Detecting and classifying defects on unpatterned wafers is a key part of wafer front-end inspection. Defect inspection schemes vary depending on the type and location of the defects. In this paper, the structure of the prototype is designed to meet the requirements of wafer surface and edge defect inspection. This prototype has four inspection channels: scattering, reflection, phase, and contour, with two working conditions: surface and edge inspection. The key structure of the prototype was simulated using Ansys. The simulation results show that the maximum deformation of the optical detection subsystem is 19.5 μm and the fundamental frequency of the prototype is 96.9 Hz; thus, these results meet the requirements of optical performance stability and structural design. The experimental results show that the prototype meets the requirements of the inspection sensitivity better than 200 nm equivalent PSL spherical defects.

As semiconductors' critical dimension decreases, higher precision inspection instruments are needed to detect defects in the manufacturing process. Optical inspection methods based on light and dark field microscopy can detect defects on large wafer areas well without damaging the wafer, but the minimum detectable defect size is limited because the defect scattering signal is easily buried by the scattering background noise from the wafer's rough surface. To detect submicron defects on wafer surfaces, a spot-scanning laser scattering scheme is developed based on the dark-field scattering technique. Using the Finite Difference Time Domain (FDTD) method and the inspection scheme, an electromagnetic scattering model of the defect on the wafer surface is established, and the defect characteristics and electromagnetic field distribution are simulated. Moreover, the effects of the collecting aperture angle on the signal intensity of defects and the discrimination of defects of different sizes, as well as the effects of the incident angle on the scattered signal intensity of submicron defects, are examined. A spot-scanning laser scattering experimental platform was built, and 200 nm, 1 μm, and 5 μm diameter polystyrene latex (PSL) spheres were deposited on the wafer surface to verify the validity of the proposed method. Signals of the three sizes of spheres were detected in the stitched images with good discrimination of signal intensity, and the signal of the 200 nm PSL sphere displayed a peak signal-to-noise ratio of 32.07 dB. This method provides a reference for further industrialized defect detection systems on wafer surfaces.

The wafer eccentricity deviation caused by misalignment between the center of the wafer and rotary table will lead to edge image distortion and quality degradation of the defect signals during automated inspection. However, wafer end jump and edge topography change will bring great challenges to the accurate measurement of micrometer deviations. A new wafer eccentricity deviation measurement method based on line-scanning chromatic confocal sensors (LSCCSs) is proposed. Firstly, the LSCCS with Z-axis submicron resolution used in the experiment acquires the 3D profile height of the wafer edge as the turntable rotates, and the edge distance is calculated at each rotation angle. Secondly, a robust Fourier-LAR fitting method is used to fit edge distance serial to reduce sensitivity to outliers. Finally, the wafer eccentricity deviation that is equal to the wafer center coordinate can be calculated using the wafer eccentricity deviation model. In the simulated experiment, the results show that the eccentricity deviation measurement accuracy was insensitivity to noise and reached the micron level. Additionally, the measurement uncertainty of eccentricity deviation coordinate Xw,Yw was (0.53 µm, 1.4 µm) in the actual data of the 12-inch wafers.