Disclosed are embodiments of a contact formation technique that incorporates a preventative etch step to reduce interlayer dielectric material flaking (e.g., borophosphosilicate glass (BPSG) flaking) and, thereby to reduce surface defects. Specifically, contact openings, which extend through a dielectric layer to semiconductor devices in and/or on a center portion of a substrate, can be filled with a conductor layer deposited by chemical vapor deposition (CVD). Chemical mechanical polishing (CMP) of the conductor layer can be performed to complete the contact structures. However, before the CMP process is performed (e.g., either before the contact openings are ever formed or before the contact openings are filled), a preventative etch process can be performed to remove any dielectric material from above the edge portion of the substrate. Removing the dielectric material from above the edge portion of the substrate prior to CMP reduces the occurrence of surface defects caused by dielectric material flaking.