摘要:

A common result obtained in electromigration experiments carried out on Al‐Si lines using different high resolution resistometric methods, is a monotonous non‐linear resistance increase at the very beginning of the high current electromigration test, and a decrease after the high stressing current is switched off. These effects have often been attributed to the attainment of a steady state of vacancy concentration during and after electromigration. This paper shows how even small abrupt temperature steps, always present at the beginning and after electromigration tests, are the triggering events for different, often reversible, physical phenomena contributing to non‐linear resistance changes. Precipitation–dissolution of alloyed elements appears to be the most significant one. Abrupt temperature changes also induce a change of the hydrostatic stress of passivated lines. The relaxation of the hydrostatic stress could be coupled with a void volume change, and the total resistance is a function of both the hydrostatic stress (through resistivity) and of void volume. However, we demonstrate that in our experiments the effect of hydrostatic stress relaxation on resistance variations is negligible with respect to the action of precipitation–dissolution. These non‐linear, thermally induced effects, however, do not exclude possible simultaneous resistance changes due to the accumulation/relaxation of the electromigration damage. Experimental results are collected by means of different, complementary techniques. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363552

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We demonstrate that periodic exposure to zero bias duringinsituhydrogenation of reverse‐biasedp‐type Schottky barrier structures has dramatic effects on H penetration. H influx can be slowed or even stopped by such protocols. By contrast, similar pulsing techniques produce almost no changes of penetration inn‐type barriers during hydrogenation; this latter observation is in sharp contrast to the expectations that charge conversion from H+to H−would reverse the drift of H species. We suggest that these effects are caused by the charge conversion of relatively immobile H‐related defects. In thep‐type barriers this results in a weakening or reversal of the near surface electric field, effectively stopping the drift of H+into the bulk. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362825

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

This article shows that the presence of low‐temperature‐grown GaAs (LT‐GaAs) in LT‐GaAs/AlAs/GaAs:Si heterostructures increases the Al/Ga interdiffusion at the heterostructure interfaces. The interdiffusion enhancement is attributed to the presence of Ga vacancies (VGa) in the As‐rich LT‐GaAs, which diffuses from a supersaturation ofVGafrozen‐in during sample growth. Chemical mapping, which distinguishes between the AlAs and GaAs lattices at an atomic scale, is used to measure the Al concentration gradient in adjacent GaAs:Si layers. A correlation is observed between the Al/Ga interdiffusion and the gate breakdown voltage in metal‐insulator field‐effect transistor structures containing LT‐GaAs. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362742

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have explored the mechanisms underlying the gettering of Pt atoms dissolved in crystalline Si. By using Pt implantation at different fluences followed by a thermal process at 970 °C for 5 h we were able to prepare crystalline silicon wafers containing a uniform Pt concentration in the range 2×1012–2×1014atoms/cm3. Subsequently, a heavily dopedn‐type region was produced on one side of the wafer by P diffusion at 900 °C. Following this deposition process we have studied the kinetics of Pt gettering to the P‐doped region in the temperature range 700–970 °C and for annealing times ranging from 30 min to 48 h. Lifetime measurements by means of a contactless technique were used to detect the depletion of Pt in the bulk of the wafer due to the gettering process. The large range of initial Pt concentrations that we have explored allowed us to identify and separate the kinetics and thermodynamics constraints that determine the gettering efficiency and to propose a phenomenological model for the gettering of Pt. In particular, it has been found that the kinetics of the gettering process are driven by the dissolution of immobile substitutional Pt atoms into interstitial sites. This process is assisted by Si self‐interstitials and characterized by an activation energy of 0.4 eV. Moreover, the equilibrium distribution of Pt is thermodynamically determined by a segregation coefficient of the Pt atoms between the gettering sites and the silicon matrix. This segregation coefficient, and hence the gettering efficiency, decrease when the temperature of the gettering process is increased and is described by an activation energy of 2.5 eV. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362800

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Interfacial reactions, phase formation, microstructure, and composition, as functions of heat treatments (400–800 °C) were investigated in Ni90Ti10alloy thin film coevaporated on ann‐type 6H‐SiC (0001) single‐crystal substrate. The study was carried out with the aid of Auger electron spectroscopy, x‐ray diffraction, and analytical transmission electron microscopy. The interaction was found to begin at 450 °C. Ni and C are the dominant diffusing species. The reaction zone is divided into three layers. In the first layer, adjacent to the SiC substrate, the presence of Ni‐rich silicide, Ni2Si, and C precipitates, was observed. The second layer is composed mainly of TiC, while the third consists of Ni2Si. This composite structure, consisting of the silicide as a low resistivity ohmic contact, and of the carbide as a diffusion barrier, promises high‐temperature stability crucial to ohmic contact development for SiC technology. Factors controlling phase formation in the Ni–Ti/SiC system are discussed. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362801

