Precision weighing to monitor the thickness and uniformity of deposited or etched thin film

Abstract

A time delayed differential weighing procedure used with an electronic analytical balance is optimized for samples exhibiting a small change in mass, for example from deposition, etching, plating or corroding, relative to the sample mass to minimize all significant sources of error that could otherwise degrade the measurement results, such as errors resulting from air density and temperature changes that occur during the interval between the first measurement of a sample, before the sample is processed, and a subsequent measurement of the sample, after the sample is processed. A calibration standard having substantially the same density as that of the sample is weighed both times the sample is weighed, i.e. before and after processing, to track the change in the sample balance reading due to air density and temperature changes, and thereby eliminate sample related errors. Balance and weighing procedure accuracy and precision are tested by a gauge study procedure. A procedure for determining area exposed after photoresist develop on a semiconductor wafer application is also provided.

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