Photolithography is one of the core methods in the semiconductor industry for the mass production of integrated circuits (IC). It is also the driving force behind Moore’s Law, which predicts the number of transistors in an integrated circuit to double every two years. This paper aims to overview the photolithography process and its current situations, starting with the rationale behind it and its advantages. We review the photolithography process in individual steps and gave typical process parameters when applicable. Then we introduce the major photolithography system manufacturers of interest, followed by an overview of techniques used to improve the resolution of photolithographic systems, namely immersion lithography, Extreme-Ultraviolet (EUV) lithography, and Resolution Enhancement Techniques (RETs). Finally we discuss the challenges encountered in lithography technology.