Temperature Compensation by Embedded Temperature Variation Method for an AC Voltammeric Analyzer of Electroplating Baths

摘要

An in-situ sensor utilizing a variety of DC- and AC-voltammetric techniques is an integral component of the on-line monitoring system that provides a complete chemical analysis of different plating solutions by predicting concentration values of all deliberately-added bath constituents with a single device despite differences in the constituents' chemical properties. Such sensors are employed routinely for electroplating process control in semiconductor manufacturing. This voltammetric approach exploits quantitatively the physicochemical processes (like adsorption) which are temperature dependent. Therefore the accuracy of analyte concentration predictions can be affected adversely by temperature fluctuations. This paper introduces a novel comprehensive method which allows the mitigation of temperature variation effects on voltammetric scans allowing accurate concentration prediction. Specifically, this study introduces a multi-step rigorous routine for the development and subsequent validation of the analytical method utilizing a chemometric model with temperature variation embedded in regression for exemplary determination of leveler additive concentration. This approach analyses the effect on AC voltammograms resulting from two qualitatively indistinguishable sources of variation: leveler concentration and temperature. A critical step of this routine of fundamental novelty, which aims to select the variables (index points of voltammogram) to be utilized for building of the analytical model in the presence of two concurrent sources of variation, is introduced to incorporate temperature variation.