Praseodymium silicide formation at the Pr2O3/Si interface

The interface and layer structure of praseodymium (Pr) oxide layers grown on Si(0 0 1) from a high-temperature effusion cell are studied using grazing incidence X-ray diffraction. Due to the interdiffusion of praseodymium and silicon atoms, Pr silicide forms in the layers. We find that Pr silicide is the favorable structure under oxygen deficient growth conditions in the Pr oxide layer. To avoid the silicidation, additional oxygen must be supplied. The formation of Pr silicide is suppressed for layers grown with an oxygen partial pressure of 10⁻⁷ mbar at a substrate temperature of 700 °C.     

Rapid thermal annealing and titanium silicide formation

Titanium silcides have been formed on monocrystalline (111) silicon substrates by rapid thermal annealing (RTA) of Ti layers deposited on Si at 700–800 °C for 1 to 240 s. The phase composition is dependent on the annealing temperature and time: at 700° and 750 °C for short annealing, TiSi and TiSi₂ are observed. At 800 °C and by increasing the exposure time at 700 ° and 750 °C, only TiSi₂ is detected. The growth of the total silicide thickness is found to be faster for RTA than for conventional furnace annealing and governed by two different mechanisms depending on the phases formed: in the range 700–750 °C, and 750–800 °C, activation-energy values of 2.6 ± 0.2 and 1.5 ±0.2 eV are found, respectively.For a thin deposited Ti layer (< 100 nm), the whole Ti is finally transformed into TiSi₂ with 20@ cm resistivity. For thicker Ti thicknesses, titanium oxide stops the reaction.     

Ion induced silicide formation in niobium thin films

MeV ⁴He backscattering and x-ray diffraction analysis were used to examine the intermixing of niobium thin films on single crystal silicon during ²⁸Si⁺ ion bombardment. The ambient temperature dependence of the intermixing is reported. The dependence cannot be explained by either radiation-enhanced diffusion or cascade mixing alone. The silicides. NbSi₂ and Nb₅Si₃, were both observed. Silicide growth was found to be proportional to the square root of the fluence for the case in which the ion range exceeds the film thickness.     

Si growth effects on the formation of Er silicide nanostructures

In this work, an ultra-high vacuum scanning tunneling microscopy has been utilized to study the effects of Si atoms to the formation and growth evolution of Er silicide nanostructures. Si evaporation is performed on the vicinal Si(0 0 1) surface as well as Er growth under different growth conditions: growth procedure, annealing temperature and duration time. The experimental results show that the Si evaporation performed at a high temperature plays a key role on the growth of Er silicide nanostructures. The deposited Si atoms become a significant source of the Si reactant and mainly affect the early growth stage of the nanostructures. It is also shown that Er atom is possibly another diffusing species during the growth of Er silicide nanostructures on the Si(0 0 1) surface.     

The Ba/Si(100)-2 × 1 interface I. XPS and XAES studies of silicide formation

In two complementary papers we present the results and analysis of an extended study of the Ba/Si(100)−2 × 1 interface. In this paper, we will discuss X-ray excited Auger electron spectroscopy- and X-ray photoelectron spectroscopy chemical shifts, as well as plasmon losses, which have been studied to answer the question whether silicide formation occurs at this interface. It is found that no silicide formation takes place at room temperature. Two Ba-Si phases are detected as reaction products upon annealing the Ba/Si(100) system at ˜ 550 K.     

AES and factor analysis study of silicide growth at the Pd/c-Si interface

We have measured the evolution of a palladium/silicon interface under consecutive annealing periods, performed at 200°C in UHV conditions. The interface was analyzed by means of Auger electron spectroscopy combined with factor analysis applied in a sequential way. We found that silicide appears only after annealing and evolves until all the palladium is consumed. A silicon compound different from silicide, identified as Pd_xSi with x<2 is found at the interface Pd/Si and Pd₂Si/Si, before and after annealing respectively.     

Tungsten silicide formation by XeCl excimer-laser irradiation of W/Si samples

We report a study of the formation of tungsten silicide at the W-Si interface, induced by multipulse (up to 300 shots) XeCl excimer-laser irradiation of W(150 nm)/Si and W(500 nm)/Si samples. Laser fluences ranging from 0.6 to 1.8 J/cm² were used. After laser treatment the samples were examined by different diagnostic techniques: Rutherford backscattering spectrometry, X-ray scattering, resistometry, and surface profilometry. Numerical computations of the evolution and depth profiles of the temperature in the samples as a consequence of a single 30 ns laser pulse were performed as well. The results indicate that it is possible to obtain a tungsten silicide layer at the W-Si interface at quite low fluences. The layer thickness increases with the number of laser pulses. Complete reaction of the 150 nm thick W film with silicon was obtained at the fluence of 1.2 J/cm² between 30 and 100 laser pulses and at 1.5 J/cm² after 30 laser pulses. The sheet resistance of these silicides was 5–10 . At the used fluences for the 500 nm thick W film only the onset of silicide synthesis at the W-Si interface was observed.     

