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11th Edition: Challenges in Copper Interconnect Technology: Macro-Uniformity and Micro-Filling Power |
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Feb 03, 2005 at 04:08 PM |
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JACOB JORNE, Cupricon Inc., Rochester, NY, USA ABSTRACT
The main
challenges facing the electroplating of copper on wafers for
interconnection are uniformity and conformity. The difference between
these two requirements is due to the scales involved. Uniformity over
the entire wafer involves the scale of up to 30 cm, while the
conformity and the filling ability of trenches and vias involve the
scale of sub-micron. This difference requires clarification, as the
traditional concept of throwing power is not applicable here. The
non-uniformity of copper plating is due to the appreciable resistance
of the thin barrier and seed layers and depends also on the geometry of
the electroplating system
The macro-distribution depends on the ratio
of the electronic resistance of the thin copper seed layer to the
electrochemical resistance. A dimensionless parameter B, which
determines the uniformity of the deposit, is identified as the ratio
between the resistance of the thin copper layer and the resistance of
the electrolyte plus the electrochemical reaction. When the current is
fed to the periphery of the wafer, the copper layer is thicker there
and thinner at the centre of the wafer. Nonuniformity in copper plating
is expected to be more severe for large wafers (200mm). Methods to
improve the uniformity of the copper deposit include the usage of low
conductivity electrolyte and the presence of organic additives in the
electrolyte.
 Challenges in Copper Interconnect Technology: Macro-Uniformity and Micro-Filling Power in Copper
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Wafer Processing 