Fig. 1. Theoretical model and principle description. (a) Scattering of silver film surface; (b) double interaction model principle; (c) principle of polarization modulation

Fig. 2. Transmission simulation model and simulation result. (a) Simulation model; (b) transmittance simulation result; (c) K4 photoresist surface detected by 266 nm light

Fig. 3. Simulation results of brightness and dark fields detection. (a) Brightness field simulation result; (b) dark field simulation result

Fig. 4. Scattering energy of PSL and SiO₂ particles under p and s light incidence

Fig. 5. Scattering field spatial distribution of PSL particles with different diameters under p and s light incidence. (a)‒(d) Spatial distribution of scattering energy of PSL particles with radius of 20,40,60,80 nm under p light incidence; (e)‒(h) spatial distribution of scattering energy of PSL particles with radius of 20, 40, 60,80 nm under s light incidence

Fig. 6. Simulation results with different incident angles. (a) Simulation result at 0° incident angle; (b) simulation result at 30° incident angle; (c) simulation result at 60° incident angle

Fig. 7. Three-dimensional diagram of overall scheme

Fig. 8. Experimental system and process flow diagrams. (a) Experimental system; (b) schematic of the process of fabricating samples

Fig. 9. Detection results of particles on film surface with different RMS roughness values. (a)‒(c) Observation results of the samples with RMS roughness of 2.4, 4.9 and 8 nm under dark field microscope; (d) scanning results of the sample with RMS roughness of 8 nm under AFM;(e)‒(g) local areas of Figs. 9 (a), (b) and (c); (h) background noise curves under different RMS roughness values

Fig. 10. Detection results of the experimental system on the sample with RMS roughness of 2.4 nm. (a)‒(c) Detection results with three different polarized light incidence; (d) particle signal curve corresponding to Fig.10 (a), (b) and (c)

Fig. 11. Detection results of the samples with RMS roughness of 4.9 nm by our own experimental system. (a) Detection result with the polarizer at initial position; (b) detection result after 20° rotation of the polarizer; (c) background noise curves corresponding to Figs.11 (a) and (b)

Fig. 12. Particle detection result. (a) Detection results before adding 100 nm particles to the sample with RMS roughness of 2.4 nm; (b) detection results of the self-built experimental system without polarizer on the dark field receiving optical path after adding 100 nm particles; (c) detection results of the self-built experimental system after modulating the polarization state; (d) detection results of DSX1000; (e) detection results before adding 100 nm particles to the sample with 8 nm RMS roughness; (f) detection results of the self-built experimental system without polarizer on the dark field receiving optical path after adding 100 nm particles; (g) detection results of the self-built system with modulating the polarization state; (h) detection results of DSX1000; (i) detection results before adding particles to the sample with 3.4 nm RMS roughness; (j) detection results of DSX1000 after adding 50 nm particles to the sample; (k) detection results of the self-built experimental system after modulating the polarization state; (l) SEM image of the particles