Study On The Composite Light Scattering From Wafer And Defect Particles And Its Application

This dissertation presents the theoretical studies of the composite light scattering from wafer and defect particles and discusses primarily the radiation force of defect particles which the light scattering is applied to. The main aspects include the light scattering between microrough substrates and coating material, the composite light scattering between wafer and Rayleigh defect particles, the composite light scattering between wafer and defect particles located upon, inlaid and inside wafer, respectively and radiation force of defect particles illuminated by laser beam. The main works are as follows:1. The first-order vector perturbation approximation is used to investigate the light scattering of bare microrough wafer. For the microrough wafer with coatings, the micro facet polarized light scattering model is established based on the perturbation theory, and then the Polarized Bidirectional Reflectance Distribution Function is given. By the numerical results, the influences of many factors on the scattering between substrates and coating material are analyzed.2. The composite scattering between the wafer and Rayleigh defect particles upon and inside the wafer, respectively, are discussed by Jones Matrix and the Polarized Bidirectional Reflectance Distribution Function. The expressions of PBRDF with different polarize state are derived. The numerical results present the judgement of the Rayleigh defect particles position by wavelength scaling and the way to distinguish the different light scattering mechanics, such as the defect on and inside the wafer, the microroughness, and so on.3. Taking the advantage of the Bobbert-Vlieger theorem, the model of the composite scattering from the spheroid particles and two kinds of slightly non-spherical particles on wafer is established. The scattering coefficient and differential scattering cross section (DSCS) are derived by expanding the field with the vector spherical harmonic function and discussing the light scattering from the defect particals on the wafer. The influences of many factors on the composite light scattering are talked about and the location of the defect and the material of the non-spherical particles can be extracted by calculating the DSCS.4. The composite scattering between wafer and the defect particles that inlaid or inside the wafer are debated using FDTD half space method. Combing the three-wave method, the corresponding connect boundary condition is given. The reciprocity theorem is used to the near-far field extrapolation which simplify the complicated derivation. The numerical results discuss the composite scattering between sphere, columniation and spheroid particles located substrate or inside and wafe, as well as that between one or many defect particles inside the wafer. The electric field around defect particles is shown. The factors influencing the composite light scattering are discussed in detail.5. The optical tweezers technology is used in the optical nondestructive examination. The procedure of laser beam scattered by sphere defect particle is analyzed. The expressions of radiation forces are derived. The numerical results discuss radiation forces of the defect particles illuminated by the on-axis and off-axis incidence beam. The influences of beam waist radius, particle size and index of refraction on the radiation force are debated in detail.