Abstract: This study aims to define the connotation and characteristics of technological lock-in through the characteristics of technological trajectories and suggests a comprehensive method to identify the main path and technology lock-in. Taking the photolithography industry as a case study, we identify the main path through the patent citation network. Depict the dynamic evolution of technological trajectories, trace the technological contributions of different core technologies at different stages, and describe photolithography's technological diversity from a geographical and technological perspective. The results show that from 1980-2010, photolithography was in a lock-in state; however, since 2010, we have observed more diverse technological paths. We found that the photolithography industry was dominated by the US, Germany, and Japan core technologies in the early stages. The technology diversity index has gradually increased in recent years, with Korea and Taiwan contributing more to the current lithography technology, mainly focusing on photoresist technology. China's photolithography technology has a large gap compared to developed countries and has not yet appeared in the technological main path trajectories, and only involves a few technology categories. Thus, this study offers significant contributions and implications for exploring technology lock-in, identifying technological opportunities, and suggesting lock-out, China's "technology lock-in " dilemma.