Resolving the origin of a CMP-associated yield/reliability issue 'center spike'-film thickness bulge in the wafer center is CMP to be held responsible for its appearance

摘要

A long-standing CMP related yield/reliability puzzle-film thickness spike,frequently appearing at the wafer center after it is processed by CMP,was studied.Optical film thickness measurments for pre-and post-CMP film were compared with surface topography profiles.Wafter surface profiles were also studied after the oxide film was HF-etched out.It was found that the post-CMP film thickness spike actually is not caused by CMP malfunctioning,but originates to a specific bare silicon wafer defect and occurs when the bare silicon wafer has a narrow dip-like defect (depression) in its center.The dielectric film,deposited over the wafer,follows the underlying center-dipped topography,and being planarized by CMP,is transformed into a top-flat film with a thick pattern in the wafer center,filling the silicon dip.In-line and end-of-line yield related issues are discussed.