Spectral Scatterometry for 2d Trench Metrology of Low-K Dual-Damascene Interconnect

A systematic study has been conducted to evaluate accuracy and precision of spectral scatterometry used for two-dimensional (2D) characterization of trenches formed in fluorinated silicon glass (FSG). Experiments were done on short-flow dual-damascene Cu interconnect material. Trench critical dimensions (CD) obtained using KLA-Tencor's spectral scatterometer were correlated with data collected using CD atomic force microscope (AFM), CD scanning electron microscope (SEM) and transmission electron microscope (TEM). 3 major trench characteristics were analyzed: trench width, trench depth and sidewall angle. Spectral scatterometry demonstrated an excellent correlation (above 0.96) with CD AFM and SEM in tested trench width range of (80-240) nm and trench depth range of (410-450) nm. Spectral scatterometry showed acceptable correlation of 0.55 and minimal offset of 0.05degrees with AFM in tested sidewall angle range of (87.5-89) degrees. Spectral scatterometry has demonstrated better than 1.0 nm and 0.2degrees dynamic precision Q(T) for both width and height and sidewall angle, respectively. We conclude that KLA-Tencor's SpectraCD system is capable of accurate and precise 2D characterization of FSG trenches. We recommend scatterometry as a high throughput and non-destructive metrology for trench linewidth and depth monitoring in low-K dielectric interconnect manufacturing.