Simultaneous measurements of top surface and its underlying film surfaces in multilayer film structure

Abstract

With the growth of 3D packaging technology and the development of flexible, transparent electrodes, the use of multilayer thin-films is steadily increasing throughout high-tech industries including semiconductor, flat panel display, and solar photovoltaic industries. Also, this in turn leads to an increase in industrial demands for inspection of internal analysis. However, there still remain many technical limitations to overcome for measurement of the internal structure of the specimen without damage. In this paper, we propose an innovative optical inspection technique for simultaneous measurements of the surface and film thickness corresponding to each layer of multilayer film structures by computing the phase and reflectance over a wide range of wavelengths. For verification of our proposed method, the sample specimen of multilayer films was fabricated via photolithography process, and the surface profile and film thickness of each layer were measured by two different techniques of a stylus profilometer and an ellipsometer, respectively. Comparison results shows that our proposed technique enables simultaneous measurements of the top surface and its underlying film surfaces with high precision, which could not be measured by conventional non-destructive methods.

Single-shot dispersive interferometry for inline surface inspection

“…CLDI combines technologies including low-coherence interferometry and hyperspectral imaging. The output of the spectrometer, called spectral interferogram, is the spectrally decomposed interference signal I (ℎ, 𝜆) that can be mathematically described as the following formula [12] 𝐼(ℎ, 𝜆) = 𝐺(𝜆)[𝐼 𝑅 + 𝐼 𝑀 + 2√𝐼 𝑅 𝐼 𝑀 cos(𝜑(ℎ, 𝜆) + 𝜑 0 )]…”

Recent Progress on Optical Tomographic Technology for Measurements and Inspections of Film Structures

“…The fundamental principles of ellipsometry and reflectometry were established at a single point opposed to interferometry, and several research works extended the measured points using imaging optics. In reflectometry, an imaging spectrometer and an area camera were adopted to obtain spectroscopic–spatial images for the line profile of film thicknesses [ 102 , 103 , 104 ], as shown in Figure 12 . Furthermore, a wavelength-swept source was used to obtain the spectral image stack, and 3D film thickness profiles were reconstructed at once [ 41 , 42 , 44 , 45 , 46 ].…”

Porosity calibration in a 4-layer porous silicon structure to fabricate a micro-resonator with well-defined refractive indices and dedicated to biosensing applications

“…Moreover, improvement of the calculation of the theoretical reflectance spectra could be done taking into consideration interface roughness in the simulation [44]. More adaptive optical measurement could also be used to characterize the porous silicon layer both in single and multilayer system [45][46].…”