Radiation-induced structural transformations in a silicon layer of SOI (original) (raw)
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Semiconductors, 2011
Specific features of formation of radiation defects in thin silicon layer of silicon on insulator (SOI) structures have been studied. It is shown that there are differences between variations in the structural and electrical properties of the thin silicon layer and those in bulk silicon crystals (with similar electrical char acteristics) subjected to the same radiation effect. It is established that the embedded insulator in the SOI structure represents a barrier for motion of radiation induced intrinsic interstitial silicon atoms, which brings about an increase in the dose of bombarding ions, which leads to the loss of single crystallinity of the silicon layer in a SOI structure. It is shown that γ ray irradiation with doses unaffecting the electrical conduc tivity of bulk silicon crystals appreciably affects the conductivity of the silicon layer in the SOI structures. In addition, variation in the conductivity of silicon layer is related to variation in the density of surface states at the interface between the silicon layer and the built in insulator, rather than to generation of conventional radiation induced structural defects in silicon.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1996
The strain versus interstitials correlation for as-implanted (100) silicon crystal was studied comparing the strain profiles with the displaced atom profiles and the strain integral with the total fraction of displaced atoms as measured by X-ray diffractometry and Rutherford backscattering-channeling spectrometry, respectively. Light/medium (B, N and 0) and heavy (Si and As) mass ions at low (50 keV) and high (0.7 or 0.8 MeV) energy, low dose rate (< 3 X 10" ion/cm*/s> and fluences between 2 X IO'* and 3 X 10" ion/cm* were implanted at room temperature and random incidence in (100) Si wafers. Independently of the ion energy two correlations between strain and displaced atoms can be given depending on the ion mass and the damage level. For light mass ions at low damage level (I N 6%) a linear relation exists between strain and interstitials. For heavy mass ions at any damage level and for low mass ions at damage level > u 6%, the correlation between strain and displaced atoms is sublinear. Isochronal annealing treatments show that the predominant defects produced by high mass ions are different from those produced by low mass ions. Once interpreted in the frame of the elastic theory of solid, the linear relation between strain and interstitials may allow an evaluation of the relative volume increase per interstitial in silicon.
Irradiation effects on polycrystalline silicon
Solar Energy Materials and Solar Cells, 2002
Intrinsic point defect population in polycrystalline silicon is of the particular importance due to the influence on the electronic properties of material. A study of intrinsic point defect behavior is additionally complicated due to the interaction with the present impurities and different structural defects. Experiments were performed on EFG polycrystalline silicon material rich with carbon and different structural defects such as dislocations and various grain boundaries. Samples were irradiated with g-rays from a 60 Co source to the doses of 300 Mrad to introduce simple point defects into the bulk of the material. The results obtained with deep level transient spectroscopy (DLTS) showed that upon formation of the vacancyinterstitial pairs, silicon selfinterstitials get trapped by larger structural defects, creating therefore a vacancy rich bulk of the material. r
High resolution X-ray diffraction study of proton irradiated silicon crystals
Modern Electronic Materials, 2016
Radiation-induced modification of semiconductors is achieved by controlled introduction of intrinsic structural and impurity defects. Conventionally, introduction of radiation-induced defects is used as an efficient tool for controlling the lifetime of metastable carriers in local areas of silicon based devices and supporting mechanisms of avalanche-like breakdown through radiation-induced defect levels. Desired parameters of damaged layers are typically achieved during post-implantation heat treatment. There are recent applications of proton irradiation in silicon technology. A significant growth of luminescence was observed in proton irradiated silicon and attributed to the formation of special rod-shaped clusters of interstitial type radiation defects. We have studied the transformation of radiation-induced defects forming as a result of proton implantation into n silicon crystals with a resistivity of 100 Ω cm using high resolution X-ray diffraction and shown that sequential implantation of 100, 200 and 300 keV protons with a fluence of 2.10 16 cm À 2 causes the formation of a 2.4 μm thick damaged layer with a greater lattice parameter. The layer forms simultaneously with intrinsic clusters of vacancy and interstitial type radiation-induced defects. Vacuum annealing of the irradiated crystals at 600 1C increases the power of the radiation-induced defects of both types and reduces their quantity. Interstitial type defects dominate after annealing at 1100 1C. We have assessed the power of the defects at every transformation stage.
Crystallography Reports, 2013
The influence of the implantation of silicon single crystals by fluorine, nitrogen, oxygen, and neon ions on the distribution of strain and the static Debye-Waller factor in the crystal lattice over the implanted layer depth has been investigated by high resolution X ray diffraction. The density depth distribution in the surface layer of native oxide has been measured by X ray reflectometry. Room temperature implantation conditions have ensured the equality of the suggested ranges of ions of different masses and the energies trans ferred by them to the target. It is convincingly shown that the change in the structural parameters of the radi ation damaged silicon layer and the native oxide layer depend on the chemical activity of the implanted ions.
