Challenges to quantitative energy-dispersive X-ray spectrometry and its application to graded embedded silicon-germanium for high-performance complementary metal oxide semiconductor devices

摘要

Energy-dispersive X-ray spectrometry (EDXS) in the transmission electron microscope (TEM) is applied for accurate spatially resolved quantitative chemical analysis of SiGe structures implemented into high-performance complementary metal oxide semiconductor (CMOS) transistors. For fast and high-quality TEM target specimen preparation, an advanced focused ion beam (FIB)-based lift-out technique employing Be half ring grids is developed to significantly minimize post-specimen scatter artifacts during EDXS data recording. Based on systematic variation of acquisition parameters (dwell time, sampling area) at fixed beam current, the influence of electron irradiation on microstructure and composition of SiGe alloys is studied, and a critical electron fluence for beam-induced damage is identified. While chemical analysis is unaffected for smaller values, higher electron fluences cause atom displacement by surface sputtering. Applying optimal acquisition parameters for accurate composition analysis at standard TEM settings, spatially confined graded embedded SiGe cavities, introduced into the CMOS process flow to transfer compressive stress into the pMOS transistor channel, are characterized.