Effect of Oxidizer on the Galvanic Behavior of Cu ∕ Ta Coupling during Chemical Mechanical Polishing

The effect of oxidizer addition, namely, H 2 O 2 , KIO 3 , and Fe(NO 3 ) 3 , on the galvanic behavior of the Cu/Ta coupling in 0.01 M Na 2 SO 4 + 1 wt % Al 2 O 3 base slurry was studied. Both open-circuit potentials of the uncoupled Cu and Ta as well as galvanic current of the Cu/Ta were measured in static and under chemical mechanical polishing conditions to analyze the roles of these additives. The results showed that Fe(NO 3 ) 3 was more effective than H 2 O 2 and KIO 3 in promoting the passivation of Ta, which in turn caused the change of polarity between Cu and Ta. The effect of Cu/Ta area ratio on the galvanic behavior of the coupling was also investigated. The results showed that in Fe(NO 3 ) 3 -containing slurry, Ta was the anode with a Cu/Ta area ratio of 5:1 but became the cathode with an area ratio of 1:1.

[1]  K. Maex,et al.  Investigation of barrier and slurry effects on the galvanic corrosion of copper , 2002 .

[2]  S. Raghavan,et al.  Electrochemical investigations during the abrasion of aluminum/titanium thin-film stacks in iodate-based slurry , 2004 .

[3]  Karen Holloway,et al.  Tantalum as a diffusion barrier between copper and silicon: Failure mechanism and effect of nitrogen additions , 1992 .

[4]  E. A. Charles,et al.  A theoretical approach to galvanic corrosion, allowing for cathode dissolution , 1988 .

[5]  D. Zeidler,et al.  Characterization of Cu chemical mechanical polishing by electrochemical investigations , 1997 .

[6]  Ronald J. Gutmann,et al.  Chemical Mechanical Planarization of Microelectronic Materials , 1997 .

[7]  S. Raghavan,et al.  Electrochemical Behavior of Copper in Tetramethyl Ammonium Hydroxide Based Solutions , 1999 .

[8]  Ki-Bum Kim,et al.  Comparative study of tantalum and tantalum nitrides (Ta2N and TaN) as a diffusion barrier for Cu metallization , 1996 .

[9]  S. Kondo,et al.  Slurry Chemical Corrosion and Galvanic Corrosion during Copper Chemical Mechanical Polishing , 2000 .

[10]  F. Mansfeld.  Area Relationships in Galvanic Corrosion , 1971 .

[11]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[12]  F. Mansfeld,et al.  Laboratory Studies of Galvanic Corrosion of Aluminum Alloys , 1976 .

[13]  D. Zeidler,et al.  The interaction between different barrier metals and the copper surface during the chemical-mechanical polishing , 1997 .

[14]  Ronald J. Gutmann,et al.  Pattern Geometry Effects in the Chemical‐Mechanical Polishing of Inlaid Copper Structures , 1994 .

[15]  F. Mansfeld.  The Relationship Between Galvanic Current and Dissolution Rates , 1973 .

[16]  M. Pourbaix.  Atlas of Electrochemical Equilibria in Aqueous Solutions , 1974 .