In 65nm and beyond generations, contact/via patterning is more challenging due to the complexity of manufacturing masks and the weak lithography process window. High NA scanners and suitable illumination can provide the desired resolution and dense pitch. However, there are trade-offs between process window, mask error enhancement factor (MEEF), and proximity effect. Some assistant technology is reported in literature, such as thermal flow, RELACS, SAFIER and sub-resolution assistant features. In this paper, we report a detailed study of the feasibility and limitations of these kinds of methods. Finally, we describe sub-resolution assistant features when used in QUASAR illumination with lower sigma, which have shown great promise to reduce the proximity effect and MEEF to get a larger lithography process window.

In recent years, green energy has been the subject of many studies and has attracted great attention throughout the world. Many studies have focused on illumination with sunlight as a means of saving energy and creating healthy lighting. In this research, we present a novel circle-focus Fresnel type concentrator. Each part of the reflector corresponds to different angles of incident rays, the purpose being to increase the tolerance of the concentrator. This strategy is different from the conventional approach but is easy to implement.