Single crystals 4H-SiC were implanted with 50 keV helium ions at temperatures up to 600 °C and fluences in the range 1×1016–1×1017cm−2. The helium implantation-induced swelling was studied through the measurement of the step height. The different contributions of swelling were determined by combining simulations of x-ray diffraction curves and transmission electron microscopy observations. At room temperature, amorphization occurs between 1 and 2×1016cm−2, inducing the decrease in density of about 15%. For high-temperature implants, amorphization does not occur. The strain profiles show saturation in the near-surface region, indicating that a threshold concentration of defects is reached. All the additional point defects created during the implantation have been supposed to annihilate. In the region of high-energy deposition density, the value of strain increases with fluence up to values larger than 6%. The elastic contribution to swelling has been obtained by integration of the strain profile determined by x-ray diffraction simulations. Then, the contribution of helium bubbles to the step height is found to be linear with the fluence: 0.8nm∕1016He∕cm2.

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The strain induced by room temperature helium implantation into 4H-SiC below the threshold amorphization dose results from both point and He-related defects. When the helium concentration is lower than 0.5% the strain profile follows the point defect profile, whereas at higher concentrations the He ions have a dominant effect on the strain. Upon annealing, the near surface strain progressively relaxes up to 1500 °C while the maximum strain relaxation stops at a temperature where helium ions agglomerate into platelets. When the vacancies become mobile, the platelets evolve into bubble clusters that expel dislocation loops whose migration is enhanced by the strain.

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Direct current magnetron sputtering was used to produce AlN x O y thin films, using an aluminum target, argon and a mixture of N 2 +O 2 (17:3) as reactive gases. The partial pressure of the reactive gas mixture was increased, maintaining the discharge current constant. Within the two identified regimes of the target (metallic and compound), four different tendencies for the deposition rate were found and a morphological evolution from columnar towards cauliflower-type, ending up as dense and featureless-type films. The structure was found to be Al-type (face centered cubic) and the structural characterization carried out by X-ray 2 diffraction and transmission electron microscopy suggested the formation of an aluminumbased polycrystalline phase dispersed in an amorphous aluminum oxide/nitride (or oxynitride) matrix. This type of structure, composition, morphology and grain size, were found to be strongly correlated with the electrical response of the films, which showed a gradual transition between metallic-like responses towards semiconducting and even insulating-type behaviors. A group of films with high aluminum content revealed a sharp decrease of the temperature coefficient of resistance (TCR) as the concentration ratio of non-metallic/aluminum atomic ratio increased. Another group of samples, where the non-metallic content became more important, revealed a smooth transition between positive and negative values of TCR. In order to test whether the oxynitride films have a unique behavior or simply a transition between the typical responses of aluminum and of those of the correspondent nitride and oxide, the electrical properties of the ternary oxynitride system were compared with AlN x and AlO y systems, prepared in similar conditions.

He ϩ ions were implanted into silicon with a fluence of 5ϫ10 16 cm Ϫ2 at different temperatures ranging from 473 to 1073 K. Samples were analyzed by thermal helium desorption spectroscopy and by transmission electron microscopy. As far as cavity formation is concerned, the behavior can be divided into three stages depending on the implantation temperature. However, it is found that helium release from cavities is governed by a single mechanism regardless of the implantation temperature. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1525059͔With the miniaturization of microelectronic devices, the purity requirements of semiconductors become extremely severe. In particular, the density of metallic impurities in the active region of the devices must be extremely low. Such an impurity level can only be reached by a gettering treatment.In the last few years, work 1,2 has shown that helium induced cavities in silicon can be used as very efficient gettering sites. Cavities in silicon are usually formed by high dose He ion implantation. During subsequent annealing at temperatures above 700°C, bubbles grow and He is released from them by gas outdiffusion, leading to void formation, i.e., empty cavities. Metallic impurities can be trapped on the cavities at their internal surfaces. 1 Numerous studies have been performed varying implantation parameters 3 to optimize cavity formation. The effects of varying the implantation temperature have, however, not received much attention. In this letter, a combination of thermal helium desorption spectroscopy ͑THDS͒ and transmission electron microscopy ͑TEM͒ was used to study the effect of implantation temperature.All the experiments were performed on commercial n -n ϩ silicon wafers. The n-type layer was epitaxially grown on a ͗111͘ orientated n ϩ substrate of Czochralski silicon. The doping concentration of the 100 m thick n region was 1ϫ10 14 P cm Ϫ3 . These samples were implanted to a constant dose of 5ϫ10 16 ions cm Ϫ2 with 50 keV helium ions (Rpϭ500 nm and ⌬Rpϭ140 nm according to SRIM calculations͒. 4 The beam current was kept at 40 A. The structure of the implantation damage was studied with crosssectional TEM using a JEOL 200 CX operating at 200 kV. In order to study cavities with minimal contrast from the unavoidable accompanying lattice damage, specimens were tilted from their ͗110͘ orientation by few degrees in order to reduce diffraction effects. They were also imaged in underfocus and overfocus conditions to highlight the cavity edges with Fresnel contrast. THDS measurements were performed in an ultrahigh vacuum chamber (10 Ϫ8 Pa͒. Helium desorption was monitored using a quadrupole mass spectrometer Balzers QMG 111B while the sample was annealed with a constant heating rate of 5 K/s.The thermal desorption spectrum of helium from the sample implanted at 473 K is shown in Fig. 1͑a͒. Helium release clearly occurs partially at a low temperature from 700 to 900 K and in a high-temperature regime centered at about 1300 K with all the helium being released by 1400 K. Fo...

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