A new rule-based clustering technique for defect analysis

In joining defects on semiconductor wafer maps into clusters, it is common for defects caused by different sources to overlap. Simple morphological image processing tends to join either too many unrelated defects together or not enough together. Expert semiconductor fabrication engineers have demonstrated that they can easily group clusters of defects from a common manufacturing problem source into a single signature. Capturing this thought the process of clustering is ideally suited for rule-based systems. A system of rules was developed to join disconnected clusters based on the location of the defects. The clusters are evaluated on a pair-wise basis using the rules and are joined or not joined based on a threshold. The system continuously re-evaluates the clusters under consideration as the rules change with each joining action. The techniques used to measure the features, and methods for improving the speed of the system are developed. Examples of the process are shown using real-world semiconductor wafer maps obtained from chip manufacturers.