Fig. 1. Principle diagram of SMASH alignment technique

Fig. 2. Beam diffraction diagrams of different alignment marks. (a) Symmetric alignment mark; (b) asymmetric alignment mark

Fig. 3. Simulation model of alignment mark

Fig. 4. Asymmetric alignment marks with different shapes. (a) Round shape; (b) wedge shape

Fig. 5. Alignment measurement errors as functions of deformations of different asymmetric alignment marks under illuminations with different wavelengths and polarizations. (a) Round shape; (b) wedge shape

Fig. 6. Simulation results. (a) Ra-Rb as a function of Rb; (b) Wa-Wb as a function of Wb

Fig. 7. Alignment measurement errors caused by asymmetric alignment marks with different shapes after calibration. (a) Round shape; (b) wedge shape

Fig. 8. Principle diagrams of overlay precision measurement based on DBO technique. (a) eoverlay<0; (b) eoverlay=0; (c) eoverlay>0

Fig. 9. Overlay measurement error caused by asymmetric deformation of overlay mark

Fig. 10. Simulation model of overlay mark

Fig. 11. Overlay measurement error as a function of deformation of different asymmetric overlay marks under illuminations with different wavelengths and polarizations. (a) Round shape; (b) wedge shape

Fig. 12. Overlay measurement error as a function of alignment measurement error caused by different asymmetric deformations. (a) Round shape; (b) wedge shape

Fig. 13. Simulation results of overlay measurement errors caused by asymmetric overlay marks with different shapes after calibration. (a) Round shape; (b) wedge shape