Optical detection of planarization, breakthrough and end-point in membrane-mediated electropolishing of metal layers

Abstract

Methods and apparatus for monitoring in situ the progress of planarization and / or removal of a thin metal layer from a substrate during membrane-mediated electropolishing processes are provided.

Description

FIELD OF THE INVENTION[0001]The invention is directed to methods and apparatuses for monitoring in situ the progress of planarization and / or removal of a thin metal layer from a substrate during membrane-mediated electropolishing processes.BACKGROUND[0002]Interconnections on integrated circuits are fabricated by the Cu damascene process in which the interconnect circuit pattern is lithographically etched into the surface of a dielectric layer on the surface of the wafer. The pattern is then coated with thin conformal layers of a barrier metal, such as Ta, followed by Cu. Additional Cu in then electroplated over the entire surface of a wafer to fill completely the recessed circuit features with Cu. It is then necessary to planarize topographic features on the surface of the electroplated Cu and remove all excess Cu from the plateau areas between the circuit features so that the underlying barrier metal is exposed. Planarization and removal of excess Cu is customarily achieved by a ch...

AI Technical Summary

Problems solved by technology

In CMP the surface of the wafer is continuously flooded by a polishing slurry containing suspended colloidal particles that scatter light and complicate optical measurements.

Consequently, optical measurements can be difficult to carry out without significant modifications of the polishing pad and the platen that supports the pad.

These methods vary in sensitivity and reliability and in the cost and complexity they contribute to the equipment.

However, the method is highly intrusive, requiring process compromises or extensive hardware modifications.” Such modifications are described in U.S. Pat. No. 5,893,796; U.S. Pat. No. 5,964,643; U.S. Pat. No. 6,045,439; U.S. Pat. No. 6,280,290; and U.S. Pat. No. 6,454,630.

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