Browsing by Author "Hensen, K"

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Aging influence of poly(ethylene glycol) suppressors of Cu electrolytes on gaps filling
(2006-05-01)
Liu, SH
;
Li, TC
;
Chen, C
;
Shieh, JM
;
Dai, BT
In this study, we investigate how the degradation of poly(ethylene glycol) (PEG) additives in Cu electroplating electrolytes influences the gaps filling of damascene features and the roughness of plated surfaces. The cleavage of PEG, whose reaction is enhanced by a high bias current and more plating cycles, not only diminishes the inhibition effect of the electrolytes, but also enables the formation of enormous complexes of short-chain PEG-Cu far from the reacting surfaces. Hence, the more plating cycles performed, the worse the gaps filling characteristic and the rougher the plated surfaces. Furthermore, an overshoot phenomenon on the transient cells voltage for PEG-containing electrolytes is observed and explained well by a dynamic equilibrium between PEG absorption ability and Cu reduction speed. Accordingly, the change in overshoot shape is closely related to PEG aging and this fact is employed to examine the reliability of electrolytes.
Roles of additives in damascene copper electropolishing
(2006)
Liu, SH
;
Shieh, JM
;
Chen, C
;
Hensen, K
;
Cheng, SS
This study explores how the dissolution of damascene Cu depends on accelerators of organic acids in alcohol-containing H3PO4 electropolishing electrolytes. Four two-additive electrolytes that contain different accelerators, acetic, citric, citrazinic, and benzoic acids, are evaluated. At the bottom of damascene features, an esterification reaction between alcohols and organic acids efficiently forms a highly resistive layer and reduces the acidity of the solution. Accordingly, outside the damascene features, the rate of removal of Cu is dominated by the acidity of electrolytes but, inside the features, it is also determined by the resistance of the viscous layer. For a weak acidic additive, acetic acid, an extremely high additive concentration is introduced to sustain the moderate acidity of the solution to initiate intense esterification. Therefore, acetic-acid-based two-additive electrolytes exhibit excellent Cu planarization capability. (C) 2006 The Electrochemical Society.
Two-additive electrolytes for superplanarizing damascene Cu metals
(2005)
Liu, SH
;
Shieh, JM
;
Chen, C
;
Dai, BT
;
Hensen, K
Two-additive electropolishing (EP) electrolytes exhibit an extremely high planarization-efficiency in Cu damascene schemes, independent of pattern sizes (1- 50 mu m). This electrolyte is demonstrated by adding alcohols and organic acids to the H3PO4 electrolyte. The high wetting ability of alcohols allows such additives to easily access the damascene bottom. This mechanism, assisted by the reduced polishing rate associated with the high surface viscosity caused by alcohol additives, greatly passivates the damascene bottom from elecropolishing. Accordingly, the superpolishing functionality reported by Chang et al. [Electrochem. Solid-State Lett., 6, G72 (2003)] in the two-additive electrolyte outperforms in the one-additive electrolyte. (C) 2005 The Electrochemical Society.