Evolution Of Defects In Silicon Research Articles

Effects of crystal plane orientation on blistering kinetics and defect evolution in silicon implanted by hydrogen molecular ions

The ion-cut technology used for the fabrication of Silicon-On-Insulator (SOI) substrates involves a thermally activated layer splitting process with the evolution of hydrogenated defect complexes into microcracks in H-implanted Si. Since the layer splitting process is highly correlated to the interaction of H atoms with defects, it is expected that the blistering kinetics arising from H implantation would vary with crystal plane orientation of Si substrates. This study presents a thorough investigation of the influence of crystal plane orientation on the blistering kinetics and defect evolution in H-implanted Si. Three Si substrates of Si(100), Si(111), and Si(110) were implanted with H2+ ions at an accelerated energy of 40 keV to a fluence of 2.5 × 1016 cm−2. After ion implantation, the blistering characteristics, defect complexes, and microstructure of the specimens were characterized by SIMS, in-situ OM observation system, Raman spectra, and XTEM. The results revealed that two limiting steps of H atom diffusion dominate the blistering process in different temperature intervals. The transformation of VH3 (or V2H6) defect complex into Si:H surface state is mainly prevailing in the low-temperature interval. The blistering characteristics of Si showed a high correlation with the crystal plane orientation of Si substrates due to the difference in planar atomic density. Si(110) having a largest planar atomic density corresponds to a highest threshold temperature and a longest onset time for blister formation, followed by Si(111) and Si(100) in turn. The correlation between blistering characteristics and substrate orientation can be attributed to the fact that H implantation leads to different densities of the H-terminated platelets in Si specimens with various planar atomic densities, thus affecting the efficiency of free H atom diffusion into platelets and the blister growth as well. A conclusive finding from this study is that substrate orientation diversifies the defect density in damage layer caused by hydrogen implantation, which could change the nucleation sites of platelets available for blister formation and eventually influence the blistering efficiency and microcrack extension.

The effect of germanium doping on the evolution of defects in silicon

In the present work infrared (IR) spectroscopy measurements are taken on Ge-doped silicon samples irradiated by 2 MeV electrons to study the thermal evolution of VO defects and VO 2 complexes upon annealing. The annealing behavior of these radiation defects was found to be complicated in the presence of Ge. The main reaction VO + O i → VO 2 leading to annealing of VO defects and formation of VO 2 complexes turned out to be sensitive to concentrations of Ge impurity atoms in Czochralski grown silicon. These processes are discussed in some detail. Moreover, the rates of annealing reactions associated with self-interstitials can also be enhanced in silicon materials doped with Ge. The effects observed are most likely related to elastic strains due to Ge impurity atoms in the silicon lattice.

Dissolution of extended defects in strained silicon

The experimental and theoretical analyses performed in this work provide an insight into the impact of external stress on extended defects that form in silicon after ion implantation. It is shown experimentally that the embedded SiGe source/drain regions help to dissolve the extended defects in the adjacent silicon. The reduced amount of free and clustered interstitials is known to reduce junction leakage and increase dopant activation. These benefits are expected to improve further for the subsequent technology generations, due to the shrinking distance between the source and drain SiGe regions. A quantitative model of defect evolution in silicon with embedded SiGe is proposed. The model can be applied to optimize the combination of stress engineering, implant conditions, and thermal budget for the best device performance.

A technique for positron spectroscopy of monovacancies formed by low-temperature ion implantation of silicon

A system for positron beam-based Doppler broadening spectroscopy of the formation and evolution of monovacancy defects in silicon is described. The apparatus allows in situ ion implantation at low temperatures (∼50 K) followed by positron beam assay. First measurements for 6 keV He implantation, at post-implant temperatures between 60 and 300 K are presented. Benefits and drawbacks of this system are discussed.

