Methods and apparatus for generating a library of spectra

Abstract

A method of generating a library from a reference substrate for use in processing product wafers is described. The method includes measuring substrate characteristics at a plurality of well-defined points of a reference substrate, measuring spectra at plurality of measurement points of the reference substrate, there being more measurement points than well-defined points, and associating measured spectra with measured substrate characteristics.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority under 35 USC §119(e) to U.S. patent application Ser. No. 12 / 059,435, filed on Mar. 31, 2008, which claims the benefit of prior U.S. Provisional Application 60 / 949,498, filed Jul. 12, 2007, and U.S. Provisional Application 60 / 909,639, filed Apr. 2, 2007 the entire contents of which are hereby incorporated by reference.TECHNICAL FIELD[0002]This invention relates to metrology, and in one aspect to optical monitoring of substrates during a chemical mechanical polishing process.BACKGROUND[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. For certain applications, the filler layer is planarized until the top surface of a patterned layer is exposed. A conductive filler layer, for example,...

AI Technical Summary

Benefits of technology

[0016]Possible advantages of implementations of the invention can include one or more of the following. A library of spectra can be assembled, and the spectra can be associated with physical properties of the substrate. Spectra-based endpoint determination can be made in-situ with greater speed and accuracy, and variations in the post-polishing thickness of the substrate layer can be reduced. Spectra-based measurements of substrate characteristics can be made by in-line monitoring systems with great speed.

Problems solved by technology

However, this metrology process can be time-consuming, and the metrology equipment can be costly.

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).

Therefore, for some applications, determining the polishing endpoint merely as a function of polishing time can lead to unacceptable variations in the post-polishing thickness of the substrate layer.

However, removal of the substrate from the polishing apparatus for transportation to an in-line or stand-alone metrology station can lead to an unacceptable reduction in throughput.

However, measurements using such an in-situ system usually cannot be precisely positioned at a desired measurement location due to the motion of the substrate relative to the sensor, and the measurements can be less accurate due to noise generated by the polishing environment (e.g., absorption of light by slurry), the limited time available for measurements, and the need for real-time processing of the sensor data.

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