Contact photolithography modeling for thick photoresists layers

Contact photolithography for photoresist layers thicker than 1 micron is widely used in creating microreliefs in production technologies of microelectromechanical systems, micropackaging, optical printed circuit boards and other microdevices. Microrelief walls slope in photoresist inflicts significant influence on the microdevice output parameters. Based on analysis of the contact photolithography features, it is proposed a mathematical model based on the Fresnel diffraction of image generation in the thick photoresist layers. The model and statistical processing of results obtained on its basis adequately describe relationship between the photolithography output parameters, i.e. the microrelief sidewalls slope, and the photoresist absorption coefficient and thickness.