Nano Optical Measurement for Next-Generation Nano/Micro Manufacturing based on Localized Light Energy Control

摘要

In the nano/micro manufacturing, in-process optical inspection plays one of the most important roles for producing the advanced products with high reliability, because it has several practical advantages typified by nondestructiveness, high-throughput characteristics, and so on. Optical measurement methods, however, essentially restrict its spatial resolution due to the diffraction limit, which means that finer structures less than half of the wavelength of optical wave from the objects to be inspected, cannot be observed. This resolution limit of the optical measurement method is a critical problem especially for the nano/micro manufacturing process, where the features of submicrometer fine structures should generate special functions. This critical limit about spatial resolution can be physically explained by focusing on light energy localization property. As shown in Tablel, light energy can be mainly classified into the following three types of localizations: (1) Evanescent light generated under the total internal reflection. (2) Near-field light existing in the vicinity of tips of the near-field optical probe. (3) Interference intensity distribution of standing wave (mainly generated with two beam interference) and focusing beam (generated with multiple-beam interference), both of which consist of free-space propagating light (freely propagating light) waves. Physical principles for spatial resolution improvement are essentially different based on these types of light energy localization. In order to develop the effective optical inspection beyond the diffraction limit, it is important to recognize their super resolution property depending on their light localization. Evanescent light is known as effective near-field light illumination for surface, which can be applied to near-field scanning optical microscopic inspections.