Rapid thermal oxygen annealing formation of nickel silicide nanocrystals for nonvolatile memory

Discrete NiSi nanocrystals were synthesized by rapid thermal oxygen annealing of very thin Si/Ni/Si films on a SiO₂ tunneling layer. They were used to fabricate metal?Coxide?Csemiconductor capacitor memory. Electrical properties of the memory device such as programming, erasing and retention were characterized and good performance was achieved.     

Microstructural investigation of nickel silicide thin films and the silicide-silicon interface using transmission electron microscopy

This article discusses the results of transmission electron microscopy (TEM)-based investigation of nickel silicide (NiSi) thin films grown on silicon. Nickel silicide is currently used as the CMOS technology standard for local interconnects and in electrical contacts. Films were characterized with a range of TEM-based techniques along with glancing angle X-ray diffraction. The nickel silicide thin films were formed by vacuum annealing thin films of nickel (50 nm) deposited on (100) silicon. The cross-sectional samples indicated a final silicide thickness of about 110 nm. This investigation studied and reports on three aspects of the thermally formed thin films: the uniformity in composition of the film using jump ratio maps; the nature of the interface using high resolution imaging; and the crystalline orientation of the thin films using selected-area electron diffraction (SAED). The analysis highlighted uniform composition in the thin films, which was also substantiated by spectroscopy techniques; an interface exhibiting the desired abrupt transition from silicide to silicon; and desired and preferential crystalline orientation corresponding to stoichiometric NiSi, supported by glancing angle X-ray diffraction results.     

Nitrogen irradiation of Fe/Si bilayers: nitride versus silicide phase formation

In the course of a systematic investigation of heavy ion-irradiated Fe/Si layers, we have studied atomic transport and phase formation induced by 22-keV ¹⁴N²⁺ ion implantation in ⁵⁷Fe(30 nm)/Si bilayers at high fluences. We report here results obtained by Rutherford backscattering spectroscopy, X-ray diffraction, and conversion electron Mössbauer spectroscopy after implantation and post-implantation annealing treatments. The irradiations caused little sputtering, but significant interface mixing. During implantation, iron nitrides, but no silicides were formed, even at the highest nitrogen fluence of 2×10¹⁷ ions/cm². When heating these samples in vacuo up to 700 °C, the iron-rich phases -Fe₃N and -Fe₄N were produced. Starting at 600 °C the silicide phase -FeSi₂ was also identified. PACS 61.72.Ww; 61.80.-x; 68.35.Dv; 81.20.-n; 81.70.-q     

SHI induced silicide formation and surface morphology at Co/Si system

Ion beam mixing is a useful technique to produce modifications at the surface and interface of the solid material. In the present work, ion beam induced modifications at Co/Si interface using 120 MeV Au-ion irradiation has been studied at ion fluences in the range of 10¹² to 10¹⁴ ions/cm² by secondary ion mass spectroscopy (SIMS) technique and calculated mixing efficiency at the interface. Silicide formation has been discussed on the basis of swift heavy ion (SHI) irradiation induced effects. Surface morphology and roughness of irradiated system with fluence 5 × 10¹³ and 1 × 10¹⁴ ions/cm² is studied by scanning tunneling microscopy (STM). Roughness of the surface shows marks of melting process and confirms the appearance of some pinholes in the reacted Co/Si system. Comparative study was also undertaken on annealed sample at 300 °C and then irradiated at a dose 1 × 10¹⁴ ions/cm².     

A microcanonical model for interface formation

We describe a new cellular automaton model which allows us to simulate separation of phases. The model is an extension of existing cellular automata for the Ising model, such as Q2R. It conserves particle number and presents the qualitative features of spinodal decomposition. The dynamics is deterministic and does not require random number generators. The spins exchange energy with small local reservoirs or demons. The rate of relaxation to equilibrium is investigated, and the results are compared to the Lifshitz-Slyozov theory.     

Oxide circle formation at silicon-polymer interface

We demonstrate that precipitation of implanted erbium ions at silicon-polymer interface initiates oxidation reaction of Si(1 0 0) surface at room temperature. Oxidation reaction starts through spontaneous formation of circular patches of SiO_x and the diameter of these circles grows uniformly with time and touch each other to cover the entire surface by keeping the thickness of these patches almost fixed at 4 nm. The nucleation and in-plane growth rates of SiO_x circles are found to be dependent on the fluence of erbium-implantation, the condition of substrate and can be controlled by controlling oxygen partial pressure of the environment. In addition to the precipitation of erbium ions at silicon-polymer interface, enhancement of concentration of erbium ions was observed at periodic depths within polymer film confirming that in ultra-thin films polymer molecules form layers parallel to substrate surface due to confinement.     

Origin of ion beam mixing effects on morphological features in solid-phase titanium silicide formation

The origin of the ion beam mixing effect, which causes the formation of smooth silicide films, is investigated for the Ti/Si solid-phase silicidation reaction. Ge ion beam mixing of a conventional Ti/c-Si structure with an oxide-contaminated interface shows an obvious effect when the implant conditions are such that the Ti/Si interface is amorphized. On the other hand, silicidation without ion mixing for Ti/a-Si and Ti/c-Si structures with oxide-free interfaces, prepared by sequential deposition in UHV, results in smooth and rough film surfaces, respectively. This strongly suggests that the ion beam mixing effect primarily comes from the amorphization of the Si substrate surface rather than the destruction of the interfacial oxide film.