Pregrowth Ambient Gas Analysis of Czochralski Si Crystal Puller

Abstract

The nature of the ambient gas during vacuum bakeout of a Czochralski silicon crystal puller was investigated by using a commercially available residual gas analyzer. The ambient pressure changes observed during bakeouts were correlated with the relevant gas profiles generated from the residual gas analyzer. The partial pressures and the percent compositions of the ambient gas species were then calculated. Among the major species found during vacuum bakeouts were , ,, and . and completely vanished within 2–4h into the bakeout, and the steady‐state ambience was composed mostly of gas. The prime source of was apparently the reduction of the fused quartz crucible by its graphite holder. The partial pressure of generated from this reaction was about 95% of the total ambient pressure. It thus seemed apparent that one way to reduce the carbon level in the ambience was by controlling the direct graphite/quartz reaction. An effort to reduce the generation of through the use of a coated graphite crucible holder resulted in the reduction of partial pressure by 45%. Neither the species with a mass greater than 44 amu nor the fragments of hydrocarbons associated with vacuum grease and pump oil were found in the ambience.