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Abstract

The present invention describes a method for detecting thickness measurement error of a film mounted on a wafer substrate. The method comprises exposing a film to be measured to electromagnetic waves over a range of incident wavelengths, reflecting the electromagnetic waves from an outer surface of the film and from the film-substrate interface so that said reflected electromagnetic waves interfere with one another, and measuring an intensity of the reflected electromagnetic waves. A reflected intensity curve is then computed over the range of incident wavelengths and then compared to a theoretically calculated reflected intensity curve to obtain a goodness of fit (GOF) measurement. The above process is repeated at a plurality of different locations on the wafer to obtain a plurality of GOF measurements for the wafer. Minimum and maximum GOF measurements are determined from the plurality of GOF measurements obtained. If anyone of these GOF measurements are less than a prescribed amount, such as 0.1, then an order skipping error has been detected. Additionally, if the ratio of the minimum GOF to that of the maximum GOF is less than a predetermined amount, such as 0.6, then an order skipping has been detected and the measurement value should be rejected.

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First Claim