Diffraction-based Approaches to the In-situ Measurement of Dimensional Variations in Components Produced by Thermoplastic Micro- and Nano-embossing

We discuss the potential merits of using the diffraction of light to detect dimensional variations of microand nano-fluidic components embossed in transparent thermoplastic polymers. We describe one particular scheme for measuring the depths of an array of approximately micron-depth, parallel embossed channels. The component to be measured is placed in contact with a row of nine phase-relief holograms, the combination of part and holograms is transmissively illuminated, and the far-field diffraction patterns are interpreted. The scheme is designed to provide a depth resolution of ~200 nm without needing to know the intensity response of the sensor capturing the diffraction pattern, but linear or angular misalignments of the grating with the hologram of only a few microns or a few 10 rad can destroy the scheme’s effectiveness.