Development of Optical Imaging Technique with the Nanometer Resolution and Applications in Optical Inspection of Solar Cells

Optical coherence tomography (OCT) has the advantages of non-invasive, depth-resolved and high-speed imaging without the destruction of samples. OCT can reconstruct the two-dimensional or three-dimensional microstructures with the resolution in micrometer scale, enabling the measurable imaging depth to achieve 3 mm below the sample surface. However, the limitation of the micrometer resolution makes the applications for industrial measurements difficult. There are several approaches such as scanning electron microscopy (SEM), and transmission electron microscopy (TEM), which can be used for the measurement or the inspection of nanostructures. Although those two approaches can provide ultrahigh imaging resolution, the higher cost, expansive maintaining charge and complicated sample preparation make both of approaches difficult to be applied for optical inspection in real-time. In this proposal, we will develop a real-time, noninvasive imaging technique for optical inspection. This new approach is based on OCT technique by extracting the amplitude and phase signals from the interfered signals. With the amplitude signal, the structural images in micrometer scale can be obtained. The structural images in nanometer scale can be obtained from the phase signal as well. However, for swept-source OCT systems, phase errors make SS-OCT difficult be applied to the biological tissues and industrial samples. In the first year of this proposal, we propose a new approach to reduce the phase errors in SS-OCT systems and an algorithm to improve the 2ambiguity, which causes the evaluation errors of nanostructures. Furthermore, in the second year of this proposal, the developed system in the first year will be combined with a 2D-CCD and this optical imaging system will be applied to the optical inspection of solar cells. With the proposed system, several parameters can be obtained including the electrodes, defects in the solar cells, the roughness of p-type semiconductor and the optical property of antireflection coating.

Project ID:PB10108-2813
External Project ID:NSC101-2221-E182-056-MY2