Super-Resolution Optical Measurement for Ultra-Precision Machined Surface Defects by Using Structured Light Illumination Shift (4th report) - Experimental Verification of Super-resolution Method with Coherent Image Iterative Reconstruction

Demands for ultra-precision machined surface such as semiconductor wafer arc rapidly growing. However, because of shrinking design rules of the semiconductor, it is uprising the difficulty of detecting nano-defects. To keep process yield in manufacture line, we must develop a defect measurement system with higher resolution, throughput, non-destructiveness and robustness. As such a measurement system, we have proposed the application of the structured light illumination (SL1) microscopy. The proposed method is optical inspection system and that resolving power exceeds the diffraction limit. Conventional proposed method has a difficulty about imaging system. Despite the imaging system is coherent system, the imaging system required in conventional super-resolution algorithm is incoherent system. We proposed algorithm based on coherent system, and three-light-flux interference standing wave illumination that enables new algorithm usage. In the fourth report, to verify super-resolution method with coherent image iterative reconstruction experimentally, we develop the experimental apparatus. As the result of basic experiment, 230 nm structure which can't be resolved by conventional method is resolved by proposed method, under the condition of Rayleigh limit 541 nm.