Effect of Side Lobe Intensity and Photon Shot Noise Effect on the Missing Hole Phenomenon in Extreme Ultraviolet Lithography

The missing hole phenomenon in a wafer pattern is a critical issue in extreme ultraviolet lithography. It occurs randomly, even when the process conditions are consistent. The main reason for this phenomenon is thought to be the photon shot noise effect, which is a random reaction between photons and photoresist particles. We speculate that side lobe intensity can be another reason, since the missing hole is affected by the light distribution of the main hole pattern. To confirm the effect of side lobe intensity and photon shot noise on the missing hole phenomenon, we used an attenuated phase shift mask (PSM), whose reflectivity can be changed without varying the total absorber stack thickness. The results show that the photon shot noise effect and the side lobe intensity are both affected by the reflectivity of the PSM and are the critical factors for the missing holes.