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Surface defects on semiconductor wafers often exhibit particular spatial patterns. These patterns contain valuable information of the fabrication processes and can help engineers identify the potential root causes. In this paper, we present a control chart technique to detect spatial patterns of surface defects by using the Hough transform. An approximate distribution model of the monitoring statistic is proposed, and a comprehensive control chart design method is developed. This method is characterized by its intuitive implication and a simple design procedure which relates the statistical performance of the control chart to the design parameters. A case study is presented to validate the effectiveness of this method.