In general, the various processes used to create associated integrated circuits fall into 3 categories: film deposition, patterning, and semiconductor doping. Films of each conductor (such as polysilicon, aluminum and very recently copper) and insulators (various types of oxide, semiconductor material compounds and others) are used to connect and isolate transistors and their elements. Selective doping of assorted regions of semiconductor material allows the physical phenomenon of the semiconductor material to be changed with the application of voltage. importance of lithography The importance of lithography is often appreciated in 2 ways. First, due to the wide range of lithographic steps required in integrated circuit manufacturing, lithography typically accounts for about 30% of production value. Secondly, lithography tends to be the technical cutter for any progress in reducing the feature size and therefore the speed of semiconductor devices and semiconductor material space. Optical