Vol. 56, Issue 2, pp. 313-325 (2026)

Abstract

Semiconductor oxide thin films are extensively utilized in applications like the internal cavity mirror protection in lasers and inner wall coatings of semiconductor device owing to their unique physicochemical properties such as excellent optical transparency and high thermal stability. The film thickness is a critical parameter determining their functional performance. Conventional measurement technologies, however, face challenges in acquiring in situ spatial distribution information of film thickness within the internal structures of these devices. To address this limitation for surface thickness mapping in confined spaces, this study proposes a novel in situ film thickness measurement method that integrates a fiber optic endoscope with hyperspectral imaging. First, the intensity distribution differences caused by the honeycomb pattern in the endoscope is improved through optical defocusing. Second, the calibration of pseudo-color images is performed based on the reflectance spectra of the thin film. Finally, considering the difference in field of view angles of the endoscope, the incident angle is recalculated, and the film thickness is inverted using spectrum fitting method. Experimental results demonstrate that the developed endoscopic hyperspectral imaging system successfully captures the reflectance spectrum at each spatial point on the thin film sample surface, generating a detailed thickness distribution map. The film thickness fitting results, after correction for the incident angle, are highly consistent with the ellipsometer measurements, with an average relative error of less than 1%. This work holds significant importance for large-area thickness inspection of high-performance thin films in confined spaces and offers a promising solution for in situ quality control and process monitoring.