Analysis of a relation between the spatial frequency of electrostatic chuck and induced mask inplane distortion (IPD)

Due to potential applications of Extreme Ultraviolet Lithography (EUVL) to 22 nm half-pitch (hp) generations, EUVL is well researched. However, current SEMI standards about the chuck are based on only the local slope of roughness. Herein chuck standards, which consider the spatial frequency of the chuck surface roughness as well as the local slope of the shape, are proposed by examining the chuck roughness. To prevent a mask pattern shift when an EUVL mask is clamped by an electrostatic chuck, the roughness height must be limited. Thus, the in-plane distortion (IPD) and out-of-plane distortion (OPD) are introduced to evaluate the mask pattern shift. This research utilizes ANSYS to evaluate the relationship between the spatial frequency of chuck roughness and IPD/OPD induced on the mask surface after an EUVL mask is clamped by the chuck. The IPD depends on the local slope of the surface roughness shape of the electrostatic chuck (ESC) as well as the spatial frequency of the roughness. Therefore, re-polishing the chuck surface can decrease IPD. Moreover, the spatial frequency of roughness must be considered when a mask pattern shift correction is performed according to the surface roughness shape of the EUVL mask and ESC.