Solid State Phenomena Vols. 131-133

Abstract: Luminescence properties of silicon light emitting diodes with engineered dislocation loops were investigated. Dislocation loops were formed by Si+-ion implantation above and below metallurgical p+-n junction followed by an annealing step. The diodes showed characteristic dislocation (D-band) and band-to-band luminescence. Measurements of carrier-injection level dependence of the D-band signal intensity were performed. The results are in agreement with the model for dislocation luminescence, which suggests rediative transition between two, dislocation-related shallow levels. A gradual blue-shift of the D-band peak positions was observed with an increase in the carrier injection level in electroluminescence and photoluminescence. A supposition about existence of strong Stark effect for the excitonic dislocation states allows explaining the observations. Namely, in the build-in electric field of the p-n junction the exciton energies are red-shifted. The injected charge carriers lower the field and thus cause the blue-shift of the peak positions. A fitting of the data using the quadratic Stark effect equation suggests 795 meV for the spectral position of D1 peak at 300 K and 0.0186 meV/(kV/cm)2 for the characteristic constant.

Abstract: Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been used to compare hydrogen defects formed in p doped [001] oriented Cz silicon samples which are H+ plasma treated , H+ implanted or Si+ implanted + H+ plasma treated. Samples were studied as processed and after annealing at 250°C, 450°C and 600°C. It is found that 1 hour H+ plasma treatment at 250°C produces a low density of large defects (~100 nm) in prefered {111} plans close to the surface. H+ implantation at a dose of 3x1016 cm-2 produces high density of small (~ 20 nm) mostly {100} platelets that after 1 hour annealing at 450°C result in microcrack formation. Lower H+ implantation doses form very few microcracks at this temperature. Silicon implantation with a dose of 1015 cm2 followed by 1 hour H+ plasma treatment at 250°C and 1 hour annealing at 450°C produces similar microstructure and microcracks as the 3x1016 cm2 H+ implantation dose.

Abstract: Hydrogenated n and p doped Czochralski Si substrates have been studied by means of atomic force microscopy, scanning and transmission electron microscopy, Raman spectroscopy and microwave photoconductivity decay techniques. The measurements show that the surface is roughest in ndoped samples which are plasma treated at high frequency. The cone density was found to be highest on p-doped samples, which correlates well to the higher density of defects observed in pdoped samples. The surface cones were found to consist of nanograins, twins and stacking faults with random orientations, several hydrogen induced defects and bubbles. The size, density and formation depth of the subsurface defects were seen to depend on doping type, doping level, plasma frequency and hydrogenation time. Raman spectroscopy shows formation of nearly free hydrogen molecules, which are presumed to be located in nano-voids or platelets. These molecules dissolved at temperatures around 600°C. By means of the &-PCD measurements, it is demonstrated that hydrogen-initiated structural defects act as active recombination centres, which are responsible for the degradation of the minority carrier lifetime.

Abstract: This paper describes a series of electrical measurements and sample modifications that enabled the electrical properties of hybrid-orientation direct silicon bonded wafer interfaces to be determined. It is shown that the carrier transport across this near-surface (110)Si/(100)Si boundary is dictated by the defects present at the bond interface. These interface states are believed to pin the Fermi-level, producing a conduction barrier with a thermal activation energy Ea = 0.56eV. The defect band has been identified by deep-level transient spectroscopy and associated with the defect states typically observed in plastically deformed silicon. The carrier transport behavior across the bonding interface, as well as the observed interface trap levels are therefore attributed to the dislocation network present at the bonding interface. The spatial uniformity of the interface properties have been evaluated by TEM, electron-beam induced current microscopy, photoconductive decay and conduction measurements.

Abstract: The structure studies of single crystalline silicon implanted at 340 K or 610 K with Mn+ ions (Si:Mn) and subsequently processed under atmospheric and enhanced hydrostatic pressure at up to 1270 K are reported. The defect structure was determined by an analysis of X-ray diffuse scattering around the 004 reciprocal lattice point and by electron microscopy. High resolution X-ray diffraction techniques based on the conventional source of radiation were used for this purpose. The crystal structure of Si:Mn and the Si1-xMnx precipitates in the implantation – disturbed layer were studied by synchrotron radiation diffraction in the grazing incidence geometry. Processing of Si:Mn results in crystallization of amorphous Si within the buried implantation – disturbed layer and in formation of Mn4Si7 precipitates. Structural changes are dependent both on temperature of the Si substrate at implantation and on processing parameters.

