Towards the development of a hybrid-integrated chip interferometer for online surface profile measurements

Non-destructive testing and online measurement of surface features are pressing demands in manufacturing. Thus optical techniques are gaining importance for characterization of complex engineering surfaces. Harnessing integrated optics for miniaturization of interferometry systems onto a silicon wafer and incorporating a compact optical probe would enable the development of a handheld sensor for embedded metrology applications. In this work, we present the progress in the development of a hybrid photonics based metrology sensor device for online surface profile measurements. The measurement principle along with test and measurement results of individual components has been presented. For non-contact measurement, a spectrally encoded lateral scanning probe based on the laser scanning microscopy has been developed to provide fast measurement with lateral resolution limited to the diffraction limit. The probe demonstrates a lateral resolution of ∼3.6 μm while high axial resolution (sub-nanometre) is inherently achieved by interferometry. Further the performance of the hybrid tuneable laser and the scanning probe was evaluated by measuring a standard step height sample of 100 nm.