The principles and application examples of recently refined，computerized surface photovoltage (SPV) method are described. The SPV method was used to optimize cleaning efficiency and to monitor 'in-line' heavy metal contamination and charge during critical processing steps for Statistical Process Control (SPC). Examples of the optimization of various cleaning steps，effects of the purity of virgin and reused chemicals， and the surface topology on cleaning efficiency will be given together with examples of SPC monitoring of real problems in processing lines. Cleanliness of incoming chemicals is not always a limiting factor and often is not related to the cleanliness of chemicals at the point of use (in the cleaning station). This new method is capable of waferscale，non- contact mapping of metal contaminants in the bulk and on the surface with sensitivities as high as 10¹⁰atoms cm-³.
Surface Photovoltage Monitoring of Heavy Metal Contamination on Silicon During Chemical Cleaning in IC Manufacturing
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