Abstract: The main goal of this work is to investigate the influence of low-temperature argon ionbeam treatment on the electric and structural properties of a near-surface region of the standard commercial p-type Cz Si wafers, and to compare the effects of Ar+ and H+ ion-beam treatment. The measurements of thermo-EMF have shown that both Ar+ and H+ ion-beam treatment with the ion energy 200 eV and current density 0.15 mA/cm2 at a temperature of 30 oC during 30 min leads to the p-to-n −type overcompensation of the near-surface layer of silicon wafers. The measurements of photovoltage spectra have shown that (i) Ar+ and H+ treatments in like manner lead to the appearance of a photovoltage signal over a wide spectral region due to the formation of p-n-junction on the treated surface, and (ii) photosensitivity of the Ar+ ion-beam treated wafers in the ultraviolet (UV) spectral region (200-400 nm) is much greater as compared to the wafers subjected to H+ ion beam treatment in the same conditions. The main difference in the Ar+ and H+ ion-beam treatment effects is the formation of a thin (5-20 nm) oxygen-containing dielectric layer on the surface of hydrogenated samples and the absence of such layer in case of Ar+ ion-beam treatment.

Abstract: SIMOX (Separation-by-Implantation-of-Oxygen) is an established technique to fabricate silicon-on-insulator (SOI) structures by oxygen ion implantation into silicon. The main problem of SIMOX is the very high oxygen ion fluence and the related defects. It is demonstrated that vacancy defects promote and localize the oxide growth. The crucial point is to control the distribution of vacancies. Oxygen implantation generates excess vacancies around RP/2 which act as trapping sites for oxide growth outside the region at the maximum concentration of oxygen at RP. The introduction of a narrow cavity layer by He implantation and subsequent annealing is shown to be a promising technique of defect engineering. The additional He implant does not initiate oxide growth in the top-Si layer of SOI.

Abstract: The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation condition: temperature, cooling rate, oxidation time, impurity content. Interaction between the point defects with extended defects and impurities affects the SiO2 structure and Si-SiO2 interface properties. Hydrogen adsorption on n- and p- type wafers is different. One possible reason for that can be the strength of the magnetic interaction between the hydrogen and paramagnetic impurities of the adsorbent. The influence of point defects and impurities may be diminished and the interface properties improved by an appropriate choice of the oxidation conditions and postoxidation laser irradiation.

Abstract: Fast neutron irradiations on pre-treated Cz-grown silicon were carried out. The pretreatments involved thermal anneals at 450 oC and 650 oC under high hydrostatic pressure. We mainly examined, by means of IR spectroscopy, the effect of pre-treatments on the production of the oxygen-vacancy (VO) pair. The amplitude of the VO band was found independent on the 450 oC treatment although the amplitudes of the TDs bands were reduced. On the other hand, the amplitude of the VO band was found lower in the samples treated at 650 oC, indicating an influence on the production of the oxygen-vacancy defects. The results are discussed and explanations are suggested concerning possible interactions between thermal and radiation defects.

Abstract: We have designed a set of experiments in which a controlled supersaturation of vacancies can be maintained constant during annealing of a boron implant. In presence of voids, a remarkable reduction of boron diffusivity is observed and, for low fluence B implantation, TED can be totally suppressed. We show that the presence of nanovoids in the B implanted region is not a prerequisite condition for the reduction of B diffusivity. Large voids located at more than 100 nm apart from the B profile still show the same effect. Small voids can also be used to increase the activation of boron. All these results are consistent with the hypothesis that, during annealing, vacancies are injected from the voids region towards the Is rich region in the implanted region where they massively recombine. Finally, we show that BICs cannot be simply dissolved by injecting vacancies into the region where they stand.