Search

Laser annealing was employed to trigger the solid-state reaction of a thin Co film (2.5 nm) with undoped Si. A metastable disilicide layer was obtained after one laser pulse close to the melt threshold. Its diffraction pattern, relaxed lattice parameter, and residual resisitivity are consistent with the formation of the defective CsCl structure. The CoSi2 phase was found after prolonging the thermal treatment with additional pulses or rapid thermal annealing. Because CoSi is skipped in the phase sequence, CoSi2 layers are more uniform in thickness, have an increased superconductivity and a reduced formation temperature. This approach is compatible with the SALICIDE process and can be used to form smooth contacts in superconducting or regular transistors. [ABSTRACT FROM AUTHOR]

The reaction of a Ni 0.9 Pt 0.1 7 nm-thick thin film with the underlying Si(001) substrate as a function of the annealing temperature was studied using in situ XRD techniques as well as ex situ advanced XRD and TEM imaging on quenched samples. It was found that the Ni 0.9 Pt 0.1 /Si system initially evolves accordingly to diffusion controlled reactions via the development of nano-crystalline Ni-rich Ni 1 − x (Pt) Si x phases that combine the ability of fast kinetic growth and texture inheritance. The system remains then stable over some tens of degrees before Ni(Pt)Si nucleation occurs, once the related energetic barrier is overcome. It was additionally found that this newly observed phase sequence remains valid up to Ni 0.9 Pt 0.1 deposited layer thicknesses of about 16 nm, which is remarkable for such systems. [ABSTRACT FROM AUTHOR]

Thin films of superconducting V 3 Si were prepared by means of RF sputtering from a compound V 3 Si target at room temperature onto sapphire and oxide-coated silicon wafers, followed by rapid thermal processing under secondary vacuum. The superconducting properties of the films thus produced are found to improve with annealing temperature, which is ascribed to a reduction in defects in the polycrystalline layer. Critical temperatures (T c ) up to 15.3 K were demonstrated after thermal processing, compared to less than 1 K after deposition. The T c was always found to be lower on the silicon wafers, by on average 1.9 ± 0.3 K for the annealed samples. This difference, as well as a broadening of the superconducting transitions, is nearly independent of the annealing conditions. In situ XRD measurements reveal that the silicide layer becomes strained upon heating due to a mismatch between the thermal expansion of the substrate and that of V 3 Si. Taking into account the volume reduction due to crystallization, this mismatch is initially larger on sapphire, though stress relaxation allows the silicide layer to be in a relatively unstrained state after cooling. On oxidized silicon, however, no clear evidence of relaxation upon cooling is observed, and V 3 Si ends up with an out-of-plane strain of 0.3% at room temperature. This strain increases as the sample is cooled down to cryogenic temperatures, though the deformation of the polycrystalline layer is expected to be highly inhomogeneous. Taking into account also the reported occurrence of a Martensitic transition just above the critical temperature, this extrapolated strain distribution is found to closely match an existing model of the strain dependence of A-15 superconducting compounds. [ABSTRACT FROM AUTHOR]

Ni-GeSn based materials are promising in order to obtain contacts in complementary metal oxide semiconductor and Si photonic devices. In this work, a systematic and comprehensive study of the solid-state reaction between NiPt thin films and Ge0.9Sn0.1 layers is carried out. A particular focus is given on the impact of the addition of 10 at. % of Pt in Ni thin films. In situ X-ray diffraction and in-plane reciprocal space map measurements reveal a sequential growth in which the first phase appearing corresponds to a Ni-rich phase: (Ni0.9Pt0.1)5(Ge0.9Sn0.1)3. Then, at 245 °C, the Ni-rich phase vanishes to the benefit of the mono-stanogermanide phase (Ni0.9Pt0.1)(Ge0.9Sn0.1), which is unstable. At 360 °C, a more stable (Ni1–yPty)(Ge1–xSnx) phase is obtained concomitantly to the formation of PtSnx compounds. Finally, Sn segregation occurs at even higher temperatures. Even if Pt addition in Ni thin films complicates the phase formation sequence, it positively impacts the surface morphology and roughness, delays film agglomeration and Sn segregation, and stabilizes the electrical properties of the stanogermanide in a wide range of temperatures. [ABSTRACT FROM AUTHOR]

