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

Abstract

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 crosscontamination 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.

Communication—In-Line Detection of Silicon Surface Quality Variation Using Surface Photovoltage and Room Temperature Photoluminescence Measurements

“…14 An RTPL study on intentionally iron (Fe) contaminated lightly doped ptype and n-type Si wafers with Fe contamination ranged from 10 9 cm −3 to 10 12 cm −3 showed good correlation between photoconductance decay (PCD) lifetime, SPV diffusion length (DL) and iron readings. 15 RTPL was reported to be sensitive to iron contamination at concentrations exceeding 10 10 cm −3 (<ppb) as calibrated by SPV using lightly doped p-type silicon.…”