Electrochemical mechanical deposition and reverse linear planarisation of copper for 45 nm node ULK integration

Realization of 45 nm node interconnects will require the use of k=2.5 and below dielectrics. Porous SiOC based low k materials are the most promising for these applications. However, due to their porous structure, the weak mechanical behavior of these materials will induce several integration issues. Among them, the copper metallization and CMP will be very sensitive to adhesion issues. The work reported here describes the benefits of an integration scheme combining an electrodeposition of planar copper film followed by a low down force CMP step. The CMP step is based on a so-called "reverse linear" or "shoe shine" motion combining rotative and linear motions. In order to allow low down force, thus low removal rate CMP, the electrodeposition of Cu must be previously planarized and present a low overburden.