Inline imaging-ellipsometer for printed electronics

Abstract

Abstract:Printed electronics, e.g. organic photo-voltaic, are usually produced by roll-to-roll printing. For this fast growing market no inline-measurement method for 2D-thickness-distributions after printing exists. In many cases layer-thicknesses are in the sub-μm-range, e.g.10-300 nm, and ellipsometry is one typical technology for this range, but up to now only in the laboratory, since most ellipsometers are too slow and/or measure only a spot. A new concept, a stroboscopic imaging ellipsometer, enables fast measurement on a line, to acquire the 2D-distribution of thickness, right after printing.Keywords: Imaging-ellipsometry, printed electronics, R2R-production, thickness-control. Zusammenfassung

Towards in-situ quality control of conductive printable electronics: a review of possible pathways

“…The in-line imaging ellipsometer has been actively used to measure the production thickness of printed electronic devices in the visible and ultraviolet spectral regions [31,50,85]. The principle underlying the technique is based on the evaluation of the polarization change of the light reflected by a printed layer [85].…”

“…The in-line imaging ellipsometer has been actively used to measure the production thickness of printed electronic devices in the visible and ultraviolet spectral regions [31,50,85]. The principle underlying the technique is based on the evaluation of the polarization change of the light reflected by a printed layer [85]. Relative to the plane of incidence, the light can be decomposed into its orthogonal polarization components s and p. By normalizing the reflected s and p intensities (r s and r p ) with their incident values, the complex reflectance ratio can be calculated.…”

“…Relative to the plane of incidence, the light can be decomposed into its orthogonal polarization components s and p. By normalizing the reflected s and p intensities (r s and r p ) with their incident values, the complex reflectance ratio can be calculated. Typically, the complex reflectance ratio ρ is expressed as [85]:…”

“…It therefore provides fairly accurate and reproducible extracted values while being relatively insensitive to scattering and fluctuations. For in-line characterizations, Huemer et al [85] proposed to use a Single Crystal Photo-Elastic Modulator (SCPEM), which is a piezo-electric material. It modulates the polarization of the incident light by its stress-induced birefringence (photo-elastic effect).…”

Measurement of ellipsometric data and surface orientations by modulated circular polarized light / Messung von ellipsometrischen Daten und Oberflächenorientierungen durch moduliertes zirkular polarisiertes Licht

“…Ellipsometry is a widely used optical method for characterizing materials and thin films. The advantages of ellipsometry are high precision and non-destructive measurements [1] that might be used for process monitoring [2]. Ellipsometers can be used in various application fields, e.g., semiconductor, chemical, and display industry.…”