Relationship between Thermalization Distance and Line Edge Roughness in Sub-10 nm Fabrication Using Extreme Ultraviolet Lithography

The energy of photons used for high-volume production of semiconductor devices will enter the energy range of ionizing radiation upon the use of extreme ultraviolet (EUV) radiation. In the energy range of ionizing radiation, thermalized electrons play the major role in the sensitization of acid generators in the chemically amplified resists, the standard resist for high-volume production of semiconductor devices. In this study, the effects of thermalization distance on the line edge roughness (LER) in the sub-10 nm fabrication using EUV lithography were investigated on the basis of the sensitization mechanisms of chemically amplified EUV resists. The optimum thermalization distance in terms of the trade-off relationships between resolution, LER, and sensitivity decreased with the half-pitch of line-and-space patterns. The optimum thermalization distance decreased to less than 2 nm at 9 nm half-pitch and further decreased to less than 1 nm at 5 nm half-pitch.