Scatterometry measurement for gate ADI and AEI critical dimension of 28-nm metal gate technology

This paper discusses the scatterometry-based metrology measurement of 28nm high k metal gate after-develop inspection (ADI) and after-etch inspection (AEI) layer structures. For these structures, the critical measurement parameters include side wall angle (SWA) and critical dimension (CD). For production process control of these structures, a metrology tool must utilize a non-destructive measurement technique, and have high sensitivity, precision and throughput. Spectroscopic critical dimension (SCD) metrology tools have been implemented in production for process control of traditional poly gate structures. For today's complex metal gate devices, extended SCD technologies are required. KLA-Tencor's new SpectraShape 8810 uses multi-azimuth angles and multi-channel optics to produce the high sensitivity and precision required for measurement of critical parameters on metal gate structures. Data from process of record (POR), focus-exposure matrix (FEM) and design of experiment (DOE) wafers are presented showing the performance of this new SCD tool on metal gate ADI and AEI process structures. Metal gate AEI scatterometry measurement results are also compared to transmission electron microscopy (TEM) reference measurements. These data suggest that the SpectraShape 8810 has the required sensitivity and precision to serve as a production process monitor for 28nm and beyond complex metal gate structures.