The metallurgical properties of the Ti/InP system meet a great interest for its use as a contact in the scope of various applications such as the Si Photonics. The investigations conducted on this system highlight the initiation of a reaction between the Ti and the InP substrate during the deposition process conducted at 100 °C. The simultaneous formation of two binary phases, namely, Ti2In5 and TiP, is attributed to the compositional gradient induced in the InP by the wet surface preparation and enhanced by the subsequent in situ Ar+ preclean. Once formed, the TiP layer acts as a diffusion barrier inhibiting further reaction up to 450 °C in spite of the presence of an important Ti reservoir. At higher temperature, however, i.e., from 550 °C, the reaction is enabled either by the enhancement of the species diffusion through the TiP layer or by its agglomeration. This reaction gives rise to the total consumption of the Ti2In5 and Ti while the TiP and In phases are promoted. [ABSTRACT FROM AUTHOR]

Solid-state reactions between Ni1-uPtu (00.7Ge0.3 after rapid thermal annealing at 280 to 700 °C were studied. Numerous physical and chemical characterizations such as sheet resistance analysis, scanning electron microscopy, transmission electron microscopy, Xray diffraction measurement, and atom probe tomography were used to determine the formation and morphological degradation mechanisms of the pure Ni-based germanosilicide. In particular, atom probe tomography was used to quantitatively determine the element distribution in 3D and at the atomic scale. Similar mechanisms for the degradation were found for the Ni mono germanosilicide with and without Pt and led to Ge rich Si1-xGex regions that are etched away by the selective etch. These mechanisms, Ge out-diffusion and agglomeration, have a combined effect on the germanosilicide degradation and occurs through Ge and Ni diffusion, respectively. Adding Pt increases the thermal stability of the layer owing to changes in the phase sequence and texture and strong binding with Ge atoms. Several models are developed to explain the different steps of the film morphological degradation. The thermodynamics description of the equilibrium in the quaternary Ni-Pt-Si-Ge system allows us to rule out a pure thermodynamics explanation for the morphological stabilization due to Pt addition. [ABSTRACT FROM AUTHOR]

Thin films of Ni(Si1-xGex) are of interest for their applications in metal-oxide semiconductor transistors as contacts and interconnections. In this work, the lattice parameters and the coefficients of linear thermal expansion (γa, γb, and γc) of the orthorhombic Ni(Si1-xGex) alloys, with 0<=x<=1, were determined from high-temperature x-ray diffraction data (298–1073 K). A negative thermal expansion along the b axis of Ni(Si1-xGex) is observed for all x values of the Ge concentration: the magnitude of the thermal expansion coefficient decreases with increasing Ge concentration. The anisotropy of the thermal expansion is potentially important for the integration of Ni(Si1-xGex) in microelectronic devices. [ABSTRACT FROM AUTHOR]

The lattice parameters and the coefficients of linear thermal expansion of the orthorhombic Ni([Si.sub.1-x][Ge.sub.sub.x]) alloys were determined from high-temperature X-ray diffraction data. For all the x values of the Ge concentration, a negative thermal expansion along the b axis of Ni([Si.sub.1-x][Ge.sub.sub.x]) was observed.

Phosphorus diffusion and its distribution during the solid-state reactions between Ni0.9Pt0.1 and implanted Si substrates are studied. Silicidation is achieved through a first rapid thermal annealing followed by a selective etching and a direct surface annealing. The redistribution of phosphorus in silicide layers is investigated after the first annealing for different temperatures and after the second annealing. Phosphorus concentration profiles obtained thanks to time of flight secondary ion mass spectrometry and atom probe tomography characterizations for partial and total reactions of the deposited 7 nm thick Ni0.9Pt0.1 film are presented. Phosphorus segregation is observed at the Ni0.9Pt0.1 surface and at Ni2Si interfaces during Ni2Si formation and at the NiSi surface and the NiSi/Si interface after NiSi formation. The phosphorus is evidenced in low concentrations in the Ni2Si and NiSi layers. Once NiSi is formed, a bump in the phosphorus concentration is highlighted in the NiSi layer before the NiSi/Si interface. Based on these profiles, a model for the phosphorus redistribution is proposed to match this bump to the former Ni2Si/Si interface. It also aims to bind the phosphorus segregation and its low concentration in different silicides to a low solubility of phosphorus in Ni2Si and in NiSi and a fast diffusion of phosphorus at their grain boundaries. This model is also substantiated by a simulation using a finite difference method in one dimension. [ABSTRACT FROM AUTHOR]