| With anexposure dose too low, thin (penetration depth of exposure light > resist film thickness) photoresist develop uniformly bit slow, while in thick resist films, the substrate-near film gets not enough light for (fast) through-development.With an exposure dose too high, light will be scattered and diffracted also under the "shadowed" parts of the photomask. This enlarges the developed pattern of positive tone resists, while image reversal- and negative tone resists suffer from a surface film which is not developable. Additionally, in case of UV-transparent substrates (e.g. glasses, thick SiO2, many polymers), light is laterally guided inside the substrate and also reflected from the substrate holder. Hereby, the resist is also exposed from the rear side after through-exposure, revealing in lifting of narrow positive tone resist structures in developer, or leading to resist residuals on the substrate after development in case of image reversal-/negative tone resists.In order to determine the optimum exposure time/dose for each individual process, we strongly recommend an exposure series as starting point for each new process (see link below). |
Technical request: Exposure Dose for certain Resist/Process
Literature: Exposure and Development