Vol.:(0123456789) 1 3 Journal of Materials Science: Materials in Electronics https://doi.org/10.1007/s10854-018-9260-4 Ellipsometry-based conductivity extraction in case of phosphorus doped polysilicon A. Kemiha 1  · B. Birouk 1  · J.‑P. Raskin 2 Received: 17 January 2018 / Accepted: 8 May 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract In this work, we investigated a new method for thin flms electrical conductivity extraction based on spectroscopic ellipsom- etry. This has been enabled through the correlation between the flms conductivity and their ellipsometric properties. Indeed, it has been demonstrated that numerous ellipsometric ftting-based approaches can provide, in an indirect way, the electrical characteristics of thin flms. The study was focused on electrical conductivity, but doping level or carriers’ mobility can also be extrapolated from ellipsometric measurements. Among various possibilities leading to electrical properties extraction, we can cite the extremal values of Ψ and Δ ellipsometric angles, their associated wavelengths, the mean square error and the maximal and minimal refectivities ratio. Otherwise, the correlation between extrinsic conductivity and ellipsometric parameters evolution has been confrmed in case of low doping levels with particular behavior after annealing. This contact- less method has been successfully applied to polycrystalline silicon flms deposited on oxidized, p-type monocrystalline substrates, by low pressure chemical vapor deposition technique, and lightly or heavily phosphorus doped by difusion. The feasibility of the method has been proven in this case, but also in other cases like implanted polysilicon layers or silicon-on- insulator (not included here). 1 Introduction Spectroscopic ellipsometry is a powerful technique consid- ered as one of the most routinely used ones worldwide in laboratories and cleanrooms, mainly in thin flms optical characterization case. But when researchers study ellipso- metric technique and electrical conductivity, the aim is to characterize the thin flms from separated optical and electri- cal points of view. These properties result especially in the case of physical constants determination from the spectral or electrical responses of these flms toward an excitation. Many optical devices are used to perform optical measure- ments, and in quite all cases, theoretical or semi-empirical methods support the analyses, which must take into account the main electrical and physical characteristics of the layers. Among the infuencing parameters, we can mention doping level (carriers’ concentration), deposition temperature and layer thickness (grain size), surface quality (roughness), and so on. Ellipsometry which is an accurate, non-destructive and contactless technique based on beam light refection analysis is frequently used for extracting layer’s character- istics as thickness, refractive index, extinction coefcient and roughness [1–5]. In this work, the resulting experimental angles Ψ and Δ were studied and ftted in relation with dop- ing level and layer thickness, in order to get access to mor- phological and optical parameters. As demonstrated here- after the electrical conductivity of polycrystalline silicon layer can be extracted with pretty good accuracy by using a variety of graphical methods from Ψ and Δ curves. Polycrystalline silicon (shortened to polysilicon) has been widely studied and used throughout the world, with the main aim to substitute the monocrystalline silicon. The deposition and characterization of the polysilicon layers are carried out by using various techniques. low pressure chemical vapor deposition (LPCVD) technique is massively used due to the relative low deposition temperature, added to excellent uniformity, good step coverage, and superior cost * B. Birouk bbirouk@univ-jijel.dz A. Kemiha adel_kemiha@yahoo.fr J.-P. Raskin jean-pierre.raskin@uclouvain.be 1 Renewable Energies Laboratory (LER), Jijel University, Jijel, Algeria 2 ICTEAM, Université catholique de Louvain (UCL), Louvain-la-Neuve, Belgium