Scatterometry as technology enabler for embedded SiGe process

New material innovations such as Embedded Silicon Germanium (eSiGe) provide a substantial metrology challenge for the 45 nm node technology and beyond. We discuss the details of how scatterometry provides in-line metrology solution to measure key features of the eSiGe structure. Critical features to measure are eSiGe to gate proximity and the un-etched silicon on insulator (SOI) thickness. The proximity measurement is particularly vital because it has a major influence on device performance, yet there was no high throughput in-line metrology solution until scatterometry. Results from multiple scatterometry platforms (three) are presented along with a summary of various metrology performance metrics like precision and accuracy. We also show how scatterometry measurements have been instrumental in supporting process development efforts. The comparison of scatterometry measurements to reference data from multiple metrology techniques is presented in order to evaluate the accuracy performance of various supplier platforms. Reference metrology techniques used are thin-film measurements from un-patterned targets, transmission electron microscopy (TEM) and cross-section scanning electron microscopy (XSEM). Tool matching uncertainty (TMU) analysis and weighted reference measurement system (wRMS) technique have been utilized to assist in the interpretation of correlation data. Scatterometry results from various wafers that were generated to modulate spacer width and etch cavity are also presented. The results demonstrate good sensitivity for key measurement features, especially eSiGe proximity and un-etched SOI thickness, which have very tight process control requirements.