An application study on the stochastic effect of EUV photons (Conference Presentation)

For the past years, ArF immersion has been employed as the major lithography tool in the foundry manufacturing to fabricate the patterns of minimum pitch and size. However, for semiconductor scaling beyond N7 the application of EUV lithography is considered to be crucially important to overcome the physical limitation of ArF immersion and to realize even smaller patterns. In the case of ArF photo processes, the best mask size for a specific pitch could be selected with the consideration of optical performances such as NILS, MEEF, etc. In contrast, for the EUV processes the optical and resist stochastic effect should also be taken into account as an important factor in deciding the best mask size. In this paper, we are going to discuss the dose and mask size optimization process for an DRAM contact hole layer with EUV lithography utilizing stochastic simulations; this contains also the stochastic response of the resist. In order to calibrate a predictive stochastic resist model, which is required for this application, measurements of the stochastic resist response are necessary. In addition, the systematic and stochastic errors of CD-SEM measurements have to be estimated. We will compare experimentally obtained NILS and MEEF to simulated results, which are in very good agreement. Also, we show a comparison of experimental and computational analysis of LCDU (Local CD Uniformity).