Patterning Process of a Semiconductor Structure with a Wet Strippable Middle Layer

A lithography method is provided in accordance with some embodiments. The lithography method includes forming an under layer of a polymeric material on a substrate; forming a silicon-containing middle layer on the under layer, wherein the silicon-containing middle layer has a silicon concentration in weight percentage less than 20% and is wet strippable; forming a patterned photosensitive layer on the silicon-containing middle layer; performing a first etching process to transfer a pattern of the patterned photosensitive layer to the silicon-containing middle layer; performing a second etching process to transfer the pattern to the under layer; and performing a wet stripping process to the silicon-containing middle layer and the under layer.