Novel inorganic photoresists for three-dimensional microfabrication

Inorganic photoresists that can be directly patterned in three dimensions via both 3D laser direct writing and 3D interference lithography based fabrication approaches are attractive materials for the fabrication of complex microfluidic and micro-optical components such as chaotic mixing elements or 3D photonic crystals. Several inorganic photoresist systems have been developed or adapted for these purposes. The first resist system is based on silica microspheres with various polymer brush coatings that impart interesting solubility changes. These changes drive assembly processes or impart resistance to development, allowing for 2D and 3D fabrication of unique structures. The second system consist of custom organosilicon resists based on either a mesoporous sol gel formulation or a resin of poly(methysilsesquioxane) and various photosensitizing components. The structures formed with this system have a low index of refraction, but are stable at high temperature, which imparts compatibility with certain high temperature semiconductor manufacturing processes. The third set of resists consists of chalcogenide glass based amorphous semiconductors from the As-S-Se ternary system. The structures formed using this system have a high index of refraction and strongly non-linear optical properties, making them attractive candidates for engineered photonic crystal based devices.