Printability and propagation of stochastic defects through a study of defects programmed on EUV mask

The feasibility of using EUV lithography in high volume manufacturing makes the technology a very strong candidate for sub 20nm patterning[1,2]. However defect control remains a major challenge even today. The aim of this paper is to understand propagation of the programmed defects present on the EUV mask to wafer to get an understanding of how stochastic defects may evolve through processes and how we can mitigate it. The propagation of programmed defects from mask to post lithography to post etch at wafer level on wafers exposed on a NXE:3400 EUV lithography module with a simple stack coated with a Chemically Amplified Resist (CAR) with an in-house defectivity mask was studied (Figure 2: stack post etch- see full abstract). We focused on 32nm line/space pitch size, with mask bias of 14.5/17.5(17.5nm absorber lines on mask). We focused on 5 different types of programmed defects with varying dimensions. The programmed defects are organized as a matrix of line bridges(bumps) in a 15x10 array distribution. The biggest line bridge has a size of 20x40nm decreasing down with a fixed step size for each defect type. The smallest line bridge has a size of 6x6nm (Figure 1- see full abstract). The evolution of the defects from mask to wafer post lithography and post etch has been studied both theoretically by calculating change in defect area from a modelled script as well as experimentally with e-beam inspection and other metrology techniques. The end goal is to study the propagation of these programmed defects from post lithography to post etch on wafer through parameters like defect area, defect sizes and stack height information. References [1] EUV Mask and Wafer Defectivity: Strategy and Evaluation for Full Die Defect Inspection; Ravi Bonam, Hung-Yu Tien2, Acer Chou2, et al. [2] The analysis of EUV mask defects using a wafer defect inspection system; Kyoung-Yong Cho, Joo-On Park, Changmin Park, Young-Mi Lee, In-Yong Kang, Jeong-Ho Yeo et al.