AN INTEGRATION FOR PREVENTING AGGLOMERATION IN INTERCONNECT PROCESSING
Original Publication Date: 2002-Apr-10
Included in the Prior Art Database: 2002-Apr-10
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De-wetting or agglomeration occurs when material is allowed to be mobile on a surface and seek the energetically favorable state of a sphere or bead of material. High mobility is associated with high temperature, low melting temperature and low surface energy. These conditions occur in copper metallization after degas (an elevated temperature process) during preclean. The preclean step is used to remove contaminants and any remaining etch stop material from vias may in fact lead to the sputter of the copper line below the via. This in turn may result in the deposition of metal material directly onto the dielectric material forming the walls of the just-etched via. If the wafer is hot from a degas step or the copper material retains sufficient energy on its own, it will agglomerate on the side-wall. The resulting rough side-wall topography coupled with shadowing effects makes subsequent continuous film barrier and seed deposition processes difficult to effect. Regions where films are not continuous result in voids. We present an integration aimed at preventing copper sputtering during the preclean process by altering the process sequence so that copper never comes into contact with the pre-barrier deposition via surface. The process involves depositing a blanket layer of barrier material (e.g., Tantalum) and subsequently patterning it to protect the underlying copper before deposition of the interlayer dielectric, via etch and preclean.