Evolution of vacancy-like defects in helium-implanted (100) silicon studied by thermal desorption spectrometry (original) (raw)
Related papers
Thermal desorption spectra from cavities in helium-implanted silicon
Physical Review B, 2000
Thermal desorption spectra at constant ramp rate have been determined after helium implantation into bare silicon prepared for a large set of experimental conditions. The spectra can phenomenologically be classified as composed by two peaks: the ␣ peak, centered on a temperature of 750-800°C with a shoulder extending to lower temperature ͑down to 550°C), and the  peak, centered on a lower temperature depending on the implantation-annealing conditions. The ␣ peak is attributed to the emission from cavities, while the  peak is attributed to the emission from vacancylike defects. A detailed theory describing helium effusion from stable cavities as controlled by the interatomic helium-helium potential is proposed and found to reproduce accurately most of the ␣ peaks. The postimplantation of hydrogen into samples displaying a pure  emission results in an ␣ peak which can be described by the same model as above provided that the cavities are unstable and shrink during desorption in such a way as to maintain constant the concentration of contained helium.
Helium desorption from cavities induced by high energy 3He and 4He implantation in silicon
Materials Science and Engineering: B, 2000
A detailed study has been made of helium release from silicon wafers implanted with MeV helium ions at fluences of 5 ×10 16 cm − 2 and 10 17 cm − 2. Thermal desorption spectrometry (TDS), neutron depth profiling (NDP), non-Rutherford elastic backscattering (NREBS) and nuclear reaction analysis (NRA) have been employed to measure the helium content and release rate during isothermal annealing at annealing temperatures of 800 and 1000°C. TDS has also been used for isochronal annealing. Transmission electron microscopy (TEM) is used to monitor changes in morphology in the formed bubble layer. The helium release results can be modeled rather well when it is assumed that the helium initially is present in overpressurized bubbles. The present study reveals a single activation energy for helium release of 1.83 (0.05) eV.
Stability of cavities formed by He + implantation in silicon
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1999
Microscopic cavities are known to be ecient gettering sites for metallic impurities in silicon. In the present study, they were formed in á1 1 1ñ silicon by 40 keV room temperature He implantation at doses of 5´10 16 and 10 17 /cm 2 , followed by a heat treatment in an N 2 atmosphere using either rapid thermal annealing or conventional furnace annealing. Helium desorption and cavity evolution were studied by non-Rutherford elastic scattering of protons and Rutherford backscattering/channeling analysis. Cavities and residual defects were observed by transmission electron microscopy (TEM). The retained fraction of helium was shown to depend on the manner of annealing and was found to decrease with annealing time much more slowly than the ®rst order gas release model. TEM observations show that {3 1 1} defects and dislocations are also present close to the cavities. Channeling analysis shows that {3 1 1} defects dissolve during the ®rst minutes of annealing at 800°C. It is assumed that the self-interstitials released from these defects are able to ®ll the smallest cavities, thus causing a rapid increase of the mean cavity radius. This variation, introduced in the desorption law, leads to reasonable agreement with the experimental results. For longer annealing time the total cavity surface decreases slowly with annealing duration. Ó
Helium Bubbles Formed in Si(001) Layers after High-Dose Implantation and Thermal Annealing
Russian Microelectronics, 2018
⎯In this paper, we show that high-dose low-energy plasma-immersion ion implantation H + (E = 2-5 keV) leads to the formation of hidden layers of helium bubbles in an Si(001) substrate. The structural studies of the bubbles' layers are carried out by using X-ray reflectometry, small-angle scattering, and transmission electron microscopy. Changes in the structure of the layers of the bubbles during thermal annealing are also studied. We have shown that as a result of implanting helium ions with a dose of 5 × 10 17 cm-2 , a multilayer structure is formed in the near-surface layers of the silicon substrates that generally consists of amorphous, porous amorphous, and porous crystalline sublayers. The structural parameters of the sublayers (density, thickness, and size of the boundaries) and the concentration and size of the bubbles after annealing from 580 and 800°C are determined. It is shown that annealing leads to a bimodal distribution of the bubbles with the average size of 2 to 3 nm and 7 to 8 nm. We establish that the upper amorphous layer is 15 nm thick and can be considered as a protective layer for further processing.
