Akella Venkata Surya Satya

Understanding clustering of defects in a sub-0.5 /spl mu/m CMOS fabricator

Over two decades of bipolar-experience has previously alerted one to the fact that the extent of defect clustering, assumed in the CMOS yield models, may not hold for defects monitored on microelectronic test structures (MTS). Tracing the defect clustering from inline CMOS MTS, we now describe a viable yield prediction model using data from the various inline monitors, which also helps reconcile the questions raised earlier. Such a yield-bridge between the MTS-data and the product yield establishes the validity of the yield model and assumptions therein.

A study of clustering using microelectronic defect monitors

Clustering of defects has received extensive attention for its impact on the predicted yields of large chips and on-chip redundancy. Defect density, defined for the separation of variables, permits product-independent cross-comparisons between fabricators and technologies. Defect densities are best tracked by inline measurements on microelectronic test structures, with product identity in their sensitivity to defects. It is reported that the defects monitored via the microelectronic test structures may not have the extent of clustering that has been noted in the literature.<<ETX>>

Test structures for automated contactless inline wafer inspection

Simple but unique and space-saving microelectronic test structures were designed to afford automated inline contactless wafer inspection in a Scanning Electron Microscope (SEM) for rapid electrical defect-monitoring in the voltage contrast (VC) mode, along with in situ defect-isolation and -characterization capabilities. Such an automated technique can support accelerated yield learning on sub-0.25 /spl mu/m-rule designs as the defects get below the optical resolutions. The system is also capable of the traditional visual inspection in the secondary-electron emission mode, affording the determination of the transfer coefficients between optical inspection and electrical faults.