A limit citation network for identification of core technologies: a case of extreme ultraviolet lithography technology

The identification of core technologies is a basic and important task in technology planning practice. We propose a limit citation network based on social network analysis and use the core–periphery structure to identify core patents. Then a case study is used to verify the feasibility of the methods. The results are: We obtain 994*994 co-citation matrix to identify core technologies in the EUVL and its network has an apparent core/periphery structure. The EUVL technology network has 123 core patens and 871 periphery patents. Seven core technologies are identified through the core network visualisation of connections between core patents. There are ten companies at a main position of the EUVL core technologies patentee network, of which AMAT has a strong presence, ASML and AGC play an important role. Most companies tend to pay attention to several technology domains, and one core technology area perhaps is the focus of many companies. The limit citation network improves the accuracy of network analysis results and could be used as a basis network model for analysis in some certain technology area. The identification of core technologies and main patentees on EUVL can help companies to accurately positioning the core technology and find the potential business partners.