AVS 60th International Symposium and Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThA

Paper EM-ThA6
Selective Deposition of Cu Film in Recessed Features using a Hollow Cathode Magnetron Physical Vapor Deposition Source

Thursday, October 31, 2013, 3:40 pm, Room 102 A

Session: Materials and Process for Advanced Interconnects II
Presenter: A. Dulkin, Lam Research Corp
Authors: A. Dulkin, Lam Research Corp
I. Karim, Lam Research Corp
H. Qiu, Lam Research Corp
E. Ko, Lam Research Corp
R. Tarafdar, Lam Research Corp
K. Colinjivadi, Lam Research Corp
J. Hahn, Lam Research Corp
K. Leeser, Lam Research Corp
K. Ashtiani, Lam Research Corp
Correspondent: Click to Email
Copper filled vias and trenches in dielectrics are the building blocks of the dual damascene interconnect metallization in VLSI. The fill is traditionally done with electroplating, which is preceded by physical vapor deposition (PVD) of a Cu seed layer. PVD film is known to have poor conformality within a recessed structure, with the top of the feature sidewall getting thicker coverage than the bottom. The resulting film coverage profile is not favorable for subsequent plating. Advances in iPVD technology have improved conformality; however, as the size of the features decreased below 40nm, achieving conformal seed coverage became increasingly undesirable. Conformal deposition increases the effective aspect ratio (AR) of the features, thereby making the subsequent electrofill process more challenging. Hence, bottom-up film growth which forms a seed profile with a thick bottom and continuous but not too thick sidewall coverage is desired. We have demonstrated the feasibility of depositing such profile by balancing deposition, surface diffusion, and film resputtering using the Lam hollow cathode magnetron (HCM®) PVD source. Necessary conditions were obtained by utilization of extremely low operating pressure, Cu self-sputtering, and strong magnetic confinement of plasma in the entire volume of the deposition module. The novel configuration of the magnetic field ensured that the metal ion/neutral ratio was uniform across a 300mm wafer. With the proper metal ion/neutral ratio, more than 70% of the volume of a small feature could be filled while larger features were lined with Cu film. Thus, the aspect ratio of small features was significantly reduced, resulting in void free electrofill. PVD film is characterized by small grains which attribute to high resistivity, especially inside small features. We demonstrated that the grain size can be increased with post-deposition anneal, which resulted in improved line resistance. Deposition in very large CD and AR features, such as through-silicon vias (TSV), benefited as well. The metal ion-rich deposition formed a continuous seed on the TSV sidewall with 3-5 times less flux required than with standard PVD.