Direct detection of polystyrene equivalent nanoparticles with a diameter of 21 nm (∼λ/19) using coherent Fourier scatterometry

Abstract

Coherent Fourier scatterometry (CFS) has been introduced to fulfil the need for noninvasive and sensitive inspection of subwavelength nanoparticles in the far field. The technique is based on detecting the scattering of coherent light when it is focused on isolated nanoparticles. In the present work, we describe the results of an experimental study aimed at establishing the actual detection limits of the technique, namely the smallest particle that could be detected with our system. The assessment for particles with a diameter smaller than 40 nm is carried out using calibrated nano-pillars of photoresist on silicon wafers that have been fabricated with e-beam lithography. We demonstrate the detection of polystyrene equivalent nanoparticles of diameter of 21 nm with a signal-to-noise ratio of 4 dB using the illuminating wavelength of 405 nm.

Investigation of coherent Fourier scatterometry as a calibration tool for determination of steep side wall angle and height of a nanostructure

“…Notably, recent advancements have seen CFS successfully modeling and experimentally detecting an isolated defect in the periodic nanostructure [35]. However, compared to other techniques CFS is very sensitive to the alignment and stability of the system, and is limited by the surface roughness of the substrate and the noise of the camera pixels [36].…”

Detection of geometrical patterns of self-assembled gold nanospheres and top-down fabricated nanostructures using coherent Fourier scatterometry

“…13 There are already several reports in literature about the detection of defects or particles using CFS. 10,14,15 However, the investigation of different nanometer-range samples of different shape or geometrical arrangement, as presented in this work, has not been extensively investigated yet. However, this comprises an important advancement as it is important to identify possible directional dependencies of defects, which indicate systematic errors in semiconductor manufacturing, or to distinguish differently arranged clusters of nanoparticles.…”

Coherent Fourier scatterometry for particle detection on structured surfaces

“…CFS is an optical metrology technique based on the light scattered from the object in the far field, which is very sensitive to detect small isolated particles or small changes in parameters of nanostructrues. In addition, the technique is not limited by diffraction, and the detection of deep subwavelength-size particles present on top of a plane substrate has been recently demonstrated [2]. However, as we move towards patterned surfaces, the detection of contamination becomes more complicated as we have to consider the effects of the background structure in addition to that of the contamination itself.…”