Advanced interconnect process development utilizing wafer inspection with “on-the-fly” automatic defect classification

Wafer inspection providing classified defect density with “on-the-fly” automatic defect classification (OTF-ADC) is increasingly being utilized to obtain the detailed defect information for rapid resolution of defectivity issues. The OTF-ADC defect categories allow the critical defect types to be segregated and tracked during the actual wafer inspection without any throughput reduction. Inspection with OTF-ADC can be utilized at various interconnect steps such as post-develop, post-etch, and post-metal-CMP step for advanced process development and line monitoring. Significant benefits are realized with early defect excursion detection by tracking the classified defect counts instead of simply the total defect counts. An associated requirement is the ability to capture all of the relevant defect types at key inspection points. Utilizing the Applied Materials WF736 with a combined bright-field and dark-field architecture, the full range of yield limiting defects was captured at two key interconnect stages: post litho, and post CMP. After-development inspection (ADI) with the WF found both macro (>15 um) and micro (<15 u) defects. In some instances, the micro-defects could only be imaged with a SEM. The OTF-ADC provided good accuracy for both ADI and CMP. Using an example from post metal CMP, OTF-ADC is shown to identify hidden excursions which would have had significant yield impact and which would have gone undetected with standard “total count” inspection methods. The use of OTF-ADC provides improved time-to-information and enhances the yield potential by permitting defect sourcing which facilitates corrective action