Photolithography is the process performed in microfabrication about patterning the thin films of the substrate.ıt is highly important in the development of devices on batch. It consists of projection of a circuit into a mask due to light exposure and dissolution of the hard areas by usage of a solution bath such as acid (wet method)or oxygen ions (dry method) .The elements used in photolithography are usually: photoresist, mask, wafer, chip etc.The steps that are crucial about photolithography are: surface cleaning, barrier layer formation (oxidation), spin coating with photoresist, soft baking, mask alignment, exposure, development, hard baking and post process cleaning . Other types of photolithography include: Extreme Ultraviolet Photolithography (EUV), e-beam Lithography, Ion Beam Lithography and X Ray Lithography. Those types of photolithograpy increase the resolution compared to the classic methods . Photoresists play an important role in photolithography and the most widely used photoresists are the positive and the negative one. The positive photoresist when exposed to light becomes soluble in the photoresist developer while the negative one in the same conditions becomes insoluble.
4- Jain, K. “Excimer Laser Lithography”, SPIE Press, Bellingham, WA, 1990.