Feed forward parameter values for use in theoretically generating spectra

Abstract

A method of controlling a polishing operation is described. A controller stores an optical model for a layer stack having a plurality of layers and a plurality of input parameters including a first parameter and a second parameter. The controller stores data defining a plurality of default values for the first parameter and measures an optical property of a substrate and generates a second value. Using the optical model and the second value and iterating over the first values, a number of reference spectra are calculated. A spectrum is measured and the measured spectrum is matched to the reference spectra and the best matched reference spectrum is determined. The first value of the best matched reference spectrum is determined and is used to adjust a polishing endpoint or a polishing parameter of a polishing apparatus.

Description

TECHNICAL FIELD[0001]The present disclosure relates to optical monitoring, e.g., for control of chemical mechanical polishing of substrates.BACKGROUND[0002]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, can be deposited on a patterned insulative layer to fill the trenches or holes in the insulative layer. After planarization, the portions of the conductive layer remaining between the raised pattern of the insulative layer form vias, plugs, and lines that provide conductive paths between thin film circuits on the substrate. For other applications, such as oxide polishing, the filler layer is planarized until a p...

AI Technical Summary

Benefits of technology

The patent describes a way to compare optical spectra to a library of reference spectra to find the best match. This process is useful in monitoring and measuring the progress of a polishing process. By calculating a reference spectrum based on an optical model of the substrate, a library of reference spectra can be created that spans the range of variations of incoming substrates. This library can be reduced in size by replacing a variable parameter with a known value, which improves reliability and reduces thickness non-uniformity. The library can also be used for in-sequence monitoring and to determine the polish time or pressures for the next platen. This approach reduces the processing load and improves prediction accuracy.

Problems solved by technology

The larger library may also produce multiple possible matches, causing lower reliability or requiring other techniques to sift the possible matches and select an acceptable match.

However, a complex optical model with a large the number of variable input parameters can suffer similar problems of computational load and possible false fitting of the optical parameters.

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