MOLECULAR-BEAM SAMPLING TO ANALYZE THE REACTION-MECHANISM OF CHEMICAL-VAPOR-DEPOSITION

order to understand the chemical vapor deposition (CVD) reaction mecha nism, forming a thin him from the gas phase, it is important to identi fy the intermediate chemical active species (radicals) for each reacti on. Radicals generally have very short lifetimes; therefore, it is ver y difficult to detect them. Molecular beam sampling (MBS) is a method that can extract radicals in the gas phase using free jet expansion. A vacuum system using a MBS method was designed to analyze the CVD reac tion mechanism in the gas phase near the surface of the wafer. The sys tem consists of a thermal flow-through type CVD reactor and three diff erential pumping vacuum chambers with a quadrupole mass analyzer. The performance of the MBS system was tested with various gases. The syste m was applied to detect radicals produced in the region near the wafer in a thermal TEOS/O-3 (tetraethylorthosilicate) CVD reaction to depos it SiO2 thin films. It is proved that the radicals, from which ethoxy bases of TEOS are extracted, are formed in the gas phase and can play an important role in the thermal TEOS/O-3 CVD reaction. (C) 1996 Ameri can Vacuum Society.