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Multi-crystalline silicon ingots of 44 cm square cross section, weighing 80 kg, have been produced by a modified Heat Exchanger Method in which a graphite insulation and heat exchanger block move down from the heater during crystal growth to facilitate heat extraction from the bottom of the crucible. Wafers of 300 μm thickness and 1.2 Ω.m resistivi...
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... can be seen in Fig. 5, the average size of the grains is larger than 1 cm. The huge size of the grains might be due to the lower growth rate of the crystal in this process. In the CZ process, the growing ingot is pulled from the melt and cooled by the flowing of argon gas. However, in this process, the solidified ingot is contained in the hot crucible and ...
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Multi-crystalline silicon ingots of 44 cm square cross section, weighing 80 kg, have been produced by a modified Heat Exchanger Method in which a graphite insulation and heat exchanger block move down from the heater during crystal growth to facilitate heat extraction from the bottom of the crucible. Wafers of 300 µm thickness and 1.2 Ω-cm resistiv...
Citations
... The grains solidified grow until they contact each other forming grain boundaries between them. The cooling system used allow a solidification of melted silicon progressing from the bottom of the crucible to the top surface with velocity of 1.2 cm/h and the solid-liquid interface has a slightly convex shape [10,11]. The final crystal structure is dominated by large columnar grains parallel to the solidification direction [12]. ...
Multicrystalline silicon (mc-Si) wafers produced by directional solidification still dominate the world market, due to the factor quality/price. The performance of solar cell depends directly to the quality of wafer and impurities distribution in mc-Si ingot. In our study we investigate the distribution of the interstitial oxygen (Oi) and substitutional carbon (Cs), from the bottom to top of the silicon ingot. During the solidification process the solid-liquid interface moves upward with an average growth velocity of 1.2 cm/h, with a slightly convex form. The determination of (Oi) and (Cs) concentrations were performed thanks to the Fourier Transform Infrared Spectrometry (FTIR) technique. The results show that oxygen concentration increases near the crucible wall to the maximum value of 6.3 × 10¹⁷ atoms/cm³, and the carbon concentration decrease from maximum value of 9.59 × 10¹⁷ atoms/cm³ in the top to the minimal value of 7.84 × 10¹⁷ atoms/cm³ in the bottom of ingot. The concentration of global carbon and oxygen in the centre and corner bricks was investigated using the Secondary Ion Mass Spectroscopy (SIMS) technique. The concentration of oxygen and carbon in the center bricks were 1.8 10¹⁸ and 2 10¹⁸ atoms/cm³, and in the corner bricks 4.6 × 10¹⁹ and 9 × 10¹⁹ atoms/cm³, respectively. These results provide quantitative information on the concentration of the light impurities in the as-grown mc-Si and allow an overview of their spatial distribution within the final ingot.
... Used fluid is an average sample of the concentrate recovered within the manufacturing unit of silicon bricks. The cutting fluid used (slurry) is mainly composed of HS20 loaded with SiC and iron wire waste that are produced during the sawing process [9][10][11][12]. The pH of the slurry is around 6.9 and the whole operation is conducted at room temperature. ...
The main objective of the work was to regenerate a cutting fluid HS20 used in the manufacturing of silicon wafers. Centrifugation at ambient temperature is initially considered for the treatment of the cutting fluid HS20. However, the slurry being heavily loaded with mineral colloids, tests conducted following the use of this process, have proved its efficiency to be low. Indeed, the best results for colloidal matter abatement have never exceeded 30%. By contrast, an ultrafiltration through a polyethersulfone membrane with a cutoff of 1 kDa shows excellent efficiency and affinity towards the fluid (HS20) to be considered, allowing its full recovery by maintaining its original cutting fluid characteristics. However, this process does present some drawbacks. A strong resistance to flow across the membrane of up to 60% of the total resistance is observed and a drop in permeation flux of about 90% are observed. Given these results, reinforcement of ultrafiltration, under the same operating conditions, by chemical pretreatment is considered. Chemical pretreatment with ultrafiltration offers better regeneration efficiencies under same flow conditions through the membrane as compared to an ultrafiltration process. Indeed, the fouling index is significantly reduced to around 153 × 10 s/L and a permeation flux comparable to that observed for virgin cutting fluid (HS20) is obtained.
