Effects of cleaning techniques on residual contamination in SIMOX

Since SIMOX (separation by implanted oxygen) material is formed by a high-fluence process and subsequent high-temperature anneal, any contamination in the starting material and any residual contamination from the implant process may be critical for the further device performance and yield. The residual contamination level in SIMOX substrates was evaluated with respect to a variety of wet and dry cleaning techniques. The authors used total X-ray fluorescence analysis (TXRF) and SIMS (secondary ion mass spectrometry) analysis to determine the residual contamination from transition metals and aluminum, respectively Utilizing the TXRF sensitivity, incoming bulk wafers were examined for heavy metal contamination. Unacceptable residual levels of zinc (~4×10¹² cm^-2) were found on the wafers. Wafers were also examined by TXRF and SIMS after the ion implantation process. An aluminum peak areal density on the order of 1×10¹² to 1×10¹³ atoms/cm² was identified by SIMS analysis on the ion implanted wafers. Effective reduction in aluminum contamination after traditional wet cleans for the as-implanted wafers is shown