Pressure assisted evolution of defects in silicon

AbstractThe effect of enhanced hydrostatic pressure following heat treatment on the evolution of point defects in neutron‐irradiated Czochralski‐grown silicon is investigated using infrared spectroscopy. The behavior of oxygen‐related defects, particularly of the VO and the VO2 centers, is mainly studied using samples subjected to heat treatment under hydrostatic pressure. It is observed that (1) pressure accelerates the annealing process of the VO defects and enhances the growth of the VO2 complexes and (2) the VO2 concentration is larger than expected from the corresponding decay of the VO defects. The faster decay of the VO defects is attributed to a pressure‐induced decrease of their migration energy. The larger VO2 concentration is also discussed. One possible explanation is that pressure stimulates an additional mechanism for the formation of the VO2 defects, which involves the reaction of oxygen dimers with vacancies. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Predicting Material Parameters for Intrinsic Point Defect Diffusion in Silicon Crystal Growth

The incorporation of intrinsic point defects into a growing crystal and their subsequent agglomeration into larger defects are controlled by the solidification and subsequent cooling process. The evolution of intrinsic point defects in Silicon can generally be described by a system of reaction-diffusion equations for the concentration of selfinterstitials and vacancies. The main difficulty in quantitative intrinsic point defect prediction with such an approach is the uncertainty of the temperature-dependent material properties. These properties are generally unknown. This is due to the difficulty to measure them experimentally at high temperatures. To circumvent this problem these properties can be computed by an underlying microscopic model by means of molecular dynamics simulations. A potential due to Stillinger and Weber or, alternatively, a many-body potential due to Tersoff is applied for this purpose. The calculated material data for these potentials as well as intrinsic defect concentrations during the Czochralski growth of silicon are presented. A transient process simulation with varying process conditions is performed and the influence on the intrinsic defect concentrations in the crystal is shown.

Effect of Laser Thermal Processing on Defect Evolution in Silicon

AbstractLaser Thermal Processing (LTP) involves laser melting of an implantation induced preamorphized layer to form highly doped ultra shallow junctions in silicon. In theory, a large number of interstitials remain in the end of range (EOR) just below the laser-formed junction. There is also the possibility of quenching in point defects during the liquid phase epitaxial regrowth of the melt region. Since post processing anneals are inevitable, it is necessary to understand both the behavior of these interstitials and the nature of point defects in the recrystallized-melt region since they can directly affect deactivation and enhanced diffusion. In this study, an amorphizing 15 keV 1 x 1015/cm2 Si+ implant was done followed by a 1 keV 1 x 1014/cm2 B+ implant. The surface was then laser melted at energy densities between 0.74 and 0.9 J/cm2 using a 308 nm excimer-laser. It was found that laser energy densities above 0.81 J/cm2 melted past the amorphous-crystalline interface. Post-LTP furnace anneals were performed at 750°C for 2 and 4 hours. Transmission electron microscopy was used to analyze the defect formation after LTP and following furnace anneals. Secondary ion mass spectrometry measured the initial and final boron profiles. It was observed that increasing the laser energy density led to increased dislocation loop formation and increased diffusion after the furnace anneal. A maximum loop density and diffusion was observed at the end of the process window, suggesting a correlation between the crystallization defects and the interstitial evolution.

Effect of Arsenic on Extended Defect Evolution in Silicon

ABSTRACTThe effect of arsenic on {311} defect formation was determined for temperatures ranging from 700°C to 800°C. Arsenic well structures were formed at arsenic concentrations of 3×1017, 3×1018, and 3×1019 cm−3. A 40 keV 1×1014 cm−2 silicon implant, that is known to form {311} defects, was then incorporated into the structures. Extended defect evolution and dissolution was then studied after furnace annealing at 700°C, 750°C and 800°C for various times. It was determined that arsenic has a strong affect on the nucleation of extended defects. However, once the defects were formed, the dissolution time constant was the same for all concentrations considered. The activation energy for defect dissolution was found to be 3.4eV and was also independent of arsenic concentration. Using a newly developed {311} model in the FLOOPS process simulation software, the effect of the arsenic on {311} formation and dissolution was simulated. It was found that by using a pair model with an arsenic-interstitial binding energy of 0.95eV, the experimental results were able to be simulated.