases with time while that of the other contact in the pair remains constant. Transmission electron microscopy shows that the silicide formation is not uniform at the damaged contacts. A mixture of dominant epitaxialNiSi2and a minor amount of polycrystallineNiSi2phases was identified. We have proposed mechanisms to explain the polarity effect on failure: wear-out mechanism for the damaged positive contacts ofNi/n+-Si,electromigration enhanced silicide formation for the damaged negative contacts ofNi/Ni2Si/n+-Siand electron-hole recombination mechanism for the damaged negative contacts ofNi/p+-SiandNi/Ni2Si/p+-Si.©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366047

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

High quality GaN epitaxial layers were grown on 6H–SiC substrates by using low-pressure metalorganic chemical vapor deposition method. Samples employing a three-periodGaN/Al0.08Ga0.92N(100 Å/100 Å)as a buffer layer produce a good quality GaN epitaxial layer, with mobility and carrier concentration of612 cm2/V⋅sand1.3×1017 cm−3(at 300 K), respectively. The enhanced electron mobility in theAl0.08Ga0.92N/GaNheterostructures is also observed. By using the van der Pauw method of Hall measurement, the sheet carrier density and mobility at 4.2 K for theAl0.08Ga0.92N/GaNheterostructure are5.8×1012 cm−2and5300 cm2/V⋅s,respectively. Strong SdH (Shubnikov–de Haas) oscillations were observed to confirm the two-dimensional electron gas (2DEG) phenomenon at the AlGaN/GaN top heterointerface. In addition, an extra SdH oscillation also resulted from the high-quality 2DEG channel of the GaN/AlGaN bottom heterointerface. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366048

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The role of crystallographic texture in electromigration resistance of interconnect lines is well documented. The presence of a strong (111) fiber texture results in a more reliable interconnect structure. It is also generally accepted that grain-boundary diffusion is the primary mechanism by which electromigration failures occur. It has been difficult to this point, however, to obtain statistically reliable information of grain-boundary structure in these materials as transmission electron microscopy investigations are limited by tedious specimen preparation and small, nonrepresentative, imaging regions. The present work focuses upon characterization of texture and grain-boundary structure of interconnect lines using orientation imaging microscopy, and particularly, upon the linewidth dependence of these measures. Conventionally processed Al–1&percent;Cu lines were investigated to determine the affects of a postpatterning anneal on boundary structure as a function of linewidth. It was observed that texture tended to strengthen slightly with decreasing linewidth subsequent to the anneal procedure. Grain morphology changed substantially as the narrow lines became near bamboo in character and the crystallographic character of the boundary plane changed as a function of linewidth. These results are contrasted with those obtained from Al–1&percent;Cu lines, which were fabricated using the damascene process. The damascene lines show a marked weakening in texture as the linewidth decreases, accompanied by a more random misorientation distribution. A description of the competing energetics, which result in the observed microstructures, is included. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365763

出版商:AIP    

年代:1997

数据来源: AIP