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Cu Interconnect and its Formation with Mn on Top Surface

IP.com Disclosure Number: IPCOM000178919D
Original Publication Date: 2009-Jan-29
Included in the Prior Art Database: 2009-Jan-29
Document File: 1 page(s) / 25K

Publishing Venue

IBM

Abstract

Oxygen implantation is used in Mn-Cu interconnect metallurgy to manipulate the location of Mn atoms. Thus, the electromigration benefit of Mn is obtained without the resistivity penalty.

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Cu Interconnect and its Formation with Mn on Top Surface

As the device dimension shrinks, the current density in interconnects increases dramatically because the supply voltage does not change while the interconnect width and height are shrunk in accordance with the device shrinkage. This leads to reliability crises in the electromigration due to high current density and in TDDB due to the non-scaled supply voltage. One method to improve the electromigration performance is to add Mn (manganese) into Cu at the copper seed layer which is generally formed by PVD ( physical vapor deposition). Such incorporated Mn atoms redistribute during thermal processes to the copper/barrier interface and to the copper top surface at the interface of copper/dielectric cap layer. Such redistributed and segregated Mn atoms form an interface to copper which has a high resistance against nucleation of electromigration voiding. However, the drawback to incorporate Mn in Cu is the increase in the copper resistivity. In order for Cu resistivity to be reduced sufficiently, Mn atoms need to be sawed away from the copper bulk region to migrate and segregate at the copper top surface. However, the migration and the segregation do not take place enough because the driving force of the migration (diffusion) of Mn to the top copper surface which is in short. The driving force is generally presence of oxygen in the ambient during thermal processes when the copper top surface is exposed to the ambient. Once a layer composed of Mn and O is formed on top of the copper surface, the...