Use of optical metrology techniques for uniformity Control of 3D stacked IC's

This paper describes a study that evaluates various optical metrology techniques for in-line control of the uniformity of 3D stacked structures. Among the 3D process integration flow, key 3D process steps were identified and characterized in order to quantify their specific intra-wafer dispersion signature. The cross correlation between the various intra-wafer process step signatures was then analyzed to verify the data set consistency. The analysis indicated that the measurement data are consistent over the process integration flow, and that a simple model explains the final intra-wafer signature. The results highlight the importance of controlling those specific steps and provide a new alternative for advanced process control implementation.