Enabling Efficient Strain Analysis of Advanced Nodes with STEM Nanobeam Diffraction Enhanced by Beam Precession at Sub-2nm Spatial Resolution

Abstract

The dimensions of transistors become smaller while their architecture becomes more complex in 3D due to the demand for faster data processing, faster signal transmission, and decreasing power consumption. Consequently, requirements on the accuracy and quality of TEM lamellae and the established and conventional analytical STEM (scanning transmission electron microscopy) techniques are stretched to or beyond their limits. Especially for strain analysis in the advanced technology nodes, electron diffraction mapping (4D-STEM) must be enhanced by beam precession for achieving the required precision and accuracy, while the spatial resolution must be sufficient to resolve thin stacked layers in the 3D architecture. However, conventional setups with beam precession modules cannot typically reach sufficient spatial resolution due to inaccuracy in microscope optics alignments, while alternative techniques have other shortcomings. Improvements in TEM sample preparation that result in minimal amorphization and curtaining effects due to parallel beam used for FIB milling of inverted lamellas as well as integration of dedicated hardware for precise beam precession in an analytical STEM microscope (TENSOR) facilitate high quality of 4D-STEM data for strain analysis at spatial resolution under 2 nm. Consequently, strain analysis of the latest and future advanced nodes can still be performed by precession-enhanced 4D-STEM measurements that provide fast and robust analysis of large regions of interest (transistor circuits). Moreover, microscope alignments and setup of such strain analysis measurements have been automated, allowing routine operation even by non-specialist TEM operators in semiconductor lab settings.