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The electrical activation of boron implanted in crystalline and preamorphized silicon has been investigated during rapid thermal annealing performed with halogen lamps. Samples implanted with B+ fluences ranging between 5×1014 and 1×1016cm−2 and treated at temperatures between 900°C and 1100°C have been examined. When boron is implanted in crystalline Si, activation proceeds slowly atT

Polycrystalline zirconium samples, implanted with Ti and Ni ions at doses ranging from 5 × 10 15 to 5 × 10 16 ions/cm 2 were oxidized in dry oxygen flow at 450°C and then analyzed by means of the Rutherford backscattering of a He + microbeam, a few microns in diameter, and by EPMA. A new etching technique of the sample provided a way of obtaining in-depth information from EPMA. Different computer analysis and simulation programs gave the depth profile for oxygen and for the implanted elements. Diffusion coefficients for oxygen in α-zirconium were drawn from the oxygen concentration profiles and they were found to be in agreement with those reported in the literature. The oxidation strongly modifies the LSS profiles of the implanted impurities, both in shape and position. In particular the oxidation reducing species, Ni, migrates inwards following the oxide-metal interface, whereas the oxidation enhancing species, Ti, migrates outwards.

From experiments of thermal predeposition of phosphorus in silicon, performed at 920 °C and followed by neutron activation analysis and TEM observations, it is concluded that SiP precipitation takes place in the furnace during the isothermal process. In fact, the surface concentration of phosphorus increases with predeposition time attaining values well above the solid solubility; in addition the flat rodlike SiP precipitates grow with the time of predeposition, according to a parabolic law. Finally, considerations of the size of the precipitates indicate that they are not formed during the cooling stage subsequent to predeposition.

High‐dose, high‐current arsenic implantation in silicon produces a partial recrystallization during the implantation process. The phenomenon presents the disadvantage that the recrystallized region is highly defective and remains nearly unchanged during subsequent low temperature thermal treatments. Instead, in implantation conditions leading to an amorphous layer, similar treatments should give rise to a solid‐phase epitaxial regrowth. In this work the nature of the damaged region is investigated by electrical, analytical and structural techniques.

Titanium nitride films have been prepared by implanting 3.4×1017 cm−2 N+2 ions in 600‐A‐thick titanium layers deposited on silicon single crystals. Unlike the films obtained by evaporation or sputtering, both low electrical resistivity and fairly good optical properties were found even in the as‐implanted samples. Moreover, thermal treatments up to 700 °C performed both in vacuum and H2 atmosphere resulted in a further improvement of the overall films characteristics. This opens interesting perspectives of applications for TiN as a transparent (antireflective) conducting material in photovoltaic field, which are presently being investigated.

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 550 °C only TiSi2 is observed; at higher temperatures (>600 °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...

Good quality p+/n and n+/p shallow junctions (< 0.15 um) with reverse current density of few nA/cm2 and low contact resistivity (∼ 5×10–7 Ω cm2) have been fabricated by using Mo suicide and Rapid Thermal Annealing (RTA). The processes of implantation through Mo films and into MoSi2 layers have been comparatively analysed on the basis of SIMS and carrier concentration profiles, TEM observations and DLTS measurements. In the case of n+/p diodes fabricated by ITM technology slightly worse leakage currents have been observed, in spite of the better planarity of the silicide-silicon interface exhibited by these structures.

TiN films prepared by implantation onto evaporated Ti layers are tested as diffusion barriers in contact with a thick Al overlayer. Both the TiN/Al and TiSi2/TiN/Al contact structures are evaluated, after thermal treatments up to 600 C, on shallow junction diodes and four terminal resistor test patterns for contact resistance measurements. It is shown that, upon annealing at 600 C, the TiSi2/TiN/Al contact system still exhibits excellent electrical performances. The degradation is found to depend on TiSi2 thickness and contact area.

The apparent width of the SiO2Si interface was evaluated with Auger electron spectrometry, secondary ions mass spectrometry and transmission electron microscopy for thin silicon dioxide films grown at temperature ranging from 900 to 1100°C, both on single- and poly-crystalline silicon (polysilicon), with the aim of finding the meaning of this kind of measurement for this particular system. The width of the transition between SiO2 and polysilicon was found to depend on both the oxidation temperature and polysilicon doping method, being lower for ion implanted than for gas phase (POCl3) doped samples and for oxides grown at higher temperature. The possible causes for the differences in the interface width are discussed and attributed, in the present case, to the oxide thickness non-uniformity. This is due, in turn, to the lower oxide growth rate, particularly for the lower oxidation temperature, on the silicon grains protruding out of the surface.

