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Increasing levels of metallization, shrinking device geometries, and stringent defect density requirements have led to a continuous focus in the semiconductor manufacturing community to reduce defects generated during metal deposition by PVD techniques. Pareto analysis of in-film defects in currently used interconnect metallization schemes suggest that a considerable portion of the in-film defects (up to 50%) are caused by Unipolar arcing during Aluminum deposition. Due to their unusual molten appearance, these defects are commonly referred to as `Splats'. These defects can be as large as 500 micrometers , and because of their metallic nature have a high probability of causing device failure. Due to their frequency of occurrence and size, these Splats can significantly impact device yield in a manufacturing environment. Systematic investigations have been carried out for the identification and characterization of these in-film defects, using a combination of Tencor Surfscan, Optical and Ultrapointe Microscopy and SEM FIB analysis. This analysis has revealed these Splats result from localized melting or explosions on the target surface, due to Unipolar arcing. This Unipolar arcing can be strongly correlated to presence of undesirable metallurgical attributes such as Alumina inclusions, porosity, oxygen content etc. in the target. The results of this study indicate that by the reduction/elimination of these various undesirable metallurgical attributes in the Aluminum alloy targets a significant improvement in defect generation during sputter deposition of Aluminum films, and hence an improvement in device yield, is possible. |
