Ta-rich atomic layer deposition TaN adhesion layer for Cu interconnects by means of plasma-enhanced atomic layer deposition

Low via yield caused by low adhesion between Cu and a barrier metal is a cost issue when the atomic layer deposition (ALD) barrier metal process is integrated with Cu interconnection. To overcome this issue, an adhesion layer consisting of Ta-rich TaN obtained by plasma-enhanced ALD [i.e., ALD Ta(N)] is proposed. A 2 nm thick ALD Ta(N) film, deposited by exposing a substrate to pentakisdimethylaminotantalum (Ta(N(CH3)(2))(5)) and He/H-2 plasma in turn, demonstrated strong adhesion comparable to that of a conventional physical vapor deposition Ta/TaN barrier. Both the via yield and the robustness against stress-induced voiding of single-damascene Cu/porous-low-k interconnects were improved by substituting an ALD Ta(N) adhesion layer for the conventional ALD TaN layer. (c) 2005 American Vacuum Society.