The Convergent Beam Electron Diffraction technique (CBED) has been applied to determine the lattice strain in Si 1-x Ge x /Si heterostructures and below patterned films on silicon substrates. The well known problem of the stress relaxation which occurs in thinned TEM samples has been overcome, in the case of the heterostructures, by applying the isotropic elasticity theory to the lattice constants measured along different crystallographic directions through the shift of the High Order Laue Zone (HOLZ) lines in the central disk of the CBED patterns. In this way bulk strain values have been obtained, in good agreement with values deduced from independent techniques. In patterned structures, the high spatial resolution of the CBED technique has been applied to determine the distribution of the components of the strain tensor induced into oxidized silicon substrates by Si 3 N 4 stripes. A good agreement with the results obtained using numerical computations has been found.

The codiffusion of B and Sb implanted in Si with a dose of 2 × 1016 cm−2, corresponding to concentration far above the solid solubility, is investigated at 900 and 1000 °C on the basis of SIMS and carrier profile measurements and TEM observations. The comparison of the codiffusion data with the corresponding ones obtained by the diffusion of each element alone revealed several anomalous effects due to dopant interaction. In particular, our experimental results support the hypothesis of the formation of mobile donor-acceptor pairs and of the increase of the Sb solubility in the region where a high concentration of acceptors is present. On the basis of this feature, a diffusion model that takes pairing and precipitation into account is presented. A simulation program including this model allows us to foresee most of the anomalous phenomena occurring in the high concentration codiffusion experiments and shows in general a satisfactory agreement with experimental profiles.

The basic features of the convergent beam electron diffraction technique (CBED) ina transmission electron microscope (TEM) for the quantitative strainan alysis of silicon nanoregions are described. Details on the procedure employed to obtain the components of the strainten sor from anexp erimental CBED patternare given. The CBED methodology has been recently applied to the analysis of straininthe field of microelectronics; as anexample, the investigationof 0.22 μm wide electrically active silicon regions, underlying silicon nitride stripes in shallow trench isolation structures for non volatile memories, is reported. It is found that the strain field can be related to the different technological steps.

High resolution electron microscopy images of small cubic SiP particles in silicon are computed by means of the programme SHRLI (Simulated High Resolution Lattice Images). A super cell consisting of 4 × 4 silicon unit cells (a = 2.172 nm; b = 1.536 nm), which includes three SiP molecules, is assumed in the multislice calculations. A contrast is evidenced in the image only if preferential etching of the sample at the particles is taken into account. The SiP precipitates result to be darker than the surrounding matrix in both, axial and tilted three beam illumination, in agreement with the experimental observations. Die im Hochauflosungselektronenmikroskop erhaltenen Abbildungen kubischer SiP-Ausscheidungen in -Silizium werden mit Hilfe des SHRLI (Simulated High Resolution Lattice Images)-Programms berechnet. Das „multislice”-Rechenverfahren wird auf eine aus 4 × 4 Si-Einheitszellen bestehenden Uberzelle angewandt, die drei SiP-Molekule enthalt. Ein Kontrast entsteht in den berechneten Abbildungen nur, wenn eine bevorzugte Atzung der Probe an den Teilchen in Betracht gezogen wird. Die SiP-Ausscheidungen treten im Bild dunkler auf als die Umgebung, sowohl in der axialen als auch in der gekippten Beleuchtung. Dieses Ergebnis ist mit den experimentellen Beobachtungen in Ubereinstimmung.

A structural study on the epitaxial relationships of TiSi2 on silicon has been carried out by transmission electron microscopy. Metallic films, heat treated at high temperatures (750 and 850°C), react with silicon forming the orthorhombic TiSi2 phase with quite large grains, up to 5 µm in diameter, which present some orientation relationships with the crystalline bulk. They are [011]TiSi2 //[001]Si, [110]TiSi2 //[001]Si, [010]TiSi2 //[001]Si.