Solubilities and Equilibrium Distribution Coefficients of Oxygen and Carbon in Silicon

Narushima, Takayuki; Yamashita, Atsushi; Ouchi, Chiaki; Iguchi, Yasutaka

doi:10.2320/matertrans.43.2120

Cited by 21 publications

(9 citation statements)

References 39 publications

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“…Li's experiments [5] showed that the thickness of the continuous SiC layer formed on the glassy carbon surface was B6 mm after 1 h at 1430 C, and they also noted that most of the SiC layer was formed in the first few minutes. Zhou's results [25] also showed that the thickness of the beta-SiC layer [20,22] formed on the glassy carbon surface at 1430 C in 10 min is B4 mm. Although all these analyses show that a B3 mm graphite particle will transform into an SiC particle in minutes, FTIR measurements did not detect the absorption peak due to SiC located at 780-820 cm À1 .…”

Section: Reactions In the Molten Silicon-particles Systemmentioning

confidence: 89%

Secondary phase inclusions in polycrystalline sheet silicon

Rozgonyi

Rand³

et al. 2004

Journal of Crystal Growth

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Section: Reactions In the Molten Silicon-particles Systemmentioning

confidence: 89%

Secondary phase inclusions in polycrystalline sheet silicon

Rozgonyi

Rand³

et al. 2004

Journal of Crystal Growth

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“…[11] From Aalberts and Verheijke. [12] # From Narushima et al [13] : presented a range of segregation coefficients for O and C reported by different authors. **From Nozaki et al [14] From Hopkins et al [15] : The segregation coefficients were referred to as effective coefficients, which might be equal to or larger than the actual equilibrium coefficients.…”

Section: B Macrosegregation In Silicon Ingotsmentioning

confidence: 97%

“…Finally, Eq. [13] guarantees that the concentration at the edge of the stagnant layer equals that in the outside mixed liquid, enforcing continuity of the concentration profile throughout the liquid.…”

Section: Mathematical Model Of Macrosegregation For Unidirectionamentioning

confidence: 98%

“…In Table I, the equilibrium segregation coefficient and the solubility of several impurities in solid Si (considering the equilibrium with solid precipitates) are shown. [8][9][10][11][12][13][14][15][16][17] If the Si-impurity binary phase diagram is available, this solubility is usually the maximum concentration at the solvus line. Because of macrosegregation, the initial part of the solidified ingot is much purer than the remaining ingot, indicating a refining of the feedstock composition.…”

Section: Introductionmentioning

confidence: 99%

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Macrosegregation of Impurities in Directionally Solidified Silicon

Martorano

Neto

Oliveira

et al. 2010

Metall Mater Trans A

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Directional solidification of molten metallurgical-grade Si was carried out in a vertical Bridgman furnace. The effects of changing the mold velocity from 5 to 110 lm seconds -1 on the macrosegregation of impurities during solidification were investigated. The macrostructures of the cylindrical Si ingots obtained in the experiments consist mostly of columnar grains parallel to the ingot axis. Because neither cells nor dendrites can be observed on ingot samples, the absence of precipitated particles and the fulfillment of the constitutional supercooling criterion suggest a planar solid-liquid interface for mold velocities £10 lm seconds -1 . Concentration profiles of several impurities were measured along the ingots, showing that their bottom and middle are purer than the metallurgical Si from which they solidified. At the ingot top, however, impurities accumulated, indicating the typical normal macrosegregation. When the mold velocity decreases, the macrosegregation and ingot purity increase, changing abruptly for a velocity variation from 20 to 10 lm seconds -1 . A mathematical model of solute transport during solidification shows that, for mold velocities ‡20 lm seconds -1 , macrosegregation is caused mainly by diffusion in a stagnant liquid layer assumed at the solid-liquid interface, whereas for lower velocities, macrosegregation increases as a result of more intense convective solute transport.

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“…In this calculation, the relative distance from the ingot base was adopted as the solid fraction, the average carbon concentration was assumed as 1200 ppmw, and a solute partition coefficient of 0.034, which is one of the lowest values reported in the literature, [11] was considered. The discrepancy between the measured and calculated profiles is evident.…”

Section: Effects Of Mold Pulling Velocity On Carbon Macrosegregationmentioning

confidence: 99%

Effects of Solidification Rate and Settling Time of SiC Particles on the Macrosegregation of Carbon in Silicon Ingots

Ribeiro

Neto

Martorano

2014

Metallurgical and Materials Transactions E

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The macrosegregation of carbon in silicon was studied aiming for silicon refining for photovoltaic applications. Experiments of directional solidification upward and of settling of SiC particles in the melt were carried out in a Bridgman furnace using electronic grade silicon intentionally contaminated with carbon. Mold pulling velocities in the range between 5 and 80 lm/s and settling time periods of 1 and 6 hours were adopted in the experiments. In the resulting cylindrical ingots, the macrosegregation of carbon along the axial direction was measured and their macro and microstructures revealed and examined. In all directional solidification experiments, the carbon concentration increases to the ingot top as result of an accumulation of SiC particles in this region. For the lower velocities (<40 lm/s), a larger particle accumulation and columnar grains aligned axially and pointing to the ingot top are seen, which is consistent with the pushing of SiC particles by a planar solid-liquid interface. For the settling experiments, the carbon concentration increases from the ingot top to the bottom as a result of the accumulation of SiC particles at the bottom. This accumulation is probably caused by the settling of SiC particles, but an increase in the settling time from 1 to 6 hours have no significant effect in the macrosegregation profile. Finally, in the conditions of the present experiments, the directional solidification of silicon at mold pulling velocities lower than 40 lm/s is more effective to remove carbon from silicon than the settling of SiC particles during times up to 6 hours.

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Solubilities and Equilibrium Distribution Coefficients of Oxygen and Carbon in Silicon

Cited by 21 publications

References 39 publications

Secondary phase inclusions in polycrystalline sheet silicon

Secondary phase inclusions in polycrystalline sheet silicon

Macrosegregation of Impurities in Directionally Solidified Silicon

Effects of Solidification Rate and Settling Time of SiC Particles on the Macrosegregation of Carbon in Silicon Ingots

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