Online process monitoring of direct laser interference patterning using an infrared camera system

Abstract

Direct laser interference patterning enables the fabrication of homogeneous microstructures in the sub µm range. Generally, the topography of fabricated structures is characterized ex-situ using for instance confocal microscopy or white light interferometry. These methods require at least few seconds to fulfill a measurement and therefore are not suitable for online process observation. In this study, an IR camera system is used for the first time, for capturing the average temperature during the DLIP treatment in real time. To determine a correlation between the average temperature and the topographical parameters, the treated surfaces are analyzed using confocal microscopy. A linear dependency between the applied laser fluence (in the range from 0.7 to 4.9 J/cm2) and the average measured temperature could be established. In addition, in this fluence range, significant changes in the surface roughness, skewness and kurtosis occurred, which could be associated to a certain process average temperature.