C. Cohen

Growth and structure of titanium silicide phases formed by thin Ti films on Si crystals

The silicide formation with a titanium film deposited on 〈100〉 single‐crystal silicon, has been studied by using nuclear microanalysis, x‐ray diffraction, and transmission electron microscopy. The presence of interfacial defects and their possible role in the early stages of the reaction has been evidenced. The phase composition was dependent on the annealing temperature and time: at 550u2009°C only TiSi2 is observed; at higher temperatures (>600u2009°C), a thin TiSi2 layer at the interface is again observed, but Ti‐rich silicides grow on top of this layer by increasing the annealing time. For longer annealing times, all the reacted layer progressively transforms into TiSi2. The amount of reacted silicon grows with a (time)1/2 law; the activation energy of 1.8 eV reported for the growth of TiSi2 onto amorphous Si may be appropriate even in this case. The reaction proceeds at a rate of one order of magnitude higher than previously reported for reaction between silicon and an oxygen saturated titanium film. The kin...

Titanium and nickel silicide formation after Q‐switched laser and multiscanning electron beam irradiation

The use of Q‐switched ruby laser and multiscanning electron‐beam annealing to produce the reaction of thin Ti and Ni films deposited onto silicon single crystals has been studied. Rutherford Backscattering (RBS), 16O(d,u2009p)17O* nuclear reaction, scanning electron microscopy (SEM) observation, and x‐ray diffraction were used to characterize the reacted layers. It was found that laser annealing produces a reaction only at the metal‐semiconductor interface: the reacted layers are not uniform in composition and more similar to a mixture than to a well‐defined phase. On the contrary, the silicide layers produced by multiscanning e beam result from the solid‐state reaction of the whole metal film and have a layered structure with well‐defined phase composition and sharp interfaces both between the silicide phases and the underlying semiconductor in Ti/Si system. It was observed that the TiSi2 growth mechanism during e irradiation cannot be explained with the parabolic ’’diffusion controlled’’ mechanism operating...

The Si surface yield as a calibration standard for RBS

Abstract The Rutherford backscattering spectroscopy (RBS) surface height of a pure bulk material can be used as an absolute standard value to calibrate the detector solid angle. This work presents the results of an international collaboration started at the beginning of 1998 to define the surface height of the RBS spectrum ( H 0 ) of Si, amorphized by ion implantation to avoid channeling. The analyses were performed with 1–3 MeV He beams and 170° scattering angle. The detector solid angle was estimated in the different laboratories either by geometrical measurement or by a calibrated standard. The agreement of the experimental H 0 values is of the order ±2%, the claimed accuracy for RBS. The results are also consistent at 2% level with both the stopping power measurements of Konac et al. (1998), and the measurements of Lennard et al. (1999).

Transient annealing as a tool for the investigation of thin‐film–substrate solid‐phase reactions

The solid‐phase reaction of a thin film and a substrate induced by a transient annealing in the solid phase is analyzed in detail. The technique is based on the scanning of a line‐shaped energy beam. At a given point on the sample the transient process can be considered equivalent to an isothermal one at an effective temperature for an effective time. Whatever the assumed reaction process is, it has an exponential dependence on the temperature; moreover, the real annealing time of the transient treatment is quite short so that the effective temperature can be chosen equal to the maximum value reached and the effective time can be computed by solving the heat equation numerically. The beam scanning induces a temperature gradient on the sample along the scanning direction so that each irradiated point is annealed at slightly different effective temperatures. In the present work the annealing temperatures range from 600u2009°C up to 1100u2009°C and the effective times from 0.7 to 1.5 sec, owing to the different expe...