The effect of ion-beam specimen preparation techniques on vacancy-type defects in silicon
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2006
Ion bombardment is frequently used in the preparation of thin foils of a variety of materials for analysis by transmission electron microscopy (TEM) and related techniques. We have studied in detail the effects of such specimen preparation techniques on nanometre-sized cavities in silicon by comparing ion-beam milled cross-sectional specimens with those prepared using a small-angle cleavage technique. The cavities have been formed by a prior implantation of energetic helium ions and a high-temperature anneal. In the specimens prepared by ion-beam techniques in two different commercial systems, there is a clear effect on the small cavities. Specifically, the cavities are observed to migrate away from the original surface at both room temperature and liquid nitrogen temperature. The effect is discussed in the context of the interaction of the cavities with mobile vacancies and interstitials injected by the ion bombardment. We believe this to be an important effect that must be taken into account when using TEM techniques to study defects in semiconductors.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
Defect structures created in implantations of radioactive 57 Mn þ ions into silicon-based semiconductors held at temperatures of 77-500 K have been studied by M€ o ossbauer spectroscopy on the 14 keV c-radiation emitted in the decay of the 57 Fe daughter atoms. For implantations at <300 K, the majority of Fe atoms is located in a specific defect structure, likely within an ''amorphous pocket'', which anneals partially at 100-200 K and completely at 300-450 K. The latter is proven to occur within minutes by isothermal time delayed measurements and results in a substitutional incorporation of the 57 Mn probe atoms. The atomic structure of the annealing defect is compared to that of Fe in amorphous silicon upon 57 Mn implantation.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2006
Thermally grown silicon oxide layer was implanted at room temperature with 300 keV Xe at fluences ranging from 0.5 to 5 · 10 16 Xe/ cm 2 . Bubbles created after Xe-implantation provided a low-k silicon oxide that has potential use as a dielectric material for interconnects in Si integrated circuits. Transmission Electron Microscopy (TEM), Rutherford Backscattering Spectrometry (RBS) and Positron Annihilation Spectroscopy (PAS) were used to provide a comprehensive characterization of defects (bubbles, vacancy, gas atoms and other types of defects) created by Xe implantation in SiO 2 layer. These measurements suggest that the bubbles observed with TEM for all fluences were a consequence of the interaction between Xe and vacancies (V), with V n Xe m complexes created in the zone where V and Xe profiles overlap. Negatively charged defects such as (Si-O À , Si-O-O À and O À 2 ) are also created after implantation.
Nanotechnology and Precision Engineering, 2020
To investigate the effect of dislocation structures on the initial formation stage of helium bubbles, molecular dynamics (MD) simulations were used in this study. The retention rate and distribution of helium ions with 2 keV energy implanted into silicon with dislocation structures were studied via MD simulation. Results show that the dislocation structures and their positions in the sample affect the helium ion retention rate. The analysis on the three-dimensional distribution of helium ions show that the implanted helium ions tend to accumulate near the dislocation structures. Raman spectroscopy results show that the silicon substrate surface after helium ion implantation displayed tensile stress as indicated by the blue shift of Raman peaks.
Ultradense gas bubbles in hydrogen- or helium-implanted (or coimplanted) silicon
Materials Science and Engineering: B, 2000
Both hydrogen (as H 2 ) and helium are dissolved endothermically in crystalline silicon. Once implanted into silicon, they have therefore a tendency to segregate in the vacancy clusters produced by the implantation itself, possibly transforming them in more or less stable cavities. Since the amount of vacancies generated in silicon by the implantation of hydrogen or helium at low energy, and surviving the spontaneous recovery of the radiation damage, may be lower than the amount of the implanted species, the atomic density attained after the cluster-to-cavity transformation may exceed the silicon one, with the formation of ultradense gas bubbles. The major difference between hydrogen and helium is that the pristine state of hydrogen in as-implanted silicon is not the molecular one, so that the formation of cavities requires preliminarily the transformation of hydrogen-involving species in H 2 . This paper highlights the mechanisms of cavity formation by helium or hydrogen implantation and sketches analogies and differences between these processes; coimplantation is discussed too.
The formation, migration, agglomeration and annealing of vacancy-type defects in self-implanted Si
Journal of Materials Science: Materials in Electronics, 2007
The evolution of vacancy-type defects has been studied by variable-energy positron annihilation spectroscopy (VEPAS) in samples of high-quality FZ p-type (001) silicon wafers implanted with 4 MeV Si 2+ ions at room temperature to doses of 10 12 -10 14 cm -2 . The average vacancy concentration increases as (ion dose) 0.70 ± 0.06 . Progressive isochronal annealing measurements show that open-volume point defects (having a VEPAS signature close to that for divacancies) anneal between 500-600°C. VEPAS with enhanced depth sensitivity (via progressive etching) verified that single 30 min anneals to 550 and 600°C lead to the formation of buried clusters V N with an average N of 3.5 lying between depths of 2.2 and 3.6 lm (both ± 2 lm), close to the peak of vacancy damage just shallower than the ion range predicted by simulation. The concentration of these clusters increases as (ion dose) 2.6 ± 0.1 . Single anneals to higher temperatures reduce all open-volume point defect concentrations to below the limit detectable by VEPAS.