SPARSE (spatially phase-retarded spectroscopic ellipsometry) for real-time film analysis

Abstract

In this Letter, we propose a novel type of spectroscopic ellipsometer, named spatially phase-retarded spectroscopic ellipsometry (SPARSE), based on the spatial polarization distribution opposed to the temporal polarization changes. SPARSE can collect all information necessary to characterize film structures with a single image acquisition, and it has the benefit of real-time measurements. For the verification, feasible experiments with single film-layered certificated reference materials and multi-layered film specimens were carried out.

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

“…As another approach, spatial ellipsometry, which spatially detected the intensity variations instead of rotating optical components, was proposed by using a spatial phase retarder or a polarization pixelated camera, as shown in Figure 5 [ 37 ]. The spatially phase-retarded spectroscopic ellipsometry used a pseudo depolarizer, which consisted of a rotating liquid crystal (LC) periodic array as the spatial phase retarder, and it was able to collect all information necessary to characterize film structures with a single image acquisition with the benefit of real-time measurements.…”

“…The desirable scheme for high-speed measurement is snapshot measurement, and several approaches to realize snapshot film measurements have been attempted. In ellipsometry, the temporal polarization variations were replaced with the multi-channeled configuration [ 105 ], spatial polarization device based on spatial phase retardation [ 37 ]. In addition, a polarization pixelated CMOS camera (PCMOS) was used instead of a rotating analyzer to obtain four different polarized data [ 32 ], as shown in Figure 13 A.…”

“… ( A ) Schematic of spatially phase-retarded spectroscopic ellipsometry and ( B ) operating principle of spatial phase retarder (sub-panels: ( a ) acquisition of the single image containing intensity variations corresponding to polarization changes and wavelengths, ( b ) depolarizer based on a rotating LC array as a SPR, and ( c ) intensity variation of linearly polarized light by SPR) (reprinted/adapted with permission from [ 37 ] © The Optical Society); P, polarizer; S, specimen; BE, beam expander; SPR, spatial phase retardation plate; A, analyzer; IL, imaging lens; IS, imaging spectrometer. …”

Super-resolution spectral interference fitting method for the simultaneous measurement of the thin film thickness and surface profile

“…Ellipsometry * Author to whom any correspondence should be addressed. [5,6] and reflectometry [7] have the advantage of being nondestructive and highly sensitive but cannot obtain the surface profile of film.…”

Spectral interferometry for thin film information by fitting Fourier transform spectrum

“…is more accurate, but will inevitably damage the sample surface, and therefore only suitable for sampling detection 3,4 . Common non-contact measurement methods also have their own drawbacks, such as ellipsometry can only point sampling style detection 5,6 , white light interferometer is difficult to take into account the high axial accuracy and high-speed measurement 7 . Therefore, we need a film thickness detection technology that can take into account the four aspects of z-axis minimum measurable thickness of less than one micron, xy-axis large-area detection, high-speed, non-destructive detection.…”