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The initial stages of epitaxial growth of Ag on InP(100) have been studied usinginsituandexsituelectron microscopy. Vicinal InP substrates were cleaned by heating to about 400 °C in ultrahigh vacuum. Silver was deposited at substrate temperatures between 350 and 500 °C. The microstructural evolution was monitored for coverage between 0.5 and 8 monolayers usinginsituhigh spatial resolution secondary electron microscopy andexsituplan‐view transmission electron microscopy (TEM). At sub‐monolayer coverage, uniform, faceted islands of Ag are formed with edges aligned along InP ⟨110⟩ directions. Continued deposition leads to growth of preexisting islands followed by coalescence. During coalescence, a reduction in the island height, an increase in island‐substrate interfacial area, and a disappearance of faceting are observed. At high coverage, during high temperature (450 °C) growth, the formation of faceted pits are observed. For higher temperatures (500 °C) and at low coverage, islands transform from square to rectangular shapes. Plan‐view TEM indicates that the smallest Ag islands (∼5 nm) are not coherent with the substrate and that there are two distinct epitaxial relationships between the Ag islands and the InP substrate. For high‐temperature growth, the (110)Ag plane is parallel to InP(100) substrate and there is evidence for chemical reaction and presence of In on the surface. For lower temperature depositions (350–400 °C), the (100)Ag is parallel to (100) InP. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362802

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A structural study of the initial interface region formed by titanium on silicon (111) was undertaken. Thin films (100 A˚) of titanium were deposited in ultrahigh vacuum (UHV) conditions onto atomically clean silicon(111) wafers and annealedinsituat 25 °C intervals between 300 and 475 °C. Structural characterization of the evolving interface was performed primarily via extended x‐ray absorption fine structure (EXAFS) measurements. Results indicate that a major structural rearrangement takes place between 400 and 425 °C. EXAFS fitting analysis reveals this transition to be from a disordered TiSi‐like phase to a more ordered C49‐like disilicide state. The results are compared with those previously reported for the zirconium:silicon system. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362803

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The stability of TiN barriers deposited between Si or SiO2substrates and AlSiCu metallic alloy contacts was investigated as a function of the sintering temperature and of the application of an oxidation step to the barrier. It was found that Al penetrates the barrier during the sintering at 450 °C for 1 h, which also results in the diffusion of Ti inside the Al alloy. This mutual interdiffusion increases with temperature but when oxygen is present at the barrier surface, the intensity of diffusion processes decreases considerably. It is also established that the barrier remains more stable on SiO2than on the Si substrate. It is suggested that the better reaction resistance of oxidized TiN compared with oxygen‐free nitride may be due to the blocking of fast‐diffusion paths of Al diffusion by oxygen and subsequently the formation of Al2O3, AlN, and TiAl3phases during sintering. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362804

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Bi/Mn/Al/Bi/Mn multilayers with different Al‐interlayer thickness have been deposited on glass substrates at room temperature. The multilayers are not protected by a passivating layer, such as SiOx, in order to investigate the interplay between Al‐interlayer thickness and homogeneity, granularity, and topography before and after annealing. Due to the Al interlayer, the diffusion across the Bi/Mn/Al/Bi/Mn stack was reduced as demonstrated by x‐ray analysis, scanning electron microscopy, and Rutherford backscattering spectrometry. During annealing, two (MnxBi100−x)100−yAlylayers are formed which are separated by an Al interlayer. After annealing, polar Kerr hysteresis loops as measured from the front side of the films show a superposition of two hysteresis loops, opposite in sign, with different coercive fields. The presence of different coercive fields is explained by different granularity of the top and bottom (MnxBi100−x)100−yAlylayer. The coercive field of the top (MnxBi100−x)100−yAlylayer reaches values up to 1.25 T, while the bottom layer shows a constant value of 0.3 T independent of the Al‐interlayer thickness. The opposite sign of the two contributions to the Kerr loops is explained by the different relative index of refraction at the air/(MnxBi100−x)100−yAlyand the Al/(MnxBi100−x)100−yAlyinterface. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362781

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The surface states of sol‐gel derived PbTiO3thin films on Si substrates before and after Ar+sputtering were studied by x‐ray photoelectron spectroscopy (XPS). The results showed that there was no residual carbon or other impurity element in the films except some carbon surface contamination due to specimen handling or pumping oil. A large amount of absorbed oxygen was near the surfaces of the films. The chemical composition of the films was found to be stoichiometric, as proved by inductively coupled plasma results. The valence states of the ions indicated that the films were PbTiO3with perovskite structure. The XPS spectra of the films after Ar+sputtering for 10 min differed greatly from those of as‐prepared films. This probably results from the preferred sputtering of lead atoms and the production of many new dangling bonds during Ar+bombardment. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362805

出版商:AIP    

年代:1996

数据来源: AIP