In-process characterization tool for optically produced sub-100-nm structures

Abstract

In this paper an in-process measurement tool based on coherent laser light scattering by sub-100-nm structures is presented. Laser beams of high fluence are used for fabricating three-dimensional nanostructures in the sub-100-nm range for different applications and measurement of these nanostructures is vital during manufacturing for quality control, defect analysis, calibration measurements, etc. However, present offline measurement techniques such as atomic force microscopy and scanning electron microscopy prove to be too slow and, in some cases, also destructive. It is shown that by measuring the scattered laser light distribution of nanostructures such as zinc-oxide nanograss, it is possible to distinguish between defect-free and defective nanostructures. This allows for fast, contactless and nondestructive measurements of nanostructures. Using discrete dipole approximation (DDA) to simulate the scattered laser light distribution of modeled zinc-oxide nanograss and also CCD optical measurements of commercial grade nanograss, a correlation between the two sets of measurements strongly supports the concept of a tool capable of providing measurements of sub-100-nm nanostructures in a running manufacturing process.