Multi-level microstructures and mold inserts fabricated with planar and oblique x-ray lithography of SU-8 negative photoresist

For patterning thick photoresist films, x-ray lithography is superior to optical lithography because of the use of a shorter wavelength and a very large depth of focus. SU-8 negative resist is well suited to pattern tall, high-aspect ratio microstructures in UV optical and x-ray lithography with rapid prototyping capability due to its high sensitivity. The negative tone of the SU-8 resist offers advantages in fabricating multi-level and non-planar microstructures using x-ray lithography or a combination of x-ray and UV optical lithography. In this paper, we present a fabrication process for multi-level metallic mold insert by a combination of multi-layer SU-8 patterning, poly-dimethylsiloxane (PDMS) molding, and nickel electroplating to make final nickel mold inserts that are suitable for injection molding and hot embossing of plastics and ceramics.