Photolitohography on microstructured surfaces using photosensitive polyimide

Improvements in patterning microstructured surfaces by means of photosen­sitive polyimides as an alternative to standard positive and negative photoresists are presented. Two different types of polyimide photoresists are used to check step coverage and image transfer to specific test substrates. These test substrates contain mesalike steps, which can be seen as a general configuration of 3-dimensional silicon sensors. Step coverage is characterized by leakage-current measurements and scanning electron microscope (SEM) spectroscopy. Thin photosensitive polyimide layers showed better step coverage and resolution than standard photoresist. Thick photosensitive polyimide showed good planarization properties when two layers were used. However, it is necessary to use a combination of wet and dry etching to obtain good resolution.