Eddy current sensing of metal removal for chemical mechanical polishing

Abstract

A sensor for monitoring a conductive film in a substrate during chemical mechanical polishing generates an alternating magnetic field that impinges a substrate and induces eddy currents. The sensor can have a core, a first coil wound around a first portion of the core and a second coil wound around a second portion of the core. The sensor can be positioned on a side of the polishing surface opposite the substrate. The sensor can detect a phase difference between a drive signal and a measured signal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation application and claims the benefit of priority under 35 U.S.C. Section 120 of U.S. application Ser. No. 10 / 447,165, filed May 27, 2003, which is a divisional of U.S. application Ser. No. 09 / 574,008, filed on May 19, 2000, now U.S. Pat. No. 6,924,641. The disclosure of each prior application is considered part of and is incorporated by reference in the disclosure of this application.BACKGROUND [0002] The present invention relates generally to chemical mechanical polishing of substrates, and more particularly to methods and apparatus for monitoring a metal layer during chemical mechanical polishing. [0003] An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive or insulative layers on a silicon wafer. One fabrication step involves depositing a filler layer over a non-planar surface, and planarizing the filler layer until the non-planar surface i...

AI Technical Summary

Benefits of technology

[0019] Implementations of the invention can include zero or more of the following possible advantages. The endpoint detector can sense the polishing endpoint of a metal layer in-situ. The magnetic field apparatus for the endpoint detector can be embedded in the platen below a polishing pad. The magnetic field apparatus can be protected from polishing environment, e.g., corrosive slurry. The endpoint detector need not use complex electronics. Polishing can be stopped with reasonable accuracy. Overpolishing and underpolishing substrate can be reduced, thereby improving yield and throughput.

Problems solved by technology

One problem in CMP is determining whether the polishing process is complete, i.e., whether a substrate layer has been planarized to a desired flatness or thickness, or when a desired amount of material has been removed.

On the other hand, underpolishing (removing too little) of a conductive layer leads to electrical shorting.

This is a time-consuming procedure that reduces the throughput of the CMP apparatus.

Alternatively, the examination might reveal that an excessive amount of material has been removed, rendering the substrate unusable.

Unfortunately, the proposed eddy current sensing techniques typically require complex electronics.

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