Patent ID: 6281098
Filing Date: 2001-08-28
Classification: C01B,C23C,C30B,H01L

Abstract:
A process for depositing polycrystalline silicon on a substrate, comprising:placing iodine source material and silicon source material in a chamber that has a bottom portion, a mid-portion, and a top portion, and maintaining the chamber at about atmospheric pressure;heating the iodine source material and the silicon source material in the bottom portion of the chamber to a temperature sufficiently high to vaporize the iodine source material and to react some, but not all, of the iodine source material with the silicon source material at atmospheric pressure to create a deposition precursor of silicon diiodide vapor along with silicon tetraiodide vapor while maintaining the atmospheric pressure;driving the iodine vapor and the silicon diiodide vapor upwardly from the bottom portion of the chamber, through the mid-portion of the chamber, and into the top portion of the chamber to condense the iodine vapor and the silicon diiodide vapor in the top portion of the chamber, including forming a silicon diiodide cloud in the top portion of the chamber, by forming and maintaining a temperature gradient in the chamber, such that the mid-portion has a temperature that is lower than the temperature of the bottom portion, but higher than iodine boiling temperature and higher than silicon diiodide boiling temperature at atmospheric pressure, and such that the top portion has a temperature that is lower than silicon diiodide boiling temperature but higher than iodine melting temperature at atmospheric temperature;positioning the substrate in the mid-portion of the chamber under the silicon diiodide cloud, but above the silicon source material, where temperature in the mid-portion is enough lower than the temperature of the source material to drive disproportionation of the silicon diiodide into silicon and silicon tetraiodide and thereby deposit silicon on the substrate;maintaining the temperature gradient and atmospheric pressure in the chamber and allowing the iodine vapor and the silicon diiodide vapor to condense in the top portion of the chamber and to flow back to the bottom portion of the chamber while iodine, silicon, and silicon tetraiodide vapor, in the bottom portion of the chamber continue to react to form additional silicon diiodide vapor for disproportionation and deposition of silicon on the substrate until a desired thickness of silicon is deposited on the substrate; andremoving the substrate with the silicon deposited thereon from the chamber.