Precise optical characterization of SiGe thin films for next generation transistor metrology

Silicon germanium (SiGe), a well-established material in transistor technology, continues to play a crucial role in next-generation architectures, including complementary FETs (CFETs), gate-all-around FETs (GAAFETs), and FinFETs. Precise thickness control and material characterization at sub-nanometer precision are essential for optimizing device performance. Accurate determination of SiGe’s optical constants is fundamental for metrology, process modeling, and semiconductor fabrication. This work presents a detailed optical characterization of 45 nm and 50 nm SiGe thin films with 21% and 38% Ge content, respectively, focusing on the determination of optical constants (ñ = n + ik = (1 - <i>&delta;</i>) + i<i>&beta;</i>) in the extreme ultraviolet (EUV) range (5-20 nm). By analyzing the dispersive component (<i>&delta;</i>) and extinction coefficient (<i>&beta;</i>), we provide essential data for modeling layer thickness, interface sharpness, and variations in Ge content. Our results enhance metrology techniques such as reflectometry, ellipsometry, and scatterometry, facilitating better control of SiGe-based device fabrication.