Articles you may be interested inEffect of oxygen precipitates and induced dislocations on oxidation-induced stacking faults in nitrogen-doped Czochralski silicon Silicon crystals doped with nitrogen from the melt contain shallow thermal donors ͑STDs͒ detected both optically and electrically. Annealing samples at 600 and 650°C results in a saturated STD concentration that depends on the nitrogen concentration approximately by a square-root law. This indicates the involvement of only one nitrogen atom in every STD species. The model of STDs consistent with the present data is the NO m complex of a nitrogen interstitial and m oxygen atoms; the concentration of every STD species reaches the equilibrium value during annealing. The temperature dependence of the equilibrium reaction constant allows us to estimate the average number of oxygen atoms m of the STD complexes as 3.
Czochralski silicon crystals, grown with different interstitial oxygen concentrations ͑group I͒ or different types of intrinsic defects ͑group II͒, were analyzed by X-ray section topography, diffuse X-ray scattering, surface photovoltage, microwave photoconductive decay, and Fourier infrared spectroscopy. The samples of group I showed that the main factor influencing the X-ray section topography images is the amount of precipitated oxygen. The increase in this amount involves a decrease in size and an increase in density of the oxygen precipitates. A strong reduction in the minority carrier diffusion length is observed after precipitation. These effects seem to be dependent on the positions along the ingot axis at which the samples were taken, which would indicate the influence of the sample thermal history on the detectability of oxygen precipitates by means of these techniques. The samples of group II are characterized by vacancy-rich, interstitial-rich, and defect-free regions. After copper decoration, the different defects were observed to have different sizes, densities, shapes, and depth distributions. This feature allows one to clearly distinguish between crystal zones where vacancy or interstitial clusters prevail and where defects are absent. Minority carrier lifetime values are directly related to the defect volume densities. The combined use of different characterization techniques proved itself a powerful tool to study different defect types in Czochralski silicon.The study of crystalline defects in Czochralski ͑CZ͒ silicon ͑Si͒ has been an active area of research for decades. Far from decreasing, the interest of the scientific community in this field has increased considerably in the last years, as the rapid shrinking of ultralarge scale integrated device dimensions has put more stringent requirements on the crystalline perfection of the starting wafer. Investigations have focused on two main defect classes, particularly critical for achieving good device yields: oxygen precipitates and point defect clusters. Oxygen precipitates are formed because the interstitial oxygen present in the wafer is supersaturated at the typical temperatures of device processing. It is well known that oxygen precipitates can have both a harmful and a beneficial role for device yield: if present in the near-surface region where devices are fabricated, they can cause device failure. On the other hand, their presence in the wafer bulk is often desirable, in order to ensure a good intrinsic gettering for metallic impurities. Point defect ͑vacancy and interstitial͒ clusters in CZ grown Si have been studied since the early seventies. 1 At that time, they were called swirls or microdefects, and their nature ͑vacancy or interstitial͒ was not always clear. The recent discovery, in the early nineties, that vacancy clusters can give origin to pits on the surface of a polished wafer ͑crystal originated particle, COP 2 ͒ and cause degradation of the gate oxide integrity, 3 has renewed the interest for this subject and promoted huge ad...
Grown‐in voids in silicon are strongly affected by donor dopants. For As‐doped wafers, voids (revealed as light‐scattering surface defects observed after cleaning) show a pronounced increase in their density up to [As] = 1.7 × 1019 cm−3, but at higher [As] the void density drops sharply. A similar behaviour was found for P‐doped wafers where a sharp drop occurs at [P] > 2.9 × 1019 cm−3. Such a dependence is accounted for by an effect of minor impurity species: vacancy‐impurity complexes (trapped vacancies) and interstitial impurity atoms (trapped self‐interstitials). The total incorporated concentration of the vacancy species is first incremented due to the trapped vacancies. At higher impurity concentrations, it is reduced due to an increased contribution of negatively charged interstitial impurity species. The simulated dependence of void density and size on the impurity concentration is well consistent with the experimental data.
The impact of antimony doping on the formation of vacancy-and interstitial-type microdefects in Czochralski silicon is studied by growing test crystals with different Sb doping levels, in the range from 0 (undoped) to 3x10 18 cm -3 , and with different pulling rates. Antimony is found to cause a shift from interstitial-to vacancytype microdefects, observable already at a concentration of ≈10 17 cm -3 . The shift coefficient K for antimony is estimated to be 7.2×10-19 cm 3 .
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