Developing an understanding of electron beam imaging of deep contact hole structures using Monte Carlo and spatial charge distribution simulations

Abstract

Charging effects on secondary electron (SE) profiles with bias voltage in deep contact holes are investigated. To enhance imaging capability for deep contact holes, the technique of applying a high bias voltage between the objective lens and the sample ground has been developed. However, the physics responsible for the mechanism of extraction of secondary electrons from deep within these structures is not well understood. Following previous work we use Monte Carlo simulations to compute the trajectories of numerous electrons while modeling the charging phenomena to calculate the resultant SE beam profile in a deep contact hole. This software derives the spatial charge distribution within the sample that results from the incident e-beam. The resultant surface potential, arising from areas of positive and negative charge within the sample, creates conditions, which require that the sample be included as an electron-optical element within the system. All of this information is used to calculate the ejected SE trajectories from the deep contact hole structures and to construct quantitative image profiles under specific scanning electron microscope (SEM) operating conditions and contact hole dimensions. The simulated results are compared to experimental results in order to develop a better understanding of e-beam imaging of deep contact hole structures.