Characterization method for new resist formulations for HAR patterns made by X-ray lithography

At the Karlsruhe Institute of Technology (KIT), Institute of Micro Structure Technology (IMT) high aspect ratio (HAR) micro structures are manufactured by means of deep X-ray lithography and gold electroplating (LIGA technology). The technology is used to fabricate grating structures for differential phase contrast X-ray imaging (DPCI). Using an epoxy based negative resist material; electroplated grating structures are fabricated having absorber lamellas with heights up to 100 μm and a period down to 2.4 μm. However, in DPCI there is an increasing demand for improved quality gratings with periods down to 1 μm, areas larger than 50 mm × 50 mm with a high homogeneity in terms of the lamella height distribution and defect-free grating patterns. Pattern deformations are due to limited mechanical stability of the resist during the development process as well as to resist shrinkage during crosslinking, affecting mostly gratings with small periods and HARs. The purpose of this contribution is to present a methodology for the characterization of different epoxy based negative resist formulations, aiming to increase the quality of the HAR free standing grating lamellas by increased mechanical stability of the resist.