Development of a Grayscale Lithography Process with a Pixelated Grayscale Mask for the Fabrication of Gradient Inlet Structures for Nanochannels Enabling DNA Analysis

Grayscale lithography can be used to create a three-dimensional topography in the substrate. This method can be utilized in the fabrication of microfluidic chips, for lab-on-chip (LoC) applications. Here, a grayscale lithography process is shown that creates gradient inlet structures for nanochannels. Nanochannels are a tool for optical DNA analysis, when the molecules are linearized inside of the channels. A pixelated grayscale mask was designed for the process with a minimal structure size of 300 nm, which still allowed the creation of structures with features in the size of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1 \mu ~\mathrm{m}$</tex> without the need for a reduction system. An etch recipe was created that etches the substrate with the same etch rate as the photoresist to transfer the topology into the substrate.