Ion mixing of yttrium and amorphous silicon bilayers was measured as a function of fluence and temperature using 600-keV Xe++ ions between 80 and 498 K. At 80 K the mixing rate was in excellent agreement with a theoretical model based on thermal spike mixing. For temperatures up to ≊372 K, the temperature-dependent contributions accounted for less than 50% of the overall mixing rate. For mixing at or above 400 K, our results revealed the formation of an ion-beam-induced orthorhombic Y-Si phase, which is not normally formed during thermal anneals of such bilayers.
We study the dealloying of Ti from alloy films on oxidized Si substrates in the temperature range of 375 to 490°C and an estimated partial pressure of . Reaction products were determined to be and and possibly at the free surface, and at the interface, according to Rutherford backscattering spectrometry and Auger electron spectroscopy. We found that the Cu lattice parameter varies linearly with Ti concentration, and this variation is independent of temperature in this composition range. As a consequence, we were able to study the dealloying kinetics using in situ x‐ray diffraction by monitoring the time dependence of the Cu lattice parameter. We observe that the reaction kinetics obey a parabolic rate law, i.e., , with a single activation energy of , suggesting that one process governs dealloying kinetics over this temperature range. In addition, we note a pronounced composition dependence, in that the reaction rate increases sharply with increasing Ti concentration. These observations suggest that Ti diffusion in Cu is the rate‐limiting kinetic process for the dealloying reactions in this temperature regime. We model the dealloying reaction and in so doing estimate the diffusion coefficient for Ti in these alloy films.
We describe a rapid nondestructive approach to predict the failure time for thin-film interconnects. The prediction is made on the basis of the percolation theory and the scaling model, and is verified by experimental results. Al-Cu fuses are used as our thin-film test structures that were subjected to overstressed conditions for failure. A brief description about the test structure and the experimental procedure is presented. The discrepancy between the exact failure time and the predicted failure time is significantly low, which clearly expresses the strength of this prediction technique. Moreover, this technique is nondestructive and possesses great potential to be widely used as a cost efficient and time efficient reliability test technique in semiconductor industries.
The evolution of microstructure during Au-mediated solid phase epitaxial growth of a SixGe1−x alloy film on Si(001) was investigated by in situ sheet resistance measurements, x-ray diffraction, conventional and high-resolution transmission electron microscopy, energy dispersive x-ray spectroscopy, and Rutherford backscattering spectrometry. Annealing amorphous-Ge/Au bilayers on Si(001) to temperatures below 120 °C caused changes primarily in the microstructure of the Au film. Near ≊130 °C, Ge from the top layer diffused and crystallized along the grain boundaries of Au. The Ge that had reached the Au/Si (001) interface mixed with Si from the substrate, to form epitaxial SixGe1−x islands on Si (001). Si from the substrate had dissolved into Au before entering the growing epitaxial islands. Meanwhile, the Au that was displaced by Ge that filled the Au grain boundaries, diffused into the top layer along columnar voids in the amorphous Ge film. With increasing temperature, more Au was displaced to the top by the flux of Ge towards the substrate, facilitating further epitaxial growth and the coalescence of epitaxial SixGe1−x islands. At 310 °C, the initial Au film was displaced completely to the top by a laterally continuous SixGe1−x epilayer of uniform composition (x≊0.15). The epilayer thickness was limited by that of the initial Au film. Twins and residual amounts of Au trapped near the SixGe1−x/Si(001) interface were the predominant defects observed in the completely strain-relaxed SixGe1−x epilayer.
Pure Ag layers were cladded with thin alloy (Ag with 3 at. % aluminum) layers to form a [Ag(Al)∕Ag∕Ag(Al)] structure on SiO2. The effective resistivity of the cladded Ag metallization is slightly greater than pure silver and less than the Ag(Al) alloy metallization. The clad structures showed a nearly 38 times enhancement in electromigration resistance when compared to pure Ag and seven times greater than the Ag(Al) alloy. The enhancement in lifetime of the clad structure was attributed to enhanced thermal stability due to segregation of Al2O3 at the Ag grain boundaries leading to reduced grain size and changes in thermodynamic properties and also reduced atomic mobility because of the topmost layer acting as a passivation layer.
Amorphous indium gallium zinc oxide (a-IGZO) thin films of the highest transmittance reported in literature were initially deposited onto flexible polymer substrates at room temperature. The films were annealed in vacuum, air, and oxygen to enhance their electrical and optical performances. Electrical and optical characterizations were done before and after anneals. A partial reversal of the degradation in electrical properties upon annealing in oxygen was achieved by subjecting the films to subsequent vacuum anneals. A model was developed based on film texture and structural defects which showed close agreement between the measured and calculated carrier mobility values at low carrier concentrations (2–6 × 1019 cm−3).
Chemical and structural evolution of hydroxyapatite thin films produced by sol‐gel synthesis is characterized by ion beam analysis, X‐ray diffraction, and Fourier transform infrared spectroscopy. Formation of the hydroxyapatite structure began at 500°C; no other phases were observed at higher temperatures. Elimination of residual organics was observed in the form of the disappearance of excess oxygen, hydrogen and carbon. Crystal size increases with increasing anneal temperature; spectroscopy indicates the formation of highly crystalline films. The analytical methods chosen provide insight into subtle chemical and structural changes which occur in films produced by this synthetic route.
There has recently been increasing use of MeV ion beams for materials modification. When compared to more common lower, keV-energy implantation, MeV-ion irradiation has a broader variation in the type of damage along the ion path. This is because of the more significant difference between damage and range distributions in the case of MeV implants as opposed to keV implants. Previous works showed that MeV-implanted Si-ions react differently with various types of lattice damage in silicon; interactions range from simple point-defect annihilation to the formation of extended defects. Earlier investigations of Au implanted into previously amorphized silicon have observed Au segregation as a result of its being expelled from the recrystallizing amorphous layer during ion-beam irradiation. In this study, the interaction of MeV Au ++ atoms with the different types of damage produced along the MeV-ion beam path is investigated. Silicon (100) single crystal wafers were given a HF dip and were then mounted on a copper sample stage; the stage functions as a heat-sink. The stage together with the specimen was then placed in a Tandem ion-implanter. The specimens were implanted with gold; implant-energies varied from 1.8 - 4.4 MeV and fluences ranged between 0.1 - 10×10 16 Au ++ /cm 2 .
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