Purified tetraethoxysilane and method of purifying

DETAILED DESCRIPTION OF THE INVENTION The invention in its broader aspects relates to a method of purifying tetraethoxysilane, comprising injecting impure tetraethoxysilane in the gaseous phase into a gas chromatograph column as a series of spaced pulses, heating the gas chromatograph column to a temperature less than the boiling point of pure tetraethoxysilane, passing the impure tetraethoxysilane through the gas chromatograph column by a flow of carrier gas, separating impurities in the impure tetraethoxysilane from purified tetraethoxysilane which results in elution of purified tetraethoxysilane from the gas chromatograph column at a different time than the impurities, and receiving the purified tetraethoxysilane at a location distinct from that of the impurities.
Alternatively, purification of TEOS without significant decomposition may be effected in at least a partial vacuum where all the TEOS in the separating column is present in the vapor state.
It is believed that the process of purifying a material in a gas chromatograph column at a temperature below the boiling point of the material can be beneficially practiced on materials other than tetraethoxysilane.
The invention also relates to the purified tetraethoxysilane produced by this process, which is orders of magnitude purer than that which is conventionally obtainable.
The resulting purified tetraethoxysilane has up to two orders of magnitude fewer metallic impurities than conventionally available purified product, allowing improved silicon dioxide thin films to be manufactured, such as for semiconductor devices.
The use of the TEOS purified by this process increases the device yield on the wafers used for device fabrication because of the reduced impurities compared to other silicon dioxide sources and TEOS of lesser purity.
The invention also relates to the construction of the separating column component, which provides for a uniform flow of the TEOS pulse along the length of the column to optimize separation of impurities from the TEOS