Real Time Characterization of Non-Ideal Surfaces and Thin Film Growth by Advanced Ellipsometric Spectroscopies

ABSTRACTThe development of multichannel ellipsometers with photodiode array-based detection systems has enabled real time spectroscopic ellipsometry (SE), a technique now being used widely to study surface modification and thin film growth. Multichannel ellipsometers based on the rotating-element design acquire spectroscopic data in parallel and thus offer advantages over other designs. The simplest rotating-element multichannel ellipsometers are constructed using a rotating polarizer or analyzer for polarization state modulation or detection. These configurations have a number of drawbacks, in particular, their insensitivity when measuring samples that reflect linearly polarized light and their susceptibility to errors when measuring samples having unrecognized non-idealities (e.g., macroscopic inhomogeneities) that generate a mixture of polarization states in the reflected beam. In this review, we describe recent advances in multichannel ellipsometry including (i) enhancement of the spectral range of the rotating-polarizer multichannel ellipsometer to 1.5–6.5 eV, (ii) adaptation of the rotating-compensator configuration to multichannel ellipsometry for studies of weakly absorbing and macroscopically inhomogeneous materials, and (iii) development of a dual rotating-compensator multichannel ellipsometer design for real time studies of optically anisotropic materials. As a recent example of the application of rotating-compensator multichannel ellipsometry, we describe analyses of (i) a macroscopically-rough (textured) tin-oxide (Sno2) film on a glass substrate and (ii) the fabrication of the p-layer component of an amorphous silicon-based p-i-n solar cell on the textured SnO2 film surface at a temperature of 200°C.