Comparative investigation of damage induced by diatomic and monoatomic ion implantation in silicon
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1994
The damaging effect of mono- and diatomic phosphorus and arsenic ions implanted into silicon was investigated by spectroscopic ellipsometry (SE) and high-depth-resolution Rutherford backscattering and channeling techniques. A comparison was made between the two methods to check the capability of ellipsometry to examine the damage formed by room temperature implantation into silicon. For the analysis of the spectroscopic ellipsometry data we used the conventional method of assuming appropriate optical models and fitting the model parameters (layer thicknesses and volume fractions of the amorphous silicon component in the layers) by linear regression. The depth dependence of the damage was determined by both methods. It was revealed that SE can be used to investigate the radiation damage of semiconductors together with appropriate optical model construction which can be supported or independently checked by the channeling method. However, in case of low level damage (consisting mainly of isolated point defects) ellipsometry can give false results, overestimating the damage using inappropriate dielectric functions. In that case checking by other methods like channeling is desirable.
The European Physical Journal Applied Physics, 2002
The number of scattering centres measured using channeled particles passing through a cavity layer formed by He implantation in silicon is shown to depend on the probe energy. This unusual result is explained in terms of interaction of channeled particles with atoms of cavity walls and dislocation lines. The Rutherford backscattering analysis in channeling incidence (RBS-C) is then used to study the time evolution of cavity and dislocation populations during annealing. It is shown that cavities are actually bubbles in equilibrium with the silicon matrix. The time to reach this equilibrium is related to the gas desorption. For our experimental conditions (40 keV, 5 × 10 16 cm −2 and 800 • C), this equilibration time is about 10 minutes. Strain and dislocation build-up occur under shorter time scales, during which bubbles are probably overpressurized. The pinning of bubbles at dislocations must be taken into account to explain the evolution of these extended defects over a longer period. PACS. 61.85.+p Channeling phenomena (blocking, energy loss, etc.)-61.72.Tt Doping and impurity implantation in germanium and silicon-61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, X-ray topography, etc.
Damage accumulation in Si during high-dose self-ion implantation
Journal of Applied Physics, 2004
Accumulation and annealing of damage in Si implanted with self-ions to high doses were investigated using a combination of grazing incidence diffuse x-ray scattering, high-resolution x-ray diffraction scans, and transmission electron microscopy. During implantation at 100°C, small vacancy and interstitial clusters formed at low doses, but their concentrations saturated after a dose of Ϸ3 ϫ 10 14 cm −2. The concentration of Frenkel defects at this stage of the implantation was Ϸ1 ϫ 10 −3. At doses above 1 ϫ 10 15 cm −2 , the concentration of implanted interstitial atoms began to exceed the Frenkel pair concentration, causing the interstitial clusters to grow, and by Ϸ3 ϫ 10 15 cm −2 , these clusters formed dislocation loops. Kinematical analysis of the rocking curves illustrated that at doses above 1 ϫ 10 15 cm −2 the "plus one" model was well obeyed, with one interstitial atom being added to the dislocation loops for every implanted Si atom. Measurements of Huang scattering during isochronal annealing showed that annealing was substantial below 700°C for the specimens irradiated to lower doses, but that little annealing occurred in the other samples owing to the large imbalance between interstitial and vacancy defects. Between 700 and 900°C a large increase in the size of the interstitial clusters was observed, particularly in the low-dose samples. Above 900°C, the interstitial clusters annealed.
Correlation of Radiation Damage Effects in High Rsistivity Silicon
Neutron irradiated high resistivity silicon detectors have been subjected to isochronous annealing in order to study the changes in the full depletion voltage and the leakage current. The corresponding evolution of bulk damage induced defect levels was monitored using the TSC method. A single TSC peak is found to be correlated with the transient decay of the depletion voltage which is observed after elevated temperature annealing of inverted detectors. In conjunction with deep level parameters obtained from an I-DLTS study and changes observed in the effective doping concentration and in the leakage current after exposure to high doses of 60 Co-gammas, new insight is gained into the radiation induced device deterioration and the corresponding annealing behavior.
Damage to Crystalline Silicon Following Implantation by Low Energy Silicon Ions
MRS Proceedings, 1992
A new approach to investigate low energy defect formation and annealing in a crystal is developed, based on experimental observations of the total number of interstitials. The model is applied to damage in crystalline silicon caused by low energy implantation of Siatoms during 40eV implants at 300°Kand 685*K. The model has two versions, analytical and computational, and includes two kinds of diffusing species, self-interstitials and vacancies, their interaction, surface motion of the growing crystal, and a constant source of defects. The source was calculated using a modified TRIM code (TRIMCSR). The focal point of the analysis is the number of interstitials per ion dose surviving at the end of the deposition time (damage to dose ratio or DDR),which is found to be an informative quantity and can be calculated for more sophisticated models including precipitation.