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

Abstract

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.

Precision metrology: from bulk optics towards metasurface optics

“…However, there are still major practical challenges in: manufacturing, for both monolithic and hybrid integration approaches; efficiency of coupling light on and off-chip; costs associated with effective packaging for real-world use. Although most of the components developed so far for metrological sensors have been integrated onto a chip [54], they still tend to make use of probes based on bulk optic objective lenses.…”

A review of interferometry for geometric measurement

“…In order to further enhance the flexibility and realize online measurements, chip-level interferometers that integrate various components of the interferometric sensor system onto a single optical chip are becoming more attractive [231,232]. The chip-level interferometers are not only insensitive to electromagnetic noise, suitable for applications in a harsh environment, but also have the advantages of high integration, better reliability, ability for mass production, and low cost [233].…”