Iron Cross-Contamination Dynamics at Elevated Temperatures in Oxygen Gas Flow

One major source of metals contamination during high temperature processing are metals pre-deposited on the wafers surface before thermal treatment and metals cross- contamination from other wafers and/or furnace components. This study investigates the mechanism of metals transfer via gas phase vs. temperature and oxygen gas flow conditions. We also investigated the cross-contamination from Silicon Carbide (SiC) components at elevated temperatures. Cross-contamination from SiC can be explained as (a) metal diffusion from the direct contact area between silicon wafer and SiC (MDD - Metals Direct Diffusion) and (b) metal desorption from the SiC surface and re-adsorption on the silicon wafer surface from the gas phase (MAG - Metals Adsorption from Gas Phase). Both MDD and MAG contamination components are driven by SiC surface metal contamination. Using high resolution Surface Photo- Voltage (SPV) iron mapping we investigated the character of iron cross-contamination. Iron diffusion and desorption activation energies were experimentally determined.