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AN INTEGRATION FOR PREVENTING AGGLOMERATION IN INTERCONNECT PROCESSING

IP.com Disclosure Number: IPCOM000007634D
Original Publication Date: 2002-Apr-10
Included in the Prior Art Database: 2002-Apr-10

Publishing Venue

Motorola

Related People

Valli Arunachalam: AUTHOR [+4]

Related Documents

WO9936952: PATENT [+7]

Abstract

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.

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AN INTEGRATION FOR PREVENTING AGGLOMERATION IN INTERCONNECT PROCESSING

Valli Arunachalam, Peter L.G. Ventzek, Shahid Rauf, and Dean Denning

Abstract

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. 

During fabrication of Cu interconnects in integrated circuits, it is important to fill vias with Copper (that connect metal lines) without voids.  Voids can degrade the electrical performance of circuits and cause reliability problems.[1],[2] Deposition of conformal and smooth barrier and seed layers provides the electrical continuity to ensure void free fill during the subsequent electroplating step.  By barriers we refer to diffusion barriers (often a refractory material like Tantalum) that are thin films between a good metal conductor in the via (now Copper) and the interlayer dielectric.  By seed we refer to the thin conducting layer (Copper) placed on top of a barrier to allow good electrical conduction for an electroplating step used to fill the via with metal (Copper).  It is also important that the barrier is continuous and sufficiently thick to prevent diffusion of copper into the dielectric.  Agglomeration (associated with de-wetting) of Cu (Fig. 1) during an RF preclean step[3],[4] preceding barrier and seed deposition has made it challenging to obtain good barrier and seed layers.[5],[6] This paper describes an integration to eliminate copper agglomeration formation characterized by the deposition of a patterned barrier layer with a sequence of process steps ensuring that the RF pre-clean never sees Copper. The underlying idea is that one can deposit a prote...