Quartz crucibles used in Czochralski technology


For quartz crucibles used in Czochralski technology, a 3 nm thick inner layer of quartz crucible is fabricated by fusing and coating synthetic quartz powder instantaneously on the inner surface of a quartz crucible formed of natural quartz through the arc plasma process. Since the inner layer is in direct contact with molten poly-Si at a high temperature of ~1500 °C during the growth process, the purity level of the synthetic quartz powder is required to be more than 99.9999% (6 nines, 6 N). In particular, the inner layer of the crucible coated with the synthetic quartz powder should have a lower level of metallic impurity than 100 ppb because metallic impurities are a source of bubbles and defects in the inner layer and can easily affect the quality of the grown ingot. To date, to synthesize quartz powder used in the semiconductor industry, the alkoxide silica-based sol–gel process was developed, where the silica sol–gel process through hydrolysis and condensation involves chemical reactions of tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) with ethanol and NH4OH]. However, this synthesis process has drawbacks in maintaining consistent quality and competitive prices of quartz powder due to the complicated process steps and the high material cost. In addition, the synthesized quartz powder derived from TEOS contains residual carbon impurities that generate bubbles up to 100 μmm in size when the quartz glass and quartz wares are manufactured. Since organic material (i.e., ethanol) is used to induce the condensation and hydrolysis of TEOS or TMOS, the bubbles can be formed by CO2 and CO gases due to residual carbon in the quartz powder during the melting process at a high temperature. This adversely affects the transmittance and the heat resistance properties of quartz parts and acts as a source of defects in quartz crucibles, resulting in defects in Si ingots. Therefore, there are studies to minimize the carbon content in silica by controlling the heat-treatment process conditions. Still, a small amount of residual carbon inevitably remains due to using organic materials. If you are looking for high quality, high purity, and cost-effective Quartz powder, or if you require the latest price of Quartz powder, please feel free to email contact mis-asia.

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