Fig. 1. Physical drawings of piezoelectric ceramic objective locator and piezoelectric ceramic controller. (a) Piezoelectric ceramic objective locator; (b) piezoelectric ceramic controller

Fig. 2. Microdisplacement detection optical path

Fig. 3. Position relation diagram of optical elements in astigmatism method based on double cylindrical lens. (a) Schematic diagram of optical path; (b) characteristic spots with different shapes; (c) spot on surface of FQD

Fig. 4. Schematic diagram of astigmatism method based on double cylindrical lens. (a) Schematic diagram of imaging relationship before and after beam passing through cylindrical lens CL_x; (b) schematic diagram of imaging relationship before and after beam passing through cylindrical lens CL_y

Fig. 5. Simulation curve and actual curve of FES value and defocus amount ∆a0.(a) Simulation curve of FES value and defocus amount ∆a0; (b) relationship curve actually detected under specific parameters

Fig. 6. Input voltage signal of piezoelectric ceramic controller and FES value detected by FQD. (a) Input voltage signal of piezoelectric ceramic controller; (b) FES value detected by FQD

Fig. 7. FES feedback value of piezoelectric ceramic objective locator under different input signals. (a) Amplitude-frequency response curves of piezoelectric ceramic objective locator under signals with four different amplitudes; (b) FES amplitude attenuation percentage; (c) amplitude-frequency response characteristic of sinusoidal input voltage signal with amplitude of 0-10 μm and frequency of 10-250 Hz; (d) phase-frequency response characteristic of sinusoidal input voltage signal with amplitude of 10 μm and frequency of 10-250 Hz; (e) relationship between lag time corresponding to phase difference and frequency

Fig. 8. Partial schematic diagram of polar coordinate laser direct writing lithography device and photo of device. (a) Partial schematic diagram; (b) photo of device

Fig. 9. Control schematic diagram of focus locking module

Fig. 10. 30 mm diameter wafer sample after exposure. (a) Exposure sample when focus locking is not working; (b) exposure sample with rotary table rotating speed of 4 r/s when focus locking is on; (c) exposure sample with rotary table rotating speed of 20 r/s when focus locking is on

Fig. 11. Defocus of wafer surface detected during lithography when rotating speed of rotary table is 4 r/s. (a) FES value at center of wafer; (b) FES value at wafer radius of 14 mm; (c) distribution diagram of maximum defocus at different radii of wafer; (d) three-dimensional distribution diagram of defocus on wafer surface

Fig. 12. FES value of wafer surface detected after turning on focus locking. (a) FES curve at 1 mm wafer radius; (b) FES curve at 14 mm wafer radius; (c) two-dimensional diagram of defocus distribution on wafer surface; (d) wafer sample engraved under same engraving conditions

Fig. 13. Complementary signal Ft of morphological characteristic signal of rotary table surface, and its amplitude-frequency characteristic curve and phase-frequency characteristic curve. (a) Complementary signal Ft; (b) amplitude-frequency characteristic curve of Ft;(c) phase-frequency characteristic curve of Ft

Fig. 14. Exposure uniformity test of sample. (a) 30 mm diameter wafer written at rotary table rotating speed of 6 r/s; (b) simulated defocus distribution during engraving when rotating speed of rotary table is 17 r/s; (c) 30 mm diameter wafer written at rotary table rotating speed of 17 r/s; (d) microscope photograph of uniform area in Fig. 14(c)

Fig. 15. Engraving results of mask graphics. (a) Original mask; (b) photo of 30 mm diameter wafer sample; (c) photograph of sample taken with microscope at 50× magnification; (d) photograph of sample taken with microscope at 100× magnification