Study of ytterbium implanted calcia stabilized zirconia thin films and yttria stabilized zirconia single crystals

Abstract Calcia stabilized zirconia thin films and yttria stabilized zirconia single crystals were Yb implanted at 150 and 210 keV, and at various doses up to 1.3 × 1017 ions/cm2 in order to modify locally the oxygen transport properties. Rutherford back-scattering and nuclear microanalysis on the implanted thin films give information about the implantation profiles and sputtering yields. The results show that the ratio of the sputtering rates of two elements of the film is equal to their concentration ratio. At high implantation doses the Yb profile is nearly flat in the surface region with [Yb]/[Zr] = 1.1. 18O tracing experiments demonstrate that a significant oxidation of the implanted samples occurs in air at room temperature. Further oxidation takes place during a 500 °C annealing in air which does not modify the Yb profile and leads to a final mean composition (ZrO2)x(Yb2O3)y (CaO)z. For the YSZ single crystals, channelling measurements demonstrate that the implanted region is highly damaged. As YSZ...

Silicon loss during TiSi2 formation

When Ti‐Si diffusion couples are annealed in vacuum to form TiSi2, most of the oxygen contamination in the as‐deposited metal film is lost. An experiment demonstrating that a Si loss also takes place is presented, thus confirming that the oxygen loss occurs by SiO sublimation.

Ion implantation of silicon in gallium arsenide: Damage and annealing characterizations

Abstract The purpose of this work is twofold: (i) to study the damage induced by ion implantation, with special attention to low implanted doses; (ii) to study the efficiency of annealing techniques — particularly incoherent light annealing — in order to relate the electrical activity of implanted atoms to damage annealing. We have used three methods to study the damage induced by ion implantation: (1) RBS (or nuclear reactions) in random or in channeling geometry (2) RX double crystal diffractometry and (3) electrical measurements (free carrier profiling). Damage induced by silicon implantation at doses >1014at/cm2 can be monitored by all three techniques. However, the sensitivity of RBS is poor and hence this technique is not useful for low implantation doses. As device technology requires dopant levels in the range of 5 × 1012 atoms/cm2, we are particularly interested to the development of analytical techniques able to detect the damage at this implantation level. The sensitivity of such techniques was checked by studying homogeneously doped (5 × 1016 e−/cm3) and semi-insulating GaAs samples implanted with 3 × 1012 silicon atoms/cm2 at 150 keV. The substrate temperature during implantation was 200°C. The damage produced in these samples and its subsequent annealing are evidenced by strong changes in X-ray double crystal diffraction spectra. This method hence appears as a good monitoring technique. Annealing of the implanted layers has been performed using incoherent light sources (xenon lamps) either in flash or continuous conditions. Reference samples have also been thermally annealed (850°C, 20 min in capless conditions). The results are compared, and the electrical carrier profiles obtained after continuous incoherent light irradiation indicate that the implanted silicon atoms are almost dully activated. The advantages and disadvantages of incoherent light irradiation are discussed (surface oxidation, surface damage) in comparison with standard thermal treatment.

Channeling in virgin and Yb implanted yttria stabilized zirconia crystals

Abstract Channeling experiments have been performed on [111] yttria stabilized zirconia (YSZ) single crystals with uniform Y concentration of 19 mol %. These crystals have the fluorite structure and contain 5% of oxygen vacancies. Various axial and planar, mixed (Zrue5f8O) and single crystallographic directions have been investigated. The results show a strong oxygen-oxygen vacancy interaction: the nearest neighbours of a vacancy (i.e. 6 oxygen atoms) are displaced from regular lattice sites by a distance greater than 0.5 A. The other oxygen atoms are also certainly displaced but by smaller quantities. No preferential direction could be evidenced for this displacement. A cation relaxation is not excluded by our results but its amplitude should not exceed ≅0.1 A . Some YSZ crystals were implanted with 1.2×1016 and 1.2×1017 Yb atoms/cm2 at 210 keV. The lattice parameters of YSZ and ytterbium stabilized zirconia are identical. For the low implantation dose, a full crystalline recovery is observed after a 1000°C annealing and Yb is 100% substitutional. A 1300°C annealing is required for the high implantation dose, for which the concentration ratio [Yb]/[Zr]≅1.1 in the implanted region. This region appears, after annealing, in full epitaxy with the substrate and the behaviour of Yb and Zr atoms is identical. However, the rather high minimum yields measured are indicative of strong atom relaxation.