Dresden 2009 – wissenschaftliches Programm
DS 15.2: Vortrag
Dienstag, 24. März 2009, 15:45–16:00, GER 38
Characterization of strained Si films by variable angle spectroscopic ellipsometry and Raman spectroscopy — •Zhijiat Chong, Martin Weisheit, Michael Hecker, and Ehrenfried Zschech — AMD Fab 36 LLC & Co. KG, Wilschdorfer Landstr. 101, D-01109 Dresden, Germany
Strain applied to silicon films modifies the mobility of charge carriers and is thus employed to enhance the performance of semiconductor devices. Methods to determine the thickness and the stress in these films non-destructively are indispensable in the manufacturing process, in which both precision and speed are crucial for high yield. Two optical methods are investigated here for this purpose. Due to the effect of stress on the electronic band structure and the lattice phonon frequencies, stress can be measured via variable angle spectroscopic ellipsometry (VASE) and Raman spectroscopy respectively. Based on bending experiments to induce stress in silicon-on-insulator stripes, VASE was used to characterize the change of the dielectric function at 1.2-6.4 eV due to stress. A novel stress-parameterized model of the dielectric function was constructed from the data using a summation of Tauc-Lorentz functions. This can be applied to determine the stress in silicon layers from ellipsometric measurements. The stress induced on the sample was also measured by the sample curvature and verified by Raman spectroscopy. The result shows that stresses can be measured with a sensitivity of about 30 MPa in thin silicon films by VASE.