Contamination Behavior of Bare Silicon Wafer Surface During Single-Wafer Process Using Deionized Water Containing Ultra-Trace Metal Impurities

In semiconductor manufacturing, low-level metal contamination control is required when using deionized water (DIW). However, the adsorption behavior of metals at the pg/l level on wafer surfaces is unclear. In this study, we rinsed a bare Si wafer with DIW containing pg/l-level metal impurities during a single-wafer process and evaluated the metal concentration correlation between DIW and the wafer surface. Al, Ti, Mn, Co, Cu, Sr, and Pb exhibit strong correlations with increasing metal concentration in DIW. Additionally, the adsorption ratio of Cu (2.6−3.3%) is the highest among the aforementioned metals. The adsorption behaviors of Al and Ti were drastically changed as the wafer surface became more hydrophilic with the increasing rinse time. The adsorption ratio of Cu remained constant with the concentration in DIW and the rinse time, whereas it changed with the supply flow rate. We assumed that the adsorption probability decreased owing to the thinner boundary layer with the increased radial velocity associated with the increasing supply flow rate. These findings provide new insights by showing that the supply flow rate is one of a key factor as a parameter for contamination control in addition to reducing the concentration in DIW during single-wafer process.