Reliability hazard characterization of wafer-level spatial metrology parameters based on LOF-KNN method

摘要

The devices with abnormal parameters often have higher early failure rates or lower reliability. The outliers identified using the wafer-level spatial metrology parameters may have high risk with the hidden reliability hazards though their parameters may meet product specifications. These devices are dangerous and are difficult to identify by existing methods. In this paper, the method was proposed to identify the wafer-level spatial metrology parameters outliers caused by defects based on LOF-KNN algorithm. First, the coordinate system of the device on the wafer was established; then the KNN (k-Nearest Neighbor) algorithm was used to characterize the spatial variation of the device, and the LOF (Local Outlier Factor) was used to characterize the local outlier of the device; finally, outliers were identified. The method was applied in the MOSFET and JBS devices cases based on the MOSFET Vth and the JBS VF wafer-level spatial metrology key parameters respectively. The outliers were obtained using the proposal algorithm. The results shown: in the MOSFET case, all non-compliant devices were identified; in additional some devices that meet product specifications but have abnormal parameters compared with their neighbors were detected. In the JBS case, where the devices all meet the product specifications, the algorithm also identified the outlier's devices with appealing abnormal parameters. Based on this work, it was demonstrated that using spatial information for outlier detection has the benefit of reducing costs and improving device reliability, which is a valuable technique.